Optical measurement system with multiple launch sites

Abstract

To provide optical measurement systems that can selectively output light to different sets of launch sites.SOLUTION: Various embodiments disclosed herein describe optical measurement systems for characterizing a sample. The optical measurement systems may selectively emit light from different numbers of launch groups, and may include a multi-stage optical switch network that may be controlled to route light to a desired number of launch groups. The optical measurement systems may further measure light using a corresponding number of detector groups. The optical measurement systems may perform measurement using a plurality of different wavelengths, where different groups of these wavelengths may be measured using different numbers of launch groups (and corresponding detector groups).SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The described embodiments generally relate to optical measurement systems. More specifically, the described embodiments describe an optical measurement system that can selectively output light to different sets of emission sites.

[0002] (Cross - reference to related applications) This application is non - provisional and claims the benefit under 35 U.S.C.§119(e) of U.S. Provisional Patent Application No. 63 / 323,721, filed on March 25, 2022, the content of which is incorporated herein by reference as if fully disclosed herein.

Background Art

[0003] Optical measurement systems can be used to identify the presence, type, and / or one or more characteristics of objects or substances in an environment surrounding the system. In some cases, an optical measurement system can perform spectroscopic 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 regarding the nature of the material being measured. As the number of wavelengths and the number of unique measurement positions measured by an optical measurement system each increase, these optical systems may require an increasingly complex architecture that can further increase the power consumption and / or measurement time required to perform the measurements. Thus, a compact, time - and power - efficient optical measurement system may be desired.

Summary of the Invention

[0004] An optical measurement system and method for determining one or more characteristics of a sample are described herein. In some of these embodiments, the optical measurement system includes a light source unit capable of generating light at any of a plurality of wavelengths, a multi-stage optical switching network optically connected to the light source unit and having a plurality of outputs, and a plurality of emission groups each optically connected to a corresponding output of the plurality of outputs. The optical measurement system further includes a plurality of detector groups and a controller configured to execute a measurement sequence using the light source unit, the multi-stage optical switching network, the plurality of emission groups, and the plurality of detector groups. The measurement sequence includes dividing the plurality of wavelengths into a plurality of groups, where each group of the plurality of groups is associated with a different corresponding output configuration, and performing a set of measurements for each wavelength of the plurality of wavelengths in the corresponding output configuration.

[0005] In some cases, the plurality of groups includes a first group associated with a first output configuration and a second group associated with a second output configuration. Performing a set of measurements for each wavelength of the plurality of wavelengths includes performing a first set of measurements for a first wavelength of the first group. Each measurement of the first set of measurements includes generating light of the first wavelength using the light source unit, emitting the generated light from a corresponding set of emission groups selected from the plurality of emission groups and having a first number of emission groups corresponding to the first output configuration, and measuring the return light received during the emission of the generated light using a corresponding set of detector groups selected from the plurality of detector groups and having the first number of detector groups.

[0006] The measurement of the set of measurements also includes performing a second set of measurements for a second wavelength of a second group. Each measurement of the second set of measurements includes generating light of the second wavelength using a light source unit, emitting the generated light from a corresponding set of emission groups selected from a plurality of emission groups and having a second number of emission groups corresponding to a second output configuration, and measuring the return light received during the emission of the generated light using a corresponding set of detector groups selected from a plurality of detector groups and having a second number of detector groups.

[0007] In some cases, the first set of measurements includes a plurality of measurements having different corresponding sets of emission groups and different corresponding sets of detector groups. Additionally or alternatively, each measurement of the first set of measurements includes configuring a multi-stage optical switching network to route light of the first wavelength to a corresponding set of emission groups. In some cases, each of these measurements further includes measuring the background light received prior to the emission of the generated light using a corresponding set of detector groups, whereby configuring the multi-stage optical switching network in each measurement of the first set of measurements is performed at least partially simultaneously with measuring the background light.

[0008] In other of these embodiments, the optical measurement system includes a light source unit capable of generating light at any of a plurality of wavelengths, a multi-stage optical switching network optically connected to the light source unit, and a plurality of emission groups. The multi-stage optical switching network includes a plurality of outputs, each of the plurality of outputs being optically connected to a corresponding emission group of the plurality of emission groups. Further, the multi-stage optical switching network is controllable to selectively route the light generated by the light source unit to a plurality of emission groups of different output configurations. In some cases, the multi-stage optical switching network includes a plurality of inputs.

[0009] In some variations, the optical measurement system further includes a photonic integrated circuit, and the photonic integrated circuit includes a light source unit, a multi-stage optical network, and a plurality of emission groups. In some of these variations, each emission group includes a corresponding outcoupler configured to emit light from the photonic integrated circuit. Additionally or alternatively, the optical measurement system further includes a plurality of detector groups and an interposer, and the photonic integrated circuit and the plurality of detector groups are mounted on the interposer.

[0010] Additionally or alternatively, the optical measurement system may include a first wavelength locking unit. In some of these variations, the multi-stage optical switch network includes a first stage and a second stage, and the first stage includes a first controllable switch. The first controllable switch includes a first tap, and the first wavelength locking unit is optically connected to the multi-stage optical switch network via the first tap. In some of these variations, the first stage also includes a second controllable switch having a second tap, and the second wavelength locking unit is optically connected to the multi-stage optical switch network via the second tap.

[0011] In other embodiments, a method of characterizing a sample includes selecting a plurality of wavelengths and performing a measurement sequence to generate a plurality of sets of output signals. The measurement sequence includes dividing the plurality of wavelengths into a plurality of groups, each group of the plurality of groups being associated with a different corresponding output configuration. The measurement sequence also includes performing a set of measurements of the sample for each wavelength of the plurality of wavelengths in the corresponding output configuration and generating, for each set of measurements, a corresponding set of output signals of the plurality of output signals. The method further includes determining one or more characteristics of the sample using the plurality of sets of output signals.

[0012] In some of these methods, the plurality of groups includes a first group associated with a first output configuration and a second group associated with a second output configuration. Performing a set of measurements of a sample for each wavelength of a plurality of wavelengths includes performing a first set of measurements of the sample for a first wavelength of the first group. Each measurement of the first set of measurements includes generating light of the first wavelength and emitting the generated light from a corresponding set of emission groups selected from a plurality of emission groups and having a first number of emission groups corresponding to the first output configuration. Each measurement also includes measuring the return light received during the emission of the generated light using a corresponding set of detector groups selected from a plurality of detector groups and having a first number of detector groups.

[0013] Performing a set of measurements of a sample for each wavelength of a plurality of wavelengths includes performing a second set of measurements of the sample for a second wavelength of the second group. Each measurement of the second set of measurements includes generating light of the second wavelength and emitting the generated light from a corresponding set of emission groups selected from a plurality of emission groups and having a second number of emission groups corresponding to the second output configuration. Each measurement also includes measuring the return light received during the emission of the generated light using a corresponding set of detector groups selected from a plurality of detector groups and having a second number of detector groups.

[0014] In some of these methods, the first set of measurements includes multiple measurements having different corresponding sets of emission groups and different corresponding sets of detector groups. Additionally or alternatively, each measurement of the first set of measurements further includes configuring a multi-stage optical switch network to route light generated at a first wavelength to a corresponding set of emission groups. In some of these methods, each measurement of the first set of measurements further includes measuring background light received prior to the emission of the generated light using a corresponding set of detector groups. In these cases, configuring the multi-stage optical switch network in each measurement of the first set of measurements is performed at least partially simultaneously with measuring the background light.

[0015] In other variations of these methods, the measurement sequence is divided into multiple sub-sequences. In some examples, each sub-sequence has a corresponding set of wavelengths of the multiple wavelengths and a corresponding set of emission groups selected from the multiple emission groups. Each sub-sequence includes measuring samples for each wavelength within the corresponding set of wavelengths, during which light of the wavelength is emitted from the corresponding set of emission groups.

[0016] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by referring to the drawings and considering the following description. The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements.

Brief Description of the Drawings

[0017]

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Embodiments for Carrying Out the Invention

[0018] The proportions and dimensions (whether relative or absolute) of the various features and elements (as well as their collections and subsets), and the boundaries, separation points, and positional relationships presented between them, are provided in the accompanying figures merely to facilitate the understanding of the various embodiments described herein, and thus may not necessarily be presented or illustrated to scale, and it should be understood that there is no intention to indicate any preference or requirement for the illustrated embodiments, excluding the embodiments described with reference thereto.

[0019] Terms indicating directions, such as "top", "bottom", "upper", "lower", "front", "back", "over", "under", "above", "below", "left", "right", "vertical", "horizontal", etc., are used with reference to the orientations of some components in some of the drawings described below and are not intended to be limiting. Since the components in various embodiments may be arranged in many different orientations, the terms indicating directions are used for illustrative purposes only and are not limiting in any sense. The terms indicating directions are intended to be broadly interpreted, and thus should not be construed as excluding components arranged in different manners. Also, as used herein, the phrase "at least one" preceding a series of items, together with the terms "and" or "or" separating any of the items, modifies the list as a whole rather than each element of the list. The phrase "at least one" 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, and / or at least one of any combination of the items, and / or at least one of each of 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 can be understood that the order of elements presented for a combined list or a separated list provided herein should not be construed as limited to that order in which the present disclosure is provided.

[0020] Here, representative embodiments illustrated in the accompanying drawings are described in detail. It should be understood that the following description is not intended to limit these embodiments to one preferred embodiment. On the contrary, the following description is intended to encompass alternative forms, modifications, and equivalents that can be included within the spirit and scope of the described embodiments as defined by the appended patent claims.

[0021] The following disclosure relates to embodiments of an optical measurement system having a plurality of emission sites and methods of performing measurements using these optical measurement systems. The optical measurement system can simultaneously route light to an adjustable number of emission groups (each associated with one or more emission sites), thereby enabling the optical system to perform a plurality of measurements, each using a different number of emission groups. In other words, a first set of measurements includes simultaneously emitting light from a first number of emission groups, and a second set of measurements includes simultaneously emitting light from a second number (different from the first number) of emission groups.

[0022] The optical measurement system may perform a measurement sequence using a plurality of wavelengths, and one set of individual measurements (e.g., at least one measurement) is performed for each wavelength of the plurality of wavelengths. In these cases, the plurality of wavelengths are divided into groups, each group being associated with a different number of emission groups (i.e., the light generated by the optical measurement system is divided). Thus, one set of individual measurements for a given wavelength is performed using some simultaneous emission groups that are set based on the group to which the wavelength is assigned.

[0023] When spectroscopic measurements are performed using a plurality of different wavelengths, there may be variations in signal quality depending on the wavelength. Depending on what is being measured by the optical measurement system (e.g., the type or characteristics of the sample being measured in the environment surrounding the optical measurement system), the signal-to-noise ratio ("SNR") for individual measurements at different wavelengths can be limited by different noise sources. For example, measurements of a sample taken at some wavelengths are limited by fundamental noise. In these cases, the SNR can be increased by increasing the amount of light introduced into the sample for these wavelengths. On the other hand, measurements made at other wavelengths may be limited by coherent noise. In these cases, the SNR is not improved by increasing the amount of light introduced into the sample at these wavelengths. The optical measurement system described herein can take into account different noise sources expected when measuring a sample and, accordingly, can select different measurement types for different wavelengths (as will be described in more detail below).

[0024] The optical measurement system described herein typically includes a light source unit, a multi-stage optical switching network, a plurality of emission groups, and a plurality of detector groups. The light source unit has one or more outputs and can generate light at any of a plurality of different wavelengths (including a corresponding set of wavelengths for each output of the light source unit). In other words, at any given point in time, the light source unit can be controlled to generate light at a wavelength selected from a plurality of different wavelengths (i.e., the plurality of different wavelengths do not need to be generated simultaneously).

