MANAGEMENT OF THE CONTROL OF OPTICAL PHASED ARRAYS WITH MULTIPLE OPTICAL SOURCE CONNECTIONS

Abstract

Directing light involves: providing, from a plurality of optical source ports, a respective optical wave tuned over different respective wavelengths within different respective time slots; emitting at least a portion of the light from at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grating antennas; distributing at least a portion of the light using at least one optical distribution network (ODN) comprising: one or more ODN input ports and two or more ODN output ports, each coupled to a different respective optical phase shifter;and coupling at least part of the light using at least one optical coupler (OC) comprising: at least one OC input terminal coupled to one of the optical source terminals, and at least one OC output terminal coupled to one of the one or more ODN input terminals.

Description

CROSS-REFERENCE TO RELATED REGISTRATION(S)

[0001] This application claims the priority and benefits of the preliminary US application No. 63 / 462,606 entitled “MANAGING CONTROL OF OPTICAL PHASED ARRAYS WITH MULTIPLE OPTICAL SOURCE PORTS”, filed on April 28, 2023, which is incorporated herein by reference. TECHNICAL AREA

[0002] This disclosure concerns the management of the control of optical phased arrays with multiple optical source connections. BACKGROUND

[0003] Some photonic integrated circuits (PICs) can enable beam steering, for example, by using one or more optical phased arrays (OPAs). Some OPAs have a linear distribution of optical antennas (also called optical emitters) along an array direction. Beam steering about a first axis perpendicular to the array direction can be achieved by modifying the relative phase shifts in phase shifters optically coupled to each of the optical antennas. Such beam steering can be performed in a solid-state manner, quickly and possibly with random access, but may be limited to one dimension. Other techniques can be used to steer about a second axis orthogonal to the first.

[0004] One application of beam steering can be found in some LiDAR systems, where an optical beam from an optical source (e.g., a laser) can be transmitted using an optical pathfinder (OPA) to target one or more objects at a given distance, and the light backscattered by the target objects can be collected using another OPA. Various techniques, such as modulation and / or time-of-flight measurement, can be used to determine the distance to the target object(s) based on information associated with a detection event. Another application where beam steering can be relevant is free-space optical communication.

[0005] In some examples, an optical source can provide an optical beam (also called an optical wave) that has a narrow linewidth and peak wavelength falling within a certain range (e.g., between about 100 nm and about 1 mm or a subrange thereof), which is also referred to herein simply as 'light'. SUMMARY

[0006] In one aspect, a device generally comprises the following: a plurality of optical source ports, each configured to provide a respective optical wave tuned over different respective wavelengths and provided within different respective time slots; at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grid antennas, including two or more optical grid antennas, each coupled to another respective optical phase shifter; at least one optical distribution network (ODN), comprising: a plurality of ODN input ports and a plurality of ODN output ports, each including two or more ODN output ports, each coupled to another respective optical phase shifter.wherein each of the two or more ODN output ports is coupled to one of the plurality of ODN input ports; and at least one passive multiport optical coupler (PMOC) comprising: a plurality of PMOC input ports, each containing two or more PMOC input ports coupled to a different respective optical source port, and a plurality of PMOC output ports, each containing two or more PMOC output ports coupled to a different respective optical source port, wherein a first of the two or more PMOC input ports is coupled to a first and a second of the two or more PMOC output ports via different respective propagation paths exhibiting a first relative optical phase shift.and a second of the two or more PMOC input terminals is coupled to the first and the second of the two or more PMOC output terminals via the different respective propagation paths, which exhibit a second relative optical phase shift that differs from the first relative optical phase shift.

[0007] In another aspect, a method for directing light generally comprises the following: providing, from a plurality of optical source ports, a respective optical wave tuned over different respective wavelengths within different respective time slots; emitting at least a portion of the light from at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grating antennas, including two or more optical grating antennas each coupled to a different respective optical phase shifter; and distributing at least a portion of the light using at least one optical distribution network (ODN) comprising: a plurality of ODN input ports and a plurality of ODN output ports, including two or more ODN output ports.each of the optical phase shifters is coupled to another of the respective optical phase shifters, wherein each of the two or more ODN output ports is coupled to one of the plurality of ODN input ports; and coupling at least a portion of the light using at least one passive multiport optical coupler (PMOC) comprising: a plurality of PMOC input ports, including two or more PMOC input ports, each coupled to another of the respective optical source ports, and a plurality of PMOC output ports, including two or more PMOC output ports, each coupled to another of the respective optical source ports, wherein a first of the two or more PMOC input ports is coupled to a first and second of the two or more PMOC output ports via different respective propagation paths,which have a first relative optical phase shift, and a second of the two or more PMOC input terminals is coupled to the first and second of the two or more PMOC output terminals via the various respective propagation paths, which have a second relative optical phase shift that differs from the first relative optical phase shift.

[0008] Aspects may include one or more of the following characteristics.

[0009] The device further comprises a circuit configured to provide a control signal to at least one of the first optical phase shifters for controlling an optical phase shift imposed by the first of the optical phase shifters.

[0010] The control signal is based at least partially on the first relative optical phase shift and the second relative optical phase shift.

[0011] The control signal is based at least partially on the first relative optical phase shift during a first of the time slots associated with a first of the optical source terminals, and is based at least partially on the second relative optical phase shift during a second of the time slots associated with a second of the optical source terminals.

[0012] Each of the two or more PMOC input ports is coupled to all of the two or more PMOC output ports.

[0013] Each of the two or more PMOC input ports is coupled to at least one of the two or more PMOC output ports with an optical loss of less than 50%.

[0014] Each of the two or more PMOC input ports is coupled to at least one of the two or more PMOC output ports with an optical loss of less than 20%.

[0015] The different wavelengths for different optical source connections do not overlap.

[0016] The different respective time slots for different optical source connections do not overlap.

[0017] The device further comprises a plurality of optical sources coupled to different optical source connections, each optical source being configured to provide one of the respective optical waves.

[0018] In another aspect, a device generally comprises: a plurality of optical source ports, each configured to provide a respective optical wave tuned over different respective wavelengths and provided within different respective time slots of a plurality of time slots; at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grid antennas, including two or more optical grid antennas, each coupled to a different respective optical phase shifter; at least one optical distribution network (ODN) comprising: one or more ODN input ports and a plurality of ODN output ports, including two or more ODN output ports, each coupled to a different respective optical phase shifter;and at least one optical coupler (OC) comprising: one or more OC input ports, including at least one OC input port coupled to one of the optical source ports, and one or more OC output ports, including at least one OC output port coupled to one of the one or more ODN input ports;wherein a single period of a repeating pattern of wavelengths is provided by the plurality of optical source ports in the plurality of time slots, the plurality of time slots comprising: a first time slot in which a first of the plurality of optical source ports provides an optical wave tuned to a first wavelength, a second time slot beginning at or after an end of the first time slot in which a second of the plurality of optical source ports provides an optical wave tuned to a second wavelength different from the first wavelength, and a third time slot beginning at or after an end of the second time slot in which the first of the plurality of optical source ports provides an optical wave tuned to a third wavelength between the first wavelength and the second wavelength.

[0019] In another aspect, a method for directing light generally comprises the following: providing, from a plurality of optical source connections, a respective optical wave tuned over different respective wavelengths within different respective time slots of a plurality of time slots; emitting at least a portion of the light from at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grating antennas, including two or more optical grating antennas, each coupled to a different respective one of the optical phase shifters;Distributing at least a portion of the light using at least one optical distribution network (ODN) comprising: one or more ODN input ports and a plurality of ODN output ports, including two or more ODN output ports, each coupled to a different optical phase shifter; and coupling at least a portion of the light using at least one optical coupler (OC), comprising: one or more OC input ports, including at least one OC input port coupled to one of the optical source ports, and one or more OC output ports, including at least one OC output port coupled to one of the one or more ODN input ports;wherein a single period of a repeating pattern of wavelengths is provided by the plurality of optical source ports in the plurality of time slots, the plurality of time slots comprising: a first time slot in which a first of the plurality of optical source ports provides an optical wave tuned to a first wavelength, a second time slot beginning at or after an end of the first time slot in which a second of the plurality of optical source ports provides an optical wave tuned to a second wavelength different from the first wavelength, and a third time slot beginning at or after an end of the second time slot in which the first of the plurality of optical source ports provides an optical wave tuned to a third wavelength between the first wavelength and the second wavelength.

[0020] Aspects may include one or more of the following characteristics.

[0021] The at least one optical coupler comprises two or more optical couplers, the at least one optical distribution network comprises two or more optical distribution networks, and the at least one optical phased array comprises two or more optical phased arrays, wherein the two or more optical phased arrays comprise: a first optical phased array (OPA) and a second optical phased array (OPA); the two or more optical distribution networks comprise: a first optical distribution network (ODN) coupled to the first OPA, and a second optical distribution network (ODN) coupled to the second OPA;and the two or more optical couplers comprise: a first optical coupler comprising a first waveguide that couples the first of the plurality of optical source ports to the first ODN, and a second optical coupler comprising a second waveguide that couples the second of the plurality of optical source ports to the second ODN.

[0022] The at least one optical coupler comprises an optical switch that switches the at least one OC output terminal between different ones of the one or more OC input terminals, including an OC input terminal coupled to the first of the plurality of optical source terminals and an OC input terminal coupled to the second of the plurality of optical source terminals.

[0023] The at least one optical coupler comprises a passive optical multiport coupler that includes a variety of OC input ports and a variety of OC output ports.

[0024] Aspects may have one or more of the following advantages.

[0025] The techniques described herein can be used to electronically calibrate the phase shifters of an OPA to facilitate beam steering using multiple wavelength-matched optical sources. When the optical wavelengths are combined as described herein, a larger beam steering range can be achieved without the loss that can be suffered when using other techniques for combining multiple wavelength-matched optical sources.

[0026] Further features and advantages will become apparent from the following description and from the figures and requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The revelation is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, in accordance with common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features have been arbitrarily enlarged or reduced for the sake of clarity. Fig. 1A and Fig. Figure 1B shows schematic diagrams of an exemplary time-multiplexed steerable optical system. Fig. 1C and Fig. 1D are exemplary curves of the optical power emitted by a first laser and the optical power emitted by a second laser. Fig. Figure 2A is a schematic diagram of an exemplary steerable optical system. Fig. Figure 2B is a schematic diagram of an exemplary steerable optical system. Fig. 2C is a schematic diagram of an exemplary steerable optical system. Fig. Figure 3 is a schematic diagram of an exemplary interface bus that provides input to an electronic integrated control circuit. Fig. Figure 4 is a schematic diagram of the emission from an exemplary ID array of antennas in an optical phased array. Fig. Figure 5 is a schematic diagram of the emission from an exemplary 2D array of antennas in an optical phased array. Fig. Figure 6 is a schematic diagram of an exemplary 1D steering model. Fig. Figure 7 is a schematic diagram of an exemplary 2D steering model. Fig. Figure 8A is a schematic diagram of an exemplary time-division multiplexed steerable optical system. Fig. Figure 8B is a schematic diagram of an exemplary time-division multiplexed steerable optical system. Fig. 8C is a schematic diagram of an exemplary time-division multiplexed steerable optical system. Fig. Figure 9 is a schematic diagram of an exemplary 1D steering model. Fig. 10A and Fig. 10B are phase shift curves as a function of time and offset release curves as a function of time. Fig. Figure 11 is a schematic diagram of an exemplary time diagram for time-division multiplexing. Fig. Figure 12 is a schematic diagram of an exemplary time-multiplexed steerable optical system. DETAILED DESCRIPTION

[0028] Some steerable optical systems (SOSs), such as LiDAR systems, use an optical beam that is directed across a field of view to determine estimated distances to targets within that field. Wavelength-based steering can be performed in an SOS that uses an optical phased array (OPA), which comprises an array of optical antennas (e.g., grating-based optical antennas) emitting light at different angles for different wavelengths. For example, one dimension of steering can be provided by phase-based steering, obtained by controlling phase shifters coupled to the optical antennas, and another dimension of steering can be provided by wavelength-based steering, obtained by tuning an optical source (e.g., a laser) over a range of wavelengths.

[0029] To achieve a wide field of view by performing wavelength-based steering with an OPA, an optical source with a large optical bandwidth can be used. However, typical optical gain media in some optical sources may have a limited optical bandwidth, and thus multiple different optical sources in a SOS can be used to span the desired wavelength range. In some examples, optical waves emitted by different respective lasers can be multiplexed to allow all optical waves to be emitted from the SOS. One technique to achieve this is to use wavelength-selective structures that allow multiple beams to be emitted simultaneously. However, these structures can come at the cost of additional optical losses and control complexity.Therefore, an alternative technique involves supplying light from a single laser to the SOS at any given time and switching between which laser is used to provide light for the SOS. Such an SOS can be implemented with reduced excessive loss and reduced control complexity.

[0030] Some exemplary implementations described herein are based on the principle of time-division multiplexing (TDM). In some TDM examples, only light provided by a single laser is emitted by a single optical sensor (SOS) at any given time. For example, after a first laser has traversed one or more wavelengths within the wavelength range spanned by its gain medium, the first laser is switched off and a second laser is switched on. The SOS then switches to emit light provided by the second laser instead of the first, and the second laser traverses one or more wavelengths within its wavelength range. Such a process can continue until all lasers have been activated and all their corresponding wavelength ranges have been sampled, at which point the entire cycle can be repeated.

[0031] Fig. 1A and Fig. Figure 1B shows an exemplary time-division multiplexed SOS 100 comprising a first laser 102A and a second laser 102B, each optically coupled to an optical circuit 104. The optical circuit 104 is optically coupled to an OPA 106, which emits light over a range that depends on the wavelength of the light. With reference to Fig. 1A The second laser 102B emits no light for a first time period, while the first laser 102A emits a first set of optical waves 108A, characterized by a first range of wavelengths, which are then emitted by the OPA 106 over a first range 110A (i.e., part of a field of view). With reference to Fig. During a second time period, the first laser 102A emits no light, while the second laser 102B emits a second set of optical waves 108B, characterized by a second range of wavelengths, which are then emitted by the OPA 106 over a second range 110B. Each range can correspond to a different field of view. In some examples, the first time period and the second time period are the same (i.e., the first set of optical waves 108A and the second set of optical waves 108B are emitted over the first range 110A and the second range 110B, respectively, for an equivalent time period). In addition to emitting light in a beam formed by constructive and destructive interference between light from the different antennas in a transmit mode, the OPAs can also receive light from directions corresponding to the beam's field of view in a receive mode.The phase shifters can be used to direct both the transmission and reception directions. In general, the time-division multiplexed SOS 100 can be generalized to a time-division multiplexed SOS comprising two or more lasers (and / or other coherent optical sources) that provide optical waves at different times and optionally across different wavelength ranges for transmission and / or reception within different spatial regions.

[0032] Fig. 1C or Fig. Figure 1D shows exemplary curves of the optical power emitted by a first laser and the optical power emitted by a second laser (e.g., the first laser 102A and the second laser 102B in the time-division multiplexed SOS 100, which is in Fig. 1A and Fig. (as shown in 1 B). In this example, the first laser emits light pulses over a first set of times, while the second laser emits light pulses over a second set of times, with the first set of times and the second set of times not overlapping in time.

[0033] A variety of techniques for controlling and steering OPAs are described herein, first in the context of phase-based steering, followed by techniques for switching between multiple optical sources used for wavelength-based steering. In some implementations, the steering described herein may refer to steering an angle from which a beam is received from a SOS and / or an angle from which a beam is transmitted from a SOS.

[0034] An individual optical phase-shifting element (or simply "phase-shifter") can be electronically controlled by adjusting the voltage across the phase-shifter, by adjusting the current through the phase-shifter, and / or by adjusting the power supplied to the phase-shifter. In some SOS implementations, one or more electronic integrated circuits (EICs) include digital-to-analog converters (DACs) to provide individual control of each phase-shifter. For example, digital electronic input codes can instruct a single DAC to provide an individual phase-shifter with a specific phase setting. In such an SOS, the EIC may be designed collectively to meet system constraints (e.g., small footprint or low power consumption). The EIC may incorporate integrated digital logic (e.g.,a digital beamforming control) to provide the appropriate digital electronic input codes for the DACs to steer and / or calibrate an OPA, which may include information used to implement the wavelength-based steering described herein. The digital logic may be implemented, for example, in the circuitry of an application-specific integrated circuit (ASIC), in the circuitry of a field-programmable gate array (FPGA), or in any of a variety of different types of digital circuitry, including any number of central processing or graphics processing cores or other processing units that may be contained within or communicate with the EIC.

[0035] An op-amp with a relatively large number of phase-shifting elements (e.g., thousands of them) can benefit from optimized control, such as an array of electronic phase-shifting drivers controlled, for example, by an integrated digital beam control (DBC). The electronic phase-shifting driver circuits can be implemented as DACs, which are jointly designed and optimized to provide the appropriate voltages and / or currents to the phase-shifting elements, enabling specific phase control in adjustable increments (e.g., up to and above 2π radians). Each individual DAC accepts digital electronic inputs to instruct a specific phase setting for the corresponding phase-shifting element.In an array of thousands of such DACs, the amount of digital data required to direct electronic inputs to those thousands of DACs can be substantial, creating design compromises in performance, timing, bandwidth, crosstalk / interference, wiring overload, and area. An on-chip DBC can reduce the system input data by logically performing calculations, which can be based on a phased-array computational steering model, to compute DAC input codes locally.

[0036] Fig. Figure 2A shows an exemplary SOS 200A comprising an OPA 202 located on a PIC 204 and controlled by two control EICs 206, each electrically connected to a respective interface bus 208. In general, one or more control EICs 206 could control a single OPA. DAC outputs 210 from each control EIC 206 are electrically connected to phase shifters 212. Input light 214 is optically coupled to an optical distribution network (ODN) 216, which optically couples the input light 214 to the phase shifters 212. The phase shifters 212 are optically coupled to antennas 218, which emit at least a portion of the input light 214. The input light 214 can be provided by a coherent optical source (e.g. a laser) coupled to (or integrated with) the PIC 204.As used herein, the term antenna refers to an element capable of both emitting and receiving an optical wave, and may also be called an optical antenna.

[0037] Fig. Figure 2B shows an exemplary SOS 200B comprising a first OPA 222A and a second OPA 222B, each located on a PIC 224 and controlled by a control EIC 226, which is electrically connected to an interface bus 228. The control EIC 226 has DAC outputs 230 that are electrically connected to phase shifters 232 of the first OPA 222A, and DAC outputs 230 that are electrically connected to phase shifters 232 of the second OPA 222B. A first input light 234A is optically coupled to a first ODN 236A, which optically couples the first input light 234A to phase shifters 232 of the first OPA 222A. The phase shifters 232 of the first OPA 222A are optically coupled to antennas 238 of the first OPA 222A. A second input light 234B is optically coupled to a second ODN 236B, which optically couples the second input light 234B to phase shifters 232 of the second OPA 222B.The phase shifters 232 of the second OPA 222B are optically coupled to antennas 238 of the second OPA 222B.

[0038] In some examples, a single DAC output can be used to control multiple phase shifters, such as when the beam shaping control implemented by one or more DAC outputs applied to one OPA can also be used for one or more additional OPAs.

[0039] Fig. Figure 2C shows an exemplary SOS 200C comprising a first OPA 242A and a second OPA 242B, each located on a PIC 244 and controlled by a control EIC 246, which is electrically connected to an interface bus 248. The control EIC 246 has DAC outputs 250, each electrically connected to phase shifters 252 of both the first OPA 242A and the second OPA 242B. A first input light 254A is optically coupled to a first ODN 256A, which optically couples the first input light 254A to phase shifters 252 of the first OPA 242A. The phase shifters 252 of the first OPA 242A are optically coupled to antennas 258 of the first OPA 242A. A second input light 254B is optically coupled to a second ODN 256B, which optically couples the second input light 254B to phase shifters 252 of the second OPA 242B. The phase shifters 252 of the second OPA 242B are optically coupled to antennas 258 of the second OPA 242B.In this example, each of the DAC outputs 250 is sent to at least one of the phase shifters 252 of the first OPA 242A and to at least one of the phase shifters 252 of the second OPA 242B.

[0040] Fig. Figure 3 shows an exemplary interface bus 302 that provides an input to a control EIC 304, which includes output stage DBCs 306 for calculating codes that are used as input to DACs 308 acting as phase-shift drivers. Thus, the control EIC 304 acts as an integrated DBC that can be configured to use data compression algorithms to simplify (or in some cases eliminate the need for) the interface bus 302, thereby reducing communication power consumption and / or communication time.The control EIC 304 can accept (possibly simple) input commands on a dual-purpose interface bus and an upstream stage DBC 310, such as a steering command specifying one or more desired OPA tilt angles, focus distances, phase information, Zernike polynomial terms, calibration commands used for OPA factory tuning, or other terms that can be used to direct the emission of light from an OPA. Alternatively, the control EIC 304 could accept no input and operate automatically based on a predetermined behavior, thus enabling the removal of the interface bus 302.

[0041] With renewed reference to Fig. 3. In some examples, the control EIC 304 can calculate the appropriate input codes for the DACs 308 at least partially based on a provided input command that is fed to a logically implemented phased-array computation model (also known as a steering model). Fig. Figure 6 shows an example of such a steering model for a single steering angle, θ, which in this example is defined based on a tilt angle, although multiple simultaneous steering angles or multi-axis steering are also possible (e.g., Figure 6 shows). Fig. 7 a model for the 2D steering of an OPA, such as the one in Fig. (5 shown). An alternative architecture for the control EIC 304 can have a pre-programmed table of steering angles, so that only a simple trigger signal (or alternatively a predetermined number of input clock signals or a predefined time duration) is used as an indication of when to steer to the next angle. The logic calculation blocks can be distributed across the control EIC 304 (e.g., in different levels of DBCs) so that the final logic calculation of the appropriate input codes for DACs 308 is performed locally at those DACs 308. The control EIC 304 could also include a clock generator (e.g., instead of using an external clock input).

[0042] Fig. Figure 4 shows an exemplary 1D array of antennas 400, comprising antennas 402 emitting light 403 from an OPA (not shown). From an assumed tilt angle θ of a planar wavefront 404 formed by constructive and destructive interference of the light 403 emitted by the antennas 402, the relative phase difference between the light 403 emitted by adjacent antennas 402 can be determined using the following expression: d · k · tan(θ). In this expression, d is the distance between the centers of adjacent antennas 402 and k is the wavenumber, which is equal to 2π / λ, where λ is the wavelength of the light 403. Alternatively, a normalized wavenumber k can be used. norm= k / (2π) instead of the wavenumber k, which would allow a phase shift to be provided (and stored) as a value in the range between 0 and 1 instead of in the range between 0 and 2π. While an ideal plane wave corresponds to an infinite number of antennas, in a practical implementation there is a finite number of antennas, M, that form a specific array pattern with a main lobe of a beam propagating in the direction of the tilt angle θ.

[0043] Fig. Figure 5 shows an exemplary 2D array of antennas 500, comprising antennas 502 that emit a beam with a main lobe propagating along a propagation axis 504 defined by two angles θ x and θ y can be characterized. Along a first direction, the distance between two adjacent antennas 502 is defined by d xGiven. Along a second direction, perpendicular to the first direction, the distance between two adjacent antennas 502 is given by d y given.

[0044] In general, a different antenna arrangement can include 1D or 2D arrays of antennas exhibiting any of a variety of emission characteristics. In some OPAs, the antennas are not point antennas emitting light from a single location, but rather linear antennas emitting light along the length of a grating, for example, or other extended antennas emitting light over the shape of an emission region. Different antenna arrangements affect the shape of the emitted beam, but similar calculations can be performed to determine a relative phase shift between antenna elements based on information about a desired beam tilt angle.

[0045] One advantage of reduced data communication to an EIC can be a reduction in crosstalk and interference with other sensitive circuits nearby, such as DAC circuits or receivers. In a compact LiDAR sensor, for example, the EIC may be physically co-localized or co-integrated with sensitive transimpedance amplifiers. In some implementations, digital clocking near such circuits may be undesirable due to the noise caused by clock signals. By simplifying the interface to the EIC and performing DAC input code computation on-the-fly, the amount of digital switching performed for signals propagating over the interface bus can be significantly reduced. In some examples, the DBC is not clocked during a significant portion of the point-to-point steering time (e.g., when steering according to the [unclear]). Fig. (as shown in the timing diagram in Figure 11). Thus, the clock signal can be switched off at these times (e.g., during periodic silent intervals), allowing for less noisy operation of the noise-sensitive components during these times, as described in more detail below.

[0046] A control EIC, comprising one or more DBCs, can accept several different types of input from the interface bus. For example, a control EIC can receive a digital representation of one or more desired steering angles on the interface bus and then calculate the adjacent antenna phase differences to generate the specified pitch angle(s). In some examples, a control EIC can receive a digital representation of the adjacent antenna phase differences on the interface bus to reduce the amount of computation required on the control EIC. Furthermore, a control EIC can have a memory table that stores a list of possible steering angles or adjacent antenna phase differences and advance to the next steering angle or phase difference based on a trigger input on the interface bus.In some examples, a control EIC calculates the next steering angle based on a given representation of the angular resolution from the interface bus or from stored memory that is integrated with or otherwise coupled to the control EIC. The memory can be implemented, for example, using flip-flops, a register file, static random access memory (SRAM), and / or dynamic random access memory (DRAM).

[0047] Fig. Figure 6 shows an exemplary 1D steering model 602, which is based on a control EIC (e.g., by the one in Fig. 3 shown final stage DBCs 306) can be carried out, which are used to control a 1D array of antennas (e.g. the one shown in Fig. The 1D steering model 602 uses the 1D array of antennas shown in Figure 400. In this example, the 1D steering model 602 takes a tilt angle θ of an OPA as an input. The 1D steering model 602 calculates the tangent of the tilt angle θ (e.g., using a lookup table) and multiplies the result by the wavenumber and the antenna spacing (i.e., the distance between adjacent antenna elements) to determine an adjacent antenna phase difference 604. An alternative version of the 1D steering model 602 could directly accept the adjacent antenna phase difference 604 as an input. Another alternative version could implement multi-axis steering if the OPA supports it, such as with a 2D array of antennas (e.g., the one shown in Figure 400). Fig. 5 shown 2D array of antennas 500). For each antenna, the adjacent antenna phase difference 604 is multiplied by the antenna position. The resulting product is summed with the calibration offset for the antenna to compute a phase, and the phase mod 2π is provided as input to a phase-to-DAC input code converter 606, which generates a DAC input code 608 corresponding to the antenna under consideration. The calibration offset can be programmed to change based on a suitable phase offset used for wavelength-based steering according to a time-division multiplexing pattern, or a separate phase offset, which can be enabled or disabled as required, can be added in addition to the calibration offset (e.g., as in Fig. 9 shown).

[0048] Fig. Figure 7 shows an exemplary 2D steering model 702, which is based on a control EIC (e.g., by the one in Fig. 3 shown final stage DBCs 306) can be carried out, which are used to control a 2D array of antennas (e.g. the one in Fig. The 2D steering model 702 is used in Figure 5, which shows 2D arrays of antennas 500. In this example, the 2D steering model 702 takes two input tilt angles of an OPA as inputs. For each of the two input tilt angles, the 2D steering model 702 calculates a first adjacent antenna phase difference 704A and a second adjacent antenna phase difference 704B in a manner similar to the calculation of the in Figure 5. Fig. The 1D steering model 602 shown in Figure 6 is similar. An alternative version of the 2D steering model 702 could directly accept one or both adjacent antenna phase differences as inputs. For each antenna and direction, the adjacent antenna phase difference is multiplied by the respective antenna position along that direction (e.g., the first adjacent antenna phase difference 704A is multiplied by the antenna position in x, and the second adjacent antenna phase difference 704B is multiplied by the antenna position in y). The resulting products are summed and added with a calibration offset for the antenna to compute a phase, and the phase mod 2π is provided as input to a phase-to-DAC input code converter 706, which generates a DAC input code 708 corresponding to the antenna under consideration.

[0049] Some SOSs are configured to perform calibration procedures to correct manufacturing defects (e.g., to calibrate one or more OPAs of the SOS). In some examples, a DBC may include a calibration mode to provide functional and speed improvements to SOS calibration. For example, improvements in calibration speed can be achieved by incorporating on-board logic that automatically sequences through an OPA's calibration sequence. Such a calibration sequence can be internally time-controlled, synchronized with an external trigger input, or generated by an external trigger output.

[0050] In general, an optical switch is not necessarily required to implement a time-division multiplexed architecture. For example, each optical source in such a time-division multiplexed SOS can be optically coupled to its own dedicated OPA, which is only active when the corresponding optical source is active.

[0051] Fig. Figure 8A shows an exemplary time-division multiplexed SOS 800A, comprising a separate OPA for each optical source. In this example, a first optical source 802A is optically coupled to a first amplifier 804A (e.g., an optical amplifier), which amplifies the optical power it receives from the first optical source 802A based at least partially on one or more control signals provided by a first current driver 806A. A second optical source 802B is optically coupled to a second amplifier 804B, which amplifies the optical power it receives from the second optical source 802B based at least partially on one or more control signals provided by a second current driver 806B.The first current driver 806A and the second current driver 806B each provide control signals that regulate the amount of optical power gain provided by their respective amplifiers. The first amplifier 804A is optically coupled from its optical source connection to a first OPA 808A via a first ODN 810A, and the second amplifier 804B is optically coupled from its optical source connection to a second OPA 808B via a second ODN 810B.

[0052] With renewed reference to Fig. In 8A, a single-input / single-output optical coupler (e.g., a waveguide) optically couples the output of the first amplifier 804A and the output of the second amplifier 804B to their respective ODNSs (e.g., a binary tree of 1x2 dividers, also called a binary divider ODN), each of which is optically coupled to an array of phase shifters and optical antennas of its respective OPA. This type of architecture benefits from a simpler control scheme, where turning the current drivers on and off can be used to switch between the first optical source 802A and the second optical source 802B, which emit light from their respective OPAs.For example, over a first time period, the current drivers can be configured such that the first amplifier 804A amplifies the optical power it receives from the first optical source 802A, while the second amplifier 804B does not significantly amplify the optical power it receives from the second optical source 802B. Similarly, over a second time period, the current drivers can be configured such that the first amplifier 804A does not significantly amplify the optical power it receives from the first optical source 802A, while the second amplifier 804B does amplify the optical power it receives from the second optical source 802B. However, this type of architecture can have an increased footprint due to the additional OPAs used. This type of architecture can also be generalized to include N OPAs (i.e., one OPA for each of the N lasers in the SOS).

[0053] Fig. Figure 8B shows an exemplary time-division multiplexed SOS 800B, which includes an optical switch 811 that can be used to reduce the number of op-amps, thereby reducing the footprint of the time-division multiplexed SOS 800B. A first optical source 812A is optically coupled to a first amplifier 814A, which amplifies the optical power it receives from the first optical source 812A, based at least partially on one or more control signals provided by a first current driver 816A. A second optical source 812B is optically coupled to a second amplifier 814B, which amplifies the optical power it receives from the second optical source 812B, based at least partially on one or more control signals provided by a second current driver 816B.The first amplifier 814A and the second amplifier 814B are each optically coupled from their respective optical source connections to the optical switch 811. In this example, the optical switch 811 is an active 2x1 switch that selectively couples one of two optical inputs optically to an ODN 820, which is optically coupled to an OPA 818 emitting the selected optical input. The state of the optical switch 811 can be set based on the optical source that is active. For time-division multiplexed SOSs comprising N lasers, the optical switch 811 can be generalized to be an Nx1 switch. The design of the optical switch 811 can be based, at least in part, on the desired optical power, as for long-range LiDAR systems. In some examples, it can be challenging to design the optical switch 811 to operate at higher optical powers.

[0054] To overcome some of the design challenges associated with an optical switch (e.g., the one in Fig. If the optical switch shown in 8B (811) can be connected, a passive optical coupler can be used.

[0055] Fig. Figure 8C shows an exemplary time-division multiplexed SOS 800C, which includes a passive coupler 821 (also called a passive optical multiport coupler or passive optical combiner). A first optical source 822A is optically coupled to a first amplifier 824A, which amplifies the optical power it receives from the first optical source 822A, based at least partially on one or more control signals provided by a first current driver 826A. A second optical source 822B is optically coupled to a second amplifier 824B, which amplifies the optical power it receives from the second optical source 822B, based at least partially on one or more control signals provided by a second current driver 826B.The first amplifier 824A and the second amplifier 824B are each optically coupled from their respective optical source terminals to respective input terminals of the passive coupler 821. In this example, the passive coupler 821 is a 2x2 coupler, optically coupling its two input terminals to two output terminals of the passive coupler 821, and the two output terminals of the passive coupler 821 are optically coupled to two input terminals of an ODN 830. The two input terminals of the ODN 830 are optically coupled to two or more output terminals of the ODN 830, which are optically coupled to phase shifters (not shown) of an OPA 828. In some examples, each of the two or more output terminals of the ODN 830 is coupled to a single input terminal of the ODN 830.One or more control signals applied to phase shifters in the OPA 828 can select whether a beam is formed with light originating from the first optical source 822A or with light originating from the second optical source 822B.

[0056] With renewed reference to Fig. 8C is optically coupled to the first of the two input terminals of the passive coupler 821 with the first and second of the two output terminals of the passive coupler 821 via different propagation paths, which exhibit a first relative optical phase shift. Additionally, a second of the two input terminals of the passive coupler 821 is optically coupled to the first and second of the two output terminals of the passive coupler 821 via different propagation paths, which exhibit a second relative optical phase shift that differs from the first relative optical phase shift.

[0057] With renewed reference to Fig. For time-division multiplexed SOSs comprising N lasers, the passive coupler 821 can be an NxN coupler (also called an NxN combiner). In such examples, the N lasers can be passively combined with the passive coupler 821 and optically coupled to the ODN 830. In some examples, the ODN 830 is a modified binary divider ODN that has been modified by removing a selected number of the initial stages of the binary divider ODN to optically couple the OPD 830 and the OPA 828 to the N output terminals of the passive coupler 821. For example, removing the first stage allows the ODN 830 to have two input terminals, while removing the first two stages provides four input terminals. This technique of using an NxN coupler can reduce optical losses (e.g., resulting in losses of less than 50%, 20%, 10%, 1%, or essentially lossless) compared to a passive Nx1 combiner.When a passive 2x1 coupler is used to optically couple a full binary divider ODN (i.e., with one input terminal), there is an inherent 3 dB loss from the optical source terminal of the amplifier to the output of the passive 2x1 coupler. Similarly, a passive 4x1 coupler would have a 6 dB loss, and so on.

[0058] With renewed reference to Fig. To account for the optical phase difference in the two optical signals transmitted from the output terminals of the passive coupler 821, the phase shifter settings in the OPA 828 can be adjusted, at least partially, based on whether the first optical source 822A or the second optical source 822B is active. Specifically, the phase shifter settings can be adjusted to ensure that the light in each waveguide of the OPA 828, downstream of the phase shifters, has the appropriate phase relationship to produce a desired far-field emission pattern. For example, a phase ramp between all adjacent elements in the OPA 828 produces a single point at a specific angular location in the far field. Fortunately, a completely new phase shifter calibration table for each input terminal of a passive NxN coupler may not be necessary.Information representing the optical transfer function of the passive NxN coupler provides a description of the specific phase settings that can be applied to specific phase shifters in the OPA 828 to ensure the desired far-field pattern is achieved. For example, a passive 2x2 multimode interference coupler has a 90° phase difference between its two output terminals, which can be applied to the relevant phase shifters in the OPA 828. Thus, using a predetermined phase relationship in this example, only one calibration is required for the individual optical input source channel, and a 1D steering model (e.g., as in [reference]) can be applied. