Optical measurement system with multi-wavelength emission

Abstract

The invention relates to an optical measurement system with multi-wavelength emission. Various embodiments disclosed herein describe photonic integrated circuits and associated optical measurement systems. The photonic integrated circuit may be configured to simultaneously output light of different wavelengths from different outputs of the multiplexer. A switching network, which may include multiplexed photonic switches, may be used to selectively route the different wavelengths to a common set of emission groups from which light may be emitted from the photonic integrated circuit.

Description

Technical Field

[0001] The present disclosure generally relates to optical measurement systems that utilize multiple light sources to generate light during measurement. More specifically, the present disclosure relates to optical measurement systems that include a routing arrangement that combines light and emits multiple wavelengths of light during measurement. Background Art

[0002] An optical measurement system may be used to identify the presence, type, and / or one or more characteristics of an object or substance in the system's surrounding environment. In some cases, an optical measurement system may perform spectral measurements by emitting light at multiple wavelengths and measuring the light returned to the system. The relative amount of light returned at each wavelength may provide information about the properties of the material or materials being measured. Depending on the one or more characteristics being measured, individual measurements performed at certain wavelengths may have a low signal-to-noise ratio ("SNR"). Therefore, it may be desirable to provide an optical measurement system that can improve the SNR of one or more measurements performed by the optical measurement system. Summary of the invention

[0003] Optical measurement systems as well as photonic integrated circuits and individual components such as light source units and switching networks used in the optical measurement systems are described herein.

[0004] Some embodiments relate to a light source unit including an Echelle grating multiplexer, wherein the Echelle grating includes a plurality of inputs and a plurality of outputs positioned to receive light from the plurality of inputs. The light source unit includes a plurality of light source groups, wherein each light source group is operable to emit a plurality of wavelengths, wherein each light source in the plurality of light source groups is connected to a corresponding input in the plurality of inputs, and the plurality of inputs are positioned such that: i) light generated by a first light source in each of the plurality of light source groups is routed to a first output in the plurality of outputs, and ii) light generated by a second light source in each of the plurality of light source groups is routed to a second output in the plurality of outputs.

[0005] In some variations, the plurality of inputs are positioned such that light generated by a third light source in each of the plurality of light source groups is routed to a third output in the plurality of outputs. In some variations, the plurality of light source groups includes a first light source group, and a first light source and a second light source in the first light source group are connected to immediately adjacent inputs in the plurality of inputs.

[0006] In some variations, the plurality of light source groups include a first light source group and a second light source group. The first light source in the first light source group is connected to a first input in the plurality of inputs. The second light source in the first light source group is connected to a second input in the plurality of inputs. The first light source in the second light source group is connected to a third input in the plurality of inputs. The second light source in the second light source group is connected to a fourth input in the plurality of inputs. The third input is positioned between the first input and the second input.

[0007] The plurality of light source groups may include a first light source group and a second light source group. In some variations, a first light source in the first light source group and a first light source in the second light source group are positioned on the first laser chip. Additionally or alternatively, a second light source in the first light source group and a second light source in the second light source group are positioned on the second laser chip.

[0008] In some variations, the first output is connected to a first wavelength locking unit and the second output is connected to a second wavelength locking unit. In some of these variations, the plurality of inputs are positioned so that light generated by a third light source in each of the plurality of light sources is routed to a third output in the plurality of outputs; and the third output is connected to a third wavelength locking unit. In some variations, the first light source and the second light source in each of the plurality of groups generate light having a common frequency difference.

[0009] Other embodiments relate to a light source unit comprising a first plurality of light sources operable to emit light of a first wavelength and light of a second wavelength, wherein the first wavelength and the second wavelength are separated by less than a threshold amount. A second plurality of light sources operable to emit light of a third wavelength and light of a fourth wavelength, wherein the third wavelength is separated from the fourth wavelength by less than a threshold amount. A multiplexer comprises a first input positioned to receive light of a first wavelength emitted by the first plurality of light sources, a second input positioned to receive light of a second wavelength emitted by the first plurality of light sources, a third input positioned to receive light of a third wavelength emitted by the second plurality of light sources, a fourth input positioned to receive light of a fourth wavelength emitted by the second plurality of light sources, a first output, and a second output, wherein the multiplexer is configured to route light received from the first input and the third input to the first output, and the multiplexer is configured to route light received from the second input and the fourth input to the second output.

[0010] In some variations, the multiplexer is an echelle multiplexer. In some variations, the third output is positioned between the first input and the second output. In some of these variations, the first wavelength is longer than the second wavelength. Additionally or alternatively, the second input may be positioned between the third input and the fourth input. In some cases, the first plurality of light sources are positioned on a first laser chip and the second plurality of light sources are positioned on a second laser chip. The light source unit may include a first wavelength locking unit and a second wavelength locking unit, wherein the first output is connected to the first wavelength locking unit and the second output is connected to the second wavelength locking unit.

[0011] Other embodiments relate to a method of operating a light source unit, the method comprising using a first plurality of light sources to simultaneously emit light of a first wavelength and light of a second wavelength during a first period. The method comprises receiving light of the first wavelength and light of the second wavelength at a multiplexer during the first period. The method comprises outputting light of the first wavelength from a first output of the multiplexer during the first period. The method comprises outputting light of the second wavelength from a second output of the multiplexer during the first period. The method comprises using a second plurality of light sources to simultaneously emit light of a third wavelength and light of a fourth wavelength during a second period. The method comprises receiving light of the third wavelength and light of the fourth wavelength at the multiplexer during the second period. The method comprises outputting light of the third wavelength from the first output of the multiplexer during the second period. The method comprises outputting light of the fourth wavelength from the second output of the multiplexer during the second period.

[0012] In some variations, light of a first wavelength is emitted from a first light source and light of a second wavelength is emitted from a second light source, and the first light source and the second light source are connected to adjacent inputs of a multiplexer. In some variations, the first light source is positioned on a first laser chip, and the second light source is positioned on a second laser chip. In some variations, light of the first wavelength and light of the second wavelength have a first frequency difference, and light of the third wavelength and light of the fourth wavelength have a first frequency difference. In some variations, the first output is connected to a first wavelength locking unit, and the second output is connected to a second wavelength locking unit.

[0013] Other embodiments relate to a photonic integrated circuit including a photonic switch, the photonic switch being configured to simultaneously route light of a first wavelength and light of a second wavelength, the light of the first wavelength and the light of the second wavelength having a predetermined frequency difference. The photonic switch includes a first coupler having a first input, a second input, a first output, and a second output. The photonic switch includes a second coupler having a third input, a fourth input, a third output, and a fourth output. The photonic switch includes a first pin, the first pin connecting the first output of the first coupler to the third input of the second coupler. The photonic switch includes a second pin, the second pin connecting the second output of the first coupler to the fourth input of the second coupler, wherein the length difference between the first pin and the second pin provides a free spectral range. The photonic switch includes a first phase shifter, the first phase shifter being positioned and controllable to selectively provide a first phase shift to light traveling between the first coupler and the second coupler. The free spectral range is selected based on a predetermined frequency difference such that light of a first wavelength received at the first input and light of a second wavelength received at the second input will be routed to a common selection of the third output and the fourth output, and the first phase shifter at least partially controls the common selection of the third output and the fourth output.

[0014] In some variations, the photonic switch is controllable to split the light of the first wavelength and the light of the second wavelength between the third output and the fourth output of the second coupler. Additionally or alternatively, the photonic switch is controllable to selectively route the light of the first wavelength and the light of the second wavelength to a single output of the third output and the fourth output.

[0015] In some variations, the second phase shifter is positioned and controllable to selectively provide a second amount of phase shift to light traveling between the first coupler and the second coupler. In some variations, the first phase shifter is positioned on the first pin, and the first phase shifter provides a first phase shift to light traveling through the first pin. In some variations, the second phase shifter is positioned on the second pin, and the second phase shifter provides a second phase shift to light traveling through the second pin. In some variations, the controllable switch includes a variable optical attenuator optically connected to the first input.

[0016] Other embodiments relate to a photonic integrated circuit comprising a plurality of light sources, the plurality of light sources comprising a first light source and a second light source, wherein the first light source is operable to emit light of a first wavelength and the second light source is operable to emit light of a second wavelength. Other embodiments include a photonic switch, the photonic switch comprising a first coupler, the first coupler comprising a first input, a second input, a first output, and a second output. The photonic switch comprises a second coupler, the second coupler having a third input, a fourth input, a third output, and a fourth output. The photonic switch comprises a first pin, the first pin connecting the first output of the first coupler to the third input of the second coupler. The photonic switch comprises a second pin, the second pin connecting the second output of the first coupler to the fourth input of the second coupler, wherein the length difference between the first pin and the second pin provides a free spectral range. The photonic switch includes a first phase shifter positioned and controllable to selectively provide a first phase shift to light traveling between the first coupler and the second coupler, wherein the free spectral range is selected based on a predetermined frequency difference so that light of a first wavelength received at the first input and light of a second wavelength received at the second input will be routed to a common selection of a third output and a fourth output, and the first phase shifter at least partially controls the common selection of the third output and the fourth output. In some variations, the controllable switch includes a variable optical attenuator optically connected to the first input.

[0017] In other embodiments, a method of operating a photonic integrated circuit having a plurality of light sources and a photonic switch, the photonic switch comprising a first coupler, a second coupler, a first pin connecting the first coupler to the second coupler, a second pin connecting the first coupler to the second coupler, and a plurality of phase shifters. The method includes using the plurality of light sources to simultaneously generate light of a first wavelength and light of a second wavelength during a first time period, the light of the first wavelength and the light of the second wavelength having a predetermined frequency difference. The method also includes receiving light of the first wavelength at a first input of the photonic switch and receiving light of the second wavelength at a second input of the photonic switch during the first time period. Applying a first phase shift to the first pin during the first time period to simultaneously route the light of the first wavelength and the light of the second wavelength to a first common selection of an output of the photonic switch. Additionally, a length difference between the first pin and the second pin provides a free spectral range of the photonic switch, and the free spectral range is selected based on the predetermined frequency difference so that the light of the first wavelength received at the first input and the light of the second wavelength received at the second input are combined into the same output of the photonic switch.

[0018] In some variations, the method includes simultaneously receiving light of a third wavelength at a first input of the photonic switch and receiving light of a fourth wavelength at a second input of the photonic switch during a second time period, wherein the light of the third wavelength and the light of the fourth wavelength have a predetermined frequency difference. In some cases, the method includes applying a first phase shift to the first pin during the second time period to simultaneously route the light of the third wavelength and the light of the fourth wavelength to a first common selection of the output of the photonic switch. In other cases, the method includes applying a second phase shift to the first pin during the second time period to simultaneously route the light of the third wavelength and the light of the fourth wavelength to a second common selection of the output of the photonic switch. In some variations, the photonic switch includes a first phase shifter positioned to apply the first phase shift to the first pin and a second phase shifter positioned to provide a second phase shift to the second pin. In some of these variations, the method includes applying a second phase shift to the second pin during the first time period.

[0019] Other embodiments relate to a photonic integrated circuit, the photonic integrated circuit comprising a light source unit and a multiplexer, the light source unit comprising a plurality of light sources, the multiplexer being optically connected to the plurality of light sources and comprising a first output and a second output. The photonic integrated circuit also comprises a switch network optically connected to the first output and the second output and comprising a plurality of outputs, wherein (1) the light source unit is controllable during a first time period to simultaneously output light of a first wavelength from the first output and light of a second wavelength from the second output, and (2) the switch network is controllable during the first time period to simultaneously route the light of the first wavelength and the light of the second wavelength to a first common selection of the plurality of outputs.

[0020] In some variations, the light source unit is controllable during the second time period to simultaneously output light of a third wavelength from the first output and light of a fourth wavelength from the second output. In some variations, the switch network is controllable during the second time period to simultaneously route light of a third wavelength and light of a fourth wavelength to a second common selection of the plurality of outputs. In some variations, the light of the first wavelength and the light of the second wavelength have a first frequency difference. In some variations, the light of the third wavelength and the light of the fourth wavelength have a first frequency difference. In some variations, the light source unit is controllable during the third time period to simultaneously output light of a fifth wavelength from the third output and light of a sixth wavelength from the fourth output. In some variations, the switch network is controllable during the third time period to simultaneously route light of a fifth wavelength and light of a sixth wavelength to a third common selection of the plurality of outputs.

[0021] In some variations, the switch network includes a first passive optical combiner optically connected to the first output and the second output, wherein the first passive optical combiner is configured to combine light having a first predetermined frequency difference from the first output and the second output into the first waveguide. In some variations, the switch network includes a second passive optical combiner optically connected to the third output and the fourth output, wherein the second passive optical combiner is configured to combine light having a second predetermined frequency difference from the third output and the fourth output into the second waveguide.

[0022] In some variations, the switch network includes a first controllable switch optically connected to the first waveguide and the second waveguide. In some variations, the switch network includes a first multiplexing optical switch optically connected to the first output and the second output, wherein the first multiplexing optical switch is configured to combine light having a first predetermined frequency difference from the first output and the second output into a common selection of outputs of the first multiplexing photonic switch.

[0023] In some variations, the switch network includes a second multiplexing optical switch optically connected to the third output and the fourth output, wherein the second multiplexing optical switch is configured to combine light having a second predetermined frequency difference from the third output and the fourth output into a common selection of an output of the second multiplexing photonic switch.

[0024] In some variations, the photonic integrated circuit includes a first wavelength locking unit optically connected to the first output and the third output, and a second wavelength locking unit optically connected to the second output and the fourth output.

[0025] Other embodiments relate to a photonic integrated circuit having a light source unit, the light source unit comprising a first plurality of light sources and a second plurality of light sources. The light source unit comprises a first multiplexer optically connected to the first plurality of light sources and having a first output and a second output. The light source unit comprises a second multiplexer optically connected to the second plurality of light sources and having a third output and a fourth output. The photonic integrated circuit comprises a switch network comprising a plurality of outputs and optically connected to the first output, the second output, the third output, and the fourth output. The light source unit is controllable during a first time period to simultaneously output light of a first wavelength from the first output and light of a second wavelength from the second output. The switch network is controllable during a second time period to simultaneously route light of the first wavelength and light of the second wavelength to a first common selection of the plurality of outputs.

[0026] In some variations, the light source unit is controllable during the second time period to simultaneously output light of a third wavelength from the first output and light of a fourth wavelength from the second output. In some variations, the switch network is controllable during the second time period to simultaneously route light of a third wavelength and light of a fourth wavelength to a second common selection of the plurality of outputs. In some variations, the light of the first wavelength and the light of the second wavelength have a first frequency difference. In some variations, the light of the third wavelength and the light of the fourth wavelength have a first frequency difference. In some variations, the light source unit is controllable during the third time period to simultaneously output light of a fifth wavelength from the third output and light of a sixth wavelength from the fourth output. In some variations, the switch network is controllable during the third time period to simultaneously route light of a fifth wavelength and light of a sixth wavelength to a third common selection of the plurality of outputs.

[0027] In some variations, the switch network includes a first passive optical combiner optically connected to the first output and the second output, wherein the first passive optical combiner is configured to combine light having a first predetermined frequency difference from the first output and the second output into the first waveguide. Additionally or alternatively, the switch network includes a second passive optical combiner optically connected to the third output and the fourth output, wherein the second passive optical combiner is configured to combine light having a second predetermined frequency difference from the third output and the fourth output into the second waveguide. In some variations, the switch network includes a first controllable switch optically connected to the first waveguide and the second waveguide.

[0028] In some variations, the switch network includes a first multiplexing optical switch optically connected to a first output and a second output, wherein the first multiplexing optical switch is configured to combine light having a first predetermined frequency difference from the first output and the second output into a common selection of outputs of the first multiplexing photonic switch. In some variations, the switch network includes a second multiplexing optical switch optically connected to a third output and a fourth output, wherein the second multiplexing optical switch is configured to combine light having a second predetermined frequency difference from the third output and the fourth output into a common selection of outputs of the second multiplexing photonic switch. In some variations, a first wavelength locking unit is optically connected to the first output and the third output, and a second wavelength locking unit is optically connected to the second output and the fourth output.

[0029] In other embodiments, a method of operating a photonic integrated circuit having a light source unit and a switch network includes: during a first time period, simultaneously outputting light of a first wavelength from a first output of a first multiplexer of the light source unit and outputting light of a second wavelength from a second output of the first multiplexer; and routing the light of the first wavelength and the light of the second wavelength to a first common selection of outputs of the switch network using the switch network.

[0030] In some variations, the method includes: during a second time period, simultaneously outputting light at a third wavelength from the first output and light at a fourth wavelength from the second output; and routing the light at the third wavelength and the light at the fourth wavelength to a second common selection of outputs of the switching network using the switching network.

[0031] In some embodiments, the method includes: during a third time period, simultaneously outputting light of a fifth wavelength from a first output of a second multiplexer of the light source unit and light of a sixth wavelength from a second output of the second multiplexer; and routing the light of the fifth wavelength and the light of the sixth wavelength to a third common selection of the output of the switching network using a switching network.

[0032] Other embodiments relate to an optical measurement system including a photonic integrated circuit, wherein the photonic integrated circuit includes a light source unit. The light source unit includes an echelle grating multiplexer, the echelle grating multiplexer including multiple inputs and multiple outputs positioned to receive light from the multiple inputs. The light source unit also includes multiple light sources configured to generate a first plurality of wavelengths, wherein: each of the multiple light sources is connected to a corresponding input of the multiple inputs, the multiple light sources include a first light source group operable to emit light in a first group of light wavelengths, the emission group is optically coupled to the light source unit and is configured to emit light received from the light source unit. The optical measurement system also includes a detector group and a controller.

[0033] The controller is configured to perform a first series of coded measurements using the light source unit, the emission group, and the detector group, wherein each coded measurement in the first series of coded measurements includes: (i) generating light of a corresponding plurality of wavelengths using the light source unit, wherein the corresponding plurality of wavelengths is a corresponding subset of the first group of wavelengths, (ii) simultaneously emitting the generated light of the corresponding plurality of wavelengths from the emission group, and (iii) measuring return light received during the simultaneous emission of the corresponding plurality of wavelengths using the detector group.

[0034] In some variations, the controller is configured to use the first series of coded measurements to generate a derived measured intensity for each wavelength in the first set of wavelengths. Additionally or alternatively, the plurality of light sources may include a second light source group operable to emit light of a second set of wavelengths, and the controller may be configured to perform a second series of coded measurements using the light source unit, the emission group, and the detector group. Each coded measurement in the second series of coded measurements may include: (i) generating light of a corresponding plurality of wavelengths using the light source unit, wherein the corresponding plurality of wavelengths is a corresponding subset of the second set of wavelengths, (ii) emitting the generated light of the corresponding plurality of wavelengths simultaneously from the emission group, and (iii) measuring return light received during the simultaneous emission of the corresponding plurality of wavelengths using the detector group.

[0035] In some variations, the first group of wavelengths is selected from adjacent wavelengths in the first plurality of wavelengths. The photonic integrated circuit includes a passive optical combiner configured to optically couple multiple outputs of the mid-step grating multiplexer to a common waveguide. Additionally or alternatively, the first light source group includes a first light source operable to emit light of a first wavelength, a second light source operable to emit light of a second wavelength, and a third light source operable to emit light of the second wavelength. In these variations, the multiple outputs of the mid-step grating multiplexer may include a first output, a second output, and a third output, such that: i) the mid-step grating multiplexer is configured to route light of a first wavelength generated by the first light source to the first output, ii) the mid-step grating multiplexer is configured to route light of a second wavelength generated by the second light source to the second output, and iii) the mid-step grating multiplexer is configured to route light of a third wavelength generated by the third light source to the third output. In some variations, the optical measurement system includes a reference detector configured to measure the intensity of light emitted by the emission group.

[0036] Some embodiments relate to methods for performing spectral measurements using an optical measurement system, the methods comprising performing a first series of coded measurements for a first set of wavelengths using a photonic integrated circuit and a detector group of the optical measurement system to generate a first plurality of coded measurement intensities. In these variations, the photonic integrated circuit may include a light source unit and an emission group, and the light source unit may include an echelle grating multiplexer having multiple outputs. In these methods, performing the first series of coded measurements may include, for each coded measurement in the first series of coded measurements: i) generating light of a corresponding plurality of wavelengths at a corresponding subset of the plurality of outputs of the echelle grating multiplexer, wherein the corresponding plurality of wavelengths is a corresponding subset of the first set of wavelengths; ii) simultaneously emitting the generated light of the corresponding plurality of wavelengths from the emission group, and iii) using the detector group to measure return light received during the simultaneous emission of the corresponding plurality of wavelengths to generate a corresponding coded measurement intensity in the first plurality of coded measurement intensities.

[0037] In some variations, the method further includes decoding the first plurality of encoded measurement intensities to generate a corresponding derived measurement intensity for each wavelength in the first set of wavelengths. Additionally or alternatively, the plurality of outputs of the echelle multiplexer include a first output, a second output, and a third output, and the first set of wavelengths includes a first wavelength, a second wavelength, and a third wavelength. In some of these variations, the first series of encoded measurements includes a first encoded measurement. During a first encoded measurement in the first series of encoded measurements: light of a first wavelength is generated at the first output, light of a second wavelength is generated at the second output, light of the first wavelength and light of the second wavelength are simultaneously emitted from the emission group, and the detector group generates a first encoded measurement intensity in the first plurality of encoded measurement intensities. The first series of encoded measurements may also include a second encoded measurement. During a second encoded measurement in the first series of encoded measurements: light of a first wavelength is generated at the first output, light of a third wavelength is generated at the third output, light of the first wavelength and light of the third wavelength are simultaneously emitted from the emission group, and the detector group generates a second encoded measurement intensity in the first plurality of encoded measurement intensities.

[0038] In some variations, the method includes performing a second series of coded measurements for a second set of wavelengths using a photonic integrated circuit and a detector group to generate a second plurality of coded measurement intensities. In these variations, performing the second series of coded measurements includes, for each coded measurement in the second series of coded measurements: i) generating light of a corresponding plurality of wavelengths at a corresponding subset of a plurality of outputs of an echelon grating multiplexer, wherein the corresponding plurality of wavelengths is a corresponding subset of the second set of wavelengths, ii) emitting the generated light of the corresponding plurality of wavelengths simultaneously from an emission group; iii) measuring the return light received during the simultaneous emission of the corresponding plurality of wavelengths using a detector group to generate a corresponding coded measurement intensity in a second plurality of coded measurement intensities. In some of these variations, the method also includes decoding the second plurality of coded measurement intensities to generate a corresponding derived measurement intensity for each wavelength in the second set of wavelengths. Additionally or alternatively, the first set of wavelengths and the second set of wavelengths have a common number of wavelengths. In some of these variations, the first set of wavelengths and the second set of wavelengths have a common set of frequency differences.

[0039] Other embodiments relate to a method for performing spectral measurements using an optical measurement system, wherein the method includes performing a first series of encoded measurements for a set of wavelengths using the optical measurement system to generate a plurality of encoded measurement intensities. The method also includes decoding the plurality of encoded measurement intensities to generate a corresponding derived measurement intensity for each wavelength in the set of wavelengths, and decoding a plurality of encoded reference intensities to generate a corresponding derived reference intensity for each wavelength in the set of wavelengths. The method also includes generating a corresponding reference-corrected derived measurement intensity for each wavelength in the set of wavelengths using the corresponding derived measurement intensity and the corresponding derived reference intensity.

[0040] In some variations, the series of coded measurements is performed using a photonic integrated circuit, a detector group, and a reference detector of an optical measurement system, the detector group generating the plurality of coded measurement intensities, and the reference detector generating the plurality of coded reference intensities. In some of these variations, the photonic integrated circuit includes a light source unit and an emission group, the light source unit including an echelle grating multiplexer having a plurality of outputs. In some of these variations, performing the series of coded measurements includes, for each coded measurement in the series of coded measurements: i) generating a corresponding plurality of wavelengths of light at a corresponding subset of the plurality of outputs of the echelle grating multiplexer, wherein the corresponding plurality of wavelengths is a corresponding subset of the first set of wavelengths; ii) simultaneously emitting the generated light of the corresponding plurality of wavelengths from the emission group, and iii) using the detector group to measure return light received during the simultaneous emission of the corresponding plurality of wavelengths to generate a corresponding coded measurement intensity in the first plurality of coded measurement intensities, and iv) using the reference detector to measure a portion of the generated light emitted from the emission group.

[0041] Other embodiments relate to a photonic integrated circuit having a light source unit, wherein the light source unit includes a set of tunable light sources and an echelle grating multiplexer having a plurality of inputs and a plurality of outputs positioned to receive light from the plurality of inputs. Each tunable light source in the set of tunable light sources is connected to a corresponding input in the plurality of inputs. Each tunable light source in the set of tunable light sources is operable to selectively emit light of a corresponding plurality of wavelengths including a first corresponding wavelength and a second corresponding wavelength, such that: i) light of the first corresponding wavelength emitted by each tunable light source in the set of tunable light sources is routed to a first output in the plurality of outputs, and ii) light of the second corresponding wavelength emitted by each tunable light source in the set of tunable light sources is routed to a second output in the plurality of outputs.

[0042] In some variations, the corresponding plurality of wavelengths of each tunable light source in the set of tunable light sources includes a third corresponding wavelength, and light of the third corresponding wavelength emitted by each tunable light source in the set of tunable light sources is routed to a third output in the plurality of outputs. Additionally or alternatively, the set of tunable light sources includes a plurality of tunable light sources. In some of these variations, the corresponding first wavelength and the corresponding second wavelength emitted by each tunable light source in the plurality of tunable light sources have a common frequency difference.

[0043] Additionally or alternatively, the light source unit includes a set of light source groups, each light source group being operable to emit a corresponding plurality of wavelengths. In these variations, each light source in the set of light source groups is connectable to a corresponding input in the plurality of inputs, and the plurality of inputs are positioned such that: i) light generated by a first light source in each of the set of light source groups is routed to a first output in the plurality of outputs, and ii) light generated by a second light source in each of the set of light source groups is routed to a second output in the plurality of outputs. In some variations, the photonic integrated circuit includes a passive optical combiner configured to optically couple the plurality of outputs of the mid-step grating multiplexer to a common waveguide.

[0044] Other embodiments relate to a photonic integrated circuit having a light source unit, the light source unit including a group of tunable light sources and a plurality of light sources. The photonic integrated circuit includes a first multiplexer optically connected to the plurality of tunable light sources and including a first plurality of outputs, and a second multiplexer optically connected to the plurality of light sources and including a second plurality of outputs, wherein: the light source unit is controllable during a first time period to output light of a first wavelength from a first output in the first plurality of outputs, and is controllable during a second time period to output light of a second wavelength from a second output in the first plurality of outputs. The first wavelength and the second wavelength are generated by tunable light sources in the group of tunable light sources. The light source unit is also controllable during a third time period to simultaneously output light of a third wavelength from a first output in the second plurality of outputs and output light of a second wavelength from a second output in the second plurality of outputs;

[0045] In some variations, the photonic integrated circuit includes a switch network optically connected to the first plurality of outputs and the second plurality of outputs and including a third plurality of outputs. In some of these variations, the switch network is controllable during a first time period to route light of a first wavelength to a first common selection of the third plurality of outputs, and during a second time period to route light of a second wavelength to a second common selection of the third plurality of outputs. Additionally or alternatively, the switch network is controllable during a third time period to simultaneously route light of a third wavelength and light of a fourth wavelength to a third common selection of the third plurality of outputs.

[0046] In some variations, the switch network includes a multiplexed photonic switch configured to receive light of a third wavelength from a first output of the second plurality of outputs and light of a fourth wavelength from a second output of the second plurality of outputs, and to combine the third wavelength light and the fourth wavelength light into a common selection of outputs of the multiplexed photonic switch.

[0047] In some variations, the switch network includes a controllable switch optically connected to a first output of the first plurality of outputs and a second output of the first plurality of outputs. The first multiplexer and / or the second multiplexer may be an echelle multiplexer. In some variations, the light source unit includes a set of wavelength locking units.

[0048] Some embodiments relate to a method of operating a light source unit of a photonic integrated circuit, the method comprising: i) emitting light of a first wavelength using a first tunable light source during a first time period, ii) receiving the light of the first wavelength at a first input of an echelle grating multiplexer during the first time period, and iii) outputting the light of the first wavelength from a first output of the echelle grating multiplexer during the first time period. The method also comprises: i) emitting light of a second wavelength using the first tunable light source during a second time period, ii) receiving the light of the second wavelength at the first input of the echelle grating multiplexer during the second time period, and iii) outputting the light of the second wavelength from a second output of the echelle grating multiplexer during the second time period.

[0049] In some variations, the method further includes: i) emitting light of a third wavelength using a second tunable light source during a third time period, ii) receiving the light of the third wavelength at a second input of the echelle grating multiplexer during the third time period, and iii) outputting the light of the third wavelength from a first output of the echelle grating multiplexer during the first time period. The method may also include: i) emitting light of a fourth wavelength using a second tunable light source during a fourth time period, ii) receiving the light of the fourth wavelength at a second input of the echelle grating multiplexer during the fourth time period, and iii) outputting the light of the fourth wavelength from a second output of the echelle grating multiplexer during the fourth time period. In some of these variations, the light of the first wavelength and the light of the second wavelength have a first frequency difference, and the light of the third wavelength and the light of the fourth wavelength have a first frequency difference.

[0050] In some variations, a passive optical combiner optically couples a first output and a second output of the echelle grating multiplexer to a common waveguide. Additionally or alternatively, the method may include simultaneously emitting light of a fifth wavelength and light of a sixth wavelength using a first plurality of light sources during a fifth time period. In these variations, the method may include: i) receiving light of a fifth wavelength and light of a sixth wavelength at the echelle grating multiplexer during the fifth time period, ii) outputting light of a fifth wavelength from a first output of the echelle grating multiplexer during the fifth time period, and iii) outputting light of a sixth wavelength from a second output of the echelle grating multiplexer during the fifth time period.

[0051] In addition to the illustrative aspects and embodiments described, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present disclosure will be readily understood through the following detailed description in conjunction with the accompanying drawings, in which like reference numerals represent like structural elements, and in which:

[0053] Figure 1A Shown is a partial cross-sectional side view of a device incorporating an optical measurement system as described herein. Figure 1B Shows Figure 1A view of your equipment.

[0054] Figure 2 A schematic diagram of a variation of an optical measurement system as described herein is shown.

[0055] Figure 3A A schematic diagram showing a variation of a photonic integrated circuit incorporating a light source unit with a single-output echelle multiplexer is shown. FIG. 3B to FIG. 3J A schematic diagram of a variation of a photonic integrated circuit incorporating a light source unit with a multi-output echelle multiplexer as described herein is shown. Figure 3K Schematic diagram showing a variation of a photonic integrated circuit incorporating a light source unit having a multi-output echelle multiplexer and a set of tunable light sources.

[0056] Figure 4A and Figure 4B Schematic diagram showing a variation of a passive optical combiner that may be used with the photonic integrated circuits described herein.

[0057] FIG. 5A to FIG. 5C Schematic diagram showing variations of photonic switches that may be used with the photonic integrated circuits described herein.

[0058] Fig. 6A and Figure 6B A photonic switch (such as that described herein) is shown. Figures 5A to 5C Schematic diagram of a variant of a switching network (those described).

[0059] Fig. 7A and Figure 7B Schematic diagram showing variations of photonic integrated circuits that may be used with the optical measurement systems described herein.

[0060] Fig. 8A and Figure 8B Schematic diagram showing variations of photonic integrated circuits that may be used with the optical measurement systems described herein.

[0061] Fig. 9A Schematic diagram showing variations of photonic integrated circuits that may be used with the optical measurement systems described herein. Fig. 9B Shows that Fig. 9A Schematic diagram of a variation of a switching network for use with a photonic integrated circuit.

[0062] Fig.10 Depicted are example wavelength encoding matrices that may be used with the optical measurement systems described herein to perform a series of encoded measurements.

[0063] Fig.11 Variations of methods of performing spectral measurements comprising one or more series of encoded measurements are depicted.

[0064] Fig.12 A variation of an optical measurement system utilizing both a detector group and a reference detector is shown.

[0065] Fig.13 Variations of methods of performing spectral measurements comprising one or more series of encoded measurements are depicted.

[0066] It should be understood that the proportions and sizes (relative or absolute) of the various features and elements (and sets and subsets thereof), and the boundaries, spacings, and positional relationships presented therebetween, are provided in the accompanying drawings solely to facilitate understanding of the various embodiments described herein, and therefore may not necessarily be presented or shown to scale and are not intended to indicate any preference or requirement for the illustrated embodiments to exclude the embodiments described in conjunction therewith.

[0067] Directional terms, such as "top", "bottom", "upper", "lower", "front", "rear", "above", "below", "above", "below", "left", "right", "vertical", "horizontal", etc., are used with reference to the orientation of some components in some of the figures described below, and are not intended to be limiting. Since components in various embodiments can be positioned in a plurality of different orientations, directional terms are used for illustrative purposes to demonstrate the relative orientation between components of the systems and devices described herein. Directional terms are intended to be interpreted broadly and therefore should not be interpreted to exclude components oriented in different ways. In addition, as used herein, the phrase "at least one of" following a series of items that separate any of the items in the items with the terms "and" or "or" is to modify the list as a whole, rather than modifying each member of the list. The phrase "at least one of" does not require selection of at least one of each of the listed items; rather, the phrase allows for the meaning of including at least one of any of the items in the items and / or at least one of any combination of the items and / or at least one of each of the items in the items. By way of example, the phrases "at least one of A, B, and C" or "at least one of A, B, or C" each refer to only A, only B, or only C; any combination of A, B, and C; and / or one or more of each of A, B, and C. Similarly, it should be understood that the order in which elements are presented for either a combined or separate list provided herein should not be construed to limit the present disclosure to only the order provided. DETAILED DESCRIPTION

[0068] Reference will now be made in detail to the representative embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to a preferred embodiment. On the contrary, it is intended to cover substitutions, modifications and equivalents that may be included in the essence and scope of the described embodiments defined by the appended claims.

[0069] The following disclosure relates to optical measurement systems and photonic integrated circuits and individual components thereof for use in optical measurement systems. The optical measurement systems described herein are configured to emit light simultaneously including multiple wavelengths of light from one or more emission sites. The optical measurement system can be configured to perform different individual measurements as part of a spectral measurement, and can be configured to emit light of different wavelengths (or wavelengths) during different individual measurements. In this way, the optical measurement system can collect information about how the sample being measured responds to light of different wavelengths, and can use this information to determine one or more properties of the sample.

[0070] Thus, in some variations, a photonic integrated circuit as described herein may include a light source unit having multiple outputs. The light source unit may be operated to simultaneously output light of different wavelengths, wherein each wavelength is output via a different output of the light source unit. The light source unit may be combined with one or more mid-step grating multiplexers, each mid-step grating multiplexer having multiple outputs, such as described in more detail herein. Light from these outputs may be combined into a common output so that the light may be routed to a set of emission locations (e.g., a single emission location or multiple emission locations) on the photonic integrated circuit and emitted from the set of emission locations. Light emitted from the photonic integrated circuit may be emitted from an optical measurement system and introduced into a sample being measured. One or more detector groups may measure the amount of light returned from the sample to the optical measurement system as part of a spectral measurement or a separate measurement thereof.

[0071] In some variations, the switch network may receive light of different wavelengths generated from a light source unit and may i) combine the light of different wavelengths and ii) selectively route the light of the combined wavelength to a common set of emission groups, where the common set of emission groups may include a single emission group or multiple emission groups. In this way, each emission group in the common set of emission groups will emit light that simultaneously includes these different wavelengths. In some cases, the switch network may include a multiplexed photonic switch having multiple outputs and configured to selectively route light of different wavelengths to the same selected output of the multiplexed photonic switch.

[0072] As part of a spectral measurement, the optical measurement system described herein can be used to perform one or more series of coded measurements. Each series of coded measurements utilizes multiple individual coded measurements, during which multiple wavelengths of light are simultaneously emitted from the emission site of the optical measurement system. Within a series of coded measurements, different coded measurements are performed using different combinations of wavelengths selected from a set of target wavelengths. The optical measurement system is configured to generate corresponding multiple coded measurement intensities for each series of coded measurements. Each coded measurement intensity corresponds to the light intensity measured by the optical measurement system for the wavelength combination emitted during the corresponding coded measurement. The multiple coded measurement intensities can be analyzed to generate a derived measurement intensity for each wavelength in the set of target wavelengths. The derived measurement intensity can be used alone or in combination with the results of other individual measurements performed as part of the spectral measurement when determining one or more properties of the sample.

[0073] In some variations, the light source unit may include a set of one or more tunable light sources and an echelle grating multiplexer having multiple outputs. The tunable light sources may be selectively operated to generate light of different wavelengths. In this way, the echelle grating multiplexer may receive light of different wavelengths during different time periods from the tunable light sources. Different wavelengths may be routed to different outputs of the echelle grating multiplexer. When the light source unit is configured to output a specific plurality of wavelengths, the use of tunable light sources may reduce the number of light sources required to output these wavelengths, which may reduce the number of electrical connections associated with the light source unit and / or the overall size of a photonic integrated circuit incorporating the light source unit.

[0074] It should be understood that when an optical measurement system or a component thereof (e.g., a photonic integrated circuit, a light source unit, or a light source) is discussed herein as operating during different time periods (e.g., to generate or emit light of different wavelengths), it should be understood that these time periods may occur in any order that may be desired. For example, if the light source unit is discussed herein as generating light of a first wavelength during a first time period and generating light of a second wavelength during a second time period, the first time period may occur before the second time period, or vice versa. Similarly, if the light source unit generates light of a third wavelength during a third time period, the third time period may occur before, after, or between the first time period and the second time period.

[0075] refer to Figures 1A to 13 These and other embodiments are discussed. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustrative purposes only and should not be construed as limiting.

[0076] Embodiments of the optical measurement systems described herein may be incorporated into a device having a housing. The device (which may be wearable in some cases) may operate alone to perform measurements using the optical measurement system, or may be a multi-function device capable of performing additional functions, as will be readily understood by one of ordinary skill in the art. For example, in some cases, the optical measurement system may be incorporated into a smartphone, a tablet computing device, a laptop or desktop computer, a smartwatch or other wearable device, or other electronic device (collectively referred to herein as an "electronic device" for ease of discussion).

[0077] The device may include a display (which may be a touch screen display) that provides a graphical output that can be viewed through or at the outer surface of the device. When the display is configured as a touch screen, the display may be able to receive touch input at the outer surface. The device may include a cover sheet (e.g., cover glass) located above the display, which forms at least a portion of the outer surface. The display is capable of providing graphical output and, when configured as a touch screen, is capable of receiving touch input through the cover sheet. In some embodiments, the display includes one or more sensors (e.g., capacitive touch sensors, ultrasonic sensors, or other touch sensors) positioned above, below, or integrated with the display portion. In various embodiments, the graphical output of the display responds to input provided to the electronic device. In some cases, the optical measurement system described herein may be controlled in response to user input provided to the device (e.g., via a touch screen display). Additionally or alternatively, the display may provide information about the progress and / or results of the spectral measurement performed by the optical measurement system. The portable electronic device may include additional components typical of a computing device, including a processing unit, a memory, an input device, an output device, additional sensors, and the like.

[0078] Figure 1A and Figure 1B An example of an apparatus 100 housing an optical measurement system 102 as described herein is shown. Figure 1A A side view of a device 100 is shown, which includes, for example, a housing 104 having a top outer surface 106 (the housing 104 is Figure 1A 104 to illustrate a side view of components of the optical measurement system 102 positioned within the housing 104). The top outer surface 106 defines a sampling interface 107 for the optical measurement system 102 through which light emitted by the optical measurement system 102 may exit the device 100 and re-enter the device 100 to return to the optical measurement system 102. The sampling interface 107 includes at least one window that defines one or more emission regions 108 through which light emitted by the optical measurement system 102 may exit the device 100 and one or more collection regions 110 through which light entering the device 100 may reach a predetermined portion of the optical measurement system 102, such as a detector. Figure 1A and Figure 1B In the variant shown, the device comprises a plurality of emission regions 108 and a plurality of collection regions 110. Figure 1A and Figure 1B An equal number of emission regions 108 and collection regions 110 are depicted, but in other cases the sampling interface 107 has an unequal number of emission regions 108 and collection regions 110 .

[0079] Each emission region 108 serves as a corresponding emission site of the optical measurement system 102 from which light can be emitted from the optical measurement system 102. Similarly, each collection region 110 can serve as a corresponding collection location of the optical measurement system 102 from which light can be received and measured by the optical measurement system 102. Each emission region 108 and collection region 110 is transparent at any one or more wavelengths (collectively referred to as "measurement wavelengths") used by the optical measurement system 102 to perform the spectral measurements discussed herein. Each emission region 108 and collection region 110 can be defined by corresponding windows (transparent at the measurement wavelength) that are separated from each other by one or more opaque portions of the housing (i.e., absorbing or otherwise blocking light transmission at the measurement wavelength). In other variations, some or all of the emission regions 108 and / or collection regions 110 are defined in a common window (e.g., using a mask that is opaque at the measurement wavelength). Additionally or alternatively, the device 100 may include barriers, baffles, or other light blocking structures (not shown) that may at least partially define some or all of the emission region 108 and the collection region 110. These light blocking structures block stray light and act as guides to limit the paths that light may take between the optical measurement system 102 and the sampling interface 107.

[0080] like Figure 1A and Figure 1BAs shown, the optical measurement system 102 includes a photonic integrated circuit 112. The photonic integrated circuit 112 includes a set of one or more emission groups and is capable of selectively emitting light from each emission group. In the case where the photonic integrated circuit 112 includes multiple emission groups, the photonic integrated circuit 112 is capable of emitting light from each of these emission groups. The light emitted from each emission group of the photonic integrated circuit 112 can leave the device 100 through the sampling interface 107 (e.g., via the corresponding emission area 108). In some variations, the optical measurement system 102 optionally includes one or more light modification components (schematically shown as box 114) positioned between the photonic integrated circuit 112 and the sampling interface 107, which modify the light emitted from the photonic integrated circuit 112 before it reaches the sampling interface 107. For example, the light modification component 114 may include one or more lenses (which change the divergence and / or direction of the light), one or more diffusers, reflectors, etc. Additionally or alternatively, the sampling interface 107 itself may act as a light modifying component (e.g., it may have an integrated lens capable of changing the divergence and / or direction of light passing therethrough, etc.). Light emitted from a given emission group interacts with the sampling interface 107 and any intervening components (such as the light modifying component 114) to control the location at which the light exits the device 100 and, thus, define an emission site for the optical measurement system 102. Where the photonic integrated circuit 112 includes multiple emission groups, the optical measurement system 102 may include multiple different emission sites from which light may be emitted from the optical measurement system 102 (and, thus, from the device 100 incorporating the optical measurement system 102 via the sampling interface 107).

[0081] The optical measurement system 102 also includes one or more detector groups 116, each of which includes a corresponding set of detector elements. Each detector group 116 is positioned within the device 100 to receive light that has entered the device 100 through the sampling interface 107 (e.g., via the corresponding collection area 110). In some variations, the optical measurement system 102 includes one or more light modification components (schematically shown as box 118) positioned between the sampling interface 107 and at least one detector group 116, which modify the light entering the device 100 before reaching the corresponding detector group (or groups). The light modification component 118 may include one or more lenses (which change the divergence and / or direction of the light), one or more diffusers, reflectors, etc. Additionally or alternatively, the sampling interface 107 may act as a light modification component (e.g., it may have an integrated lens capable of changing the divergence and / or direction of the light passing therethrough, etc.), which modifies the light before it reaches the detector group 116.

[0082] In some cases, the photonic integrated circuit 112 and the one or more detector groups 116 are mounted to a common component. Figure 1A and Figure 1B In the illustrated variations, the optical measurement system 102 includes an interposer 120. In these cases, the photonic integrated circuit 112 and one or more detector groups 116 are all mounted on the interposer 120, which in turn can act as an electrical interface for these components (e.g., routing signals to and / or from these components). In some cases, the interposer also acts as a heat sink. In other variations, the photonic integrated circuit 112 is mounted to a component separate from some or all of the detector groups 116. In other variations, some or all of the detector groups 116 are directly mounted on (or otherwise integrated into) a portion of the photonic integrated circuit 112.

[0083] Each detector group 116 can measure light received by the optical measurement system 102 during a measurement (e.g., light that has been emitted from the optical measurement system toward the sample and returned to the optical measurement system). The light measured by the group of detector groups during a measurement can be analyzed to determine one or more properties of the environment surrounding the optical measurement system 102 (e.g., the presence, type, and / or one or more characteristics of an object measured by the optical measurement system). The optical measurement system can be configured to measure one or more properties of a particular type of object, material, etc. (collectively referred to herein as a "sample"). Light can be measured by the detector group when the corresponding emission group is emitting light (for determining how the emitted light interacts with the sample), and can also optionally be measured when the corresponding emission group is not actively emitting light (for measuring background light that can aid in background correction operations).

[0084] Each detector group 116 can be associated with a corresponding emission group such that each detector group 116 is positioned to measure light that has been emitted by the corresponding emission group and returned to the optical measurement system 102 (e.g., by interacting with a sample positioned external to the optical measurement system, such as placed in contact with the sampling interface 107). The optical measurement system 102 can be configured so that when the optical system is used to measure aspects of a sample of a predetermined type, light emitted by one emission group will not reach detector groups associated with other emission groups. In this way, each emission group and its corresponding detector group can perform measurements of a corresponding portion of the sample without interfering with other measurements being performed simultaneously by another emission group / detector group.

[0085] For example, the photonic integrated circuit 112 may include: a plurality of emission groups, the plurality of emission groups including a first emission group and a second emission group; and a plurality of detector groups, the plurality of detector groups including a first detector group and a second detector group. The components of the optical measurement system 102 may be controlled (e.g., using a controller as described herein) to perform a first measurement using the first emission group and the first detector group and to perform a second measurement using the second emission group and the second detector group. The first measurement and the second measurement may be performed simultaneously, such that the first emission group and the second emission group emit light simultaneously for at least a portion of each of the first measurement and the second measurement.

[0086] Figure 2 A schematic diagram of an optical measurement system 200 as described herein is shown. The optical measurement system 200 includes a set of emission groups 202a-202d, a light generating assembly 204, and a set of detector groups 206a-206d. The light generating assembly 204 is configured to generate light and route the light to the set of emission groups 202a-202d, thereby allowing some or all of the emission groups 202a-202d to emit light. Thus, light may exit the optical measurement system 200 via the set of emission groups 202a-202d, and the optical measurement system 200 may use some or all of the detector groups 206a-206d to measure the light returning to the optical measurement system 200. Although the optical measurement system 200 is Figure 2 202a to 202d and four detector groups 206a to 206d, it should be understood that the optical measurement system 200 may include any number of emission groups and detector groups. For example, some embodiments of the optical measurement systems described herein may include a single emission group and a single detector group. Indeed, certain concepts are discussed herein in the context of a single emission group / detector group pair of an optical measurement system, but these principles can be extended to any or all of the other emission groups and detector groups of a given optical measurement system.

[0087] The light generation assembly 204 may include a light source unit 208 having a group of light sources (not shown), each of which is selectively operable to emit light at a corresponding set of wavelengths. The group of light sources may be controlled to generate light routed from the light generation assembly 204 to the group of emission groups 202a to 202d. Each light source may be any component capable of generating light of one or more specific wavelengths, such as a light emitting diode or a laser. The laser may include a semiconductor laser, such as a laser diode (e.g., a distributed Bragg reflector laser, a distributed feedback laser, an external cavity laser), a quantum cascade laser, etc. A given light source may be single frequency (fixed wavelength) or may be tunable to selectively generate one of a plurality of wavelengths (i.e., the light source may be controlled to output different wavelengths at different times). The group of light sources may include any suitable combination of light sources and may work together to generate light of any wavelength in a plurality of different wavelengths.

[0088] For example, depending on its design, a tunable light source may be operable to selectively adjust the wavelength of the emitted light across the tuning range of the light source. Some light sources, such as distributed Bragg reflector lasers and distributed feedback lasers, may be configured to be tunable over a relatively small tuning range, such as about a single nanometer. Other light sources, such as sampled grating distributed Bragg reflector (SGDBR) lasers and reflective semiconductor optical amplifier (RSOA) lasers, may be tunable over a wider tuning range, such as about tens or hundreds of nanometers.

[0089] In some variations, the light source unit 208 includes a plurality of light source groups, wherein each light source group is associated with a corresponding emission group in the set of emission groups 202a to 202d. In these cases, each emission group may receive light generated from a different group of light sources in the light source unit 208. In other variations, multiple emission groups in the set of emission groups 202a to 202d may receive light from a common light source group in the light source unit 208. For example, the light generation assembly 204 may include a switch network 210 configured to selectively route light generated by the light source unit 208 to any or all of the emission groups in the set of emission groups 202a to 202d.

[0090] Specifically, the switch network 210 receives light from the light source unit 208 via one or more inputs, each of which is optically connected to a corresponding output of the light source unit 208 to receive light therefrom. The switch network 210 may include a plurality of outputs, each of which is connected to a corresponding emission group in the set of emission groups 202a to 202d. The switch network 210 may be controllable to obtain light received at one of its inputs and simultaneously direct the light to some or all of its outputs. For example, the switch network 210 may be configured in a first case to route light from the light source unit 208 to a single emission group (e.g., the first emission group 202a), or may simultaneously route light to multiple emission groups (e.g., all four emission groups 202a to 202d). In these cases, the light source unit may include relatively fewer light sources because a single group of light sources may be used to provide light to multiple emission groups.

[0091] It should be understood that in some variations, the optical measurement systems described herein do not include the switch network 210. For example, the light source unit 208 may be optically connected to each of the emission groups 202a to 202d in the set of emission groups such that the light generation assembly 204 does not select which emission group 202a to 202d receives light from the light source unit 208. For example, the light generation assembly 204 may include M×N couplers (e.g., M×N star couplers) or a cascaded array of optical couplers such that light generated by the light source unit 208 is distributed between each of the emission groups 202a to 202d in the set of emission groups.

[0092] The light source unit 208 may include additional components in addition to the group of light sources. For example, the light source unit 208 may include one or more multiplexers (e.g., a mid-step grating multiplexer, an arrayed waveguide grating (AWG) multiplexer, a ring resonator multiplexer, etc.) that can be configured to reduce the number of outputs of the light source unit 208. Specifically, the multiplexer may include a plurality of inputs (each of which may be connected to a corresponding light source) and one or more outputs, and may be configured so that light received at a given input is routed to a corresponding output. The output of the multiplexer may be optically connected to a corresponding input of the switch network. In this way, the switch network 210 may be able to receive light from several different light sources using a relatively small number of inputs.

[0093] In some variations, the light source unit 208 includes one or more wavelength locking units. Each wavelength locking unit may output a corresponding set of output signals indicative of the wavelength or wavelength variation of light received by the wavelength locking unit, which may be used by a controller (e.g., the controller 212 of the optical measurement system 200) to control the light source unit 208 (e.g., to control the light source within the light source unit that is generating the light) to stabilize or otherwise adjust the wavelength of the light emitted by the light source unit 208. Even for fixed wavelength lasers, the exact emission wavelength may vary slightly with changes in temperature and / or injection current, and thus the wavelength locking unit may provide feedback to the controller 212 to set a stable wavelength output before or during a measurement. In the case where the light source unit 208 includes one or more multiplexers, the wavelength locking unit may receive light output by the one or more multiplexers by tapping light from corresponding outputs of the one or more multiplexers.

[0094] Each wavelength locking unit may include any components that may be required to generate a corresponding set of output signals. For example, in some variations, the wavelength locking unit may include a set of interferometric measurement components (e.g., a single interferometric measurement component or multiple interferometric measurement components) configured to generate a set of wavelength-dependent interference signals. Specifically, the set of interferometric measurement components may include one or more Mach-Zehnder interferometers, multimode interference waveguides, etc., which are configured to output one or more interference signals, wherein the intensity of each interference signal depends on the wavelength of light received by the set of interferometric measurement components. The wavelength locking unit may include a set of detector elements configured to measure the set of interference signals to generate the set of output signals. A controller (e.g., controller 212) may use the set of output signals to control a light source so that the light source outputs at a target wavelength.

[0095] Each detector group in the group of detector groups 206a to 206d includes one or more groups of detector elements. Each detector element is capable of generating a corresponding signal representing the light incident thereon, which can collectively form a set of output signals for the detector group. A separate detector element can be an independent detector or a single sensing element of a larger detector array (e.g., a photodiode of a photodiode array). It should be understood that different sensing elements of a single detector array can be associated with different detector groups. For example, a detector array can include a first subset of sensing elements associated with a first detector group and a second subset of sensing elements associated with a second detector group. It should also be understood that the detector elements within a given detector group in the group of detector groups 206a to 206d do not need to be adjacent to each other. In general, the group of detector groups 206a to 206d measures light that has been emitted from the optical measurement system 200 via the group of emission groups 202a to 202d and returned to the optical measurement system 200 (e.g., after interacting with a sample), which can facilitate various measurements described herein.

[0096] As discussed herein, each of the emission groups 202a-202d is formed as part of a photonic integrated circuit 214. Some or all of the light generating components of the light generating components 204 (e.g., the light source unit 208 and / or the switch network 210) may also be integrated into the photonic integrated circuit 214. For example, in some cases, the light sources of the light source unit 208 are all integrated into the photonic integrated circuit 214, such as Figure 2 As shown. In other cases, some or all of the light sources generate light from outside the photonic integrated circuit 214, and the light from these light sources is coupled into the photonic integrated circuit 214 to reach one or more of the emission groups 202a to 202d. It should be understood that the photonic integrated circuit 214 may include multiple photonic dies, so that different components of the photonic integrated circuit 214 are formed in different photonic dies. For example, the light source of the light source unit 208 may be formed as part of one or more laser chips. Additionally or alternatively, if desired, other components of the photonic integrated circuit 214 may be distributed between different photonic dies.

[0097] The photonic integrated circuit 214 may utilize waveguides to optically connect components on the photonic integrated circuit 214. For example, in Figure 2 In the illustrated embodiment, each of the emission groups 202a to 202d can be optically connected to the light generating assembly 204 via a corresponding waveguide. In these cases, each of the emission groups 202a to 202d is configured to emit at least one corresponding light beam from the photonic integrated circuit 214. Specifically, each emission group includes one or more groups of emitters (e.g., a single emitter or multiple emitters), wherein each group of emitters is configured to emit a corresponding light beam from the photonic integrated circuit 214. Each emitter can be configured as an external coupler (e.g., an edge coupler, a vertical output coupler, etc.) that is configured to emit light from the photonic integrated circuit at a predetermined position and angle relative to the photonic integrated circuit 214. In the case where the emission group includes multiple emitters configured to generate a single light beam, each of these emitters can emit a corresponding individual light beam from the photonic integrated circuit 214. The individual light beams generated by the group of emitters can overlap at least partially, thereby collectively forming a larger total light beam emitted by the emission group (also referred to herein as a "transmitted light beam").

[0098] Each emitter of the emission group is optically connected to the light source unit 208 so that the emitter can receive light generated by the light source unit 208. For example, a group of emitters of the emission group can be optically connected to a corresponding output (or multiple outputs) of the switch network 210 so that the switch network 210 can route light from the light source unit 208 to the group of emitters. In some variations, the photonic integrated circuit 214 includes one or more optical splitters configured to receive light from the output of the switch network 210 and split the received light between some or all of the emitters of the emission group. For example, the one or more optical splitters may include a star coupler, a cascaded array of optical splitters (e.g., a 1×2 optical splitter, etc.), other 1×N or M×N optical splitters, combinations thereof, etc.

[0099] The optical measurement system 202 may be configured such that when the optical system is used to measure various aspects of a predetermined type of sample, light emitted by one of the emission groups 202a to 202d will not reach the detector groups associated with the other emission groups 202a to 202d. For example, in some variations, the first emission group 202a is paired with the first detector group 206a, while the second emission group 202b is paired with the second detector group 206b. In these cases, the optical measurement system 202 may be configured such that the first detector group 206a is positioned such that it will receive light generated by the first emission group 202a and will not receive light generated by the second emission group 202b during operation of the optical measurement system 202. Similarly, the second detector group 206b is positioned such that it will receive light generated by the second emission group 202b and will not receive light generated by the first emission group 202a during operation of the optical measurement system 200. In this way, two emission group-detector group pairs can simultaneously perform measurements on different portions of the sample without crosstalk. Additionally, in these variations, each emission group-detector group pair may be associated with a different emission region 108 and collection region 110 , as discussed herein, or may be associated with the same emission region 108 and collection region 110 .

[0100] Figure 2Also shown is a controller 212, which controls the operation of the optical measurement system 200 to perform various measurements as described herein. Specifically, the controller 212 can control the light generation component 204 to generate light and route the light to one or more emission groups in the group of emission groups 202a to 202d. For example, in the case where the light generation component 204 includes a light source unit 208 and a switch network 210, the controller 212 can control one or more light sources of the light source unit 208 to generate light of a selected wavelength (or multiple selected wavelengths). The controller 212 can also control the switch network 210 to route the light received from the light source unit 208 to a selected number of emission groups 202a to 202d. The controller 212 can also control the group of detector groups 206a to 206d to generate output signal sets from some or all of the detector groups 206a to 206d, wherein the output signal sets represent the light received by the detector elements of the detector groups 206a to 206d. These output signal sets can be processed and analyzed to determine one or more properties of the sample. Controller 212 may include any combination of software, hardware, and firmware necessary to perform these functions (including any method steps described below), including, for example, one or more processors and / or application specific integrated circuits (ASICs).

[0101] As described herein, each emission group of a photonic integrated circuit can be used to emit light from the photonic integrated circuit, which light can also be emitted from an optical measurement system to perform measurements of a sample. When the light source of the light source unit described herein includes a coherent light source (such as a laser), measurements performed using coherent illumination may suffer from coherent noise (also referred to herein as "speckle" noise). Specifically, interference of the coherent light as it is scattered through the sample can result in spatial intensity variations of the light received by the detector group, which can reduce the SNR of a given measurement.

[0102] Depending on which aspect or aspects of a sample the optical measurement system is measuring, the SNR of separate measurements at different wavelengths may be limited by different noise sources, such as fundamental noise sources or coherent noise sources. When separate measurements at a given wavelength are limited by coherent noise, the SNR will not be improved by increasing the amount of light introduced into the sample at that wavelength. When measurements at a given wavelength are limited by fundamental noise, the SNR may be increased by increasing the amount of light introduced into the sample at that wavelength. In these cases, it may be desirable to increase the amount of light emitted at a given wavelength to exceed the amount of light that a single light source can generate. Depending on how the light is routed in the optical measurement system, it may be difficult to generate and combine light of the same wavelength without incurring optical losses or losing the ability to individually monitor the wavelength of light generated by each light source. Therefore, some of the optical measurement systems described herein are configured to use multiple different wavelengths to improve the output power of one or more separate measurements of the optical measurement system.

[0103] For example, when performing a spectral measurement, the optical measurement system may perform multiple individual measurements, each of which is associated with a different emission wavelength. During the individual measurements, the emission group (e.g., Figure 2 In some embodiments, the emission groups 202a to 202d of the present invention may emit light corresponding to the emission wavelength. Each emission group is associated with a corresponding set of emission sites, so that light emitted from the photonic integrated circuit 214 from a given emission group will leave the optical measurement system via each emission site in the corresponding emission site of the group. In the case where the emission group is associated with multiple emission sites, the light emitted from the emission group may leave the optical measurement system at multiple locations. In some of these variations, the detector group associated with the emission group may include multiple groups of detector elements, wherein each group of detector elements is positioned to measure light collected from different collection areas of the sampling interface. In these variations, different groups of detector elements can use the light emitted by the emission group to measure multiple different areas of the sample. For ease of discussion, each emission group will be discussed as emitting light that leaves the optical measurement system via a corresponding emission site, but it should be understood that each emission group may also emit light that leaves the optical measurement system via one or more additional emission sites, if desired.

[0104] Thus, during a single measurement, light of an emission wavelength may be emitted from an emission group (e.g., Figure 2 The light is emitted from one of the emission groups 202a to 202d of the optical measurement system, the light leaves the optical measurement system via the corresponding emission site, and (for example, Figure 2 A corresponding detector group in the detector groups 206a to 206d of the detector groups 206a to 206d can measure return light (e.g., light that re-enters the optical measurement system after interacting with the sample) that is received when the emission group emits light. This measurement and the resulting intensity of the return light measured by the detector group can indicate how a given sample interacts with the emission wavelength. For example, a portion of the light introduced into the sample can be absorbed as it passes through the sample. The amount of light absorbed depends at least in part on the contents of the sample (e.g., the presence and concentration of different substances within the sample) and the wavelength of the light. Therefore, the light intensity measured during the measurement can depend at least in part on the amount of light introduced into the sample and the amount of light absorbed by the sample. Multiple measurements can be made at different emission wavelengths, and these individual measurements can be analyzed together to derive one or more properties of the sample (e.g., using spectral analysis techniques). As will be readily appreciated by one of ordinary skill in the art, the optical measurement system can facilitate a wide range of analytical techniques.

[0105] For some individual measurements, the emission group may emit light of a single wavelength. In these cases, the emission group emits light at the emission wavelength used for the individual measurement. Additionally or alternatively, the optical measurement system described herein may be configured to perform one or more individual measurements, wherein the emission group simultaneously emits light of multiple different wavelengths, so that the optical measurement system simultaneously emits light of these wavelengths from the emission sites corresponding to the emission groups. For example, the optical measurement system may be configured to simultaneously emit light with a pair of different wavelengths from the emission sites. When two wavelengths of light are emitted simultaneously from a given emission group and its corresponding emission site, the detector group measuring the return light may not be able to distinguish between the different wavelengths. Therefore, the output signal generated by the detector group represents the collective light measured at two wavelengths.

[0106] In some cases, the wavelength difference between a pair of wavelengths may be small enough that the pair of wavelengths may be considered a single wavelength for the purpose of performing spectroscopic measurements. For example, when an optical measurement system performs a measurement using a particular emission wavelength, the optical measurement system may be able to tolerate certain wavelength variations as part of the measurement without meaningfully affecting the accuracy of the spectroscopic measurement. Thus, the optical measurement system may be configured to simultaneously emit two wavelengths of light from an emission group and its corresponding emission sites during a separate measurement, where the two wavelengths are close enough in wavelength to be considered a single emission wavelength for analyzing the separate measurement.

[0107] The same principle can be applied to multiple different emission wavelengths, so that the optical measurement system can be able to emit light of different wavelength pairs. In these cases, each pair of wavelengths is considered a corresponding single emission wavelength for the purpose of performing and analyzing individual measurements. Therefore, the optical measurement system can perform a series of individual measurements at multiple different emission wavelengths, and the optical measurement system can emit light of certain emission wavelengths that actually include two wavelengths of light (e.g., a corresponding pair of wavelengths). In order for each of these different wavelength pairs to be considered a single emission wavelength, the allowable spacing between each pair of wavelengths can depend on the design of the optical measurement system and the type of sample to be measured by the optical measurement system. For example, the optical measurement system can be configured so that the two wavelengths within each pair of wavelengths are less than one nanometer apart. By emitting a pair of wavelengths in this manner, the optical measurement system can be able to increase the optical power of the light emitted during the individual measurements. Additionally, depending on the spacing between a pair of wavelengths, emitting the pair of wavelengths simultaneously can reduce the noise associated with the individual measurements compared to the case where a similar optical power of a single wavelength is emitted by the optical measurement system.

[0108] Additionally or alternatively, the spectral measurements may include one or more series of encoded measurements. Figures 10 to 13These series of coded measurements described in more detail may utilize measurements during which the optical measurement system simultaneously emits multiple different wavelengths. In these cases, the different wavelengths are sufficiently spaced apart in wavelength so that they are not considered a single emission wavelength for analyzing these measurements. Instead, each coded measurement is considered to include light of two or more different emission wavelengths. The coded measurements may be analyzed to generate corresponding derived measurement intensities for different emission wavelengths. The derived measurement intensities corresponding to an emission wavelength represent an estimate of the light measured by the optical measurement system for that emission wavelength. The optical measurement system may use the derived measurement intensity for a given measurement wavelength as if the optical measurement system had performed a separate measurement using only that emission wavelength.

[0109] As part of a spectral measurement, the optical measurement system may obtain a plurality of intensities corresponding to a plurality of emission wavelengths. The relative intensities of different wavelengths may indicate one or more properties of the sample being measured, and may therefore be analyzed using spectral analysis techniques to determine one or more properties of the sample. Depending on the spectral measurement, the plurality of intensities may include measured intensities (e.g., generated as part of a separate measurement during which the optical measurement system emits a single emission wavelength formed by light having a single wavelength or a pair of closely spaced wavelengths) and / or derived measured intensities (e.g., generated from a series of coded measurements during which the optical measurement system emits a plurality of different emission wavelengths).

[0110] In order to make the emission group of the photonic integrated circuit emit light of multiple wavelengths simultaneously, the light source unit (e.g. Figure 2 The light source unit 208 may be configured to simultaneously output light of multiple wavelengths. Specifically, it may be desirable for the light source unit to include a wavelength selective multiplexer so that the multiplexer can simultaneously receive and output light of multiple different wavelengths. For example, Figure 3A An example of a photonic integrated circuit 300 that can be used with the optical measurement system described herein is shown. As shown, the photonic integrated circuit 300 includes a light source unit 301, wherein an echelle multiplexer 304 is configured to multiplex multiple inputs into a single output. In this example, the light source unit 301 includes a plurality of light sources 302a to 302m, each of the plurality of light sources being configured to generate light at a different corresponding wavelength and frequency, and the echelle multiplexer 304 is configured to multiplex the light received from the plurality of light sources 302a to 302m into a single output 306.

[0111] For purposes of illustration, when a light source unit is described herein as having a plurality of light sources (e.g., such as Figure 3A When the light sources 302a to 302m are labeled, these light sources will be labeled in a manner that represents a sequential, monotonic change in wavelength between consecutively labeled light sources. FIG. 3A to FIG. 3JIn the various examples described in , the light sources are labeled in a manner that indicates increasing wavelengths. For example, light source 302a is operable to emit light of a first wavelength, which is the shortest wavelength among the wavelengths emitted by the plurality of light sources. Light source 302b is operable to emit light of a second wavelength that is longer than the first wavelength, light source 302c is operable to emit light of a third wavelength that is longer than the second wavelength, and so on. Thus, in Figure 3A In the variation shown, the thirteenth light source 302m will emit light at a thirteenth wavelength, which represents the longest wavelength emitted by the plurality of light sources 302a through 302m.

[0112] exist Figure 3A In the light source unit 301 of the embodiment, each light source is optically connected to a corresponding input of the echelle grating multiplexer 304. In this way, light emitted from a given light source of the plurality of light sources 302a to 302m will be received at the corresponding input of the echelle grating multiplexer. Due to the wavelength-dependent mapping between the input and output of the echelle grating multiplexer, the positioning of each of the plurality of inputs will depend on the wavelength of light it will receive (e.g., from a corresponding light source of the plurality of light sources 302a to 302m). For example, the first input of the echelle grating multiplexer 304 may receive light of a first wavelength from the light source 302a, and the first input may be positioned to maximize the transmission between the first input and the output 306 for the first wavelength. Similarly, the second input of the echelle grating multiplexer 304 may be positioned to maximize the transmission of light of a second wavelength received from the light source 302b, and so on. In this way, light generated by any one of the plurality of light sources 302a to 302m will be routed to the first output 306.

[0113] By operating two or more of the plurality of light sources 302a to 302m simultaneously to generate light, the first output 306 may include light having a plurality of different wavelengths. Thus, the photonic integrated circuit 300 may include a switch network 310 positioned to receive the light from the first output 306. The switch network 310 may route the light to one or more of a set of emission groups 312a to 312d, thereby allowing each of the emission groups to emit light simultaneously including a plurality of wavelengths. Combining these wavelengths into a single output 306 of the echelle multiplexer 304 may provide a single input to the switch network 310 (which may reduce the complexity associated with the switch network 310). However, a wavelength locking unit 308 (such as described in more detail herein) that monitors the light in the output 306 will receive light of all wavelengths carried in the output 306 at a given time, which may make it difficult to control the operation of a single light source. Additionally, the echelle multiplexer 304 may have limitations when the plurality of light sources 302a to 302m are configured to emit light of a wavelength pair having a small wavelength difference.

[0114] For a given size and configuration of the echelle multiplexer 304, there may be constraints on how close the two input waveguides may be positioned adjacent to each other. This may similarly constrain the wavelength spacing between different pairs of light sources within the plurality of light sources 302a to 302m. For example, if the wavelength spacing between the first wavelength and the second wavelength (generated by the first light source 302a and the second light source 302b, respectively) is sufficiently small, it may not be possible to position the first input and the second input at respective positions that will maximize the transmission of the two wavelengths to the output 306. In these cases, one or both of these inputs may be positioned at a position that results in increased optical losses, or the size of the echelle multiplexer 304 may be increased to better facilitate the placement of the first input and the second input.

[0115] To address this issue, some variations of the light source unit described herein include an echelle multiplexer with multiple outputs. In these variations, the light source unit can be operated to simultaneously output light having multiple wavelengths during a first time period, such that multiple outputs of the echelle multiplexer simultaneously output light. In these cases, each output can carry light of a different wavelength. For example, Figure 3B A variation of a photonic integrated circuit 320 is shown that includes a light source unit 321 incorporating a multi-output echelle multiplexer 314. Specifically, the echelle multiplexer 314 has multiple inputs and multiple outputs. The light source unit includes a plurality of light sources 302a to 302m, each of which is configured to emit light of a different wavelength, such as about Figure 3A as described, and optically connected to corresponding inputs of the echelle multiplexer 314.

[0116] exist Figure 3B In the variation shown, multiple light sources 302a to 302m include multiple light source groups. Each light source in a given light source group is configured to emit light of different corresponding wavelengths and frequencies, and is optically connected to the corresponding input of the mid-step grating multiplexer 314. These inputs are positioned so that the light generated by the different light sources in the light source group is routed to different outputs in the multiple outputs. Additionally, each light source group may include multiple light sources that generate adjacent wavelengths so that the multiplexer is not optically connected to another light source of the light emitting intermediate wavelengths.

[0117] For example, in Figure 3BIn the illustrated variation, the echelle multiplexer 314 includes three outputs (e.g., a first output 316a, a second output 316b, and a third output 316c). In these cases, each of the plurality of light source groups includes three light sources. For example, the plurality of light sources 302a to 302m may include a first group having light sources 302a to 302c, a second group having light sources 302d to 302f, a third group having light sources 302g to 302i, and a fourth group having light sources 302j to 302l. It should be understood that the plurality of light sources 302a to 302m may include one or more light sources (e.g., light source 302m) that are not part of a light source group or are part of a group that includes only two light sources. The light generated by these light sources may still be routed to the corresponding outputs of the echelle multiplexer 314 (e.g., light source 302m is routed to the first output 316a of the echelle multiplexer 314) and may be used to generate light as part of one or more separate measurements performed by the optical measurement system described herein.

[0118] The multiple inputs of the echelle multiplexer 314 are positioned so that light generated by the first light source in each of the multiple light source groups is routed to the first output 316a, light generated by the second light source in each of the multiple light source groups is routed to the second output 316b, and light generated by the third light source in each of the multiple light source groups is routed to the third output 316c. For example, within the first light source groups 302a to 302c, light generated by the first light source 302a is routed to the first output 316a, light generated by the second light source 302b is routed to the second output 316b, and light generated by the third light source 302c is routed to the third output 316c. Similarly, within the second light source groups 302d to 302f, light generated by the first light source 302d is routed to the first output 316a, light generated by the second light source 302e is routed to the second output 316b, and light generated by the third light source 302e is routed to the third output 316c. For purposes of illustration, the same type of lines (eg, specific dashed or solid lines) are used to depict the multiplexers positioned to route light to the multiplexers (such as those described herein). FIG. 3A to FIG. 3J The input of a specific output of the multiplexer).

[0119] It should be understood that the relative positions of the inputs and outputs of the echelle multiplexer 314 (and other echelle multiplexers depicted in the drawings) are not shown to scale. Figure 3A The light source unit 301 and Figure 3B If the same wavelength is emitted from the light source unit 321 of the same size, then for a given size of the corresponding echelle multiplexer 304, 314, there will be different spacings between the inputs. Figure 3BCompared to the inputs of the echelle multiplexer 314 associated with the light sources 302a, 302b, Figure 3A The inputs of the echelle multiplexer 304 associated with the same light sources 302a and 302b may be separated further.

[0120] By routing different light sources within a given group to different outputs of the echelle multiplexer 314, the light sources may be able to emit different wavelengths having relatively small wavelength intervals without increasing the size of the echelle multiplexer 314. For example, the first and second light sources 302a, 302b in the first group may emit light having a wavelength difference less than a first threshold amount, and the second and third light sources 302b, 302c in the first group may emit light having a wavelength difference less than a second threshold amount. Similarly, the first and second light sources 302d, 302e in the second group may emit light having a wavelength difference less than a first threshold amount, and the second and third light sources 302e, 302f in the second group may emit light having a wavelength difference less than a second threshold amount. The first threshold amount and the second threshold amount may be the same or different, and may depend on the requirements of the optical measurement system in which the light source unit 321 is incorporated. In some variations, the first threshold amount and the second threshold amount are each one nanometer.

[0121] In some cases, such as will be described in more detail herein, it may be desirable for each of the plurality of light source groups to have light sources separated by a particular frequency difference. This may facilitate routing the groups of light sources to the same set of outputs of the echelle multiplexer. Specifically, the plurality of light source groups may be configured such that the first light source in each group and the second light source in each group have a first common frequency difference. For example, in Figure 3B In the illustrated variation, the first and second light sources 302a, 302b in the first group may emit light at corresponding wavelengths having a first common frequency difference, the first and second light sources 302d, 302e in the second group may emit light at corresponding wavelengths having a first common frequency difference, and so on. In the case where one or more groups have a third light source, the plurality of light source groups may be configured such that the second light source in each group and the third light source in each group have a second common frequency difference. For example, in Figure 3B In the illustrated variation, the second and third light sources 302b, 302c in the first group may emit light at corresponding wavelengths having a second common frequency difference, the second and third light sources 302e, 302f in the second group may emit light at corresponding wavelengths having a second common frequency difference, etc. In some variations, the first common frequency difference may be the same as the second common frequency difference.

[0122] A given light source group may be operated so that multiple light sources within the group generate light simultaneously. In these cases, the echelle multiplexer 314 may output light at multiple outputs of the multiple outputs 316a to 316c simultaneously. Taking the first light source group 302a to 302c as an example, during a first time period, the first light source and the second light source 302a, 302b may generate light simultaneously, during which the echelle multiplexer 314 will output light simultaneously at the first output and the second output 316a, 316b. At other times, different combinations of the first light source group (e.g., the second light source and the third light source 302b, 302c, the first light source and the third light source 302a, 302c, or all three light sources 302a to 302c) may be operated simultaneously so that the echelle multiplexer 314 outputs light simultaneously at two or more of its outputs 316a to 316c. Thus, the light source unit 321 may be operated such that the echelle multiplexer 314 (and thus the light source unit 321 ) simultaneously outputs light of multiple wavelengths.

[0123] Light of multiple wavelengths can be routed to a common set of emission groups, which can allow the optical measurement system to emit light that includes multiple wavelengths simultaneously. For example, the photonic integrated circuit 320 may include a switch network 330 positioned to receive light from the light source unit 321. In these cases, the switch network 330 includes three inputs. Each of the multiple outputs 316a to 316c of the mid-step grating multiplexer 314 is optically connected to a corresponding input of the switch network 330. Therefore, the outputs 316a to 316c of the mid-step grating multiplexer 314 can thereby serve as the corresponding outputs of the light source unit 321.

[0124] When the middle step grating multiplexer 314 simultaneously emits light of different wavelengths at different corresponding outputs of the middle step grating multiplexer 314, the switching network 330 can simultaneously receive light of different wavelengths, so that each wavelength is received at a different corresponding input of the switching network 330. The switching network 330 can be configured to i) combine light of different wavelengths and ii) route the combined wavelengths to one or more emission groups in a set of emission groups 312a to 312d. Therefore, one or more emission groups can each emit light that includes multiple different wavelengths simultaneously. In some variations, the switching network 330 is configured to selectively route the combined wavelengths to a target selection of the set of emission groups 312a to 312d, so that different emission groups (or combinations of emission groups) receive light from the light source unit 321 at different times.

[0125] Because the light source unit 321 includes multiple outputs, the photonic integrated circuit 320 may include multiple wavelength locking units 318a to 318c. For example, the photonic integrated circuit 320 may include a first wavelength locking unit 318a that is configured to monitor light traveling through the first output 316a of the echelle multiplexer 314. Specifically, a portion of the light traveling through the first output 316a may be tapped and routed to the first wavelength locking unit 318a. The signal generated by the first wavelength locking unit 318a may be used (e.g., by a controller as described herein) to control a corresponding light source (e.g., a first light source in a light source group) that is currently being used to generate light along the first output 316a, such as with respect to Figure 2 316a to 316c of the echelle multiplexer 314 before the different outputs (and thus the different wavelengths of light) are combined, the light source unit 321 may be able to individually monitor and control the light sources that actively generate light.

[0126] Although Figure 3B The light source unit 321 utilizes an echelle multiplexer 314 having three outputs, but it should be understood that in other variations, the echelle multiplexer may alternatively have two or four or more outputs if desired. For example, Figure 3C Variations of a photonic integrated circuit 340 are shown that include a light source unit 341 incorporating a dual-output echelle multiplexer 324. In these variations, the dual-output echelle multiplexer 324 includes multiple inputs and two outputs (e.g., a first output 326a and a second output 326b). The light source unit 341 includes a plurality of light sources 302a to 302h, each of which is configured to emit light of a different wavelength, such as about Figure 3B as described.

[0127] The plurality of light sources 302a to 302h include a plurality of light source groups, wherein each light source group includes a pair of light sources (e.g., a first light source and a second light source). Each light source within a given light source group is configured to emit light of a different corresponding wavelength and frequency and is optically connected to a corresponding input of the echelle multiplexer 314. The inputs are positioned such that light generated by the first light source in each group is routed to the first output 326a, and light generated by the second light source in each group is routed to the second output 326b.

[0128] For example, the plurality of light sources 302a to 302h may include a first group having light sources 302a and 302b, a second group having light sources 302c and 302d, a third group having light sources 302e and 302f, and a fourth group having light sources 302g and 302h. It should be understood that the plurality of light sources 302a to 302h may include one or more light sources (not shown) that are not part of a light source group. The light generated by these unpaired light sources may still be routed to a corresponding output (e.g., first output 326a or second output 326b) of the echelle multiplexer 324 and may be used to generate light as part of one or more separate measurements performed by the optical measurement system described herein.

[0129] The multiple inputs of the echelle multiplexer 324 are positioned so that light generated by a first light source in each of the multiple light source groups is routed to a first output 326a, and light generated by a second light source in each of the multiple light source groups is routed to a second output 326b. For example, within the first light source group 302a-302b, light of a first wavelength generated by the first light source 302a is routed to the first output 326a, and light of a second wavelength generated by the second light source 302b is routed to the second output 326b. Similarly, within the second light source group 302c-302d, light of a third wavelength generated by the first light source 302c is routed to the first output 326a, and light of a fourth wavelength generated by the second light source 302d is routed to the second output 326b.

[0130] and Figure 3B Like the echelle multiplexer 314, Figure 3C The echelle multiplexer 324 may allow pairs of light sources to emit closely spaced wavelengths without increasing the size of the echelle multiplexer 324. For example, the first and second light sources in each group may be configured to emit light having a wavelength difference of less than a threshold amount. In this manner, the wavelengths emitted by light sources 302a and 302b in the first group may be separated by less than a threshold amount, the wavelengths emitted by light sources 302c and 302d in the second group may be separated by less than a threshold amount, and so on. In some variations, the threshold amount is one nanometer.

[0131] Additionally, to facilitate routing the first and second light sources in each group to the respective first and second outputs, the first and second light sources in each group can be configured to emit light having a common frequency difference. For example, the wavelengths emitted by the light sources 302a and 302b in the first group can be separated by a first common frequency difference, the wavelengths emitted by the light sources 302c and 302d in the second group can be separated by a first common frequency difference, and so on.

[0132] A given light source group may be operated so that two light sources in the group generate light simultaneously. In these cases, the echelle multiplexer 324 may output light from the first output and the second output 326a, 326b simultaneously. For example, during a first time period, the first and second light sources 302a, 302b in the first group may generate light simultaneously, in which case the echelle multiplexer 324 will output light simultaneously at the first and second outputs 326a, 326b. Specifically, the first output 326a will output light at a first wavelength emitted by the first light source 302a in the first group, and the second output 326b will output light at a second wavelength emitted by the second light source 302b in the first group. Similarly, during a second time period, the first and second light sources 302c, 302d in the second group may generate light simultaneously, in which case the first output 326a will output light at a third wavelength emitted by the first light source 302c in the second group, and the second output 326b will output light at a fourth wavelength emitted by the second light source 302d in the second group. Therefore, the light source unit 341 can be configured to output two wavelengths of light simultaneously (via the first and second outputs 326a, 326b of the echelle multiplexer 324), and the two wavelengths of light can be changed by controlling different groups of emitted light.

[0133] The photonic integrated circuit 340 may include a switch network 331 positioned to receive light from a light source unit 341. In these cases, the switch network 331 includes two inputs, each input receiving light from a corresponding output of the light source unit 341. When the light source unit 341 is operated to output light of two wavelengths simultaneously, the switch network 331 may receive light of two wavelengths simultaneously, so that each wavelength is received at a different corresponding input of the switch network 331. The switch network 331 may be configured to i) combine the light of the pair of wavelengths into a set of common waveguides and ii) route the pair of wavelengths to one or more emission groups in a set of emission groups 312a to 312d. In this way, one or more emission groups may each emit light including multiple wavelengths. In some variations, the switch network 331 is configured to selectively route the combined wavelength to a target selection of the set of emission groups 312a to 312d, so that different emission groups (or combinations of emission groups) receive light from the light source unit 321 at different times.

[0134] In some of these variations, the photonic integrated circuit 340 may include a first wavelength locking unit 328a and a second wavelength locking unit 328b. The first wavelength locking unit 328a may be configured to monitor light traveling through the first output 324a of the echelle multiplexer 326 (e.g., to control a second light source in the light source group) to control the first light source in the light source group, and the second wavelength locking unit 328b may monitor light traveling through the second output 326b (e.g., to control the second light source in the light source group). In these cases, the light source unit 341 may be able to individually control each light source in the light source group that is actively generating light.

[0135] In the case where the light sources of the light source unit are lasers, the various light sources may be formed as part of one or more laser chips that may be incorporated into a photonic integrated circuit as part of the light source unit. As used herein, a "laser chip" refers to a group of lasers formed on a common substrate (e.g., via epitaxial growth). The distribution of multiple light sources among multiple laser chips may increase yield and may allow for improved thermal isolation between light sources positioned on different laser chips. The various light sources may be divided across different light source bars in any suitable manner.

[0136] For example, in Figure 3C In the variation of the light source unit 341 shown, a plurality of light sources 302a to 302h are distributed between two laser chips (e.g., a first laser chip 342a and a second laser chip 342b). As shown, light sources 302a to 302d are positioned on the first laser chip 342a, and light sources 302e to 302h are positioned on the second laser chip 342b. In this case, the first laser chip and the second laser chip 342a, 342b each include four light sources. Figure 3D Another variation of a photonic integrated circuit 345 is shown, which can be configured with Figure 3C The photonic integrated circuit 340 is the same as that of the photonic integrated circuit 340, except that the plurality of light sources 302a to 302h of the light source unit 341 are all positioned on the first laser chip 342a. Therefore, the first laser chip 342a includes eight light sources in this case. In general, the number of laser chips and the distribution of light sources among these laser chips may depend at least in part on the total number of light sources, the wavelengths generated by these light sources, and how the light sources are connected to the echelle grating multiplexer 324.

[0137] Additionally, when an echelle multiplexer is used to route light from multiple light sources to multiple outputs, the light sources may be connected to the echelle multiplexer in any suitable manner. For example, in some variations, the light sources in a given light source group may be connected to immediately adjacent inputs of the echelle multiplexer. Two inputs to the multiplexer are considered to be "immediately adjacent" in the absence of an intervening input to the multiplexer. For example, in Figure 3B In the variation of the light source unit 321 shown, the first, second and third light sources 302a to 302c in the first light source group are connected to three adjacent inputs of the mid-step grating multiplexer 314. Specifically, the first and second light sources 302a, 302b in the first group are connected to the first pair of adjacent inputs, and the second and third light sources 302b, 302c in the first group are connected to the second pair of adjacent inputs. Similarly, in Figure 3C In the variation of the light source unit 341 shown, the first and second light sources 302 a , 302 b of the first light source group are connected to adjacent inputs of the echelle multiplexer 324 .

[0138] In some of these variations, the inputs of the echelle multiplexer may be configured such that for some of the light source groups, the wavelength associated with each input varies monotonically along a given direction. In other words, the light sources connected to the multiplexer are ordered such that light sources emitting immediately adjacent pairs of wavelengths (e.g., the multiplexer does not receive an intervening wavelength from another light source) are connected to immediately adjacent inputs.

[0139] exist Figure 3B In the variation of the light source unit 321 shown, the plurality of light sources 302a to 302m are arranged such that the wavelength of light received by the echelle multiplexer 314 increases monotonically across these inputs. Figure 3C In the illustrated variations of the light source unit 341, the plurality of light sources 302a to 302h are arranged such that the wavelength of light received by the echelle multiplexer 324 increases monotonically across the inputs. Specifically, in these variations, light source 302a (which emits the shortest first wavelength) is connected to the first input, light source 302b (which emits the second longest wavelength) is connected to the second input immediately adjacent to the first input, light source 302c is connected to the third input immediately adjacent to the second input, light source 302d is connected to the fourth input immediately adjacent to the second input, and so on. In this manner, each input is positioned to receive light at a wavelength between the wavelengths received by its two adjacent (e.g., immediately adjacent) inputs.

[0140] The frequency difference between a given set of wavelengths determines the relative spacing between the outputs of the multiplexer. Figure 3DIn a variation of the light source unit 341 shown, the first output waveguide 326a may be positioned closer to the multiple inputs than the second output 326b so that the longer wavelengths emitted by each light source group are routed to the second output waveguide 326b. However, if the common frequency difference between the wavelengths emitted by each group is small enough, the order of the outputs may be switched. For example, Figure 3E A variation of photonic integrated circuit 350 is shown that is configured the same as photonic integrated circuit 345, except that the common frequency difference between the wavelengths emitted by each group is smaller. In these cases, first output waveguide 326a can be positioned farther from the multiple inputs than second output 326b. The longer wavelengths emitted by each light source group are still routed to second output waveguide 326b, which is instead positioned closer to the multiple inputs (compared to first output 326a).

[0141] In some cases, it may be desirable to change the order of the light sources within a given group. For example, if the wavelength difference between different light source groups (e.g., between the longest wavelength generated by one light source group and the shortest wavelength generated by another light source group) is small enough, it may be difficult to place the corresponding input waveguides in a way that maximizes the transmission of the light sources of both groups. Therefore, in some variations, the inputs of the echelle multiplexer may be arranged such that for some of the light source groups, the light sources are arranged such that the wavelength of the light decreases along a given direction within the light source group, but increases along the same direction between different light source groups.

[0142] Figure 3F One such example of a photonic integrated circuit 355 is shown. The photonic integrated circuit 355 may be configured to Figure 3D The photonic integrated circuit 345 is the same as that of the photonic integrated circuit 345, except that the order of the plurality of light sources has been changed. Specifically, the plurality of light sources 302a to 302h are arranged such that in a direction from an input connected to the light source 302a to an input connected to the light source 302h, the wavelength of light decreases between adjacent inputs associated with light sources of the same group and increases between adjacent inputs associated with different groups.

[0143] Specifically, the second light source 302b in the first group is connected to the first input, and the first light source 302a in the first group is connected to the second input that is immediately adjacent to the first input. The second light source 302d in the second group is connected to the third input that is immediately adjacent to the second input, the first light source 302c in the second group is connected to the fourth input that is immediately adjacent to the third input, and so on. In this way, the second input receives light of a first wavelength that is shorter than the wavelength of light received at any one of its immediately adjacent inputs. Similarly, the third input receives light of a fourth wavelength that is longer than the wavelength of light received at any one of its immediately adjacent inputs. Arranging multiple light sources in this manner can provide more uniform spacing between the inputs of the mid-step grating multiplexer 324.

[0144] Figure 3G Shown is applied to Figure 3B The same principle of the photonic integrated circuit 320 is used. Specifically, Figure 3G A photonic integrated circuit 360 is shown, which can be configured to Figure 3B The photonic integrated circuit 320 is the same as that of the photonic integrated circuit 320, except that the order of the plurality of light sources has been changed. Specifically, the plurality of light sources 302a to 302m are arranged such that in a direction from an input connected to the light source 302a to an input connected to the light source 302m, the wavelength of light decreases between adjacent inputs associated with light sources of the same group and increases between adjacent inputs associated with different groups.

[0145] Specifically, the third light source 302c in the first group is connected to the first input, the second light source 302b in the first group is connected to the second input immediately adjacent to the first input, and the first light source 302a in the first group is connected to the third input immediately adjacent to the second input. The third light source 302f in the second group is connected to the fourth input immediately adjacent to the third input, the second light source 302e in the second group is connected to the fifth input immediately adjacent to the fourth input, the first light source 302d in the second group is connected to the sixth input immediately adjacent to the fifth input, etc. Thus, the wavelength received by the inputs may sequentially decrease from the first input to the third input, may increase from the third input to the fourth input, may sequentially decrease from the fourth input to the sixth input, and so on.

[0146] When multiple light sources of the light source unit are Figure 3E and Figure 3F When arranged as shown, different groups of light sources can be interleaved with each other. Figure 3H A variation of a photonic integrated circuit 365 is shown, which may be configured to Figure 3EThe photonic integrated circuit 355 is the same as that of the photonic integrated circuit 355, except that the plurality of light sources 302a to 302h of the light source unit 341 are arranged so that the first light source group and the second light source group are staggered. In these cases, the second light source 302d in the second light source group 302c, 302d is connected to a corresponding input positioned between the first pair of inputs connected to the first light source group 302a, 302b. Similarly, the first light source 302a in the first light source group 302a, 302b is connected to a corresponding input positioned between the second pair of inputs connected to the second light source group 302c, 302d.

[0147] In other words, the second light source 302b in the first group can be connected to the first input of the mid-step grating multiplexer 324, the second light source 302d in the second group can be connected to the second input adjacent to the first input, the first light source 302a in the first group is connected to the third input adjacent to the second input, and the first light source 302c in the second group is connected to the fourth input adjacent to the third input. In this way, the wavelength of light received by these inputs will increase from the first input to the second input, decrease from the second input to the third input, and increase from the third input to the fourth input. The third and fourth light source groups can be similarly staggered, such as Figure 3E Increasing the spacing between light sources of a given group to accommodate the staggering may result in an increased spacing between the first and second outputs 326a, 326b.

[0148] Fig. 3I A variation of a photonic integrated circuit 370 is shown, which may be configured with Figure 3H The photonic integrated circuit 365 is the same as that of the photonic integrated circuit 365, except that the multiple light sources 302a to 302h of the light source unit 341 are arranged so that the first light source group, the second light source group, the third light source group and the fourth light source group are all staggered with each other. As shown in the figure, the second light source (e.g., light source 302d, 302f and 302h, respectively) from each light source group in the second light source group, the third light source group and the fourth light source group is connected to the corresponding inputs respectively positioned between the first pair of inputs connected to the first light source group 302a, 302b. In addition, the first light source (e.g., light source 302a, 302c and 302e) from each light source group in the first light source group, the second light source group and the third light source group is connected to the corresponding inputs respectively positioned between the second pair of inputs connected to the fourth light source group 302g, 302h.

[0149] In other words, the second light source 302b in the first group may be connected to the first input, the second light source 302d in the second group may be connected to the second input immediately adjacent to the first input, the second light source 302f in the third group may be connected to the third input immediately adjacent to the second input, and the second light source 302h in the fourth group may be connected to the fourth input immediately adjacent to the third input. Similarly, the first light source 302a in the first group may be connected to the fifth input immediately adjacent to the fourth input, the first light source 302c in the second group may be connected to the sixth input immediately adjacent to the fifth input, the first light source 302e in the third group may be connected to the seventh input immediately adjacent to the sixth input, and the first light source 302g in the fourth group may be connected to the eighth input immediately adjacent to the seventh input. In this manner, the wavelength of light received by the multiple inputs may increase from the first input to the fourth input, decrease between the fourth and fifth inputs, and increase from the fifth input to the eighth input.

[0150] Although the plurality of light sources 302a to 302h are Fig. 3I 342a, but staggered multiple light source groups may allow different light sources from a given group to be positioned on different laser chips. Figure 3J A variation of a photonic integrated circuit 375 is shown, which may be configured to Fig. 3I The photonic integrated circuit 370 is the same as that of the photonic integrated circuit 370, except that the plurality of light sources 302a to 302h are separated between the two laser chips. Specifically, the first light source from each group in the first to fourth groups (e.g., light sources 302a, 302c, 302e, and 302g, respectively) is positioned on the second laser chip 342b, and the second light source from each group in the first to fourth groups (e.g., light sources 302b, 302d, 302f, and 302h, respectively) is positioned on the first laser chip 342a. In the case where only one light source group in the light source group is used to generate light at a given time, during that time, only one light source will generate light on each laser chip. This can reduce thermal crosstalk that may occur when multiple light sources on a laser chip emit light simultaneously.

[0151] In some variations, the light source unit may include a multi-output echelle multiplexer and a set of one or more tunable light sources. In these cases, the tunable light sources are operable to selectively emit light of multiple wavelengths, such that light emitted by the tunable light sources may be routed to different outputs of the echelle multiplexer depending on the wavelength of light currently being emitted. For example, Figure 3K FIG. 3 shows a variation of a photonic integrated circuit 380 including a light source unit 381. The light source unit 381 is Figure 3K is shown as including a dual output echelle multiplexer 324, such as described herein with respect to Figure 3CAs described above, the light source unit 341 of FIG. 34 may be a plurality of outputs having different numbers of outputs (eg, three or four or more outputs).

[0152] The light source unit 381 includes a set of tunable light sources 382a to 382b, each of which is connected to a corresponding input of the plurality of inputs of the echelle multiplexer 324. The set of tunable light sources 382a to 382b may include a single tunable light source or a plurality of tunable light sources. Figure 3K In the variation shown, the group of tunable light sources 382a to 382b includes a first tunable light source 382a and a second tunable light source 382b. Each tunable light source in the group of tunable light sources 382a to 382b is operable to selectively emit corresponding multiple wavelengths of light, the multiple wavelengths including at least a first corresponding wavelength and a second corresponding wavelength. The input corresponding to each tunable light source is positioned so that i) the light of the first corresponding wavelength emitted by the tunable light source in the group of tunable light sources 382a to 382b is routed to the first output 326a of the mid-step grating multiplexer 324, and ii) the light of the second corresponding wavelength emitted by the tunable light source in the group of tunable light sources 382a to 382b is routed to the second output 326b of the mid-step grating multiplexer 324. This principle can be applied to additional outputs of the mid-step grating multiplexer 324. In the mid-step grating multiplexer 324, a third output (e.g., Figure 3B In some variations of the third output 316c of the echelle multiplexer 314, the corresponding plurality of wavelengths of each tunable light source in the set of tunable light sources 382a to 382b may also include a third corresponding wavelength. In these cases, light of the third corresponding wavelength emitted by the tunable light sources in the set of tunable light sources 382a to 382b is routed to the third output.

[0153] Each tunable light source in the set of tunable light sources 382a-382b is operable to emit light of a single wavelength at a given moment, such that the light generated by a given tunable light source is routed to a single output of the echelle multiplexer 324. For example, Figure 3K In the illustrated variation, the first tunable light source 382a may be tunable to selectively emit at least a first wavelength λ a1 and the corresponding second wavelength λ b1 During the first time period, the first tunable light source 382a can be controlled to emit a first wavelength λ a1 During the first time period, the first wavelength λ a1The light of the first wavelength λ is received at the first input of the echelle grating multiplexer 324 and output from the first output 326a of the echelle grating multiplexer 324. During the second time period, the first tunable light source 382a can be controlled to emit the second wavelength λ b1 During the second time period, the second wavelength λ b1 The light of the first tunable light source 382a is received at the first input of the echelle grating multiplexer 324 and output from the second output 326b of the echelle grating multiplexer 324. It should be understood that the first tunable light source 382a can emit light of a wavelength different from the first wavelength λ a1 and the second wavelength λ b1 wavelengths of light, but these wavelengths may not be routed to the output of the mid-step grating multiplexer 324.

[0154] Similarly, the second tunable light source 382b may be tunable to selectively emit at least a first wavelength (referred to herein as the "third wavelength λ a2 ”) and the corresponding second wavelength (referred to herein as the “fourth wavelength λ b2 During the third time period, the second tunable light source 382b may be controlled to emit a third wavelength λ a2 During the third time period, the third wavelength λ a2 The light of the chèche grating multiplexer 324 is received at the second input and output from the first output 326a of the chèche grating multiplexer 324. During the fourth time period, the second tunable light source 382b may be controlled to emit a fourth wavelength λ b2 During the fourth time period, the fourth wavelength λ b1 The light is received at the second input 326 b of the echelle multiplexer 324 and output from the second output 326 b of the echelle multiplexer 324 .

[0155] Therefore, in Figure 3K In the illustrated variation, the light source unit 381 can use two tunable light sources to generate four different wavelengths, which can reduce the number of light sources associated with the light source unit 381 compared to a light source unit that utilizes a different light source for each wavelength output by the light source unit. This can reduce the number of electrical connections required to operate the light source unit 381.

[0156] In some variations, the difference between the corresponding first wavelength and the corresponding second wavelength emitted by each tunable light source is less than ten nanometers. Additionally or alternatively, the corresponding first wavelength and second wavelength of each tunable light source in the set of tunable light sources 382a-382b may have a common frequency difference. For example, in some variations, the first wavelength λ a1 and the second wavelength λ b1 can be separated by a first frequency difference, and a third wavelength λ a2 and the fourth wavelength λb2 Thus, in some variations, the passive optical combiner 384 (such as the one described herein with respect to Figure 4A and Figure 4B The passive optical combiner 384 may be configured to optically couple the multiple outputs 326a to 326b of the echelle multiplexer 324 to a common waveguide 386. In some variations, the passive optical combiner 384 may be part of a switching network as described herein. The switching network may be controllable to route the light generated by the light source unit 381 to a set of emission groups (e.g., Figure 3B The target selection of the groups 312a to 312d) is performed so that different emission groups (or combinations of emission groups) receive light from the light source unit 381 at different times.

[0157] In some variations, light source unit 381 may also include one or more additional light sources optically connected to echelle multiplexer 324. Each additional light source is operable to generate light at a corresponding wavelength and frequency, and is optically connected to a corresponding input of echelle multiplexer 324. The inputs are positioned such that when each additional light source generates light at its corresponding wavelength, echelle multiplexer 324 routes the light to one of its outputs.

[0158] In some variations, the additional light source may include one or more light source groups such that light generated by different light sources within a light source group is routed to different outputs in the plurality of outputs. Figure 3K is shown as including a plurality of light sources 302a to 302d, such as those described herein with respect to Figure 3B The light source unit 321 of the embodiment of the present invention is described. The multiple light sources 302a to 302d may include a group of light source groups, wherein each light source group is operable to emit corresponding multiple wavelengths. Each light source within a given light source group is configured to emit light of different corresponding wavelengths and frequencies, and is optically connected to the corresponding input of the mid-step grating multiplexer 324. These inputs are positioned so that the light generated by the different light sources within the light source group is routed to different outputs in the multiple outputs 326a to 326b. Additionally, each light source group may include multiple light sources that generate adjacent wavelengths, so that the mid-step grating multiplexer 324 is not optically connected to another light source that emits light of intermediate wavelengths.

[0159] For example, the plurality of light sources 302a-302d may include a plurality of groups including a first group having light sources 302a and 302b, and a second group having light sources 302c and 302d. The plurality of inputs to the echelle multiplexer 324 are positioned such that light generated by a first light source in each of the plurality of light source groups is routed to a first output 326a, and light generated by a second light source in each of the plurality of light source groups is routed to a second output 326b. For example, within the first light source group 302a-302b, light generated by the first light source 302a at a corresponding wavelength (for Figure 3K The light at the fifth wavelength λ5 (referred to in the discussion as the “fifth wavelength λ5”) is routed to the first output 326a, and the light at the corresponding wavelength (for Figure 3K The light at the sixth wavelength λ6 (referred to in the discussion as “sixth wavelength λ6”) is routed to the second output 326b. Similarly, within the second light source group 302c-302d, the light generated by the first light source 302c at the corresponding wavelength (for Figure 3K The light at the seventh wavelength λ7 (referred to in the discussion as “the seventh wavelength λ7”) is routed to the first output 326a, and the light at the corresponding wavelength (for Figure 3K 8 (hereinafter referred to as "eighth wavelength λ8") is routed to the second output 326b. For purposes of illustration, the input associated with each of the plurality of light sources 302a-302d is depicted using the same type of lines (e.g., specific dashed or solid lines) as the lines used to depict the outputs to which the corresponding wavelengths are routed. Because light from each of the tunable light sources 382a-382b can be routed to different outputs depending on the wavelength it is currently emitting, the input associated with the tunable light sources 382a-382b is depicted using different types of lines than those used to depict the outputs 326a-326b.

[0160] In some variations, two or more light sources in a group of light sources may be operated to emit light simultaneously, so that the echelle grating multiplexer 324 may output light from multiple outputs simultaneously. For example, during the fifth time period, the first light source 302a and the second light source 302b in the first light source group 302a to 302b may be operated to simultaneously emit the fifth wavelength λ5 and the sixth wavelength λ6. The echelle grating multiplexer 324 may receive these wavelengths at different inputs during the fifth time period, and may output the fifth wavelength λ5 from the first output 326a and the sixth wavelength λ6 from the second output 326b. Similarly, during the sixth time period, the first light source 302c and the second light source 302d in the second light source group 302c to 302d may be operated to simultaneously emit the seventh wavelength λ7 and the eighth wavelength λ8. The echelle grating multiplexer 324 may receive these wavelengths at different inputs during the sixth time period, and may output the seventh wavelength λ7 from the first output 326a and the eighth wavelength λ8 from the second output 326b.

[0161] It should be understood that, if desired, two or more of the tunable light sources 382a to 382b may be operated to simultaneously emit light during a corresponding time period. Additionally or alternatively, a tunable light source in the tunable light sources 382a to 382b and one of the plurality of light sources 302a to 302d may be operated to simultaneously emit light during a corresponding time period. In these cases, the echelon grating multiplexer 324 may output light of multiple wavelengths simultaneously. In some of these variations, multiple wavelengths may be emitted as part of a series of coded measurements as described in more detail herein.

[0162] It should also be understood that in variations where the echelle grating multiplexer 324 includes multiple outputs (the multiple outputs including three or more outputs), different tunable light sources and / or groups of light sources may be operated to route light to different subsets of the multiple outputs. For example, in some variations, the first tunable light source 382a is operable to selectively emit different wavelengths that are routed to a first subset of the outputs of the echelle grating multiplexer 324 (e.g., a first corresponding wavelength generated by the first tunable light source 382a may be routed to a first output of the echelle grating multiplexer 324, and a second corresponding wavelength generated by the first tunable light source 382a may be routed to a second output of the echelle grating multiplexer 324). Conversely, the second tunable light source 382b is capable of being operated to selectively emit different wavelengths of different second subsets of the outputs of the echelle grating multiplexer 324 that are routed to the echelle grating multiplexer 324 (e.g., a first corresponding wavelength generated by the second tunable light source 382b may be routed to the second output of the echelle grating multiplexer 324, and a second corresponding wavelength generated by the second tunable light source 382b may be routed to the third output of the echelle grating multiplexer 324).

[0163] Additionally or alternatively, one or more tunable light sources (e.g., the group of tunable light sources 382a-382b) may each be operable to select a corresponding plurality of wavelengths that are routed to a first subset of outputs of the echelle multiplexer 324, and one or more groups of the plurality of light sources 302a-302d may each generate light that is routed to a different second subset of outputs of the echelle multiplexer 324. For example, the first tunable light source 382a may be operable to generate a corresponding plurality of wavelengths that are routed to a first subset of outputs (e.g., a first corresponding wavelength generated by the first tunable light source 382a may be routed to a first output of the echelle multiplexer 324, and a second corresponding wavelength generated by the first tunable light source 382a may be routed to a second output of the echelle multiplexer 324). Conversely, the first light source group (e.g., first light source group 302a to 302b) can be configured such that light generated by the first light source in the first group (e.g., light source 302a) is routed to the second output of the mid-step grating multiplexer 324, and light generated by the second light source in the first group (e.g., light source 302b) is routed to the third output of the mid-step grating multiplexer 324.

[0164] It should also be understood that the various light sources associated with the echelle multiplexer 324 may be distributed over any number of laser chips as desired. Where the light source unit includes a plurality of tunable light sources optically connected to the echelle multiplexer 324, the plurality of tunable light sources may be located on a single laser chip or distributed among a plurality of laser chips. Where the light source unit includes a set of tunable light sources and one or more additional light sources, the light sources may be located on a single laser chip or distributed among a plurality of laser chips. For example, in Figure 3K In the variation shown, the set of tunable light sources 382a-382b is positioned on a first laser chip 342a, and the plurality of light sources 302a-302d is positioned on a second laser chip 324b.

[0165] In some variations, photonic integrated circuit 380 includes one or more wavelength locking units for monitoring light generated by light source unit 381. In some variations, photonic integrated circuit 380 includes a plurality of wavelength locking units, wherein each wavelength locking unit is configured to monitor light traveling through a corresponding output of echelle multiplexer 324. For example, in Figure 3K In the illustrated variation, the photonic integrated circuit 380 may include a first wavelength locking unit 328a and a second wavelength locking unit 328b, such as Figure 3CIn these cases, the first wavelength locking unit 328a and the second wavelength locking unit 328b can be operated simultaneously to control the light source to simultaneously emit light that is routed to the first output 326a and the second output 326b of the echelle multiplexer 324, respectively.

[0166] In some variations where light source unit 381 is operated to output a single wavelength of light from echelle multiplexer 324 at a given time, photonic integrated circuit 380 may include a single wavelength locking unit 328c (e.g., in place of first wavelength locking unit 328a and second wavelength locking unit 328b). Wavelength locking unit 328c may be configured to monitor light output by echelle multiplexer 324 regardless of which output waveguide is currently emitting light. For example, in Figure 3K In the variation shown, the wavelength locking element 328c can be positioned to monitor light traveling through the common waveguide 386 (e.g., after the light has been combined by the passive optical combiner 384). In other variations, the wavelength locking element 328c can be positioned to monitor light traveling through the passive optical combiner 384, such as described herein with respect to Figure 4B During certain time periods, wavelength locking unit 328c may monitor light routed to first output 326a of echelle multiplexer 324, such that during these time periods the controller may control the wavelength of light generated by the corresponding light source. During other time periods, wavelength locking unit 328c may monitor light routed to second output 326b of echelle multiplexer 324, such that during these time periods the controller may control the wavelength of light generated by the corresponding light source.

[0167] When the switch network of the optical measurement system is configured to simultaneously receive light at multiple wavelengths across different inputs, it may be desirable to combine these wavelengths into a common set of waveguides. For example, in some variations, a photonic integrated circuit as described herein may be configured to include a passive optical combiner that combines the output of the light source into a single waveguide without being actively controlled. The passive optical combiner may be included as part of the switch network so that additional components downstream of the passive optical combiner may receive light from the light source unit along a single waveguide. Figure 4A One such variation is shown of a passive optical combiner 400. The passive optical combiner 400 may include a first input 402, a second input 404, and a third input 406. The first, second, and third inputs 402, 404, 406 may each be optically connected to a respective output of a light source unit.

[0168] Specifically, the first input 402 may receive a signal having a first frequency v a The second input 404 may receive a first light having a second frequency v bThe third input 406 may receive a second light having a third frequency v c The first light, the second light, and the third light may be combined into a single output of the passive optical combiner 400. The first and second inputs 402, 404 may be connected to corresponding inputs of the first interferometer 410a. Figure 4A The first interferometer 410a configured as a Mach-Zehnder interferometer in the passive optical combiner 400 has a first output 412 and a second output 414. The first interferometer 410a may have a first free spectral range Δv1, which is selected so that the first frequency v received at the first input 402 a The light of will be routed to the second output 414 of the first interferometer 410a. Additionally, the first free spectral range Δv1 is selected such that the second frequency v received at the second input 404 b The light will be routed to the second output 414 of the first interferometer 410a. In this way, the first interferometer 410a can route the first light and the second light to a common waveguide (eg, the second output 414 of the first interferometer 410a).

[0169] Additionally, the third input 406 of the passive optical combiner 400 and the second output 414 of the first interferometer 410a may be connected to corresponding inputs of the second interferometer 410b. Figure 4A The second interferometer 410b configured as a Mach-Zehnder interferometer in the passive optical combiner 400 has a first output 416 and a second output 418. Therefore, the first output 412 of the first interferometer 410a, the first output 416 of the second interferometer 410b, and the second output 418 of the second interferometer 410b form the respective first output, second output, and third output of the passive optical combiner 400. The second interferometer 410b may have a second free spectral range Δv2, which is selected such that the first frequency and the second frequency v a 、v b Each frequency of light in (when received from the second output 414 of the first interferometer 410a) will be routed to the second output 418 of the second interferometer 410b. Additionally, the first free spectral range Δv2 is selected such that the third frequency v received by the second interferometer 410b via the third input 406 is c The light received at any or all of the first, second, and third inputs 402 to 406 and having a corresponding frequency v a to v c The light will be routed to a common output (eg, output 418).

[0170] In some cases, in order to allow the second interferometer 410b to separate the first frequency and the second frequency v a 、v b The optical routes of both are to the output 418, and the first free spectral range and the second free spectral range Δv1, Δv2 may be selected such that the ratio of these free spectral ranges (eg, Δv1 / Δv2) is an even integer. In these cases, the third frequency v c The first frequency and the second frequency v a 、v b Thus, the first frequency and the third frequency may be spaced apart by a first frequency difference, and the second frequency and the third frequency may also be spaced apart by the first frequency difference.

[0171] For example, the passive optical combiner 400 may be incorporated into Figure 3C In the photonic integrated circuit 320 of FIG. 4 , the first input 402 can be positioned to receive light from the first output 316 a of the mid-step grating multiplexer 314, the second input 404 can be positioned to receive light from the third output 316 c of the mid-step grating multiplexer 314, and the third input 406 can be positioned to receive light from the second output 316 b of the mid-step grating multiplexer 314. Thus, two or more light sources in a given light source group can be simultaneously controlled to generate light of different wavelengths. If the frequencies generated by these light sources correspond to the three frequencies v of the passive optical combiner 400, a -v c , the passive optical combiner 400 will combine these different wavelengths of light into a common output 418.

[0172] It should be understood that there may be multiple sets of frequencies, provided that there are first common frequency differences and second common frequency differences between the frequencies (such as those described herein). Figure 3B ), the multiple groups of frequencies will be routed by the passive optical combiner 400 to a common output 418. Thus, the passive optical combiner 400 can be used to combine the frequencies generated by a given light source unit (e.g., Figure 3B Once the passive optical combiner 400 has combined the multiple wavelengths into a single output (e.g., a single waveguide), the switch network incorporating the passive optical combiner 400 may include one or more switches configured to route the combined wavelengths of light to one or more emission sites.

[0173] In some variations, the passive optical combiner 400 may be configured to tap a portion of the light received by the passive optical combiner 400 that may be received by a wavelength locking unit as described herein. Figure 4B A variation of a passive optical combiner 420 is shown, which may be configured and labeled as Figure 4A4 is the same as the passive optical combiner of 410a, except that the passive optical combiner 420 includes a tap 422 positioned to tap light from the waveguide of the second interferometer 410b. Specifically, the tap 422 can be positioned so that it receives a portion of the light received by the second interferometer 410b, regardless of whether the light is received by the second output 414 or the third input 406 of the first interferometer 410a.

[0174] In other variations, it may be desirable to provide a single optical component that functions to i) combine multiple wavelengths of light and ii) selectively route the combined light to different outputs. Figure 5A A schematic diagram of a multiplexed photonic switch 500 suitable for use with the photonic integrated circuits described herein is shown. The multiplexed photonic switch 500 is configured to receive light of different wavelengths at respective inputs of the multiplexed photonic switch 500 and selectively send two wavelengths to a common set of outputs of the multiplexed photonic switch 500. Specifically, the multiplexed photonic switch 500 is configured to receive light of two wavelengths having a predetermined frequency difference.

[0175] The multiplexed photonic switch 500 includes two inputs (e.g., a first input 502 and a second input 504) and two outputs (e.g., a first output 514 and a second output 516), each of which can be formed as a corresponding waveguide. The multiplexed photonic switch 500 can be incorporated into a photonic integrated circuit (such as those described herein) such that the multiplexed photonic switch 500 is positioned to concurrently receive light having a first wavelength at the first input 502 and light having a second wavelength at the second input 504, wherein the first frequency and the second frequency have a predetermined frequency difference.

[0176] The multiplexed photonic switch 500 includes a first coupler 506 and a second coupler 512. Each of these couplers may include any suitable coupler capable of splitting light received at one or more inputs between two outputs, including but not limited to a multimode interferometer coupler, an adiabatic coupler, a co-directional coupler, etc. The first coupler 506 is optically connected to the second coupler 512 via a pair of waveguides. Specifically, a first waveguide 508 (also referred to herein as a first pin) connects a first output of the first coupler 506 to a first input of the second coupler 512, and a second waveguide 509 (also referred to herein as a second pin) connects a second output of the first coupler 506 to a second input of the second coupler 512. The first and second waveguides 508, 509 may have different lengths, so that light traveling between the first and second couplers 506, 512 travels different path lengths. The path length difference Δl may at least partially define the free spectral range of the multiplexed photonic switch 500. The free spectral range of the multiplexed photonic switch 500 may be selected based on a predetermined frequency. Specifically, the free spectral range is selected such that if two wavelengths of light having a predetermined frequency difference are introduced into different inputs of the multiplexed photonic switch 500 , they will be routed to a common selection of outputs of the multiplexed photonic switch 500 .

[0177] The multiplexed photonic switch 500 includes a first phase shifter 510 positioned on the first waveguide 508 and operable to change the phase of light traveling through the first waveguide 508. The first phase shifter 510 may be controllable to selectively route a first wavelength and a second wavelength between a common selection of outputs of the multiplexed photonic switch 500. For example, the multiplexed photonic switch 500 may be configured such that when the first phase shifter 510 is not actively changing the phase of light in the first leg (e.g., providing a phase shift of zero), light of a first wavelength received at the first input 502 will be routed to the second output 516, and light of a second wavelength received at the second input 504 will also be routed to the second output 516. In this manner, when the first wavelength and the second wavelength are simultaneously received at the inputs 502, 504, both wavelengths are simultaneously routed to the first common selection of outputs (e.g., the second output 516).

[0178] The first phase shifter 510 can be operated to apply a phase shift to light traveling through the first waveguide 508, which can change the common selection of the outputs. Assuming the predetermined frequency difference is small enough, the first phase shifter 510 will provide nearly the same phase shift to light of the first wavelength and the second wavelength. In this way, changing the phase shift provided by the first phase shifter 510 will similarly change how light of each wavelength is routed between the outputs. In some variations, the frequency difference can be selected so that for any pair of wavelengths routed simultaneously by the multiplexing photonic switch 500, the first wavelength and the second wavelength are separated by less than one nanometer.

[0179] For example, the first phase shifter 510 may provide a phase shift of π to light traveling through the first waveguide 508, in which case light of a first wavelength received at the first input 502 will be routed to the first output 514, and light of a second wavelength received at the second input 504 will also be routed to the second output 516. Thus, by varying the amount of phase shift provided by the first phase shifter 510 (e.g., between 0 and π), the first phase shifter 510 may at least partially control which output or outputs are currently selected as the common selection of outputs.

[0180] Thus, the multiplexed photonic switch 500 may be controllable to selectively change a common selection of outputs, which in turn will control where the light of the first wavelength and the second wavelength is routed. The number of different phase shifts that may be applied by the first phase shifter 510 may at least partially determine the candidate outputs to which the light of the first wavelength and the second wavelength may be routed. For example, the first phase shifter 510 may be configured to have two states (e.g., an "off" state in which the phase shifter applies a first phase shift (such as a zero phase shift) and an "on" state in which the phase shifter applies a second phase shift (e.g., a π phase shift)). In these cases, the first phase shifter 510 may be operated to change the multiplexed photonic switch 500 between two different common selections of outputs (e.g., from the first output 514 to the second output 514). In other cases, the first phase shifter 510 may be controllable to provide a wider range of possible phase shifts, which may allow the phase shifter 510 to change the multiplexed photonic switch 500 between three or more different common selections of outputs.

[0181] In some cases, the multiplexed photonic switch 500 may be controllable to select one or more common selections of outputs including a single output (e.g., the first output 514 or the second output 516). Additionally or alternatively, the multiplexed photonic switch 500 may be controllable to select one or more common selections of outputs including two outputs, such that light is split between the first output 514 and the second output 516 according to a split ratio. In some of these variations, the multiplexed photonic switch 500 may be controllable to change the split ratio. In these cases, changing the split ratio is considered to change the common selection of outputs. It should be understood that while the multiplexed photonic switch 500 is designed to simultaneously route light having two different wavelengths, it is understood that the multiplexed photonic switch 500 is also capable of operating to route light of a single wavelength received at the first input 502 or the second input 504.

[0182] In some cases, the multiplexed photonic switch 500 may be designed to have a first common selection of outputs when the first phase shifter 510 is not being effectively operated. However, manufacturing tolerances may result in slight deviations from the expected first common selection of outputs. For example, in the case where the first common selection is designed as a single output (e.g., when the first phase shifter 510 is not being effectively operated, both the first wavelength and the second wavelength are routed to the second output 516), the multiplexed photonic switch 500 as manufactured may actually split a small portion of the first wavelength and / or the second wavelength to another output. In these cases, it may be desirable to provide additional phase adjustments to correct for this.

[0183] As a non-limiting example, a variation of the multiplexing photonic switch 500 may be designed such that the first phase shifter 510 will provide a phase shift varying between 0 and π, such that a phase shift of 0 will route the two wavelengths to a first common choice of output and a phase shift of π will route the two wavelengths to a second common choice of output. When manufactured, there may be positive or negative phase errors between the pins. As an example of a negative phase error, a phase shift of 0.05*π (instead of 0) may be required to route the two wavelengths to the first common choice of output, and a phase shift of 1.05*π (instead of π) may be required to route the two wavelengths to the second common choice of output. For a positive phase error of the same magnitude, a phase shift of -0.05*π may be required instead to route the two wavelengths to the first common choice of output, and a phase shift of 0.95*π may be required to route the two wavelengths to the second common choice of output. Because phase shifters are typically not capable of providing both positive and negative phase shifts, this may require the first phase shifter 510 to provide a 1.95*π phase shift to route the two wavelengths to the first common selection of outputs, which may increase power consumption and / or optical losses associated with operating the first phase shifter 510 .

[0184] In some variations, if the range of manufacturing tolerances is known in advance, the path length difference Δl between the pins can be slightly adjusted so that a single phase shifter 510 can account for the maximum possible positive and negative phase errors with a smaller average phase shift. Using the above non-limiting example, the path length difference Δl can be selected so that the phase shifter 510 can be controlled to provide 0 and π phases when manufacturing results in a maximum positive phase error, and can be controlled to provide 0.1 and 1.1*π phase shifts when manufacturing results in a maximum negative phase error. In other variations, such as when the range of manufacturing tolerances is not known in advance, the multiplexed photonic switch may include a second phase shifter that can be operated to account for manufacturing tolerances. For example, Figure 5B A variation of a multiplexed photonic switch 501 is shown, which may be configured to Figure 5BThe multiplexed photonic switch 500 is the same as the multiplexed photonic switch 501, except that the multiplexed photonic switch 501 includes a second phase shifter 511 and a third phase shifter 513. In some variations, the second phase shifter 511 may be positioned on the second waveguide 509 so that the second phase shifter 511 is operable to change the phase of light traveling through the second waveguide 509.

[0185] For example, during operation of the multiplexed photonic switch 501, the first phase shifter 510 may apply a first phase shift to light traveling through the first waveguide 508 to change the common selection of the output. If the multiplexed photonic switch 501 is manufactured to have a positive phase error, the second phase shifter 511 may apply a second phase shift to the second pin 509 that may account for the positive phase error. Conversely, if the multiplexed photonic switch 501 is manufactured to have a negative phase error, the first phase shift may be adjusted to account for the negative phase error. In some of these variations, the multiplexed photonic switch 501 may not include the third phase shifter 513.

[0186] Alternatively, in other variations, the third phase shifter 513 is positioned in the same pin as the first phase shifter 510. In these cases, the first phase shifter 510 can provide a first phase shift to control the common selection of the output, and the third phase shifter 513 can provide a smaller third phase shift to correct any negative phase error. This can simplify the design of the first phase shifter, but requires the addition of another phase shifter. Each phase shifter of the multiplexed photonic switch described herein may include any suitable type of phase shifter, such as, for example, a thermo-optical phase shifter, a carrier-based phase shifter, an optomechanical phase shifter, etc. When a multiplexed photonic switch as described herein includes multiple phase shifters, some or all of these phase shifters may be of the same type, or each phase shifter may be of a different type.

[0187] Because the phase shift provided by the first phase shifter 510 is slightly different for the first wavelength and the second wavelength, there may be some degree of optical loss associated with combining the first wavelength and the second wavelength into a common selection for the output. In other words, the first phase shifter 510 may not be able to provide a phase shift that results in the same route between the first wavelength and the second wavelength to the group of common inputs when operated to provide a non-zero phase shift. In some variations, it may be desirable to balance this loss between the first wavelength and the second wavelength. This may be advantageous in situations where it is important for the multiplexed photonic switch described herein to output the first wavelength and the second wavelength with equal power. For example, during a series of coded measurements such as those described herein, it may be desirable to maintain a predetermined power ratio between wavelengths emitted simultaneously as part of a given coded measurement.

[0188] For example, in some variations, the path length difference Δl between the pins may be adjusted so that regardless of whether the first phase shifter 510 (or any other phase shifter positioned on the pins of the multiplexed photonic switch 500) actively applies a non-zero phase shift, there will always be a predetermined amount of loss associated with combining the first wavelength and the second wavelength. In these cases, when the multiplexed photonic switch 500 combines light into a given common selection of outputs, an additional phase shift may be applied (e.g., by the first phase shifter 510 or another phase shifter positioned on the pins of the multiplexed photonic switch 500) to control whether the predetermined amount of loss is experienced by the first wavelength, the second wavelength, or split between the first wavelength and the second wavelength. This arrangement may not require any additional components, but the multiplexed photonic switch 500 will experience the predetermined amount of loss regardless of whether power balancing between the first wavelength and the second wavelength is currently desired.

[0189] In other cases, the multiplexed photonic switch 500 may include one or more variable optical attenuators connected to one or both of the inputs 502, 504 of the multiplexed photonic switch. Figure 5C A variation of a multiplexed photonic switch 503 is shown, which may be configured to Figure 5A The multiplexed photonic switch 503 is the same as the multiplexed photonic switch 500 of FIG. 5, except that the multiplexed photonic switch 503 includes a first variable optical attenuator (VOA) 518 and a second VOA 520. The first VOA 518 is optically connected to the first input 502 of the multiplexed photonic switch 503 and can be controlled to selectively attenuate light of a first wavelength received by the first input 502. Similarly, the second VOA 520 is optically connected to the second input 504 of the multiplexed photonic switch 503. The second VOA 520 can be controlled to selectively attenuate light of a second wavelength received by the second input 504. Although the multiplexed photonic switch 503 is Figure 5C The multiplexed photonic switch 503 is configured to have both first and second VOAs 518, 520, but in some variations, the multiplexed photonic switch 503 may have the first VOA 518 without the second VOA 520 (or vice versa), depending on how the multiplexed photonic switch 503 may be used in an optical measurement system.

[0190] Thus, the first VOA 518 and / or the second VOA 520 can be controlled at a given time to cause optical losses in the first wavelength and / or the second wavelength, respectively. Thus, when the phase shift applied by the phase shifter of the multiplexed photonic switch 503 produces a relative loss in light of one wavelength received at one input, the VOA corresponding to the other input can be activated to cause a corresponding loss in light of the other wavelength. For example, in the case where the phase shift in the pin causes a loss of the second wavelength, the first VOA 518 can be operated to produce a loss in light of the first wavelength. Thus, the first and second VOAs 518, 520 can be used to balance the power between the first and second wavelengths, but can also remain inactive when power balancing is not required. In this way, the multiplexed photonic switch 521 can be operated to prioritize minimizing losses in these cases.

[0191] about Figures 5A to 5C The described multiplexed photonic switches may be incorporated into a photonic integrated circuit as described herein and may be used to simultaneously route light at two wavelengths. For example, one or more of these multiplexed photonic switches may be incorporated into a photonic integrated circuit as described herein. Figures 3B to 3I One or more of the switching networks described. Fig. 6A One such example of a switch network 600 incorporating a multiplexed photonic switch 610 is shown, which may be used, for example, with respect to Figures 5A to 5C The multiplexed photonic switches 500, 501 and 521 may be configured in any manner as described.

[0192] The switch network 600 may include a plurality of inputs and a plurality of outputs. The plurality of inputs may be optically connected to corresponding outputs of a light source unit (not shown), and the plurality of outputs may be optically connected to corresponding plurality of emission groups. Fig. 6A In the illustrated variation, the switch network has two inputs (e.g., a first input 602 and a second input 604) and four outputs (e.g., a first output 620, a second output 622, a third output 624, and a fourth output 626). The first input 602 may be optically connected to a first output of a light source unit, and the second input 604 may be optically connected to a second output of the light source unit. The light source unit may simultaneously output light of a first wavelength along its first output and light of a second wavelength along its second output, such as described herein with respect to FIG. 3B to FIG. 3K In this manner, the switch network 600 can simultaneously receive light of a first wavelength at its first input 602 and light of a second wavelength at its second input 604 .

[0193] Similarly, each output is optically connected to a different emission group (e.g., the first output 620 is optically connected to the first emission group, the second output 622 is optically connected to the second emission group, the third output 624 is optically connected to the third emission group, and the fourth output 626 is optically connected to the fourth emission group). The switch network 600 can be controlled to selectively route the first wavelength and the second wavelength to a common selection of the plurality of outputs. In this manner, when the switch network 600 simultaneously receives the first wavelength and the second wavelength at its respective first input 602, 604, each emission group receiving light from the switch network will receive and emit light including both the first wavelength and the second wavelength.

[0194] To route light between multiple inputs and multiple outputs, the switch network 600 includes a multiplexing photonic switch 610, a first controllable switch 612, and a second controllable switch 614. The multiplexing photonic switch 610 may be configured as described with respect to FIG. FIG. 5A to FIG. 5C The inputs 602, 604 of the switch network may form inputs of the multiplexed photonic switch 610. A first waveguide 616 optically connects a first output of the multiplexed photonic switch 610 to a first input of a first controllable switch 612, and a second waveguide 618 optically connects a second output of the multiplexed photonic switch 610 to a first input of a second controllable switch 614. The first and second controllable switches 612, 614 may be any suitable photonic switches capable of selectively routing light received at an input between one or two outputs of a set of outputs.

[0195] The multiplexed photonic switch 610 is operable to selectively control whether light of the first wavelength and the second wavelength is routed to the first controllable switch 612, the second controllable switch 614, or split between the first controllable switch 612 and the second controllable switch 614. For example, during a first time period, the multiplexed photonic switch 610 may be controlled to route both the first wavelength and the second wavelength to the first controllable switch 612. During this time, the multiplexed photonic switch 610 will simultaneously output the first wavelength and the second wavelength along the first waveguide 616. The first controllable switch 612 may selectively route the first wavelength and the second wavelength to a first output 620 (the first output being optically connected to the first output of the first controllable switch 612), a second output 622 (the second output being optically connected to the second output of the first controllable switch 612), or split between the first and second outputs 620, 622. In this manner, the switch network 600 may be controlled to simultaneously route the first wavelength and the second wavelength to the first emission group, simultaneously route to the second emission group, or simultaneously split the two wavelengths between the first emission group and the second emission group. It should be appreciated that the first controllable switch 612 may include a second input 630 that may be configured to receive light from a different portion of the switch network 600 (eg, from a second multiplexing photonic switch).

[0196] Similarly, during a second time period, the multiplexed photonic switch 610 may be controlled to route both the first wavelength and the second wavelength to the second controllable switch 612. During this time, the multiplexed photonic switch 610 will simultaneously output the first wavelength and the second wavelength along the second waveguide 618. The second controllable switch 614 may selectively route the first wavelength and the second wavelength to a third output 624 (the third output optically connected to the first output of the second controllable switch 614), a fourth output 626 (the fourth output optically connected to the second output of the second controllable switch 614), or split between the third and fourth outputs 624, 626. In this manner, the switch network 600 may be controlled to simultaneously route the first wavelength and the second wavelength to the third emission group, simultaneously route to the fourth emission group, or simultaneously split the two wavelengths between the third emission group and the fourth emission group. It should be understood that the second controllable switch 614 may include a second input 632 that may be configured to receive light from a different portion of the switch network (e.g., from the second multiplexed photonic switch).

[0197] In still other cases, the multiplexing photonic switch 610 may be controlled to simultaneously split the first wavelength and the second wavelength between the first and second waveguides 616, 618. In these cases, the first and second controllable switches 612, 614 may be controlled to route the first and second wavelengths to two or more of the outputs (e.g., one or both of the first and second outputs 620, 622 and one or both of the third and fourth outputs 624, 626). It should also be understood that the switch network may be capable of routing light with different wavelength pairs (e.g., the different wavelength pairs having the same common frequency difference) at different times. In these cases, the first and second controllable switches 612, 614 may each be adjustable to account for the different wavelengths received by each switch at different times.

[0198] Figure 6B 602, the second input 604, and the third input 604 and a plurality of outputs (eg, Fig. 6A Another variation of the switch network 640 having four outputs (described above). In this variation, the switch network 640 includes a plurality of cascaded multiplexed photon switches, the plurality of cascaded multiplexed photon switches including a first multiplexed photon switch 642 and a second multiplexed photon switch 644. Each of the first multiplexed photon switch 642 and the second multiplexed photon switch 644 may be composed of, for example, Figures 5A to 5C The multiplexed photonic switches 500, 501 and 521 may be configured in any manner as described.

[0199] The first and second inputs 602, 604 of the switch network 640 may form inputs of a second multiplexed photonic switch 644. The first input 602 may be optically connected to a first output of a light source unit, and the second input 604 may be optically connected to a second output of the light source unit. Thus, the second multiplexed photonic switch 644 is operable to route light received at the first input 602 and the second input 604 to a first output 646 of the second multiplexed photonic switch 644. The first output 646 of the second multiplexed photonic switch 644 may form a first input of the first multiplexed photonic switch 642, and the third input 606 of the switch network 640 may form a second input of the first multiplexed photonic switch 642. The third input 606 of the switch network 640 may be optically connected to a third output of the light source unit. For example, the first input 602, the second input 604, and the third input 606 may be connected to corresponding first, second, and third outputs of an echelon grating multiplexer as described herein.

[0200] The switch network 640 can simultaneously receive light of different wavelengths at multiple inputs of the switch network 640, and can route the light to a common selection of outputs. Specifically, the first waveguide 616 optically connects the first output of the first multiplexed photonic switch 642 to the first input of the first controllable switch 612, and the second waveguide 618 optically connects the second output of the first multiplexed photonic switch 642 to the first input of the second controllable switch 614. The first controllable switch 612 and the second controllable switch 614 can be as described with respect to Fig. 6A The switching network 600 may be configured in any manner described.

[0201] For example, when two different wavelengths of light are simultaneously received at the first input 602 and the second input 604 of the switch network 640 (e.g., as part of a coded measurement as described herein), the second multiplexed photonic switch 644 can combine these different wavelengths into a first output 646 of the second multiplexed photonic switch 644. The first multiplexed photonic switch 642 can simultaneously receive two wavelengths of light at corresponding inputs of the first multiplexed photonic switch 642 and can be operated to simultaneously route the two wavelengths to one or both of the first controllable switch and the second controllable switch 612, 614. Similarly, the controllable switches 612, 614 can be operated to distribute light between multiple outputs of the switch network 640.

[0202] Similarly, two different wavelengths of light may be simultaneously received at one of the first input 602 or the second input 604 and the third input 606 of the switch network 640. In these cases, the second multiplexed photonic switch 644 routes the light received at its corresponding input to the first input of the first multiplexed switch 642. Thus, the first multiplexed photonic switch 642 may receive different wavelengths at different inputs of the first multiplexed photonic switch 642 (e.g., one wavelength from the third input 606 of the switch network 640 while receiving another wavelength via the first output 646 of the second multiplexed photonic switch 644), and may be operated to simultaneously route the two wavelengths to one or both of the first controllable switch 612 and the second controllable switch 614.

[0203] In some variations, the switch network 640 may include multiple VOAs corresponding to multiple inputs of the switch network 640. For example, the switch network 640 may include a first VOA 652 optically connected to the first input 602 of the switch network (and thereby optically connected to the first input of the second multiplexed photonic switch 644), a second VOA 654 optically connected to the second input 604 of the switch network (and thereby optically connected to the second input of the second multiplexed photonic switch 644), and a third VOA 656 optically connected to the third input 606 of the switch network (and thereby optically connected to the second input of the second multiplexed photonic switch 644). Depending on which inputs of the switch network 640 are receiving light at the same time, the corresponding VOAs may be controlled to perform power balancing between the wavelengths of light generated at the inputs of the switch network 640.

[0204] In some variations, the second multiplexing photonic switch 644 may be provided by an interferometer such as Figure 4A The first interferometer 410a) of the passive optical combiner 400 of the embodiment of the present invention is replaced with a first interferometer 410a) of the passive optical combiner 400 such that the first input 602 and the second input 604 of the switch network 640 serve as the input of the interferometer and the first output 646 serves as the output of the interferometer. In these variations, the wavelengths generated by the light source unit and the free spectral range of the first interferometer can be selected such that i) the wavelength of light received by the first input 602 is routed to the first output 646, and ii) the wavelength of light received by the second input 604 is also routed to the first output 646.

[0205] Fig. 7AA schematic diagram of a photonic integrated circuit 700 that can be used with the optical measurement system described herein is shown. The photonic integrated circuit 700 includes a light source unit 701 and a switch network 730 having multiple outputs 740a to 740d. The light source unit 701 includes multiple outputs and is optically connected to the switch network 730. The light source unit 701 is operable (e.g., controllable by a controller as described herein) to simultaneously output light of multiple wavelengths at different outputs of the light source unit 701. The switch network 730 is configured to simultaneously receive light of different wavelengths from multiple outputs of the light source unit 701, and to route the multiple wavelengths to a common selection of the multiple outputs 740a to 740d. Each of the multiple outputs can be connected to an emission group in a plurality of emission groups. Thus, one or more emission groups can receive light containing multiple wavelengths simultaneously, and can emit the light from the photonic integrated circuit 700. In Fig. 7A In the variation shown in , the switch network 730 is shown as having four outputs (eg, a first output 740a, a second output 740b, a third output 740c, and a fourth output 740d), each of which may be connected to a different firing group.

[0206] exist Fig. 7A In the variation shown, the light source unit 701 includes multiple light sources and multiple multiplexers, each multiplexer having a corresponding multiple outputs. Fig. 7A The light source unit 701 includes a first plurality of light sources 702a to 702h and a first multiplexer 704. The first multiplexer 704 (which may be an echelon grating multiplexer) has a first plurality of inputs and a first plurality of outputs 706a to 706b. Each of the first plurality of light sources 702a to 702h is optically connected to a different input of the first plurality of inputs, and the first multiplexer 704 is configured to multiplex light from the first plurality of inputs to the first plurality of outputs. The first plurality of light sources 702a to 702h and the first multiplexer 704 may be such as described herein with respect to FIG. 3B to FIG. 3K Configure in any way described.

[0207] The first multiple light sources 702a to 702h may include one or more light source groups, each light source group including a group of light sources with a common frequency difference. In this way, the first multiplexer 704 can output light simultaneously via its multiple outputs. For example, during the first time period, the first light source group (e.g., light source 702a, 702b) can be operated to simultaneously generate the light of the first wavelength and the light of the second wavelength separated by the first frequency difference. The first multiplexer 704 can simultaneously output the first wavelength via the first output 306a of the first multiplexer 704 and output the second wavelength via the second output 306b of the first multiplexer 704. During the second time period, the second light source group (e.g., light source 702c, 702d) can be operated to simultaneously generate the light of the third wavelength and the light of the fourth wavelength separated by the first frequency difference. The first multiplexer 704 can simultaneously output the third wavelength via the first output 306a of the first multiplexer 704 and output the fourth wavelength via the second output 306b of the first multiplexer 704. Therefore, the light source unit 701 can use the first multiplexer 704 to output specific wavelengths (eg, multiple wavelengths separated by a first frequency difference and / or a single wavelength) at different times.

[0208] Additionally, in some variations, Fig. 7A The light source unit 701 includes a second plurality of light sources 722a to 722h and a second multiplexer 714. The second multiplexer 714 (which may be an echelon grating multiplexer) has a second plurality of inputs and a second plurality of outputs 716a to 716b. Each of the second plurality of light sources 722a to 722h is optically connected to a different input of the second plurality of inputs, and the second multiplexer 714 is configured to multiplex light from the second plurality of inputs to the second plurality of outputs 716a to 716b. The second plurality of light sources 722a to 722h and the second multiplexer 714 may be such as described herein with respect to FIG. 3B to FIG. 3K Configure in any way described.

[0209] The second multiple light sources 722a to 722h may include one or more light source groups, each light source group including a group of light sources with a common frequency difference. In this way, the second multiplexer 714 can output light simultaneously via its multiple outputs. For example, during the third time period, the third light source group (e.g., light source 722a, 722b) can be operated to generate light of the fifth wavelength and the sixth wavelength separated by the second frequency difference simultaneously. It should be understood that in some cases, the first frequency difference may be identical to the second frequency difference, and in other cases, the first frequency difference may be different from the second frequency difference. The second multiplexer 714 can output the fifth wavelength via the third output 716a of the second multiplexer 714 and output the sixth wavelength via the fourth output 716b of the second multiplexer 714 simultaneously.

[0210] During the fourth time period, the fourth light source group (e.g., light sources 722c, 722d) may be operated to simultaneously generate light of the seventh wavelength and light of the eighth wavelength separated by the second frequency difference. The second multiplexer 714 may simultaneously output the seventh wavelength via the third output 714a of the second multiplexer 716 and output the eighth wavelength via the fourth output 716b. Thus, the light source unit 701 may utilize the second multiplexer 714 to output other wavelengths (e.g., multiple wavelengths separated by the first frequency difference and / or a single wavelength) at different times.

[0211] In some cases, the light source unit 701 includes one or more wavelength locking units shared between the first multiplexer and the second multiplexer 704, 714. Fig. 7A In the illustrated variation, the light source unit 701 includes a first wavelength locking unit 708a and a second wavelength locking unit 708b. The first wavelength locking unit 708a is optically connected to the first output 706a and the third output 716a, and the second wavelength locking unit 708b is optically connected to the second output 706b and the fourth output 716b. In this way, the first wavelength locking unit 708a can receive light from the first multiplexer 704 or the second multiplexer 714 depending on which multiplexer is currently outputting light. If the first multiplexer 704 is emitting light along the first output 706a, the first wavelength locking unit 708a can be used to control a corresponding light source in the first plurality of light sources 702a to 702h. Similarly, if the second multiplexer 714 is emitting light along the third output 716a, the first wavelength locking unit 708a can be used to control a corresponding light source in the second plurality of light sources 722a to 722h. In some cases, light received by the first and third outputs 706a, 716a may pass through a first coupler 707a such that light received from either output is routed to a common set of waveguides before reaching the first wavelength locking unit 708a.

[0212] Similarly, the second wavelength locking unit 708b can receive light from the first multiplexer 704 or the second multiplexer 714 depending on which multiplexer is currently outputting light. If the first multiplexer 704 is emitting light along the second output 706b, the second wavelength locking unit 708b can be used to control a corresponding light source in the first plurality of light sources 702a to 702h. Similarly, if the second multiplexer 714 is emitting light along the fourth output 716b, the second wavelength locking unit 708b can be used to control a corresponding light source in the second plurality of light sources 722a to 722h. In some cases, light received by the second and fourth outputs 706b, 716b can pass through the second coupler 707b so that light received from either output is routed to a common set of waveguides before reaching the second wavelength locking unit 708b.

[0213] In general, the light source unit 701 includes a first plurality of outputs corresponding to the first plurality of outputs 706a to 706b of the first multiplexer 704 and a second plurality of outputs corresponding to the second plurality of outputs 716a to 716b of the second multiplexer 704. The switch network 730 is optically connected to the first plurality of outputs and the second plurality of outputs so that the switch network 730 can simultaneously receive light of different wavelengths from the plurality of outputs of the light source unit 701. The switch network 730 is configured to route different wavelengths to a common selection of the plurality of outputs 740a to 740d. In this way, one or more emission groups can receive and emit light including multiple wavelengths simultaneously.

[0214] Fig. 7A A variation of the switch network 730 shown in FIG. 7 includes passive optical combiners that are each configured to receive light of different wavelengths from multiple inputs of a corresponding multiplexer and combine the different wavelengths into a single common output of the passive optical combiner. When it is desired to combine light from three outputs of the multiplexer into a single waveguide, the passive optical combiner may be configured as described herein with respect to Figure 4A When it is desired to combine light from two outputs of a multiplexer into a single waveguide, the passive optical combiner may be configured, for example, as Figure 4A The first interferometer 410a of the passive optical combiner 400 is shown in FIG. Figure 4A A first frequency v is received at a first input 402) of a of light, and at a second input (e.g., Figure 4A The second frequency v is received at the second input 404 b The first free spectral range Δv1 of the first interferometer 410a is selected so that the first frequency and the second frequency v a 、v a When light is received at the corresponding input, it will be routed to the common waveguide (e.g., Figure 4A The second output 414).

[0215] like Fig. 7AAs shown, the switch network 730 includes a first passive optical combiner 732a optically connected to the first output and the second output 706a, 706b of the first multiplexer 704. In other words, the first passive optical combiner 732a has a first input for receiving light from the first output 706a and a second input for receiving light from the second output 706b. The first passive optical combiner 732a has a first free spectral range selected based on a first common frequency difference of a light source group associated with the first plurality of light sources 702a to 702h. Specifically, when the light source group is operated to emit light having a pair of wavelengths separated by a first common frequency difference (e.g., light sources 702a, 702b during a first time period, light sources 702c, 702d during a second time period, etc.), the first passive optical combiner 732a will combine the pair of wavelengths into the first waveguide 733a.

[0216] The first waveguide 733a can be optically connected to a first controllable switch 734. Specifically, when the first multiplexer 704 is outputting light, a first input of the first controllable switch 734 can receive light from the first waveguide 733a. The first controllable switch 734 has a first output 735a and a second output 735b. When light is received by the first controllable switch 734 via the first waveguide 733a, the first controllable switch 734 can be controlled to selectively route the light to only the first output 735a, only the second output 735b, or to split the light between the first output 735a and the second output 735b. The switch network 730 can also include a second controllable switch 736 optically connected to the first output 735a of the second controllable switch 736. The second controllable switch 736 is controllable to selectively route light received from the first output 735a of the second controllable switch 736 to the first output 740a of the switching network 730, the second output 740b of the switching network, or to split the light between the first output 740a and the second output 740b.

[0217] Similarly, the switch network 730 may also include a third controllable switch 738 optically connected to the second output 735b of the second controllable switch 736. The third controllable switch 738 may be controlled to selectively route light received from the second output 735b of the second controllable switch 736 to the third output 740c of the switch network 730, the fourth output 740d of the switch network, or split the light between the third output 740c and the fourth output 740d. In general, by operating the first controllable switch, the second controllable switch, and the third controllable switches 734 to 738, the switch network 730 may selectively route light received by the first passive optical combiner 732a to a first common selection of outputs of the plurality of outputs 740a to 740d of the switch network. In this manner, although the switch network 730 receives light of different wavelengths from different outputs, the switch network 730 will simultaneously output these wavelengths to each output in the first common selection of outputs. In this manner, each emission group emitting light from the photonic integrated circuit 700 may be able to emit light including multiple wavelengths simultaneously.

[0218] The switch network 730 may also include a second passive optical combiner 732b optically connected to the third output 716a and the fourth output 716b of the second multiplexer 714. In other words, the second passive optical combiner 732b has a third input for receiving light from the third output 716b and a fourth input for receiving light from the fourth output 716c. The second passive optical combiner 732b has a second free spectral range selected based on a second common frequency difference of the light source group associated with the second plurality of light sources 722a to 722h. Specifically, when the light source group is operated to emit a pair of wavelengths separated by a second common frequency difference (e.g., light sources 722a, 722b during the third time period, light sources 722c, 722d during the fourth time period, etc.), the second passive optical combiner 732b will combine the pair of wavelengths into the second waveguide 733b.

[0219] The second waveguide 733b may be optically connected to the first controllable switch 734. Thus, when the first controllable switch receives light from the second waveguide 733b (e.g., at a second input of the first controllable switch), the first, second, and third controllable switches 734 to 738 may be operated to selectively route light received by the second passive optical combiner 732b to a second common selection of outputs of the plurality of outputs 740a to 740d of the switch network. Thus, the switch network 730 may flexibly combine light from different groups of outputs and controllably combine the light into a common selection of the plurality of outputs 740a to 740d. It should be understood that the number and arrangement of the passive optical combiners and controllable switches may be adjusted to accommodate different numbers of multiplexers in the light source unit 701 and / or different numbers of the plurality of outputs 740a to 740d of the switch network 730.

[0220] Figure 7B Another variation of a photonic integrated circuit 750 is shown, which can be configured with Fig. 7A The photonic integrated circuit 700 is the same as Fig. 7A The switch network 730 has been replaced by another switch network 731. Specifically, including as described herein Fig. 7A The described switch network 731 of multiple outputs 740a to 740d includes a first multiplexing photonic switch 752a optically connected to the first output and the second output 706a, 706b of the first multiplexer 704. In other words, the first multiplexing photonic switch 752a has a first input for receiving light from the first output 706a and a second input for receiving light from the second output 706b. The first multiplexing photonic switch 752a is configured to receive light of a first wavelength at the first input and receive light of a second wavelength at the second input, wherein the first wavelength and the second wavelength have a first common frequency difference. When the first multiplexing photonic switch 752a simultaneously receives light of a pair of wavelengths having the first common frequency difference, the first multiplexing photonic switch 752a can selectively route the light of the two wavelengths to a first common selection of the outputs of the first multiplexing photonic switch 752a.

[0221] Specifically, the first multiplexed photonic switch 752a has a first output 753a and a second output 753b. The first common selection of outputs may include only the first output 753a, only the second output 753b, or both the first output and the second output 753a, 753b. In this way, the first multiplexed photonic switch 752a can be controlled to simultaneously route light to only the first output 753a, only the second output 753b, or split the light between the first output 753a and the second output 753b. Specifically, when the light source group is operated to emit light having a pair of wavelengths separated by a first common frequency difference (e.g., light sources 702a, 702b during a first time period, light sources 702c, 702d during a second time period, etc.), the first multiplexed photonic switch 752a combines the pair of wavelengths into a common selection of the first output and the second output 753a, 753b of the first multiplexed photonic switch 752a.

[0222] The switch network 731 may further include a first controllable switch 754a optically connected to a first output 753a of the first multiplexed photonic switch 752a. The first controllable switch 754a may be controlled to selectively route light received from the first output 753a of the first multiplexed photonic switch to the first output 740a of the switch network 731, the second output 740b of the switch network 731, or to split the light between the first output 740a and the second output 740b. Similarly, the switch network 731 may further include a second controllable switch 754b optically connected to the second output 753b of the first multiplexed photonic switch 752a. The second controllable switch 754b may be controlled to selectively route light received from the second output 753b of the first multiplexed photonic switch 752a to the third output 740c of the switch network 731, the fourth output 740d of the switch network 731, or to split the light between the third output 740c and the fourth output 740d. In general, by operating the first multiplexing photonic switch 752a and the first and second controllable switches 754a, 754b, the switch network 731 can selectively route light received by the first multiplexing photonic switch 752a to a first common selection of outputs of the plurality of outputs 740a-740d of the switch network.

[0223] The switch network 731 may also include a second multiplexing photonic switch 752b optically connected to the third output and the fourth output 716a, 716b of the second multiplexer 714. In other words, the second multiplexing photonic switch 752b has a third input for receiving light from the third output 716a and a fourth input for receiving light from the fourth output 716b. The second multiplexing photonic switch 752b is configured to receive light of a third wavelength at the third input and receive light of a fourth wavelength at the fourth input, wherein the third wavelength and the fourth wavelength have a second common frequency difference. When the second multiplexing photonic switch 752b simultaneously receives light of a pair of wavelengths having a second common frequency difference, the second multiplexing photonic switch 752b may selectively route the light of the two wavelengths to a second common selection of the outputs of the second multiplexing photonic switch 752b.

[0224] Specifically, the second multiplexed photon switch 752b has a third output 753c and a fourth output 753d. The second common selection of outputs may include only the third output 753c, only the fourth output 753d, or both the third output and the fourth output 753c, 753d. In this way, the second multiplexed photon switch 752b can be controlled to simultaneously route light to only the third output 753c, only the fourth output 753d, or to split the light between the third output 753c and the fourth output 753d. Specifically, when the light source group is operated to emit a pair of wavelengths separated by a second common frequency difference (e.g., light sources 722a, 722b during the third time period, light sources 722c, 722d during the fourth time period, etc.), the second multiplexed photon switch 752b will combine the pair of wavelengths into the common selection of the third output and the fourth output 753c, 753d of the second multiplexed photon switch 752b.

[0225] The third and fourth outputs 753c, 753d may also be optically connected to the first and second controllable switches 754a, 754d. In this manner, by operating the second multiplexed photonic switch 752b and the first and second controllable switches 754a, 754b, light received by the second multiplexed photonic switch 752b may be selectively routed to a second common selection of outputs of the plurality of outputs 740a to 740d of the switch network 731. Thus, in Fig. 7A and Figure 7B In the variation shown, the first multiplexer 704 may output multiple wavelengths at certain points in time, during which the first and second wavelength locking units 708a, 708b may be used to control the light sources of the first plurality of light sources 702a to 702h, and the switching network (e.g., the switching network 730 or the switching network) may combine the wavelengths into a first common selection of outputs of the plurality of outputs 740a to 740d. During other points in time, the second multiplexer 714 may output multiple wavelengths, and the first and second wavelength locking units 708a, 708b may be used to control the light sources of the second plurality of light sources 722a to 722h, and the switching network may combine the wavelengths into a first common selection of outputs of the plurality of outputs 740a to 740d. Thus, an optical measurement system incorporating one of these photonic integrated circuits may have considerable flexibility in outputting one or more wavelengths of light (which may change between different individual measurements) from a common set of emission groups (which may change between different individual measurements) for any given individual measurement.

[0226] Fig. 8AAnother variation of a photonic integrated circuit 800 that can be used with the optical measurement system described herein is shown. The photonic integrated circuit 800 includes a light source unit 801, which includes a set of tunable light sources 802a to 802d, a plurality of light sources 722a to 772h, and a plurality of multiplexers. Specifically, the light source unit 801 may include, for example, Fig. 7A The photonic integrated circuit 700 is described with reference to the first multiplexer 704 and the second multiplexer 714. The set of tunable light sources 802a to 802d is optically connected to the first multiplexer 704. The set of tunable light sources 802a to 802d may include a single tunable light source or a plurality of tunable light sources. For example, Fig. 8A The set of tunable light sources 802a to 802d depicted in FIG. 8 includes four tunable light sources (eg, a first tunable light source 802a, a second tunable light source 802b, a third tunable light source 802c, and a fourth tunable light source 802d).

[0227] Each tunable light source in the set of tunable light sources 802a to 802d is connected to a corresponding input of the first multiplexer 704 and is operable to emit light of a plurality of corresponding wavelengths. The light source unit 801 is configured such that different corresponding wavelengths emitted by the tunable light sources 802a to 802d are routed to different corresponding outputs of the first plurality of outputs 706a to 706b of the first multiplexer 704, such as described herein with respect to Figure 3K As described in the light source unit 381 of the embodiment of the present invention. For example, the first tunable light source 802a can be operated at different times to generate a first wavelength and a second wavelength, wherein the first wavelength and the second wavelength are routed to different outputs in the first plurality of outputs 706a to 706b. Therefore, the first tunable light source 802a can be operated to generate a first wavelength during a first time period, and can be operated to generate a second wavelength during a second time period. In this way, the light source unit can be controlled to output a first wavelength from a first output 706a in the first plurality of outputs 706a to 706b during a first time period. Similarly, the light source unit can be controlled to output a second wavelength from a second output 706b in the first plurality of outputs 706a to 706b during a second time period.

[0228] The light source unit 801 can be configured to output additional wavelengths of light from the first multiplexer 704. For example, a tunable light source in the set of tunable light sources 802a to 802d can generate additional wavelengths (e.g., a third corresponding wavelength, etc.) that are routed to additional corresponding outputs of the first plurality of outputs 706a to 706b of the first multiplexer 704. In some variations, the light source unit 801 includes a set of additional light sources optically connected to the first multiplexer 704, such as those described herein with respect to Figure 3KThe additional light sources 302a to 302d are depicted. These additional light sources may be operated to generate additional wavelengths that are routed to corresponding ones of the first plurality of outputs 706a to 706b of the first multiplexer 704.

[0229] The plurality of light sources 722a to 722h may be as described herein with respect to Fig. 7A The light source unit 701 of the embodiment of the present invention is operated as described above, so that the second multiplexer 714 can output light via its multiple outputs simultaneously. For example, the light source unit 801 can be controlled to simultaneously output light of the third wavelength from the first output (e.g., the third output 716a) of the second plurality of outputs 716a to 716b and output light of the second wavelength from the second plurality of outputs 716a to 716b (e.g., the fourth output 716b) during the third time period. For example, the first pair of light sources in the plurality of light sources 722a to 722h can be operated to emit the third wavelength and the fourth wavelength simultaneously during the third time period.

[0230] When the photonic integrated circuit 800 is incorporated into an optical measurement system as described herein, the optical measurement system can perform spectral measurements including different individual measurements. During different individual measurements, the photonic integrated circuit 800 can emit light of a single wavelength or emit light of multiple wavelengths simultaneously. When the photonic integrated circuit 800 emits light of multiple wavelengths simultaneously, the multiple wavelengths can be treated as a single emission wavelength (e.g., to increase optical power and / or reduce noise associated with the measurement) or can be treated as different emission wavelengths (e.g., as part of a series of coded measurements).

[0231] For example, during certain individual measurements, the light source unit 801 may be operated to generate light of a single wavelength from the first multiplexer 704 (e.g., from one of the first plurality of outputs 706a-706b). During other individual measurements, the light source unit 801 may be operated to generate light of multiple wavelengths from the second multiplexer 714 (e.g., from a different output of the second plurality of outputs 716a-716b). In some variations, the light source unit 801 may be operated to generate light of multiple wavelengths as part of a series of coded measurements as described herein.

[0232] exist Fig. 8A In a variation of the photonic integrated circuit 800 shown in FIG. 8 , the photonic integrated circuit 800 includes the photonic integrated circuit 800 of the present invention. Fig. 7AThe switching network 730 described herein. The switching network 730 is operable to route light generated by the light source unit 801 to a selection of outputs 740a to 740d of the switching network 730. For example, during a first time period, the switching network may be controlled to route light of a first wavelength to a first common selection of the plurality of outputs 740a to 740d. During a second time period, the switching network may be controlled to route light of a second wavelength to a second common selection of the plurality of outputs 740a to 740d. Similarly, during a third time period, the switching network may be controlled to simultaneously route light of a third wavelength and light of a fourth wavelength to the second common selection of the plurality of outputs 740a to 740d. It should be understood that the photonic integrated circuit 800 may include any suitable switching network 730 as described herein, such as the switching network 730 described herein with respect to FIG. Figure 7B The switching network 731 is described.

[0233] exist Fig. 8A In the illustrated variation, the light source unit 801 includes one or more wavelength locking units shared between the first multiplexer 704 and the second multiplexer 714. For example, the light source unit 801 may include first and second wavelength locking units 708a, 708b and first and second couplers 707a, 707b, which are described herein with respect to Fig. 7A Configure as described. Figure 8B Another variation of a photonic integrated circuit 850 is shown, which can be configured with Fig. 8A The photonic integrated circuit 800 is the same as the photonic integrated circuit 800 , except that the light source unit 801 has been replaced by another light source unit 851 .

[0234] The light source unit 851 is configured to Fig. 8A 802a to 802d, except that the light source unit 851 includes a plurality of wavelength locking units that are not shared between the first multiplexer 704 and the second multiplexer 714. Specifically, the light source unit 851 includes a first wavelength locking unit 808a that is configured to monitor light output from any of the first plurality of outputs 706a to 706b of the first multiplexer 704. Thus, when the first multiplexer 704 is outputting a single wavelength, the wavelength locking unit 808a can be used to control the wavelength emitted by a single light source (e.g., one of the tunable light sources 802a to 802d). Additionally, the light source unit 851 includes a second wavelength locking unit 808b and a third wavelength locking unit 808c that are positioned to monitor light traveling through the respective first and second outputs 716a, 716b of the second multiplexer 706. When the second multiplexer 714 outputs two wavelengths simultaneously, the second and third wavelength locking units 808b, 808c may be used to simultaneously control the wavelengths emitted by a plurality of light sources (eg, two light sources among the plurality of light sources 722a to 772h).

[0235] exist Figure 8B In the variation shown, the first wavelength locking element 808a is positioned to monitor light traveling through the first passive optical combiner 732a, such as described herein with respect to Figure 4B In other variations, the wavelength locking unit 808a is positioned to monitor light traveling through the first waveguide 733a.

[0236] Although this article is about 7A to 8B The first multiplexer 704 and the second multiplexer 714 of the described light source unit are each shown as having two outputs, but it should be understood that similar principles can be applied to light sources in which the first multiplexer 704 and / or the second multiplexer 714 include three or more corresponding outputs. Fig. 9A Schematic diagram of a photonic integrated circuit 900 that can be used with the optical measurement system described herein is shown. The photonic integrated circuit 900 includes a light source unit 901 and a switch network 930 having a plurality of outputs 740a to 740d, such as those described herein with respect to Fig. 7A The light source unit 901 includes a plurality of outputs and is optically connected to the switch network 930. The light source unit 901 is operable (e.g., controllable by a controller as described herein) to output light of a single wavelength or to output light of multiple wavelengths simultaneously, and the switch network 930 is configured to route the light to a common selection of the plurality of outputs 740a to 740d.

[0237] exist Fig. 9AIn the illustrated variation, the light source unit 901 includes a first plurality of light sources 902a to 902n optically connected to a first multiplexer 904 (some or all of which may be tunable light sources) and a second plurality of light sources 922a to 922n optically connected to a second multiplexer 914 (some or all of which may be tunable light sources). In some variations, the first multiplexer 904 and / or the second multiplexer 914 are echelle multiplexers. The first multiplexer 904 includes a first plurality of outputs 906a to 906c, which include three outputs (e.g., a first output 906a, a second output 906b, and a third output 906c). Depending on the selection of the light source for generating the light (and the selection of the wavelength generated in the case of a tunable light source), the first multiplexer 904 may route the light generated by the first plurality of light sources 902a to 902n to some or all of the first plurality of outputs 906a to 906c. Similarly, the second multiplexer 914 includes a second plurality of outputs 916a to 916c, which includes three outputs (e.g., a first output 916a, a second output 916b, and a third output 916c). Depending on the selection of the light source used to generate the light (and the selection of the generated wavelength in the case of a tunable light source), the second multiplexer 904 can route the light generated by the second plurality of light sources 922a to 922n to some or all of the second plurality of outputs 916a to 916c.

[0238] In some cases, the light source unit 901 may include one or more wavelength locking units such as described herein. In some variations, the light source unit 901 includes a set of one or more wavelength locking units that are not shared between the first multiplexer and the second multiplexer 904, 914, such as described herein with respect to Figure 8B Additionally or alternatively, the light source unit 901 may include a set of one or more wavelength locking units shared between the first multiplexer and the second multiplexer 904, 914. For example, Fig. 9A In the illustrated variation, the light source unit 901 includes a first wavelength locking unit 908a, a second wavelength locking unit 908b, and a third wavelength locking unit 908c. The first wavelength locking unit 908a is optically connected to the first output 906a of the first multiplexer 904 and the first output 916a of the second multiplexer 914. Similarly, the second wavelength locking unit 908b is optically connected to the second output 906b of the first multiplexer 904 and the second output 916b of the second multiplexer 914, and the third wavelength locking unit 908c is optically connected to the third output 906c of the first multiplexer 904 and the third output 916b of the second multiplexer 914.

[0239] In this manner, each of the first wavelength locking unit 908a, the second wavelength locking unit 908b, and the third wavelength locking unit 908c can receive light from the first multiplexer 904 or the second multiplexer 914 depending on which multiplexer is currently outputting light. If the first multiplexer 904 is emitting light along its first output 906a, the first wavelength locking unit 908a can be used to control a corresponding light source in the first plurality of light sources 902a to 902n. Similarly, if the second multiplexer 914 is emitting light along its first output 916a, the first wavelength locking unit 908a can be used to control a corresponding light source in the second plurality of light sources 922a to 922n. In some cases, light received by the first wavelength locking unit 908a can first pass through the first coupler 907a, such as described in more detail herein. Similarly, light received by the second wavelength locking unit 908b can pass through the second coupler 907b, and light received by the third wavelength locking unit 908c can first pass through the third coupler 907c.

[0240] In some variations, the switch network 930 may include Fig. 7A 730. The switch network 730 may include a first controllable switch 734, a second controllable switch 736, and a third controllable switch 738 as described herein. Specifically, the first controllable switch 734 may receive light from the first waveguide 733a at a first input of the first controllable switch 734, and may receive light from the second waveguide 733b at a second input of the first controllable switch 734. The switch network 730 may be configured to combine light from the first plurality of wavelengths into the first waveguide 733a. For example, in some variations, the switch network 930 may include a switch that may be configured as described herein with respect to Figure 4A The passive optical combiner 400 of FIG. 1 is configured as described above to combine light from the first output 906a, the second output 906b, and the third output 906c of the first multiplexer 904 into the first waveguide 733a. Similarly, the switch network 930 may include a first passive optical combiner 932a configured as described herein with respect to the passive optical combiner 400. Figure 4A The passive optical combiner 400 described in the embodiment of the present invention is configured to combine the light from the first output 916a, the second output 916b and the third output 916c of the second multiplexer 914 into the second waveguide 733b. In other variations, the switch network 930 may utilize one or more multiplexing photonic switches to combine the light from the first multiplexer 904 into the first waveguide 733a and / or to combine the light from the second multiplexer 914 into the second waveguide 733b, such as described herein with respect to Figure 6B The switching network 640 is described.

[0241] Fig. 9BAnother variation of a switch network 950 is shown, which has multiple outputs 740a to 740d and can be connected to Fig. 9A The photonic integrated circuit 900 may be used together with (e.g., in place of the switch network 930) to route the light generated by the light source unit 901 to a common selection of the plurality of outputs 740a to 740d. Specifically, the switch network 950 may include a first multiplexing photonic switch 752a, a second multiplexing photonic switch 752b, a first controllable switch 754a, and a second controllable switch 754b, such as those described herein with respect to Figure 7B As described above with respect to the switch network 731 of FIG. 1 , light received by the first multiplexed photonic switch 752a may be selectively routed to a selection of the plurality of outputs 740a to 740d via the first controllable switch 754a and / or the second controllable switch 754b. Similarly, light received by the second multiplexed photonic switch 752b may be selectively routed to a selection of the plurality of outputs 740a to 740d via the first controllable switch 754a and / or the second controllable switch 754b.

[0242] The first multiplexing photonic switch 752a may be configured to receive the first plurality of outputs 906a to 906c of the first multiplexer 904 as corresponding inputs to the switching network 950. Fig. 9B Specifically, the switch network 950 also includes a first combiner 952a configured to combine light from the first output 906a and the second output 906b of the first multiplexer 904 into a first common waveguide 953a. In some variations, the first combiner 952a may be an interferometer, such as Figure 4A The first interferometer 410a of the passive optical combiner 400. In other variations, the first combiner 952a can be a multiplexing photonic switch, such as the one described herein. Figures 5A to 5C Those multiplexing photonic switches described.

[0243] The first multiplexed photonic switch 752a is optically connected to the third output 906c of the first multiplexer 904 and the first common waveguide 953a. In other words, the first multiplexed photonic switch has a first input for receiving light from the first combiner 952a and a second input for receiving light from the third output 906c. In the case where a plurality of the first plurality of outputs 906a to 906c simultaneously emit light of different wavelengths, the first multiplexed photonic switch 752a may simultaneously receive different wavelengths at each of its inputs (e.g., when the first output 906a or the second output 906b is emitting light together with the third output 906c) or may simultaneously receive light of multiple wavelengths at one of its inputs (e.g., when the first output 906a and the second output 906b are emitting light at the same time).

[0244] Similarly, the second multiplexing photonic switch 752b may be configured to receive from the second plurality of outputs 916a to 916c (i) of the second multiplexer 914 as corresponding inputs to the switch network 950. Fig. 9B Specifically, the switch network 950 also includes a second combiner 952b configured to combine light from the first output 916a and the second output 916b of the second multiplexer 914 into a second common waveguide 953b. In some variations, the second combiner 952b may be an interferometer, such as Figure 4A The first interferometer 410a of the passive optical combiner 400. In other variations, the second combiner 952b can be a multiplexing photonic switch, such as the one described herein with respect to Figures 5A to 5C Those multiplexing photonic switches described.

[0245] The second multiplexed photonic switch 752b is optically connected to the third output 916c of the second multiplexer 914 and the second common waveguide 953b. In other words, the second multiplexed photonic switch 752b has a first input that receives light from the second combiner 952b and a second input that receives light from the third output 916c. In the case where multiple outputs of the second plurality of outputs 916a to 916c simultaneously emit light of different wavelengths, the second multiplexed photonic switch 752b may simultaneously receive different wavelengths at each of its inputs (e.g., when the first output 916a or the second output 916b is emitting light together with the third output 916c) or may simultaneously receive multiple wavelengths of light at one of its inputs (e.g., when the first output 916a and the second output 916b are emitting light simultaneously). In some variations, the switch network may include multiple VOAs corresponding to the first plurality of outputs 906a to 906c and / or the second plurality of outputs 916a to 916c, such as with respect to Figure 6B The switching network 640 is discussed above.

[0246] In some variations, as part of a spectral measurement, the optical measurement system described herein can be used to perform one or more series of coded measurements using coded multiplexing techniques. The optical measurement system is configured to, for each coded measurement in the coded measurement series, emit light having a corresponding wavelength subset selected from a set of target wavelengths from an emission site. Each corresponding wavelength subset includes multiple wavelengths, so that the optical measurement system emits light including multiple wavelengths simultaneously from the emission site. During each coded measurement, the detector group measuring the returned light may not be able to distinguish between different wavelengths. However, the coded measurement series can be analyzed collectively to determine the relative intensity of the returned light for each target wavelength in the set of target wavelengths.

[0247] Specifically, a series of coded measurements may be performed according to a wavelength coding matrix. Fig.10 An example of a wavelength encoding matrix 1000 is shown, which can be used to perform a series of encoded measurements on a set of target wavelengths including three target wavelengths (e.g., a first target wavelength λ1, a second target wavelength λ2, and a third target wavelength λ3). The columns of the wavelength encoding matrix 1000 correspond to different wavelengths in the set of target wavelengths. For example, the first column corresponds to the first target wavelength λ1, the second column corresponds to the second target wavelength λ2, and the third column corresponds to the third target wavelength λ3. The rows of the wavelength encoding matrix 1000 correspond to different encoded measurements in the target measurement series. For example, the first row corresponds to the first encoded measurement, the second row corresponds to the second encoded measurement, and the third row corresponds to the third encoded measurement. It should be understood that the number of rows and / or columns of the wavelength encoding matrix 1000 may change with corresponding changes in the number of target wavelengths and / or encoded measurements.

[0248] Each matrix element of wavelength encoding matrix 1000 indicates whether a given target wavelength is transmitted during a given encoded measurement. Fig.10 In the example shown, each matrix element has a value of 0 or 1, where 0 indicates that the corresponding target wavelength is not transmitted during the corresponding encoded measurement, and 1 indicates that the corresponding target wavelength is transmitted during the corresponding encoded measurement. Fig.10 In an example of a wavelength encoding matrix 1000 of FIG. 1 , each encoded measurement may include a corresponding wavelength subset having two wavelengths selected from the set of target wavelengths. During a first encoded measurement, a first subset of target wavelengths (e.g., including a first target wavelength λ1 and a third target wavelength λ3) is simultaneously emitted by the optical measurement system. During a second encoded measurement, a different second subset (e.g., including a first target wavelength λ1 and a second target wavelength λ2) is simultaneously emitted by the optical measurement system. During a third encoded measurement, another third subset (e.g., including a second target wavelength λ2 and a third target wavelength λ3) is simultaneously emitted by the optical measurement system.

[0249] During each encoded measurement, the detector group may measure a corresponding intensity representing the relative amount of light for the corresponding subset of wavelengths returned to the optical measurement system. In general, the encoded measurement series may be associated with a corresponding plurality of measurement intensities, wherein each measurement intensity in the plurality of measurement intensities corresponds to a different encoded measurement. In some variations, the plurality of measurement intensities may be analyzed to generate a plurality of derived measurement intensities corresponding to the set of target wavelengths. In these cases, each derived measurement intensity represents an estimate of the intensity of light measured for a corresponding target wavelength in the set of wavelengths as part of the encoded measurement series.

[0250] use Fig.10As an example of wavelength encoding matrix 1000, a first encoded measurement may be associated with a first measurement intensity (e.g., the first measurement intensity represents the combined amount of the first target wavelength λ1 and the third target wavelength λ3 measured by the detector group during the first encoded measurement). Similarly, a second encoded measurement may be associated with a second measurement intensity (e.g., the second measurement intensity represents the combined amount of the first target wavelength λ1 and the second target wavelength λ2 measured by the detector group during the second encoded measurement), and a third encoded measurement may be associated with a third measurement intensity (e.g., the third measurement intensity represents the combined amount of the second target wavelength λ2 and the third target wavelength λ3 measured by the detector group during the third encoded measurement). The first measurement intensity, the second measurement intensity, and the third measurement intensity may be analyzed to generate a first derived measurement intensity representing the intensity of light measured for the first target wavelength λ1, a second derived measurement intensity representing the intensity of light measured for the second target wavelength λ2, and a third derived measurement intensity representing the intensity of light measured for the third target wavelength λ 3- The third derived measured intensity of the intensity of the measured light. Using the coded measurements to generate the derived measured intensities can allow for faster overall measurements for a given level of SNR (or a higher SNR for a given measurement time) compared to an example of directly measuring the intensity of the set of target wavelengths by sequentially transmitting the target wavelengths (e.g., a first measurement transmitting only the first target wavelength λ1, a second measurement transmitting only the second target wavelength λ2, and a third measurement transmitting only the third target wavelength λ3).

[0251] The derived measurement intensities may be calculated in any suitable manner. In some cases, the plurality of measurement intensities may be decoded to generate the plurality of derived measurement intensities. For example, a decoding matrix may be used that may be the inverse of a wavelength encoding matrix (e.g., wavelength encoding matrix 1000) to generate the derived measurement intensities. In these cases, the plurality of derived measurement intensities may be generated by performing a dot product between the measurement intensities of the encoded measurement series and the decoding matrix.

[0252] The optical measurement systems described herein may be configured such that during an coded measurement, light emitted from an emission site is emitted from an emission group of a photonic integrated circuit. In some of these variations, a light source unit including a multi-output mid-step grating multiplexer as described herein may be used to simultaneously generate multiple wavelengths of light that are emitted as part of the coded measurement. For example, the optical measurement system may include a photonic integrated circuit and a detector group, such as described in more detail herein. The photonic integrated circuit includes a light source unit and an emission group, the emission group being optically coupled to the light source unit and configured to emit light received from the light source unit. The light source unit may include a plurality of light sources, a mid-step grating multiplexer including a plurality of inputs and a plurality of outputs, the mid-step grating multiplexer being positioned to receive light from the plurality of inputs (such as described herein with respect to FIG. 3B to FIG. 3KEach of the plurality of light sources is connected to a corresponding input of the plurality of inputs. In some variations, the light source unit may include a plurality of light sources and a plurality of multiplexers, such as described herein. Fig. 9A Depicted light source unit 901. In some of these variations, different pluralities of light sources (and their corresponding multiplexers) may be used to perform different series of encoded measurements.

[0253] The optical measurement system may also include a controller configured to perform one or more series of encoded measurements using the light source unit, the emission group, and the detector group. Fig.11 A method 1100 of performing spectral measurements comprising one or more series of encoded measurements is depicted. For purposes of illustration, a method comprising Figure 3B A variation of the optical measurement system of the light source unit 321 of the photonic integrated circuit 320 is discussed below. Fig.11 It should be understood that a controller of the optical measurement system (eg, controller 212 ) may control various components of the optical measurement system to perform the steps of method 1100 .

[0254] At step 1110, the optical measurement system performs a first series of coded measurements for the first set of wavelengths to generate a first plurality of coded measurement intensities. For each coded measurement in the first series of coded measurements, the optical measurement system is configured to simultaneously generate light of a corresponding subset of the first set of wavelengths at step 1112. Each subset may include a corresponding plurality of wavelengths selected from the first set of wavelengths. The wavelengths generated during the first series of coded measurements may be encoded using a first encoding matrix (such as described herein with respect to Fig.10 The wavelength coding matrix 1000 described above is determined.

[0255] For example, in some variations, the first set of wavelengths includes three wavelengths (e.g., a first wavelength, a second wavelength, and a third wavelength), and the first series of coded measurements includes three coded measurements (e.g., a first coded measurement, a second coded measurement, and a third coded measurement). In these variations, each coded measurement in the first series of coded measurements includes a different subset of the first set of wavelengths. For example, the first wavelength and the second wavelength may be generated simultaneously during the first coded measurement, the first wavelength and the third wavelength may be generated simultaneously during the second coded measurement, and the second wavelength and the third wavelength may be generated simultaneously during the third coded measurement.

[0256] The first set of wavelengths may be generated by corresponding light source groups of light source unit 321 such that each subset of the first set of wavelengths is simultaneously generated at a corresponding subset of multiple outputs 316a to 316c of the echelle multiplexer 314. For example, in some variations where the first set of wavelengths includes three wavelengths, the first light source groups 302a to 302c may generate these wavelengths. In this manner, light of a first wavelength generated by light source 302a is routed to the first output 316a of the echelle multiplexer 314, light of a second wavelength generated by light source 302b is routed to the second output 316b of the echelle multiplexer 314, and light of a third wavelength generated by light source 302c is routed to the third output 316c of the echelle multiplexer 314.

[0257] In these cases, each encoded measurement in the first series of encoded measurements is associated with a different corresponding subset of the plurality of outputs 316a to 316c of the echelle multiplexer 314, such that two of the plurality of outputs 316a to 316c will simultaneously output light during each encoded measurement. Using the above example, during the first encoded measurement, light of a first wavelength is generated at the first output 316a and light of a second wavelength is generated at the second output 316b. Similarly, during the second encoded measurement, light of a first wavelength is generated at the first output 316a and light of a third wavelength is generated at the third output 316c. During the third encoded measurement, light of a second wavelength is generated at the second output 316b and light of a third wavelength is generated at the third output 316c.

[0258] For each encoded measurement in the first series of encoded measurements, the optical measurement system is configured to, at step 1114, obtain a measurement from the emission group (eg, Figure 3B The emission group 312a) of the emission group set 312a to 312d of the photonic integrated circuit 320 simultaneously emits light of a corresponding subset of the first set of wavelengths. For example, a switching network such as the switching network 330 can route the light to the emission groups, as described in more detail herein. Similarly, light of corresponding multiple wavelengths simultaneously emitted from the emission groups can be simultaneously emitted from the optical measurement system via the emission sites, so that corresponding areas of the sample simultaneously receive the corresponding multiple wavelengths.

[0259] The light generated at the corresponding subset of the multiple outputs 316a to 316c of the echelle multiplexer 314 can be routed to the emission groups in any manner as described herein. For example, a passive optical combiner (such as described herein with respect to Figure 4A and Figure 4BThe optical measurement system (described) may optically couple multiple outputs 316a to 316c of the mid-step grating multiplexer 314 to a common waveguide, which in turn may be optically connected to the emission groups. Additionally or alternatively, in some variations, the optical measurement system includes a switching network (e.g., switching network 310) that optically connects multiple outputs 316a to 316c of the mid-step grating multiplexer 314 to the emission groups. To the extent that the switching network 310 is operable to selectively route light between a set of emission groups (e.g., the set of emission groups 312a to 312d), the switching network 310 may be controlled (e.g., via a controller) to route light generated by the light source unit 321 to at least the emission group. In some cases, the light generated by the light source unit 321 may be split between multiple emission groups during a first series of coded measurements. This may allow the optical measurement system to perform multiple coded measurements for different regions of the sample simultaneously.

[0260] During each coded measurement in the first series of coded measurements, at step 1116, the detector group can measure the return light received during the simultaneous emission of the corresponding plurality of wavelengths. The detector group can generate a corresponding coded measurement intensity in the first plurality of coded measurement intensities. The coded measurement intensity represents the amount of light of the corresponding plurality of wavelengths measured during the coded measurement. As discussed in more detail herein, at least a portion of the corresponding plurality of wavelengths emitted from the optical measurement system can return to the optical measurement system after interacting with the sample, and the detector group can measure the return light.

[0261] For example, the first plurality of coded measurements includes a first coded measurement intensity that corresponds to the first coded measurement and represents the amount of returned light of the first wavelength and the second wavelength measured simultaneously by the detector group during the first coded measurement. The first plurality of coded measurements also includes a second coded measurement intensity corresponding to the second coded measurement (e.g., representing the amount of returned light of the first wavelength and the third wavelength measured simultaneously by the detector group) and a third coded measurement intensity corresponding to the third coded measurement (e.g., representing the amount of returned light of the second wavelength and the third wavelength measured simultaneously by the detector group).

[0262] Although Fig.11The first series of coded measurements of the method is discussed herein as generating a single plurality of coded measurement intensities, but it should be understood that in some variations, the first series of coded measurements may generate a variety of multiple coded measurements. For example, where the detector group includes multiple detector elements, each detector element is capable of generating a different coded measurement intensity during the coded measurement. Therefore, as part of the first series of coded measurements, the detector group may generate corresponding multiple coded measurement intensities for each detector element. For example, a first detector element may generate a first plurality of coded measurement intensities for a first series of coded measurements (e.g., including a first coded measurement intensity measured by the first detector element during the first coded measurement, a second coded measurement intensity measured by the first detector element during the second coded measurement, and so on). Similarly, a second detector element may generate a second plurality of coded measurement intensities for a second series of coded measurements (e.g., including a first coded measurement intensity measured by the second detector element during the first coded measurement, a second coded measurement intensity measured by the second detector element during the second coded measurement, and so on).

[0263] Once the first plurality of encoded measurement intensities have been generated, the optical measurement system may decode the first plurality of encoded measurement intensities at step 1120 to generate a corresponding derived measurement intensity for each wavelength in the first set of wavelengths. For example, a first plurality of derived measurement intensities may be generated that includes a first derived measurement intensity for a first wavelength, a second derived measurement intensity for a second wavelength, and a third derived measurement intensity for a third wavelength. These derived measurement intensities may be used together with other derived measurement intensities or measured intensities generated during spectral measurements to determine one or more properties of the sample being measured. It should be understood that where multiple pluralities of encoded measurement intensities are generated by multiple detector elements of a detector group, each plurality of encoded measurement intensities may be decoded to generate a corresponding plurality of derived measurement intensities for the first set of wavelengths.

[0264] In some variations, method 1100 may include performing one or more additional series of coded measurements for different sets of wavelengths. For example, at step 1130, the optical measurement system performs a second series of coded measurements for a second set of wavelengths to generate a second plurality of coded measured intensities. At least one wavelength in the second set of wavelengths may be different from a wavelength in the first set of wavelengths. In some variations, each wavelength in the second set of wavelengths is different from a wavelength in the first set of wavelengths, such that the first set of wavelengths and the second set of wavelengths do not share any common wavelengths.

[0265] For each encoded measurement in the second series of encoded measurements, the optical measurement system is configured to simultaneously generate light of a corresponding subset of the second set of wavelengths at step 1132. Each subset may include a corresponding plurality of wavelengths selected from the second set of wavelengths. The wavelengths generated during the first series of encoded measurements may be encoded using a second encoding matrix (such as described herein with respect to Fig.10 The wavelength coding matrix 1000 described above is determined.

[0266] For example, in some variations, the second set of wavelengths includes three wavelengths (e.g., a fourth wavelength, a fifth wavelength, and a sixth wavelength, which may each be different from a corresponding wavelength in the first set of wavelengths), and the second series of coded measurements includes three coded measurements (e.g., a first coded measurement, a second coded measurement, and a third coded measurement). In these variations, each coded measurement in the second series of coded measurements includes a different subset of the second set of wavelengths. For example, the fourth wavelength and the fifth wavelength may be generated simultaneously during the first coded measurement of the second series, the fourth wavelength and the sixth wavelength may be generated simultaneously during the second coded measurement of the second series, and the fifth wavelength and the sixth wavelength may be generated simultaneously during the third coded measurement of the second series.

[0267] The second set of wavelengths may be generated by a corresponding light source group of light source unit 321 such that each subset of the second set of wavelengths is simultaneously generated at a corresponding subset of the plurality of outputs 316a to 316c of the echelle multiplexer 314. For example, in some variations where the second set of wavelengths includes three wavelengths, the second light source groups 302d to 302f may generate these wavelengths. In this manner, light of a fourth wavelength generated by light source 302d is routed to the first output 316a of the echelle multiplexer 314, light of a fifth wavelength generated by light source 302e is routed to the second output 316b of the echelle multiplexer 314, and light of a sixth wavelength generated by light source 302f is routed to the third output 316c of the echelle multiplexer 314.

[0268] In these cases, each encoded measurement in the second series of encoded measurements is associated with a different corresponding subset of the plurality of outputs 316a to 316c of the echelle multiplexer 314, such that two of the plurality of outputs 316a to 316c will simultaneously output light during each encoded measurement. Using the above example, during the first encoded measurement of the second series, light of a fourth wavelength is generated at the first output 316a and light of a fifth wavelength is generated at the second output 316b. Similarly, during the second series of second encoded measurements, light of a fourth wavelength is generated at the first output 316a and light of a sixth wavelength is generated at the third output 316c. During the third encoded measurement of the second series, light of a fifth wavelength is generated at the second output 316b and light of a sixth wavelength is generated at the third output 316c.

[0269] For each coded measurement in the second series of coded measurements, the optical measurement system is configured to simultaneously emit light of a corresponding subset of the second set of wavelengths from the emission group at step 1134. Similarly, light of corresponding multiple wavelengths emitted simultaneously from the emission group can be simultaneously emitted from the optical measurement system via the emission sites so that corresponding areas of the sample measured by the first series are also measured by the second series. Light can be routed between the light source unit 321 and the emission group in the same manner as described herein with respect to step 1114. It should be understood that different emission groups, emission sites, and detector groups can also be used to perform additional series of coded measurements as part of spectral measurements.

[0270] During each coded measurement in the second series of coded measurements, at step 1136, the detector group may measure the return light received during the simultaneous emission of the corresponding multiple wavelengths. The detector group may generate corresponding coded measurement intensities in the second plurality of coded measurement intensities, such as described with respect to step 1116. For example, the second plurality of coded measurements includes a first coded measurement intensity that corresponds to the first coded measurement of the second series and represents the amount of return light at the fourth wavelength and the fifth wavelength simultaneously measured by the detector group during the first coded measurement of the second series. The second plurality of coded measurements also includes a second coded measurement intensity corresponding to the second coded measurement of the second series (e.g., representing the amount of return light at the fourth wavelength and the sixth wavelength simultaneously measured by the detector group) and a third coded measurement intensity corresponding to the third coded measurement of the second series (e.g., representing the amount of return light at the fifth wavelength and the sixth wavelength simultaneously measured by the detector group). Although Fig.11 The second series of coded measurements of the method are discussed herein as generating a single plurality of coded measurement intensities, but it should be understood that in some variations the second series of coded measurements may generate a plurality of plurality of coded measurements, as described in more detail herein.

[0271] Once the second plurality of encoded measurement intensities have been generated, the optical measurement system may decode the second plurality of encoded measurement intensities at step 1140 to generate a corresponding derived measurement intensity for each wavelength in the second set of wavelengths. For example, a second plurality of derived measurement intensities may be generated including a first derived measurement intensity for a fourth wavelength, a second derived measurement intensity for a fifth wavelength, and a third derived measurement intensity for a sixth wavelength. These derived measurement intensities may be used together with other derived measurement intensities or measured intensities generated during spectral measurements to determine one or more properties of the sample being measured. It should be understood that where multiple pluralities of encoded measurement intensities are generated by multiple detector elements of a detector group during the second series of encoded measurements, each plurality of encoded measurement intensities may be decoded to generate a corresponding plurality of derived measurement intensities for the second set of wavelengths.

[0272] It should be understood that when the optical measurement system performs multiple series of encoded measurements as part of the spectral measurement, the set of encoded measurements can be performed in any suitable order. Using method 1100 as an example, in some variations, the first series of encoded measurements can be completely performed before starting the second series of encoded measurements. In other words, all encoded measurements in the first series of encoded measurements can be performed before performing the first encoded measurement in the second series of encoded measurements. In other variations, one or more encoded measurements in the second series of encoded measurements can be interleaved with encoded measurements in the first series of encoded measurements. For example, the optical measurement system can perform at least a first group (e.g., one or more) of encoded measurements and a second group (e.g., one or more) of encoded measurements as part of the first series of encoded measurements. The optical measurement system can perform at least one measurement in the second series of encoded measurements between i) performing the first group of encoded measurements in the first series of encoded measurements and ii) performing the second group of encoded measurements in the second series of encoded measurements. Similarly, one or more encoded measurements in the first series of encoded measurements can be interleaved with encoded measurements in the second series of encoded measurements. In one example, the optical measurement system may alternate between the first series and the second series of encoded measurements.Regardless of the order in which the individual encoded measurements are performed, the optical measurement system may individually process the multiple encoded measurement intensities generated by the different series of encoded measurements.

[0273] Although the light source unit (such as Figure 3B The light source unit 321 of the embodiment of the present invention may be capable of emitting light of multiple different combined wavelengths simultaneously, but in some cases, it may be desirable that the wavelength groups associated with a series of encoded measurements have wavelengths that are relatively close in wavelength. Therefore, in some variations, for the wavelength groups associated with a series of encoded measurements, the adjacent wavelengths within the group may be separated by less than a threshold amount. For example, the adjacent wavelengths in the first group of wavelengths may be separated by less than a threshold amount (e.g., the first wavelength and the second wavelength are separated by less than a threshold amount, and the second wavelength and the third wavelength are separated by less than a threshold amount). Additionally or alternatively, the adjacent wavelengths in the second group of wavelengths may be separated by less than a threshold amount (e.g., the fourth wavelength and the fifth wavelength are separated by less than a threshold amount, and the fifth wavelength and the sixth wavelength are separated by less than a threshold amount). In some variations, the threshold amount is 15 nanometers. In some of these variations, the threshold amount is 10 nanometers.

[0274] Reducing the wavelength difference between wavelengths in a set of wavelengths can reduce the impact of wavelength-related changes that may occur to the light generated by the light source unit 321. For example, in some variations, the emission group is associated with multiple emitters so that the multiple emitters emit corresponding multiple overlapping light beams that collectively form a larger total light beam. In some of these variations, the photonic integrated circuit may include a phase shifter array that can be controlled to change the relative phase of the light emitted by the multiple emitters, such as described in U.S. Patent Publication No. US2024 / 0102856A1, filed on August 16, 2023 and entitled "Despeckling in Optical Measurement Systems", which is incorporated herein by reference in its entirety. Changing the relative phase of the light emitted by the individual emitters of the emission group can reduce the speckle noise associated with a given measurement. When these phase changes are applied during the coded measurement, it can be expected that each wavelength emitted simultaneously will experience a similar phase shift (and thereby similarly reduce speckle noise). It may therefore be desirable to use relatively closely spaced wavelengths during a series of encoded measurements as this may reduce the effects of the wavelength dependence of the phase shift provided by the phase shifter array.

[0275] When the light source unit includes a light source configured to emit multiple wavelengths, a group of wavelengths used in a series of coded measurements is selected as the immediately adjacent wavelengths in the multiple wavelengths. For example, the first group of wavelengths described for the first series of measurements is generated by the first light source group 302a to 302c emitting immediately adjacent wavelengths in multiple light sources 302a to 302m. Similarly, the second group of wavelengths described for the second series of measurements is generated by the second light source group 302d to 302f emitting immediately adjacent wavelengths in multiple light sources 302a to 302m.

[0276] Additionally, when the first group of wavelengths and the second group of wavelengths have a common number of wavelengths (e.g., three wavelengths), the wavelengths in the first group may be separated by a common set of frequency differences. This may facilitate routing each group of light sources to the same set of outputs of the mid-step grating multiplexer, as described in more detail herein. For example, the first group of wavelengths of the first series of coded measurements may be selected so that the light of the first wavelength and the light of the second wavelength are separated by a first frequency difference, and the light of the second wavelength and the light of the third wavelength are separated by a second frequency difference. The second group of wavelengths of the second series of coded measurements may be selected so that the light of the fourth wavelength and the light of the fifth wavelength are separated by a first frequency difference, and the light of the fifth wavelength and the light of the sixth wavelength are separated by a second frequency difference. In some variations, the first common frequency difference may be the same as the second common frequency difference.

[0277] In some variations, the intensity of light emitted from the emission group as part of the coded measurement may vary. For example, local temperature changes around a light source may result in corresponding changes in the output power of the light generated by the light source. Although the optical measurement system may be configured to correct for these changes, it may be desirable to understand how much the output power of the light emitted by the optical measurement system has fluctuated during the course of the coded measurement. Therefore, in some variations, the optical measurement system may include a reference detector configured to generate a reference signal representing the intensity of the light emitted by the optical measurement system during the measurement.

[0278] Fig.12 A variation of an optical measurement system 1200 including a reference detector 1210 is shown. As shown, the optical measurement system 1200 includes a photonic integrated circuit 1202 and a detector group 1208. The photonic integrated circuit 1202 includes a light source unit 1204 and an emission group 1206 optically connected to the light source unit 1204. The photonic integrated circuit 1202 is operable to generate light via the light source unit 1204 and emit a light beam (referred to herein as "emission light beam 1212") from the emission group 1206. At least a portion of the emission light beam 1212 can exit the optical measurement system 1200 through the sampling interface 1207 (e.g., via an emission region of the sampling interface 1207). Fig.12 Also shown is a sample 1201 positioned in contact with the sampling interface 1207. The optical measurement system 1200 can be configured such that when the optical measurement system 1200 emits the emission beam 1212 while the sample 1201 is positioned in contact with the sampling interface 1207, a portion of the input beam 1212 will return to the optical measurement system 1200 as a beam (referred to herein as a "collection beam 1214") after interacting with the sample 1201. The collection beam 1214 can be measured by the detector group 1208 (e.g., as an output signal as described herein), and the intensity of the collection beam 1214 can depend at least in part on the intensity of the emission beam 1212 and the properties of the sample 1201.

[0279] The reference detector 1210 is configured to measure a portion of the light generated by the light source unit 1204 before it leaves the optical measurement system 1200 as an emission beam 1212. Fig.12In the illustrated variation, optical measurement system 1200 includes a beam splitter 1211 configured to split a portion of light (referred to herein as "reference beam 1216") from emission beam 1212. After being split from emission beam 1212, reference beam 1216 is directed to and measured by reference detector 1210. There may be a predetermined relationship between the intensity of reference beam 1216 and the intensity of emission beam 1212, such that an output signal generated by reference detector 1210 may be used to determine the intensity of light introduced into sample 1201 (e.g., the intensity of emission beam 1212) during a spectral measurement. Although in Fig.12 1200 as measuring light after it has been emitted from the photonic integrated circuit 1202, but the reference detector 1210 may alternatively be positioned to measure light before the light has left the photonic integrated circuit 1202. In these cases, the output signal generated by the reference detector 1210 may still be indicative of the intensity of the emission light beam 1212 as it leaves the optical measurement system, but the reference detector 1210 may not be able to directly account for downstream components that may affect the intensity of the light emitted from the optical measurement system 1200.

[0280] For a given individual measurement, detector group 1208 may generate one measured intensity (or multiple measured intensities if detector group 1208 includes multiple detector elements), and reference detector 1210 may be used to generate one reference intensity (or multiple reference intensities if reference detector 1210 includes multiple detector elements). Because the reference intensity represents the intensity of light generated during the individual measurement (which may vary from measurement to measurement), the optical measurement system 1200 may use the corresponding reference and measured intensities to generate a reference-corrected measured intensity for the individual measurement. The reference-corrected measured intensity may be a normalized value representing a relative percentage of light that is returned to the optical measurement system as a collection beam 1214, and may therefore account for fluctuations in the intensity of the emission beam 1212 during the individual measurement and / or between different individual measurements. The reference-corrected measured intensity may be calculated using any suitable reference correction technique that will be readily understood by one of ordinary skill in the art.

[0281] When multiple wavelengths of light are simultaneously emitted from the photonic integrated circuit 1202 during an encoded measurement, the reference beam 1216 will include multiple wavelengths of light simultaneously. As with the detector group 1208, the reference detector 1210 may not be able to distinguish between the different wavelengths contained in the reference beam 1216. Therefore, the reference detector 1210 may not be able to distinguish whether a given intensity change of the reference beam 1216 is the result of an intensity change at a particular wavelength or a result of a particular combination of corresponding intensity changes at multiple wavelengths. This can affect the ability of the optical measurement system 1200 to accurately perform reference corrections for encoded measurements.

[0282] Fig.13 A method 1300 of performing spectral measurements including a series of encoded measurements that are reference corrected is depicted. At step 1302, an optical measurement system performs a series of encoded measurements on a set of wavelengths to generate a plurality of encoded measurement intensities and a plurality of encoded reference intensities. Fig.12 The series of coded measurements may be performed using the photonic integrated circuit, reference detector, and detector group described in the optical measurement system 1200 of the present invention. For example, during each coded measurement, a photonic integrated circuit (e.g., photonic integrated circuit 1202) may emit an emission beam that is simultaneously directed toward the sample. When the photonic integrated circuit emits the emission beam, the detector group (e.g., detector group 1208) may measure the collection beam returned from the sample to generate a corresponding coded measurement intensity in a plurality of coded measurement intensities. Similarly, when the photonic integrated circuit is emitting the emission beam, a reference detector (e.g., reference detector 1210) may measure a portion of the emission beam emitted by the photonic integrated circuit (e.g., reference beam 1216) to generate a corresponding coded reference intensity in a plurality of coded reference intensities. It should be understood that the coded measurements may be performed as described herein with respect to Fig.11 The series of encoded measurements may be performed in any suitable manner as described by method 1100.

[0283] The wavelengths generated during the series of encoded measurements can be determined using a corresponding encoding matrix, such as described herein with respect to Fig.10 As described by the wavelength encoding matrix 1000 of FIG. 1 , because the detector group and the reference detector measure light of the same wavelength during each encoded measurement, the plurality of encoded measurement intensities and the plurality of encoded reference intensities will be encoded according to the same encoding matrix.

[0284] Once the plurality of encoded measurement intensities have been generated, the optical measurement system may decode the plurality of encoded measurement intensities to generate a corresponding derived measurement intensity for each wavelength in the set of wavelengths at step 1304. For example, where the set of wavelengths includes three wavelengths, the plurality of derived measurement intensities may include a first derived measurement intensity for a first wavelength, a second derived measurement intensity for a second wavelength, and a third derived measurement intensity for a third wavelength.

[0285] Similarly, once the plurality of encoded reference intensities have been generated, the optical measurement system may decode the plurality of encoded reference intensities to generate a corresponding derived reference intensity for each wavelength in the set of wavelengths at step 1306. The encoded reference intensities may be decoded in the same manner as used to decode the encoded measurement intensities. Where the set of wavelengths includes three wavelengths, the plurality of derived reference intensities may include a first derived reference intensity for a first wavelength, a second derived reference intensity for a second wavelength, and a third derived reference intensity for a third wavelength.

[0286] At step 1308, the optical measurement system may generate a corresponding reference-corrected derived measurement intensity for each wavelength in the set of wavelengths using the corresponding derived measurement intensity and the corresponding derived reference intensity. By separately decoding the encoded measurement intensity and the encoded reference intensity, the optical measurement system may provide a more accurate reference correction for each wavelength in the set of wavelengths.

[0287] The above description uses specific nomenclature to provide a thorough understanding of the embodiments for explanation. However, it will be apparent to those skilled in the art that, after reading this specification, the embodiments can be practiced without specific details. Therefore, for the purpose of illustration and description, the foregoing description of the specific embodiments described herein is presented. They are not intended to be exhaustive or to limit the embodiments to the precise form disclosed. It will be apparent to those of ordinary skill in the art that, after reading this specification, many modifications and variations are possible in view of the above teachings.

Claims

1. A light source unit, comprising: an echelle multiplexer comprising a plurality of inputs and a plurality of outputs positioned to receive light from the plurality of inputs; as well as a plurality of light source groups, wherein each light source group is operable to emit a plurality of wavelengths, wherein each light source in the plurality of light source groups is connected to a corresponding input in the plurality of inputs, and the plurality of inputs are positioned such that: light generated by a first light source in each of the plurality of light source groups is routed to a first output in the plurality of outputs; and Light generated by a second light source in each of the plurality of light source groups is routed to a second output of the plurality of outputs. 2 . The light source unit of claim 1 , wherein the plurality of inputs are positioned such that light generated by a third light source in each of the plurality of light source groups is routed to a third output of the plurality of outputs.

3. The light source unit according to claim 1 or claim 2, wherein the plurality of light source groups include a first light source group; and the first light source and the second light source in the first light source group are connected to adjacent inputs in the plurality of inputs.

4. The light source unit according to claim 1 or claim 2, wherein the plurality of light source groups include a first light source group and a second light source group; A first light source in the first light source group is connected to a first input in the plurality of inputs; A second light source in the first light source group is connected to a second input in the plurality of inputs; A first light source in the second light source group is connected to a third input in the plurality of inputs; A second light source in the second light source group is connected to a fourth input in the plurality of inputs; and The third input is positioned between the first input and the second input.

5. The light source unit according to claim 1 or claim 2, wherein: The plurality of light source groups include a first light source group and a second light source group; The first light source in the first light source group and the first light source in the second light source group are positioned on a first laser chip, and The second light source in the first light source group and the second light source in the second light source group are positioned on a second laser chip.

6. The light source unit according to claim 1 or claim 2, wherein the first output is connected to a first wavelength locking unit and the second output is connected to a second wavelength locking unit.

7. The light source unit according to claim 6, wherein: wherein the plurality of inputs are positioned such that light generated by a third light source in each of the plurality of light source groups is routed to a third output in the plurality of outputs; and The third output is connected to a third wavelength locking unit. 8 . The light source unit according to claim 1 , wherein the first light source and the second light source in each of the plurality of groups generate light having a common frequency difference.

9. A light source unit, comprising: a first plurality of light sources operable to emit light at a first wavelength and a second wavelength, the first wavelength and the second wavelength being separated by less than a threshold amount; a second plurality of light sources operable to emit light at a third wavelength and a fourth wavelength, the third wavelength and the fourth wavelength being separated by less than the threshold amount; and A multiplexer, the multiplexer comprising: a first input positioned to receive light of the first wavelength emitted by the first plurality of light sources; a second input positioned to receive light of the second wavelength emitted by the first plurality of light sources; a third input positioned to receive light of the third wavelength emitted by the second plurality of light sources; a fourth input positioned to receive light at the fourth wavelength emitted by the second plurality of light sources; first output; and Second output, where: The multiplexer is configured to route light received from the first input and the third input to the first output; and The multiplexer is configured to route light received from the second input and the fourth input to the second output.

10. The light source unit according to claim 9, wherein the multiplexer is an echelle multiplexer.

11. The light source unit of claim 9, wherein the third output is positioned between the first input and the second output. 12 . The light source unit according to claim 11 , wherein the first wavelength is longer than the second wavelength.

13. The light source unit of claim 11, wherein the second input is positioned between the third input and the fourth input. 14 . The light source unit according to claim 9 , wherein the first plurality of light sources are positioned on a first laser chip, and the second plurality of light sources are positioned on a second laser chip.

15. The light source unit according to any one of claims 9 to 13, comprising: a first wavelength locking unit; as well as A second wavelength locking unit, wherein the first output is connected to the first wavelength locking unit and the second output is connected to the second wavelength locking unit.

16. A method of operating a light source unit, the method comprising: using a first plurality of light sources to simultaneously emit light of a first wavelength and light of a second wavelength during a first time period; receiving light at the first wavelength and light at the second wavelength at a multiplexer during the first time period; outputting light at the first wavelength from a first output of the multiplexer during the first time period; outputting light at the second wavelength from a second output of the multiplexer during the first time period; emitting light at a third wavelength and light at a fourth wavelength simultaneously using a second plurality of light sources during a second period of time; receiving the light at the third wavelength and the light at the fourth wavelength at the multiplexer during the second time period; outputting light at the third wavelength from the first output of the multiplexer during the second time period; as well as Light at the fourth wavelength is output from the second output of the multiplexer during the second period.

17. The method of claim 16, wherein the first wavelength of light is emitted from a first light source and the second wavelength of light is emitted from a second light source; and the first light source and the second light source are connected to adjacent inputs of the multiplexer.

18. The method of claim 16 or claim 17, wherein the first light source is positioned on a first laser chip; and the second light source is positioned on a second laser chip.

19. The method of claim 16, wherein the light of the first wavelength and the light of the second wavelength have a first frequency difference, and the light of the third wavelength and the light of the fourth wavelength have the first frequency difference.

20. The method of claim 16, wherein the first output is connected to a first wavelength locking unit and the second output is connected to a second wavelength locking unit.

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