[0025] The light source unit is optically connected to (i.e., capable of transmitting light to) a multi-stage optical switch network, thereby enabling the multi-stage optical switch network to receive light from the light source unit (e.g., via one or more outputs of the light source unit). The multi-stage optical switch network includes a plurality of outputs, each of which is optically connected to a corresponding emission group among the plurality of emission groups (it should be understood that the multi-stage optical switch network may include one or more additional outputs that are not optically connected to a corresponding emission group). The multi-stage optical switch network is controllable to selectively route light to some or all of its outputs (and thus to some or all of the plurality of emission groups), which may facilitate different measurement types as described herein. Each emission group is associated with a corresponding set of emission sites, and each emission site corresponds to a spatial position at which light is radiated externally from the optical measurement system (e.g., towards a sample). Overall, the optical measurement system can selectively emit light at different positions in a sample and may further select the number of different emission positions at which light is received simultaneously.

[0026] A plurality of detector groups measure light received by the optical measurement system (e.g., light radiated from the optical measurement system towards a sample and returned to the optical measurement system). The light measured by the plurality of detector groups may be analyzed to determine one or more characteristics of the environment surrounding the optical measurement system (e.g., the presence, type, and / or one or more characteristics of an object being measured by the optical measurement system), which are collectively referred to herein as the "sample". The light may be measured by the detector groups while the emission group is emitting light (to determine how the emitted light interacts with the sample), and optionally, while the emission group is not actively emitting light (to measure background light that can assist in a background correction operation).

[0027] For each measurement in a given measurement sequence, the optical measurement system controls the light source unit (e.g., via a controller) to generate light at the corresponding wavelength. The optical measurement system further controls a multi-stage optical switch network to route the light at that wavelength to a predetermined number of emission groups. The generated light is emitted from that set of emission groups (and thus may exit the optical measurement system), and a portion of it is returned to the optical measurement system (e.g., by interacting with a sample external to the optical measurement system). A corresponding set of detector groups measures the returned light received while the optical measurement system emits the generated light.

[0028] Embodiments of the optical measurement system described herein may be incorporated into a device having a housing. In some cases, a wearable device may operate solely to perform measurements using the optical measurement system or may be a multi-functional device that also performs additional functions (not described in detail herein). For example, in some instances, the optical measurement system may be incorporated into a smartphone, a tablet computing device, a laptop or desktop computer, a smartwatch, or other electronic device (collectively referred to herein as "electronic devices" for ease of discussion).

[0029] The device may include a display (which may be a touch screen display) that provides graphical output that can be viewed through or on the outer surface of the device. If the display is configured as a touch screen, the display may be capable of receiving touch input on the outer surface. The device may include a cover sheet (e.g., cover glass) positioned to cover the display that forms at least a portion of the outer surface. The display can provide graphic output and, when configured as a touch screen, can receive 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 graphic output of the display responds to input provided to the electronic device. The portable electronic device may include additional components typical of computing devices, including a processing unit, memory, input devices, output devices, additional sensors, and the like.

[0030] These and other embodiments are discussed with reference to FIGS. 1A-9. However, those skilled in the art will readily understand that the detailed description provided herein with reference to these figures is for illustrative purposes only and should not be construed as limiting.

[0031] Figures 1A and 1B show an example of a device 100 that houses the optical measurement system 102 described herein. As shown, the device 100 includes a housing 104 having an upper outer surface 106. This outer surface 106 defines a sampling interface 107 for the optical measurement system 102 through which light emitted by the optical measurement system 102 can exit the device 100, re-enter the device 100, and 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).

[0032] In the variant shown in FIGS. 1A and 1B, the device includes a plurality of emission regions 108 and a plurality of collection regions 110. FIGS. 1A and 1B depict an equal number of emission regions 108 and collection regions 110, but in other cases, the sampling interface 107 has an unequal number of emission regions 108 and collection regions 110. Each emission region 108 and collection region 110 is transparent at each of the wavelengths (collectively "measurement wavelengths") used by the optical measurement system 102 to perform the measurements described herein. Each emission region 108 and collection region 110 may be defined by a corresponding window (transparent at the measurement wavelengths) that is separated from each other by one or more opaque portions of the housing (i.e., that absorb or otherwise block light transmission at the measurement wavelengths). In other variants, some or all of the emission regions 108 and / or collection regions 110 are defined within a common window (e.g., using a mask that is opaque at the measurement wavelengths). Additionally or alternatively, the device 102 may include barriers, baffles, or other light-blocking structures (not shown) that may at least partially define some or all of the emission regions 108 and collection regions 110. These light-blocking structures function as guides that block stray light and limit the paths that light can take between the optical measurement system 102 and the sampling interface 107.

[0033] As shown in FIGS. 1A and 1B, the optical measurement system 102 includes a photonic integrated circuit 112. The photonic integrated circuit 112 includes at least a multi-stage optical switching network (not shown) and a plurality of emission groups (not shown), and can selectively emit light from a plurality of spatial positions on the photonic integrated circuit 112 through the plurality of emission groups. The light emitted from the photonic integrated circuit 112 can exit the device 100 through the sampling interface 107 (e.g., via the emission region 108). In some variations, the optical measurement system 102 optionally includes one or more optical modification components schematically shown as box 114 disposed between the photonic integrated circuit 112 and the sampling interface 107, which modifies the light emitted from the photonic integrated circuit 112 before it reaches the sampling interface 107. For example, the optical modification component 114 may include one or more lenses (changing the divergence and / or direction of light), one or more diffusers, mirrors, etc. Additionally or alternatively, the sampling interface itself may act as an optical modification component (e.g., it may have an integrated lens, etc. that can change the divergence and / or direction of the light passing through it). Each emission group interacts with the sampling interface 107 and any intervening components (such as the optical modification component 114) to control where the light is emitted from the device 100, and thus defines an emission site for the optical measurement system 102.

[0034] The optical measurement system further comprises a plurality of detector groups 116, each of which includes a corresponding set of detectors. Each detector group 116 is positioned within the device 100 to receive light that has entered the device 100 through the sample interface (e.g., via the corresponding collection region 110). In some variations, the optical measurement system 102 comprises one or more optical modification components, schematically shown as box 118, positioned between the sampling interface 107 and at least one detector group 116, which modifies the light entering the device 100 before it reaches the corresponding detector group(s). The optical modification component 118 may include one or more lenses (which change the divergence and / or direction of light), one or more diffusers, mirrors, etc. Additionally or alternatively, the sampling interface 107 may act as an optical modification component.

[0035] In some cases, the photonic integrated circuit 112 and the plurality of detector groups 116 are attached to a common component. For example, in the variations shown in FIGS. 1A and 1B, the optical measurement system 102 comprises an interposer 120. In these cases, the photonic integrated circuit 112 and the plurality of detectors 116 are all mounted on the interposer 120, which can then function as an electrical interface for these components (e.g., to route signals to and / or from the components). In some cases, the interposer also functions as a heat sink. In other variations, the photonic integrated circuit 112 is attached to a component separate from some or all of the plurality of detector groups 116. In yet other variations, some or all of the plurality of detector groups 116 are directly attached to (or otherwise integrated with) a part of the photonic integrated circuit 112.

[0036] The device 100 shown in FIGS. 1A and 1B can utilize any of the optical measurement systems described herein (such as those described with respect to FIGS. 2-6 below) and perform any of the measurement sequences described herein (such as those described with respect to FIGS. 7-9 below). For example, FIG. 2 shows a schematic diagram of an optical measurement system 200 described herein. The optical measurement system 200 includes a light source unit 202, a multi-stage optical switch network 204, a plurality of emission groups 206, and a plurality of detector groups 208. The optical measurement system 200 can generate light and selectively route the light to some or all of the plurality of emission groups 206. The light may exit the optical measurement system 200 via the plurality of emission groups 206, and the light returned to the optical measurement system 200 may be measured using some or all of the detector groups 208.

[0037] Specifically, the light source unit 202 includes a set of light sources (not shown), and each light source is selectively operable to emit light at a corresponding set of wavelengths. Each light source may be any component capable of generating light at one or more specific wavelengths, such as a light-emitting diode or a laser. The laser may include semiconductor lasers such as laser diodes (e.g., distributed Bragg reflector lasers, distributed feedback lasers, external cavity lasers), quantum cascade lasers, etc. A given light source may be of a single frequency (fixed wavelength) or 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 set of light sources may include any suitable combination of light sources and may operate collectively to generate light at any of a plurality of different wavelengths.

[0038] The light source unit 202 is optically connected to the multi-stage optical switch network 204 and includes one or more outputs 210 for routing light thereto. These one or more outputs 210 collectively enable the light source unit 202 to route any of a plurality of different wavelengths to the multi-stage optical switch network 204. Although a single output 210 is shown in FIG. 2, it should be understood that in some variations, the light source unit 202 includes a plurality of outputs. Each output 210 can route a corresponding set of wavelengths to the multi-stage optical switch network 204, which collectively constitutes a plurality of different wavelengths that can be routed to the multi-stage optical switch network 204. In some cases, the light source unit 202 includes more light sources than outputs 210, in which case the light source unit 202 includes one or more multiplexers (not shown) that enable a plurality of light sources to provide light to a single output 210. This enables the light source unit 202 to include several light sources while having a relatively small number of outputs 210 (and thus being able to generate several different wavelengths).

[0039] It should be understood that the light source unit 202 may further include one or more additional outputs that instead route light to other parts of the optical measurement system 200 (i.e., outputs that do not route light to the multi-stage optical switch network 204). For example, one or more of these additional outputs may route light to a wavelength locking unit (as will be described in more detail below). In some cases, the light source unit 202 can generate more wavelengths than the wavelengths that are routed to the multi-stage optical switch network 204 during operation of the optical measurement system 200 (i.e., the light source unit 202 can generate any of a plurality of wavelengths, but the optical measurement system 200 uses only a subset of the plurality of wavelengths as the measurement wavelengths for performing measurements using the multi-stage optical switch network 204). This can support additional functionality of the optical measurement system 200 beyond what is described in this application. Examples of light source units suitable for use with the optical measurement system described herein are described in more detail below with respect to FIGS. 4-6.

[0040] The multi-stage optical switch network 204 has at least one input (optionally including a plurality of inputs) and a plurality of outputs 210. The multi-stage optical switch network 204 receives light from the light source unit 202 via one or more inputs each optically connected to a corresponding output 210 of the light source unit 202. The inputs of the multi-stage optical switch network 204 are not separately labeled in FIG. 2, and it should be understood that the optical measurement system 200 may optionally include additional components (not shown) between the output 210 of the light source unit 202 and the corresponding input of the multi-stage optical switch network 204. These additional components may be useful, for example, when it is desirable to modify the light before it reaches the multi-stage optical switch network 204 as generated by the light source unit 202. Each of the plurality of outputs 202 is optically connected to a corresponding emission group of the plurality of emission groups 206, thereby enabling the multi-stage optical switch network 204 to selectively route light to some or all of the plurality of emission groups 206.

[0041] Specifically, the multi-stage optical switch network 204 is controllable to capture light of a predetermined wavelength received at one of its inputs and simultaneously direct that light to one or more of its outputs 212. In some instances, the multi-stage optical switch network 204 is controlled to direct the light to a single output 212. In other instances, the multi-stage optical switch network 204 is controlled to split the light among multiple outputs 212 such that the light is directed to the multiple outputs simultaneously. For the purposes of the present application, the “output configuration” (also referred to herein as “output resolution”) of an optical measurement system refers to the number of distinct emission groups that receive light simultaneously. The optical measurement system is capable of emitting light in different output configurations, each of which corresponds to a different number of emission groups that receive light simultaneously.

[0042] The multi-stage optical switch network can set the output configuration of the optical measurement system by setting the number of its outputs that simultaneously output the light received by the light source unit. The number of different output configurations for the optical measurement system depends on the number of outputs of the multi-stage optical switch network. For example, in the embodiment shown in FIG. 2, the multi-stage optical switch network 204 has four outputs and may output light in four different output configurations (i.e., to a single output 212 or divided among two, three, or four of the outputs 212). Within a given output configuration, specifically an output configuration that uses only a subset of the outputs of the multi-stage optical switch network 204, the optical measurement system may include a plurality of different sub-configurations in which different subsets of the outputs receive light simultaneously. In other words, there may be a plurality of distinct sets of emission groups 206 having the same output configuration, and the optical measurement system may perform individual measurements with some or all of these distinct sets of emission groups during the measurement sequence. Since the same number of emission groups receive light simultaneously, each of these individual measurements is considered to be a measurement obtained using the same output configuration. When the light is divided among multiple outputs for a given output configuration, the multi-stage optical switch network 204 may provide any distribution of the light among the outputs (equal or unequal division) as desired. Details of how the multi-stage optical switch network 204 can be controlled to switch between different output configurations (and different sets of emission groups for a given output configuration) will be described in more detail below.

[0043] The multi-stage optical switch network 204 and the plurality of emission groups 206 are formed as part of the photonic integrated circuit 214. Part or all of the light source unit 202 may also be integrated into the photonic integrated circuit 214. For example, in some cases, all of the light sources and any multiplexers of the light source unit 202 are integrated into the photonic integrated circuit 214 (as shown in FIG. 2). In other cases, part or all of the light sources generate light from outside the photonic integrated circuit 214, and the light from these light sources is coupled to the photonic integrated circuit 214 and reaches the multi-stage optical switch network 204. The photonic integrated circuit 214 may optically connect the components on the photonic integrated circuit 214 using waveguides. For example, in the embodiment shown in FIG. 2, the output 210 of the light source unit 202 and the inputs and outputs 212 of the multi-stage optical switch network 204 may be waveguides.

[0044] Each of the plurality of emission groups 206 is optically connected to a corresponding output 212 of the multi-stage optical switch network 204 and may emit the light received from the light source unit 202 from the photonic integrated circuit 214. For example, the photonic integrated circuit 214 may include a plurality of outcouplers (e.g., edge couplers, vertical output couplers, etc.) for emitting light from the photonic integrated circuit 214, and each emission group 206 may include at least one outcoupler of the plurality of outcouplers. In the variant shown in FIG. 2, each emission group 206 has an outcoupler 216. The light emitted from the photonic integrated circuit 214 (e.g., via the outcoupler 216) may exit the optical measurement system 200 (and any device incorporating the optical measurement system 200) at one or more emission sites towards the sample (e.g., via the sampling interface as described above with respect to FIG. 1).

[0045] Each emission group 206 is associated with at least one emission site such that light passed to the emission group 206 may exit the optical measurement system 200 (and any device incorporating the optical measurement system 200) at the corresponding emission site. Each emission site provides a unique entry position and / or angle to the sample. In some cases, this means that each emission site is spatially separated (and not adjacent) from other emission sites (e.g., in the sampling interface as described above with respect to FIGS. 1A and 1B). In other variations, two or more emission positions may at least partially overlap, but the light may exit the optical measurement system 200 at different angles such that the light is directed at different portions of the sample.

[0046] The emission group 206 may be associated with a single emission site or multiple emission sites. For example, in the variation shown in FIG. 2, each emission group 206 includes two outcouplers 216. In some of these variations, each outcoupler 216 within a given emission group 214 is associated with a separate emission site such that the first outcoupler of the emission group radiates light from the photonic integrated circuit 214 to the first emission site and the second outcoupler 216 within the emission group radiates light from the photonic integrated circuit 206 to the second emission site. In other variations, multiple outcouplers within the emission group radiate light from the photonic integrated circuit 214 to a single emission site. Additionally or alternatively, light emitted from the photonic integrated circuit 214 by a given outcoupler 216 can be routed to two or more emission sites, in which case the optical measurement system 200 is configured to split the light emitted by the outcoupler 216 into multiple separate beams (each routed to its own emission site).

[0047] Accordingly, light may be emitted from the optical measurement system 200 at any of a plurality of emission sites using a plurality of emission groups 206 (the selection and number of emission sites that emit light at a given instant are at least partially determined by the operation of the multi-stage optical switching network 204). This light can be used to illuminate one or more portions of the sample, and a portion of this light can be returned to the system as a result of interaction with the sample (e.g., via reflection, scattering, etc.). The returned light may be measured by some or all of the plurality of detector groups 208.

[0048] Each detector group of the plurality of detector groups 208 may be associated with a corresponding emission group 206. In these cases, the optical measurement system 200 can be configured such that a given detector group 208 receives light emitted by its corresponding emission group 206 (and returned from the environment surrounding the optical measurement system 200), but does not receive light emitted by other emission groups 206. The light received by the optical measurement system 200 depends on the actual sample being measured by the optical measurement sample, and thus it should be understood that the optical measurement system 200 can be designed assuming it is used to measure a target sample having one or more predetermined characteristics. For example, the optical measurement system 200 may be configured such that only light incident on the optical measurement system 200 at a predetermined range of positions and angles reaches the detector group 208. These positions and angles can be selected such that when measuring a sample having specific characteristics that match the target sample, the detector group 208 effectively receives light only from its corresponding emission group 206 (and the light from emission groups associated with other detector groups is minimal or not received at all).

[0049] Each detector group 208 includes one or more sets of detector elements, and each set of detector elements is schematically represented by a single box 218. Each set includes at least one detector element, and each detector element can generate a corresponding signal representing the light incident thereon. The individual detector elements can be either stand-alone detectors or sensing elements of a detector array (e.g., photodiodes of a photodiode array). It should be understood that different sensing elements of a single detector array may be associated with different detector groups 208. For example, a detector array may 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.

[0050] It should also be understood that the detector elements within a given detector group 208 need not be directly adjacent to each other. For example, in a variant of the optical measurement system 200 shown in FIG. 2, each detector group 208 includes two sets of detector elements 218. In some of these variants, the optical measurement system 200 is configured such that each set of detector elements 218 measures light from different emission sites of a corresponding emission group 206. For example, light emitted from a first outcoupler within a first emission group is measured by detector elements of a first set of a first detector group, and light emitted from a second outcoupler within the first emission group is measured by detector elements of a second set of the first detector group. This can allow for a physical separation between the emission sites of a given emission group without requiring that the light emitted by these emission sites be measured by the same detector elements. Overall, the plurality of detector groups 208 may measure the light emitted from the optical measurement system 200 via the plurality of emission groups 206, thereby facilitating the various measurements described herein.

[0051] Also, FIG. 2 shows a controller 220, which controls the operation of the optical measurement system 200 to perform various measurements as described herein. Specifically, the controller 220 may control the light source unit 202 to cause the light source unit 202 to generate light of a selected wavelength with a selected output of the light source unit 202. The controller 220 may further control the multi-stage optical switch network 204 to configure the multi-stage optical switch network 204 to route the light received from the selected output of the light source unit 202 to a selected number of outputs of the multi-stage optical switch network 204 (this in turn routes the light to a selected set of emission groups 206). The controller 220 may further control the plurality of detector groups 208 to generate output signals representing the light received by the detector groups 208 from some or all of the detector groups 208. These output signals may be processed and analyzed to determine one or more characteristics of the sample. The controller 220 may include, for example, one or more processors and / or application specific integrated circuits (ASICs) and may include any combination of software, hardware, and firmware as necessary to perform these functions (including any of the method steps described below).

[0052] In some variations, the optical measurement system 200 includes a wavelength lock unit 222. The wavelength lock unit 222 can output a signal indicating the wavelength or change in wavelength of the light received by the wavelength lock unit 222, and this signal can be used by the controller 220 to control the light source unit 202 (e.g., a light source within the light source unit generating light) to stabilize or otherwise adjust the wavelength of the light emitted by the light source unit 202. Even in the case of a fixed wavelength laser, the exact emission wavelength may vary slightly with changes in temperature and / or injection current, and thus the wavelength lock unit 222 may provide feedback to the controller 200 to set a stable wavelength output before or during the measurement.

[0053] In some cases, the wavelength lock unit 222 is optically connected to the light source unit 202 such that the wavelength lock unit 222 receives light directly from the light source unit 202. However, if the light source unit 202 has multiple outputs, the wavelength lock unit 222 needs to tap light from all the outputs from the light source unit 202 so as to be able to stabilize all the wavelengths generated by the light source unit 202. In other cases, the wavelength lock unit 222 receives light downstream of the multi-stage optical switch network 204 (i.e., the wavelength lock unit 222 taps the light after it has passed through the multi-stage optical switch network 204). In these cases, the wavelength lock unit 222 needs to tap light from each output 212 of the multi-stage optical switch network 204 or route light to the output 212 (or outputs) that is tapped to perform wavelength stabilization / locking for all of the wavelengths output by the light source unit 202.

[0054] In still other cases, as shown in FIG. 2, the wavelength lock unit 222 may receive light from a portion of the multi-stage optical switch network 204 (i.e., the wavelength lock unit 222 taps light from one or more stages of the multi-stage optical switch network 204). These cases can reduce the number of taps and / or routing requirements needed to be able to stabilize all the wavelengths generated by the light source unit 202. This example is described below with respect to FIGS. 5 and 6 below.

[0055] As described above, the optical measurement system described herein includes a multi-stage optical switch network that can selectively output light in different output configurations. To do this, the multi-stage optical switch network includes a plurality of controllable switches that are divided into a plurality of different stages (each including a corresponding set of controllable switches). Each controllable switch has at least one input and two outputs, and each input of the controllable switch receives light from either an input to the multi-stage optical switch network or a previous stage, and each output of the controllable switch directs the light to either a subsequent stage or an output of the multi-stage optical switch network. Each controllable switch may be controlled such that light of a predetermined wavelength introduced to a predetermined input of the controllable switch is controllably directed to either the first output of the switch, the second output of the switch, or divided between the first output and the second output. Collectively, the plurality of controllable switches may be controlled to configure the multi-stage optical switch network to generate a path necessary for light of a given wavelength to move from a predetermined input of the multi-stage optical switch network to a desired set of outputs of the multi-stage optical switch network.

[0056] In some variations, the controllable switch includes a first coupler, a second coupler, and a controllable phase tuner between the first coupler and the second coupler. The controllable phase tuner enables the controllable switch to selectively split light between a first output and a second output of the controllable switch. FIGS. 3A-3D illustrate variations of a controllable switch suitable for use with the multi-stage optical switch network described herein. FIG. 3A shows a variation of a 1×2 controllable switch 300 having a single input 302 and two outputs (a first output 304 and a second output 306). As shown therein, the controllable switch has a 1×2 coupler 308, a 2×2 coupler 310, and a controllable phase tuner 312 disposed between the 1×2 coupler 308 and the 2×2 coupler 310. In some variations, the 1×2 controllable switch 300 may include a 2×2 coupler instead of the 1×2 coupler 308, but one input of the 2×2 coupler remains disconnected such that the other input of the 2×2 coupler serves as the single input of the 1×2 controllable switch.

[0057] As shown in FIG. 3A, in the variation of the 1×2 controllable switch, the 1×2 coupler 308 uses the input 302 as its single input and uses the first leg 314 and the second leg 316 as outputs. The light received at the input 302 of the 1×2 controllable switch 300 is split by the 1×2 coupler 308 between the first leg 314 and the second leg 316 according to a predetermined splitting ratio. Similarly, the 2×2 coupler 310 receives the light from the first leg 314 and the second leg 316 as inputs and uses the first output 304 and the second output 306 of the 1×2 controllable switch 300 as outputs. The light received by each input of the 2×2 coupler 310 is split between the first output 304 and the second output 306 according to a corresponding predetermined splitting ratio. It should be understood that the input 302, the first output 304, the second output 306, the first leg 314, and the second leg 316 may each be a waveguide.

[0058] The relative amounts of light coupled to the first output 304 and the second output 306 depend on at least: 1) the relative amounts of light in the first leg 314 and the second leg 316 when entering the 2×2 coupler 310, 2) the phase difference between the light in the first leg 314 and the second leg 316 when entering the 2×2 coupler 310, and 3) the wavelength of the light. Thus, changing the phase difference between the first leg 314 and the second leg 316 changes the distribution of light between the first output 304 and the second output 306. Thus, the controllable phase tuner 312 is controllable to selectively adjust the phase difference between the first leg 314 and the second leg 316, thereby enabling the 1×2 controllable switch to controllably split light between its first output 304 and its second output 306. For example, the 1×2 controllable switch may use the controllable phase tuner 312 to selectively route all of the light to the first output 304, route all of the light to the second output 306, or route the light to both the first output 304 and the second output 306 simultaneously (i.e., split the light between both outputs according to a target splitting ratio). Further, the control of the controllable phase tuner 312 may be adjusted to take into account the wavelength of the light introduced into the 1×2 controllable switch such that the desired output of the 1×2 controllable switch can be achieved for any of the measured wavelengths.

[0059] To adjust the phase difference between the first leg 314 and the second leg 316, the controllable phase tuner 312 includes one or more phase shifters that selectively modulate the phase of the light passing through either the first leg 314 or the second leg 316. Examples of suitable phase shifters include, for example, an electro-optic phase shifter that changes the refractive index of a portion of a waveguide using an applied electric field (e.g., via carrier injection), a thermo-optic phase shifter that changes the refractive index of a portion of a waveguide by changing its temperature, and an opto-mechanical phase shifter (e.g., a MEMs phase shifter) that moves a movable structure (e.g., a suspended waveguide) to change the amount of evanescent coupling with the waveguide.

[0060] The controllable phase tuner 312 may include a single phase shifter positioned to change the phase of light within one leg (either the first leg 314 or the second leg 316), or may include a plurality of phase shifters (each of which may be independently controlled). In some cases, the controllable phase tuner 312 includes a plurality of phase shifters, at least one phase shifter being arranged to change the phase of light within the first leg 314 and at least one phase shifter being arranged to change the phase of light within the second leg 316. Additionally or alternatively, the controllable phase tuner 312 may include a plurality of phase tuners arranged to change the phase of light in one of the legs. For example, in a variant of the 1×2 controllable switch 300 shown in FIG. 3A, the controllable phase tuner 312 includes a first phase shifter 318 and a second phase shifter 320 each arranged to change the phase of light within the first leg 314, and a third phase shifter 322 arranged to change the phase of light within the second leg 316.

[0061] Including a plurality of phase shifters may enable the controllable phase tuner 312 to divide the tuning range (i.e., the range of phase shifts required to address different output distributions over the measured wavelengths for the 1×2 controllable switch 300) across the plurality of phase shifters. This may increase the speed at which the controllable phase tuner 312 can adjust the phase difference and / or reduce the losses associated with the adjustment of the phase difference. Additionally or alternatively, different phase shifters may be used to generate the target phase difference at different times. Specifically, different types of phase shifters may have different trade - offs between speed and optical loss (e.g., a thermo - optic phase shifter is typically lossless but is slower at changing the phase compared to a particular electro - optic phase shifter that has a loss proportional to the amount of phase added), and thus different types of phase shifters may be utilized to balance speed and loss.

[0062] For example, the first phase shifter may first provide a target phase shift amount at a first loss level. The second phase shifter may also be controlled to provide the target phase shift amount at a loss level lower than that of the first phase shifter, but it takes longer to achieve this phase shift. When the first phase shifter provides the target phase shift amount, the first phase shifter may be controlled to decrease the phase shift it provides, while the second phase shifter simultaneously increases the phase shift provided. The increase and decrease may be controlled to maintain the target phase shift amount during this transition. As a result, the controllable switch may be able to quickly provide the target phase shift amount and then gradually reduce the loss associated with providing the target phase shift amount.

[0063] In other variations, the controllable switch includes a 2×2 controllable switch. For example, FIG. 3B shows a variation of the 2×2 controllable switch 324. The 2×2 controllable switch 324 is similar to the 1×2 controllable switch 324 described above with respect to FIG. 3A, except that instead of a single input 302 supplying the 1×2 coupler 308 and the 2×2 coupler 332, the 2×2 controllable switch 300 includes a first input 326 and a second input 328 that supply the first 2×2 coupler 330 and the second 2×2 coupler 310 (like components are labeled with the same reference numerals). As shown in FIG. 3B, the first 2×2 coupler 324 receives light from the first input 326 and / or the second input 328 as an input and uses the first leg 314 and the second leg 316 as outputs. Similarly, the second 2×2 coupler 332 receives light from the first leg 314 and the second leg 316 as an input and uses the first output 304 and the second output 306 as outputs.

[0064] The light received by either the first input 326 or the second input 328 of the 2×2 controllable switch 324 is split between the first leg 314 and the second leg 316 by the first 2×2 coupler 330. The second 2×2 coupler 332 receives light from the first leg 314 and the second leg 316 and couples the light to the first output 304 and / or the second output 306 (as described in more detail with respect to FIG. 3A). The controllable phase tuner 312 (disposed between the first 2×2 coupler 330 and the second 2×2 coupler 332) may selectively adjust the phase difference between the light in the first leg 314 and the light in the second leg 316 as described above. The adjustable phase tuner 312 is shown in FIG. 3B as having only the first phase shifter 318 arranged to change the phase of the light in the first leg 314, but it should be understood that the adjustable phase tuner 312 may be configured in any manner as described above with respect to the 1×2 controllable switch 300 of FIG. 3A. By adjusting the phase difference between the first leg 314 and the second leg 316, the 2×2 controllable switch 324 can capture the light received from one of its inputs (e.g., the first input 326 or the second input 328) and selectively route the light completely to the first output 304, completely to the second output 306, or simultaneously to both the first output 304 and the second output 306 (i.e., split between the outputs according to a target splitting ratio).

[0065] In some cases, the controllable switch may also be configured to tap off a portion of the light received by the controllable switch. This may be desirable when a multi-stage optical network switch is used to pass light to a wavelength locking unit as described above. FIG. 3C shows one such example of a 2×2 controllable switch 334. The 2×2 controllable switch 334 is configured in the same manner as the 2×2 controllable switch 310 of FIG. 3A (like components are given the same reference numerals), except that the 2×2 controllable switch 334 includes a tap 336 (e.g., an optical waveguide tap) that extracts a portion of the light from a leg of the controllable switch 334 to a separate waveguide 338. The waveguide 338 may carry the light to another part of the optical measurement system (e.g., a wavelength locking unit as discussed herein). Although shown as tapping light from the leg having the phase shifter (the first leg 314 in FIG. 3C), the tap 336 may alternatively tap light from a leg that does not include a phase shifter (the second leg 316 in FIG. 3C).

[0066] Placing a tap to extract light from a leg of the controllable switch can introduce a wavelength-dependent phase shift into the leg of the controllable switch. The controllable phase tuner 312 may be controlled to account for this wavelength-dependent phase shift in accordance with the wavelength of the light currently passing through the controllable switch, but this can add complexity to the control scheme used to operate the controllable switch. To address this, in some variations, the controllable switch may be configured to include two taps such that each tap extracts a portion of the light from the corresponding leg of the controllable switch.

[0067] FIG. 3D shows one such example of a 2×2 controllable switch 340. The 2×2 controllable switch 340 is configured similarly to the 2×2 controllable switch 334 of FIG. 3C (like components are given like reference numerals), except that the 2×2 controllable switch 340 includes an additional tap 342 (e.g., an optical waveguide tap). The first tap 336 extracts a portion of the light traveling through the first leg 314 of the controllable switch 340 to a first separate waveguide 338, and the second tap 342 extracts a portion of the light traveling through the second leg 316 of the controllable switch 340 to a second separate waveguide 344. The first tap 336 and the second tap 342 may be configured to provide the same wavelength-dependent phase change at each of the first leg 314 and the second leg 316. For example, in some cases, the first tap 336 and the second tap 342 may be identical, such that these taps each extract the same proportion of light from the first leg 314 and the second leg 316 and introduce the same wavelength-dependent phase change to the first leg 314 and the second leg 316.

[0068] The first and second waveguides 338, 344 may convey light to another part of the optical measurement system (e.g., a wavelength lock unit as discussed herein). For example, in some variations, the first tap 336 and the second tap 342 route light to a single component such as a wavelength lock unit. Depending on the design of the wavelength lock unit, the first and second waveguides 338, 344 may form separate inputs to the wavelength lock unit, or may be multiplexed to form a single input to the wavelength lock unit, or may be combined in other ways (e.g., the light from the first and second taps 336, 342 may be directed to a common detector of the wavelength lock unit such that the detector measures the light collected from both the first and second taps 336, 342). When the light from the first waveguide 338 and the second waveguide 344 is combined, it may be desirable for one or both of the waveguides to include a controllable phase tuner (such as described herein) that can be used to control the relative phase of the light between the first waveguide 338 and the second waveguide 344. In other variations, the first tap 336 and the second tap 342 route light to different parts of the optical measurement system. For example, the first tap 336 may route light to a wavelength lock system, and the second tap 336 may route light to a second wavelength lock system or a different component (such as a part of the optical measurement system that performs calibration, an activation process, or monitors system performance).

[0069] The number and arrangement of controllable switches in a multi-stage optical switch network are determined at least in part based on the desired number of inputs and outputs of the multi-stage optical switch network. For example, FIG. 4 shows a portion of a variant of an optical measurement system 400 having a multi-stage optical switch network 402 with one input 401 and four outputs 403A-403D. As shown therein, the optical measurement system 400 also includes a light source unit 404 and a plurality of emission groups 406A-406D, each of which is optically connected to a corresponding output of the multi-stage optical switch network 402. Although not shown, the optical measurement system 400 may include any of the other components of the optical measurement system described above with respect to FIGS. 1A-2 (e.g., a plurality of detector groups, a controller).

[0070] The light source unit 404 has a single output optically connected to the input 401 of the multi-stage optical switch network 402. The output of the light source unit 404 is not separately labeled in FIG. 4, and it should be understood that the optical measurement system 400 may optionally include additional components between the output of the multi-stage optical switch network 402 and the input 401 as described above. In the variant of the light source unit 404 shown in FIG. 4, the light source unit 404 includes a plurality of light sources (labeled 408-1 to 408-N) connected to a multiplexer 410 that combines the outputs of the plurality of light sources into a common output (i.e., the output of the light source unit 404). Thus, the light source unit 404 may output light generated by any of the plurality of light sources 408-1 to 408-N to the multi-stage optical switch network 402. If each of the N light sources can emit a unique wavelength at least from other light sources, the light source unit 404 can generate light of at least N different wavelengths.

[0071] The multi-stage optical switch network 402 includes a first stage 414 having a 1×2 controllable switch 416 and a second stage 418 having a first 1×2 controllable switch 420 and a second 1×2 controllable switch 422. The 1×2 controllable switch 416 of the first stage 414 receives light from the input 401 (i.e., the input 401 of the multi-stage optical switch network 402 functions as an input to the 1×2 controllable switch 416) and outputs light to the second stage 418. Specifically, the first waveguide 424 connects the first output of the 1×2 controllable switch 416 of the first stage 414 to the input of the first 1×2 controllable switch 420 of the second stage 418. Similarly, the second waveguide 426 connects the second output of the 1×2 controllable switch 416 of the first stage 414 to the input of the second 1×2 controllable switch 422 of the second stage 418. The output of the first 1×2 controllable switch 420 of the second stage 418 forms the first output 403A and the second output 403B of the multi-stage optical switch network 402, and the output of the second 1×2 controllable switch 422 of the second stage 418 forms the third output 403C and the second output 403D of the multi-stage optical switch network 402. In some cases, one or more of the 1×2 controllable switches include a tap or set of taps (not shown) as described with respect to FIGS. 3C and 3D, which may be used to tap off a portion of the light received by the multi-stage optical switch network 402 (e.g., for wavelength stabilization / locking as described above). If the 1×2 controllable switch of the first stage 416 includes a tap, the tap can receive the light generated by the light source unit 404 regardless of how the multi-stage optical switch network 402 is configured to route light to its outputs 403A - 403D.

[0072] The multi-stage optical switch network 402 shown in FIG. 4 has four potential output configurations and may be controlled to selectively route light to one, two, three, or four of the outputs 403A-403D (and associated emission groups 406A-406D) simultaneously. For example, to route the light from input 401 to only the first output 403A and the first emission group 406A (i.e., an output configuration of one simultaneous output), the 1×2 controllable switch 416 of the first stage 414 is controlled to route the input light to only the first waveguide 424 (and thus only to the first 1×2 controllable switch 420 of the second stage 418). The first 1×2 controllable switch 420 of the second stage 418 is similarly controlled to route the light it receives to only the first output 403A. The multi-stage optical switch network may similarly be controlled to selectively route light to a different set of outputs (only the second output 403B, only the third output 403C, or only the fourth output 403D), and thus to a different respective set of emission groups (only the second emission group 406B, only the third emission group 406C, or only the fourth emission group 406D), in an output configuration of one simultaneous output.

[0073] To route the input light simultaneously to all four outputs 403A - 403D and all four emission groups 406A - 406D (i.e., the output configuration of four simultaneous outputs), the 1×2 controllable switch 416 of the first stage 414 is controlled to split the input light between the first waveguide 424 and the second waveguide 426. The first 1×2 controllable switch 420 of the second stage 418 is controlled to split the light received between the first output 403A and the second output 403B (i.e., via the first waveguide 424). Similarly, the second 1×2 controllable switch 422 of the second stage 418 is controlled to split the light received between the third output 403C and the fourth output 403D (i.e., via the second waveguide 426). If the controllable switches split the light evenly between their outputs, all four outputs 403A - 403D (and thus all four emission groups 406A - 406D) may receive an equal amount of light (however, it should be understood that different splitting ratios may be used to generate an unequal light distribution between the four outputs 403A - 403D and the corresponding emission groups 406A - 406D). Applying a similar principle, the light may be selectively routed simultaneously to two or three of the outputs 403A - 403D (i.e., the output configurations of two or three simultaneous outputs respectively).

[0074] FIG. 5 shows another variant of the optical measurement system 500 including a multi - stage optical switch network 502 having two inputs 501A, 501B and four outputs 503A - 503D. As shown therein, the optical measurement system 500 also comprises a light source unit 504 and a plurality of emission groups 506A - 506D, each of which is optically connected to the corresponding output 503A - 503D of the multi - stage optical switch network 502 respectively. Although not shown, the optical measurement system 500 may comprise any of the other components of the optical measurement system described above with respect to FIGS. 1A - 2 (e.g., a plurality of detector groups, a controller).

[0075] The light source unit 504 has two outputs optically connected to the input of the multi-stage optical switch network 502. Specifically, the first light source unit 504 has a first output optically connected to the first input 502A of the multi-stage optical switch network 501 and a second output optically connected to the second input 502B of the multi-stage optical switch network 501. The first and second outputs of the light source unit 504 are not separately labeled in FIG. 5, and it should be understood that the optical measurement system 500 may optionally include additional components between any output of the light source unit 504 and its corresponding input of the multi-stage optical switch network 502, as described above.

[0076] The light source unit 504 has one or more light sources optically connected to each of its outputs. In the variant of the light source unit 504 shown in FIG. 5, the light source unit 504 includes a first plurality of light sources 508-1 to 508-N connected to the first multiplexer 510 and a second plurality of light sources 512-1 to 512-M connected to the second multiplexer 514. The first multiplexer 510 combines the outputs of the first plurality of light sources into a first common output (i.e., the first output of the light source unit 504), and the second multiplexer 514 combines the outputs of the second plurality of light sources into a second common output (i.e., the second output of the light source unit 504). Thus, the light source unit 504 may output light from either the first plurality of light sources or the second plurality of light sources to the multi-stage optical switch network 502. If each of the N light sources of the first plurality of light sources and the M light sources of the second plurality of light sources can emit at least one wavelength unique to the other light sources, the light source unit 504 can generate light of at least N+M different wavelengths. Dividing the light sources between different multiplexers may enable the light source unit to generate a wider range of wavelengths while reducing the optical losses associated with multiplexing the light sources.

[0077] The multi-stage optical switch network 502 includes a first stage 515 having a 2×2 controllable switch 516 and a second stage 518 having a first 1×2 controllable switch 520 and a second 1×2 controllable switch 522. The first input 501A and the second input 501B of the multi-stage optical switch network 502 function as inputs to the 2×2 controllable switch 516. Thus, the 2×2 controllable switch 516 can receive light from either input and route the light to the second stage 518. Specifically, the first waveguide 524 connects the first output of the 2×2 controllable switch 516 to the input of the first 1×2 controllable switch 520 of the second stage 518. Similarly, the second waveguide 526 connects the second output of the 2×2 controllable switch 516 to the input of the second 1×2 controllable switch 522 of the second stage 518. The output of the first 1×2 controllable switch 520 of the second stage 518 forms the first output 503A and the second output 503B of the multi-stage optical switch network 502, and the output of the second 1×2 controllable switch 522 of the second stage 518 forms the third output 503C and the second output 503D of the multi-stage optical switch network 502.

[0078] In some cases, one or more of the controllable switches of the multi-stage optical switch network 502 include taps as described with respect to FIG. 3C. For example, in the variant shown in FIG. 5, the 2×2 controllable switch 516 includes a tap 528. The tap 528 may tap off a portion of the light received by the 2×2 controllable switch 516 as described above and route this light to a wavelength locking unit 530 as described herein. Since all the light entering the multi-stage optical switch network 502 passes through the 2×2 controllable switch 516, the tap 528 may enable the optical measurement system 500 to stabilize any wavelength of the light generated by the light source unit 504 and received by the multi-stage optical switch network 502 using the wavelength locking unit 530.

[0079] In other instances, it should be understood that the 2×2 controllable switch 516 comprises a plurality of taps as described herein with respect to FIG. 3D. In these instances, the 2×2 controllable switch 516 includes a second tap 528 such that the taps 538, 538 extract light from different legs of the 2×2 controllable switch 516. The second tap 538 may route light from the 2×2 controllable switch 516 to a second wavelength locking unit 540 as shown in FIG. 5, to a first wavelength locking unit 530, or to yet another component as described herein.

[0080] The multi-stage optical switch network 502 has four potential output configurations, captures light received by either the first input 501A or the second input 501B, and can be controlled to selectively route the light to one, two, three, or four of the outputs 503A - 503D (and associated emission groups 506A - 506D). For example, to route light from the first input 501A only to the first output 503A and the first emission group 506A, the 2×2 controllable switch 516 is controlled to route the light received from the first input 501A only to the first waveguide 524. The first 1×2 controllable switch 520 of the second stage 518 is similarly controlled to route the light it receives only to the first output 503A. Alternatively, to route light from the second input 501B, the 2×2 controllable switch 516 can be switched to route the light received from the second input 501B instead only to the first waveguide 524. In this way, the multi-stage output switch network 502 can capture light from any light source from the light source unit 504 and route it to a target set of outputs and the corresponding emission groups (either the first output 503A and the first emission group 506A, the second output 503B and the second emission group 506B, the third output 503C and the third emission group 506C, or the fourth output 503D and the fourth emission group 506D) in one simultaneous output configuration (via either the first input 501A or the second input 501B).

[0081] To route the light received from the light source unit 504 to all of the four outputs 503A to 503D and all of the four emission groups 506A to 506D simultaneously (i.e., the output configuration of four simultaneous outputs), the 2×2 controllable switch 516 is controlled to split the light received from one input (either the first input 501A or the second input 501B) simultaneously between the first waveguide 524 and the second waveguide 526. The first 1×2 controllable switch 520 of the second stage 518 is controlled to split the light it receives (i.e., via the first waveguide 524) simultaneously between the first output 503A and the second output 503B (and thus the first emission group 506A and the second emission group 506B). Similarly, the second 1×2 controllable switch 522 of the second stage 518 is controlled to split the light it receives (i.e., via the second waveguide 526) simultaneously between the third output 503C and the fourth output 503D (and thus the third emission group 506C and the fourth emission group 506D). If all of the controllable switches split the light evenly between their outputs, all of the four outputs 503A to 503D (and all of the four emission groups 506A to 506D) may receive an equal amount of light (however, it should be understood that an uneven light distribution among the four outputs 503A to 503D may be generated using different splitting ratios). Applying a similar principle, the light may be selectively routed to two or three of the outputs 503A to 503D simultaneously (i.e., the output configuration of two or three simultaneous outputs respectively).

[0082] FIG. 6 shows yet another variant of an optical measurement system 600 that includes a multi-stage optical switch network 602 having four inputs 601A-601D and four outputs 603A-603D. As shown therein, the optical measurement system 600 also includes a light source unit 604 and a plurality of emission groups 606A-606D, each of which is optically connected to a corresponding output of the multi-stage optical switch network 602. Although not shown, the optical measurement system 600 may include any of the other components of the optical measurement system described above with respect to FIGS. 1A-2 (e.g., a plurality of detector groups, a controller).

[0083] The light source unit 604 has four outputs that are optically connected to the inputs of the multi-stage optical switch network 602. Specifically, the first light source unit 604 has a first output optically connected to the first input 602A of the multi-stage optical switch network 601, a second output optically connected to the second input 601B, a third output optically connected to the third input 601C, and a fourth output optically connected to the fourth input 601D. The outputs of the light source unit 604 are not separately labeled in FIG. 6, and it should be understood that the optical measurement system 600 may optionally include additional components between any output of the light source unit 604 and the corresponding input of the multi-stage optical switch network 602, as described above.

[0084] The light source unit 604 has one or more light sources optically connected to each of its outputs. In a modification of the light source unit 604 shown in FIG. 6, the light source unit 604 includes a first plurality of light sources 608-1 to 608-N connected to a first multiplexer 610, a second plurality of light sources 612-1 to 612-M connected to a second multiplexer 614, a third plurality of light sources 616-1 to 616-P connected to a third multiplexer 618, and a fourth plurality of light sources 620-1 to 620-Q connected to a fourth multiplexer 621. Each of these multiplexers combines the outputs of its associated plurality of light sources into a common output (which collectively forms the four outputs of the light source unit 604). Thus, the light source unit 604 may output light from any of the four pluralities of light sources. If each of the light sources from the four pluralities of light sources can emit light of at least one wavelength unique to the other light sources, the light source unit 604 can generate light of at least N + M + P + Q different wavelengths. Dividing the light sources among different multiplexers may enable the light source unit to generate a wider range of wavelengths while reducing the optical losses associated with multiplexing the light sources.

[0085] The multi-stage optical switch network 602 includes a first stage 622 having a first 2×2 controllable switch 624 and a second 2×2 controllable switch 626, and a second stage 628 having a first 2×2 controllable switch 630 and a second 2×2 controllable switch 632. Each of these controllable switches has two inputs and two outputs, and as described above, can selectively route the optical signal received by one of the inputs to either or both of the outputs simultaneously. The first input 601A and the second input 601B of the multi-stage optical switch network 602 function as inputs to the first 2×2 controllable switch 624 of the first stage 622. Similarly, the third input 601C and the fourth input 601D of the multi-stage optical switch network 602 function as inputs to the second 2×2 controllable switch 626 of the first stage 622. Thus, each input of the multi-stage optical switch network 602 is routed to either the first 2×2 controllable switch 624 or the second 2×2 controllable switch 626 of the first stage 622.

[0086] Each of the controllable switches of the first stage 622 routes light to one or both of the controllable switches of the second stage 628. Specifically, the first waveguide 634 connects the first output of the first 2×2 controllable switch 624 of the first stage 622 to the first input of the first 2×2 controllable switch 630 of the second stage 628. The second waveguide 636 connects the second output of the first 2×2 controllable switch 624 of the first stage 622 to the first output of the second 2×2 controllable switch 632 of the second stage 628. Similarly, the third waveguide 638 connects the first output of the second 2×2 controllable switch 626 of the first stage 622 to the second input of the first 2×2 controllable switch 630 of the second stage 628. The fourth waveguide 640 connects the second output of the second 2×2 controllable switch 626 of the first stage 622 to the second output of the second 2×2 controllable switch 632 of the second stage 628. The output of the first 2×2 controllable switch 630 of the second stage 628 forms the first output 603A and the second output 603B of the multi-stage optical switch network 602, and the output of the second 2×2 controllable switch 632 of the second stage 628 forms the third output 603C and the fourth output 603D of the multi-stage optical switch network 602.

[0087] In some cases, one or more of the controllable switches of the multi-stage optical switch network 602 include taps as described with respect to FIG. 3C. For example, in the variant shown in FIG. 6, the first 2×2 controllable switch 624 of the first stage 622 includes a first tap 642, and the second 2×2 controllable switch 626 of the first stage 622 includes a second tap 644. The first tap 642 can tap off a portion of the light received by the first 2×2 controllable switch 624 of the first stage 622 (e.g., from one of the first plurality of light sources or the second plurality of light sources), and route this light to the first wavelength locking unit 646 as described above. Similarly, the second tap 644 can tap off a portion of the light received by the second 2×2 controllable switch 626 of the first stage 622 (e.g., from one of the third plurality of light sources or the fourth plurality of light sources), and route this light to the second wavelength locking unit 648. Although the optical measurement system 600 is shown in FIG. 6 as having two separate wavelength locking units, in other variants, the first tap 642 and the second tap 644 route the light to a single wavelength locking unit (e.g., the light from the first tap 642 and the second tap 644 can be multiplexed onto a single waveguide). Since all the light entering the multi-stage optical switch network 602 passes through one of the controllable switches of the first stage, the first tap 642 and the second tap 644 collectively can enable the optical measurement system 600 to stabilize any wavelength generated by the light source unit 604 and received by the multi-stage optical switch network 602. It should be understood that either or both of the first and second 2×2 controllable switches 624, 626 can include additional taps as described herein with respect to FIG. 3D.

[0088] The multi-stage optical switch network 602 has four potential output configurations and is controlled to take in the light received by any of the four inputs 601A - 601D and route it simultaneously to one, two, three, or four of the outputs 603A - 603D (and their associated emission groups 606A - 606D). For example, to route the light from either the first input 601A or the second input 601B only to the first output 603A and the first emission group 606A (i.e., an output configuration of one simultaneous output), the first 2×2 controllable switch 624 of the first stage 622 is controlled to route the light it receives to the selected input of only the first waveguide 634. The first 2×2 controllable switch 630 of the second stage 628 is similarly controlled to route the light received from the first waveguide 634 only to the first output 603A (and thus to the first emission group 606A). Instead, to route light from either the third input 601C or the fourth input 601D, the second 2×2 controllable switch 626 of the first stage 622 is controlled to route the light it receives at that input to the selected input of only the third waveguide 638. The first 2×2 controllable switch 630 of the second stage 628 is controlled to route the light received from the third waveguide 638 only to the first output 603A. In this way, the multi-stage output switch network 602 can take out light from any light source of the light source unit 604 and route it to the first output 603A and the first emission group 606A. The multi-stage optical switch network 602 may also be controlled to route the light from any light source of the light source unit 604 in an output configuration of one simultaneous output (either the second output 603B and the second emission group 606B, the third output 603C, or the fourth output 603D) to any other set of outputs and the corresponding set of emission groups. Applying a similar principle, light may be selectively routed simultaneously to a set of outputs including two, three, or four of the outputs 603A - 603D (i.e., an output configuration of two, three, or four simultaneous outputs).

[0089] In the case of the multi-stage optical switch network described herein, how each controllable switch is controlled depends on which inputs and outputs of the multi-stage optical switch network receive and output light, respectively, and which wavelengths of light are received by the multi-stage optical switch network. Thus, the control of the switch is modified as any of these parameters changes to achieve the desired output. Each controllable switch has its own default splitting behavior (i.e., when it is not actively controlled), and thus, the multi-stage optical switch network has its own default routing configuration based on the default behavior of its controllable switches. The controllable switches may be designed to achieve a desired routing configuration for the multi-stage optical switch network. For example, in some cases, the default switching behavior of the controllable switches is selected to minimize the average loss associated with controlling the multi-stage optical switch network to route each wavelength of the measured wavelengths during a predetermined measurement sequence. In other cases, it may be desirable to minimize the average time taken to change the multi-stage optical switch network from its default routing configuration to another set of routing configurations (which may be a subset of the entire range of routing configurations used during a predetermined measurement sequence).

[0090] It should be understood that the principle of the multi-stage optical switch network described above may be extended to provide a network that routes any number of input and output combinations. As the number of inputs and / or outputs increases, the multi-stage optical switch network may include additional stages and / or controllable switches within each stage to provide different possible routing paths between each input and multiple outputs. For example, to accommodate more than four inputs and / or more than four outputs, the multi-stage optical switch network may be configured to include more than three stages, and at least one of the stages may include at least three controllable switches. Thus, these multi-stage optical switch networks may be used with a wide range of possible optical measurement system designs to achieve a range of different output configurations.

[0091] As described above, the optical measurement system described herein can be used to measure one or more characteristics of a sample. Specifically, the optical measurement system can generate a plurality of output signals that can be used to perform a measurement sequence to determine one or more characteristics of the sample. These measurement sequences may be repeated, and the plurality of output signals associated with successive measurement sequences may be used collectively to determine one or more characteristics of the sample or to perform successive determinations of one or more characteristics of the sample at a later time. One or more parameters of the measurement sequence may be updated prior to performing subsequent measurement sequences, as will be described in more detail below.

[0092] Each measurement sequence includes a plurality of individual measurements, each of which generates at least one output signal (collectively forming the plurality of output signals of the measurement sequence). Each individual measurement is performed at a corresponding wavelength such that at least one individual measurement is performed for each of the plurality of wavelengths (i.e., light is generated and emitted from the optical measurement system at the corresponding wavelength during some of the individual measurements). The results of the individual measurements of the measurement sequence (i.e., the plurality of output signals) are used to derive one or more characteristics of the sample (e.g., using spectroscopic analysis techniques). The optical measurement system may facilitate a wide range of analysis techniques, as will be readily understood by those skilled in the art, and thus the individual techniques for deriving characteristics from the sample using measurements obtained at a plurality of different wavelengths are not discussed herein.

[0093] Figure 7 shows a method 700 for performing a measurement sequence using a plurality of different wavelengths. This method 700 may be performed by any of the optical measurement systems described herein. First, method 700 includes selecting a plurality of wavelengths in step 702. The plurality of wavelengths are the wavelengths used to measure the sample and may be selected according to the sample expected to be measured as well as the one or more characteristics desired to be determined from the sample. For example, when an optical measurement system having a light source unit as described above is used to perform a measurement sequence, the plurality of wavelengths may be a subset of the wavelengths that the light source unit may generate. Different subsets of these wavelengths may be selected for different measurement scenarios. In some cases, selecting the plurality of wavelengths includes performing a set of preliminary measurements (e.g., using one or more wavelengths) to generate a set of preliminary output signals and selecting the plurality of wavelengths using the set of preliminary output signals. For example, the preliminary measurements may enable an initial characterization or estimation of certain characteristics of the sample that may be used when selecting the plurality of wavelengths.

[0094] When multiple wavelengths are selected, at step 704, the multiple wavelengths are divided into multiple groups. Each group (and thus each wavelength within that group) is associated with a different corresponding output configuration. The number of groups may depend on how many different output configurations are desired for the measurement sequence, and it is not necessary to utilize all the output configurations achievable by a given optical measurement system. For example, if an optical measurement system has four emission groups, the multiple wavelengths may be divided into two, three, or four different groups, each associated with a different corresponding output configuration. In some cases, the assignment of a given wavelength to a group may be based on which noise source is expected to limit the SNR of the individual measurements made at that wavelength.

[0095] For example, in some cases, it may be desirable to maximize the SNR of the measurements obtained at each wavelength. Certain wavelengths may be limited by the fundamental noise regardless of the output configuration. These wavelengths may be assigned to the group with the most fine-grained output configuration (i.e., where the light is divided over the fewest number of emission groups), which may then improve the SNR at these wavelengths. As a non-limiting example, these wavelengths may be assigned to a group with an output configuration of one simultaneous output, such that only one emission group receives light at a time and receives all of the light (minus any losses associated with the optical measurement system) generated by a given light source.

[0096] Conversely, other wavelengths can be limited by different noise sources (e.g., coherent noise), regardless of the measurement output configuration. These wavelengths may be assigned to groups with the coarsest output configuration (i.e., where the light is split simultaneously across most of the emission groups), which can save time and power compared to making separate measurements in a higher output configuration (i.e., more simultaneous outputs). As a non-limiting example, these wavelengths may be assigned to a group having an output configuration of four simultaneous outputs. Each emission group receives less light than in the case of measurements in an emission group having an output configuration of one simultaneous output, but may still result in an equivalent SNR. By splitting the light simultaneously among multiple emission groups, such measurements shorten the time required to measure all of the emission groups and save power compared to multiple measurements for a finer output configuration.

[0097] Still other wavelengths can be limited by the fundamental noise in some output configurations, but can be limited by other noise sources (e.g., coherent noise) in other output configurations. These wavelengths may be assigned to groups corresponding to output configurations where the measurement is no longer limited by the fundamental noise. For example, a wavelength may be limited by the fundamental noise for measurements performed in an output configuration of four simultaneous outputs, but instead may be limited by the fundamental noise for measurements performed in an output configuration of two simultaneous outputs. In these cases, it may be desirable to assign the wavelength to a group corresponding to the output configuration of two simultaneous outputs (which may still save time and power compared to individual measurements with an output configuration of one simultaneous output). It should be understood that, merely by way of example, wavelengths may be assigned to different groups to achieve any desired trade-off of SNR, power consumption, and time requirements for performing the measurements described herein.

[0098] In some cases, each wavelength of a plurality of wavelengths has a default group (out of a plurality of groups) assigned for a given measurement sequence. In some cases, one or more parameters associated with the sample may be used when dividing the plurality of wavelengths into a plurality of groups (which may result in a deviation from the default behavior). For example, a certain characteristic of the sample (e.g., scattering coefficient or absorption coefficient, material type of the sample) may be used when dividing the wavelengths. In some cases, this information may be known in advance (e.g., manually input before measuring the sample or saved from previous measurements of the same sample).

[0099] Additionally or alternatively, a set of preliminary measurements may be used to generate a corresponding set of output signals used when dividing the plurality of wavelengths into a plurality of groups. If a set of preliminary measurements (the "first set of preliminary measurements") is performed as part of selecting a plurality of wavelengths, the set of preliminary corrections (the "second set of preliminary measurements") used to divide the plurality of wavelengths may include some or all of the first set of preliminary measurements. Additionally or alternatively, the second set of preliminary measurements may include one or more additional preliminary measurements. For example, the output signals of the preliminary measurements may be used to determine a metric of the optical power (i.e., signal intensity) at one or more detectors of a detector group (singular or plural) associated with an emission group (singular or plural). This metric of the optical power (e.g., the optical power measured by a single detector, the average or other combination of optical powers measured by a plurality of different detectors) may be used when determining to which of the plurality of groups a wavelength is assigned. For example, if this metric is below a predetermined threshold for a given wavelength, that wavelength may be assigned to a group having a finer output configuration than its default group. It should be understood that each wavelength measured using the preliminary measurements (collectively, which may be only a subset of the plurality of wavelengths) may have its own set of thresholds for determining to which group that wavelength should be assigned.

[0100] For each wavelength of a plurality of wavelengths, method 700 includes, at step 706, performing an individual measurement of a set of samples for each wavelength among the plurality of wavelengths, where each individual measurement of the set is performed in an output configuration corresponding to the wavelength. A corresponding set of output signals is generated for each individual measurement of the set, and thus the measurement sequence generates a plurality of sets of output signals composed of these corresponding sets of output signals.

[0101] As an example, the plurality of wavelength groups includes a first group associated with a first output configuration and a second group associated with a second output configuration. For each wavelength within the first group, a corresponding set of measurements is performed in the first output configuration (e.g., a measurement of a first set of samples is performed for the first wavelength within the first group). This includes generating light at the wavelength (e.g., the first wavelength), emitting the generated light from a corresponding set of emission groups selected from a plurality of emission groups (the corresponding set having a first number of emission groups corresponding to the first output configuration), and measuring the returned light received during the emission of the generated light using a corresponding set of detector groups selected from a plurality of detector groups (the corresponding set having a first number of detector groups).

[0102] Similarly, for each wavelength within the second group, a corresponding set of measurements is performed in the first output configuration (e.g., a measurement of a second set of samples is performed for the second wavelength within the second group). This includes generating light at the wavelength (e.g., the second wavelength), emitting the generated light from a corresponding set of emission groups selected from a plurality of emission groups (the corresponding set having a second number of emission groups corresponding to the second output configuration), and measuring the returned light received during the emission of the generated light using a corresponding set of detector groups selected from a plurality of detector groups (the corresponding set having a second number of detector groups).

[0103] In some cases, a set of individual measurements includes a plurality of measurements having different corresponding sets of emission groups and different corresponding sets of detectors. In the example described just above, the first set of measurements obtained at the first wavelength may include a plurality of measurements, and each measurement may have a different unique set of emission groups (while still maintaining the first output configuration). Similarly, since each emission group is associated with a corresponding detector group, the plurality of measurements may each use a different unique set of detector groups.

[0104] Additionally or alternatively, a set of individual measurements for a wavelength collectively performs at least one measurement using each emission group. Specifically, performing an individual measurement with a given output configuration includes emitting light from several emission groups (and the emission sites associated with these emission groups) towards the sample, and the number of emission groups corresponds to the given output configuration. For example, if an optical measurement system has four emission groups and the light is split simultaneously among all four emission groups, a set of individual measurements for a wavelength may include a single individual measurement. If the light is split simultaneously between two emission groups or between three emission groups, a set of individual measurements for another wavelength may include two individual measurements. For yet another wavelength, a set of individual measurements may include four individual measurements (i.e., one measurement for each emission group) if the light is sent to only one emission group at a time. In this way, the measurement sequence may ensure that each of the plurality of emission groups is used to measure all of the plurality of wavelengths.

[0105] In some of these variations, for a given wavelength, a set of individual measurements may optionally include separate measurements for each distinct set of emission groups having a corresponding output configuration (i.e., each of the possible sub-configurations of the output configuration). For example, if an optical measurement system has four emission groups, there is one distinct set of emission groups (i.e., the output configuration of four simultaneous outputs) where light is split simultaneously among all four emission groups, six distinct sets of emission groups (i.e., the output configuration of two simultaneous outputs) where light is split simultaneously between two emission groups, four distinct sets of emission groups (i.e., the output configuration of three simultaneous outputs) where light is split simultaneously among three emission groups, and four distinct sets of emission groups (i.e., the output configuration of one simultaneous output) where light is routed to only a single emission group. In other words, these output configurations have one, six, four, and four sub-configurations, respectively.

[0106] While light is being emitted by the emission group(s) for a given individual measurement, the detector group(s) corresponding to the emission group(s) measure the light received by their associated detectors. Each detector may provide its own output signal, and thus, a given individual measurement generates one or more output signals (i.e., the outputs of the detector(s) of the detector group(s) used during that measurement). Since the measurement sequence performs a set of individual measurements for each wavelength, the method generates a set of output signals for each wavelength. Additionally, in variations where the measurement sequence measures each wavelength in all emission groups, the method correspondingly generates a set of output signals for each wavelength corresponding to all emission groups. In step 708, one or more characteristics of the sample can be determined using the results of the measurement sequence (i.e., using the multiple sets of output signals resulting from the set of individual measurements).

[0107] In some cases, as shown in step 710, the method may optionally update a plurality of groups to reassign at least one wavelength to a different group (thereby allowing the reassigned wavelength to be associated with a different output configuration before subsequent measurement sequences are performed). For example, for a given wavelength, one may analyze a set of output signals obtained from a set of individual measurements performed at that wavelength to determine whether that wavelength should be assigned to different groups having different output configurations. For example, if a metric of optical power derived from one or more of the output signals meets a certain criterion for that wavelength (e.g., exceeds a threshold, is below a threshold), the wavelength may be assigned to a different default group for future measurement sequences. Thereby, the optical measurement system may adjust its measurement technique for a range of samples having a range of different characteristics, such as when measurements at a certain wavelength are expected to be limited by fundamental noise but are actually limited by coherent noise.

[0108] Although method 700 described immediately above discusses performing a measurement sequence that includes a set of individual measurements for each of a plurality of wavelengths, it should be understood that the various individual measurements may be performed in any suitable order. In some instances, it may be desirable to divide the measurement sequence into a plurality of sub-sequences, each sub-sequence including performing successive measurements at a common wavelength of the plurality of wavelengths. In other words, the individual measurements are grouped by wavelength, and all of the measurements of a set of individual measurements for a given wavelength are performed sequentially before starting measurements using a different wavelength.

[0109] In other cases, it may be desirable to group measurements by emission group set. Each subsequence of a plurality of subsequences includes consecutive measurements performed at different wavelengths for the same set of emission groups. Each subsequence has a corresponding set of wavelengths out of the plurality of wavelengths (i.e., one set of wavelengths from the group used to measure that set of emission groups). In other words, all measurements for a given set of emission groups (and thus in a given output configuration or sub-configuration thereof) are performed before moving to another set of emission groups (which may include different output configurations or different sub-configurations). This may be desirable when it is faster to switch between wavelengths than to switch between emission groups.

[0110] Figure 8 shows one such measurement sequence 800. For illustrative purposes, the plurality of wavelengths are divided into two groups and are performed using an optical measurement system having four emission groups. The first group ("Group A") has an output configuration of one simultaneous output, and thus the individual measurements acquired at these wavelengths are routed to a single emission group. In the variant shown in Figure 8, one set of individual measurements for each wavelength within Group A includes four total measurements, i.e., one measurement for each emission group (labeled "Emission Set A-1" to "Emission Set A-4"). The second group ("Group B") has an output configuration of four simultaneous outputs, and thus the individual measurements acquired at these wavelengths are split simultaneously among all four outputs ("Emission Set B-1").

[0111] The measurement sequence shown therein is separated by emission groups such that, at step 802, a first sub-sequence including individual measurements performed in a first emission group (emission set A-1) for each wavelength within group A is executed. At step 804, a second sub-sequence including individual measurements obtained in a second emission group (emission set A-2) for each wavelength within group A is executed. At step 806, a third sub-sequence including individual measurements at each wavelength within group B is executed, and the light is split among four emission groups (emission set B-1). At step 808, a fourth sub-sequence including individual measurements obtained in a third emission group (emission set A-3) for each wavelength within group A is executed. Finally, at step 810, a fifth sub-sequence including individual measurements obtained in a fourth emission group (emission set A-4) for each wavelength within group A is executed. Collectively, the first through fifth sub-sequences execute all of the measurements of the measurement sequence, including four individual measurements for each wavelength within group A and one individual measurement for each wavelength within group B. The order of these sub-sequences is for illustrative purposes only, and it should be understood that the number and order of sub-sequences can be determined at least in part by the number of groups and the number of emission groups in the unique set measured for each group.

[0112] As described above, each individual measurement involves emitting light from a set of emission groups in a predetermined output configuration and measuring the light using a set of detector groups corresponding to the set of emission groups to generate a set of output signals. It should be understood that there may be additional steps associated with each individual measurement. For example, if a multi-stage optical switch network is used to route light of a given wavelength to a particular set of emission groups (e.g., each of the first set of measurements at the first wavelength described above), each individual measurement may include a setup step in which the multi-stage optical switch network is reconfigured for its routing operation. Additionally or alternatively, wavelength lock steps may be used to set and stabilize the wavelength of the light emitted prior to measuring the light with the detector groups. Additionally or alternatively, each individual measurement may include a background measurement in which the background light is measured by one or more detector groups while the emission groups are not simultaneously emitting light (e.g., prior to the emission of the generated light). These background measurements may enable measurement corrections to account for detector dark current, stray light, and / or ambient light present during sample measurements.

[0113] The measurement sequences described above with respect to FIGS. 7 and 8 may be performed using any of the optical measurement systems described herein. In these cases, a light source unit may be used to generate each of a plurality of wavelengths and provide that light to a multi-stage optical switch network via one or more outputs of the light source unit. For each individual measurement, the multi-stage optical switch network is controlled to route the light of the wavelength generated between one of its inputs (corresponding to the output of the light source unit that is outputting light) and the selected emission group. The detector group associated with the selected emission group measures the light during the measurement and generates an output signal that is used to determine one or more characteristics of the sample being measured.

[0114] FIG. 9 shows a timing diagram of a portion of measurement sequence 900 and exemplary steps associated with individual measurements of measurement sequence 900. Measurement sequence 900 may be performed using an optical measurement system that includes a light source unit, a plurality of detector groups, and a multi-stage optical switch network that selectively routes light to a plurality of emission groups, as described in more detail above. In the variant shown in FIG. 9, the portion of measurement sequence 900 includes a group of N wavelengths, each of which is measured individually in M different sets of emission groups (e.g., M different subsequences of N individual measurements). FIG. 9 shows a first individual measurement 902 in which a first wavelength (“λ-1”) is measured for a first set of emission groups (“L-1”), a second individual measurement 904 in which a second wavelength (“λ-2”) is measured for the first set of emission groups, and a third individual measurement 906 in which an Nth wavelength (“λ-1”) is measured for the first set of emission groups, showing a subset of these measurements. Similarly, FIG. 9 shows a fourth individual measurement 908 in which the first wavelength is measured for a Mth set of emission groups (“L-M”), a fifth individual measurement 910 in which the first wavelength is measured for the Mth set of emission groups, and a sixth individual measurement 912 in which the Nth wavelength is measured for the Mth set of emission groups.

[0115] Using the first individual measurement 902 as an example, each individual measurement includes a setup step (labeled "Setup L-1 λ-1" for measurement 902). During this step, the multi-stage optical switch network routes the optical wavelength (i.e., λ-1) from the input of the network corresponding to that wavelength to one or more outputs corresponding to the selected set of emission groups (i.e., the first set of emission groups L-1) (i.e., by controlling the individual switches of the multi-stage optical switch network). It should be understood that the time required to set the multi-stage optical switch network to the desired routing configuration may depend on the previous routing configuration. As described above, in some cases, it may be faster to adjust the multi-stage optical switch network to account for a new wavelength (while maintaining the same set of emission groups) rather than switching between different sets of emission groups, as indicated by the shorter setup step (labeled "SET L-1 λ-2" for measurement 904) in the second individual measurement 904. Once the setup step is complete, the multi-stage optical switch network may be maintained in the routing configuration (labeled "Maintain L-1 λ-1" for measurement 902) during the measurement of the sample.

[0116] During the measurement of the sample, the light source unit generates light at the wavelength for that measurement (i.e., λ-1), which is labeled as "λ-1 measurement" for measurement 902. Since wavelength shifts in the generated light can affect the accuracy of the measurement, it may be desirable to confirm that the light source unit has achieved a threshold level of wavelength accuracy before measuring the sample. Thus, before measuring the sample, individual measurements may include a wavelength lock step (labeled "λ-1 lock" for measurement 902). During the wavelength lock step, the light source unit generates light and tunes the wavelength (e.g., via a wavelength lock unit as described above) until the desired wavelength (i.e., λ-1) is achieved (in some cases, with a threshold level of stability). It should be understood that the wavelength lock step may be performed at any suitable time relative to the setup step of the multi-stage optical switch network. However, in some cases, it may be desirable for the wavelength lock step and the setup step to be performed at least partially simultaneously, which can save time by enabling the wavelength lock and setup to be done concurrently.

[0117] While the light source unit is generating light (i.e., during the λ-1 measurement step), and while the multi-stage optical switch network is configured to output the generated light to a desired set of emission groups (i.e., during the maintenance L1-λ-1 step), a set of detector groups corresponding to one set of emission groups measures the light it receives (labeled "L-1 light" in measurement 902) during the emission of the generated light from the one set of emission groups. The duration of the sample measurement is defined by the amount of time that one set of emission groups is emitting light simultaneously with the set of detector groups that are active for the one set of detector groups to measure the light. The set of detector groups may output a corresponding set of output signals corresponding to the sample measurement.

[0118] In addition, in some variations, the individual measurements may also include background measurements (labeled "L-1 dark" relative to measurement 902), and one set of detector groups (i.e., the set of detector groups corresponding to the L-1 set of emission groups) measures the light incident thereon while the light source unit is not actively generating light. One set of detector groups can output one set of output signals corresponding to the background measurements, and the background measurements can be used together with one set of output signals corresponding to the sample measurements when calculating one of one or more characteristics of the sample (e.g., by performing dark signal correction on one set of output signals from the sample measurements). The background measurements can be performed either before or after the sample measurements, but in some cases (as shown in FIG. 9), it may be desirable for at least a portion of the background measurements to be performed simultaneously with the setup step of the multi-stage optical switch network. This can save time as the background measurements can be made while the optical measurement is preparing to perform the sample measurement.

[0119] The foregoing description has used specific technical terms for the convenience of explanation to provide a complete understanding of the described embodiments. However, it will be apparent to those skilled in the art that after reading this description, specific details are not required to implement the described embodiments. Thus, the foregoing description of the specific embodiments described herein is presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the embodiments to the exact form disclosed. After reading this description, it will be apparent to those skilled in the art that many modifications and variations are possible in light of the above teachings.

Claims

1. An optical measurement system, comprising: a light source unit capable of generating light of any one of a plurality of wavelengths; a multi-stage optical switch network optically connected to the light source unit and including a plurality of outputs; a plurality of emission groups, each optically connected to a corresponding output among the plurality of outputs; a plurality of detector groups; a controller configured to execute a measurement sequence using the light source unit, the multi-stage optical switch network, the plurality of emission groups, and the plurality of detector groups, the measurement sequence including: dividing the plurality of wavelengths into a plurality of groups, each group of the plurality of groups being associated with a different corresponding output configuration; for each wavelength of the plurality of wavelengths, performing a set of measurements with its corresponding output configuration; An optical measurement system comprising the above.

2. The plurality of groups includes a first group associated with a first output configuration and a second group associated with a second output configuration, Performing the set of measurements for each wavelength of the plurality of wavelengths includes: For a first wavelength of the first group, a first set of measurements, each measurement of the first set of measurements including: generating light of the first wavelength using the light source unit; emitting the generated light from a corresponding set of emission groups selected from the plurality of emission groups and having a first number of emission groups corresponding to the first output configuration; measuring the return light received during the emission of the generated light using a corresponding set of detector groups selected from the plurality of detector groups and having the first number of detector groups; For a second wavelength of the second group, a second set of measurements, each measurement of the second set of measurements including: generating light of the second wavelength using the light source unit; emitting the generated light from a corresponding set of emission groups selected from the plurality of emission groups and having a second number of emission groups corresponding to the second output configuration; Measuring the return light received during the emission of the generated light using a corresponding set of detector groups selected from the plurality of detector groups and having the second number of detector groups, and performing a second set of measurements including this. The optical measurement system according to claim 1, including this.

3. The first set of measurements includes a plurality of measurements having different corresponding sets of emission groups and different corresponding sets of detector groups. The optical measurement system according to claim 2.

4. Each measurement of the first set of measurements Configuring the multi-stage optical switch network to route the light of the first wavelength to the corresponding set of emission groups, further including this, the optical measurement system according to claim 2.

5.

5. Each measurement of the first set of measurements Further including measuring the background light received before the emission of the generated light using the corresponding set of detector groups, and in each measurement of the first set of measurements, configuring the multi-stage optical switch network is at least partially simultaneous with measuring the background light. The optical measurement system according to claim 4.

6. An optical measurement system, including A light source unit capable of generating light of any of a plurality of wavelengths, a multi-stage optical switch network optically connected to the light source unit, and a plurality of emission groups, wherein The multi-stage optical switch network includes a plurality of outputs, and each of the plurality of outputs is optically connected to a corresponding emission group among the plurality of emission groups, and the multi-stage optical switch network is controllable to selectively route the light generated by the light source unit to the plurality of emission groups with different output configurations. Optical measurement system.

7. Further comprising a photonic integrated circuit, the photonic integrated circuit including the light source unit, the multi-stage optical network, and the plurality of emission groups, the optical measurement system according to claim 6.

8. Each emission group includes a corresponding outcoupler configured to emit light from the photonic integrated circuit, the optical measurement system according to claim 7.

9. Further comprising a plurality of detector groups, the optical measurement system according to claim 7.

10. Further comprising an interposer. ​ ​ ​ ​ ​ ​ ​ The photonic integrated circuit and the plurality of detector groups are mounted on the interposer. The optical measurement system according to claim 9.

11. The optical measurement system according to claim 6, further comprising a first wavelength locking unit.

12. The multi-stage optical switch network includes a first stage and a second stage, and the first stage includes a first controllable switch. The first controllable switch includes a first tap. The first wavelength locking unit is optically connected to the multi-stage optical switch network via the first tap. The optical measurement system according to claim 11.

13. Further comprising a second wavelength locking unit, The first stage includes a second controllable switch. The second controllable switch includes a second tap. The second wavelength locking unit is optically connected to the multi-stage optical switch network via the second tap. The optical measurement system according to claim 12.

14. The first controllable switch includes an additional tap. The first tap extracts light from the first leg of the first controllable switch. The additional tap extracts light from the second leg of the first controllable switch. The optical measurement system according to claim 12.

15. A method for characterizing a sample, comprising: selecting a plurality of wavelengths; executing a measurement sequence to generate a plurality of sets of output signals, dividing the plurality of wavelengths into a plurality of groups, each group of the plurality of groups being associated with a different corresponding output configuration; performing a set of measurements of the sample in its corresponding output configuration for each wavelength of the plurality of wavelengths; for each set of measurements, generating the corresponding set of output signals among the plurality of sets of output signals; determining one or more characteristics of the sample using the plurality of sets of output signals. A method comprising.

16. The plurality of groups includes a first group associated with a first output configuration and a second group associated with a second output configuration. Performing the set of measurements of the sample for each wavelength of the plurality of wavelengths comprises: for a first wavelength of the first group, a first set of measurements of the sample, each measurement of the first set of measurements being generating light of the first wavelength; emitting the generated light from a corresponding set of emission groups selected from a plurality of emission groups and having a first number of emission groups corresponding to the first output configuration; measuring return light received during the emission of the generated light using a corresponding set of detector groups selected from a plurality of detector groups and having the first number of detector groups, and performing a first set of measurements of the sample; For a second wavelength of the second group, a second set of measurements of the sample, each measurement of the second set of measurements comprising: generating light of the second wavelength; emitting the generated light from a corresponding set of emission groups selected from the plurality of emission groups and having a second number of emission groups corresponding to the second output configuration; measuring return light received during the emission of the generated light using a corresponding set of detector groups selected from the plurality of detector groups and having the second number of detector groups, and performing a second set of measurements of the sample; The method according to claim 15, comprising: **Claim 17** The first set of measurements includes a plurality of measurements having different corresponding sets of emission groups and different corresponding sets of detector groups. The method according to claim 16. **Claim 18** Each measurement of the first set of measurements further comprises: configuring a multi-stage optical switching network to route the light generated at the first wavelength to the corresponding set of emission groups. The method according to claim 16. **Claim 19** Each measurement of the first set of measurements further comprises: measuring background light received prior to the emission of the generated light using the corresponding set of detector groups, and configuring the multi-stage optical switching network in each measurement of the first set of measurements is performed at least partially simultaneously with measuring the background light. The method according to claim 18. **Claim 20** The measurement sequence is divided into a plurality of sub-sequences, each sub-sequence having a corresponding set of wavelengths of the plurality of wavelengths and a corresponding set of emission groups selected from a plurality of emission groups. The method of claim 15, wherein each sub-sequence includes measurements of the sample for each wavelength within the corresponding set of wavelengths, during which light of the wavelength is emitted from the corresponding set of emission groups.

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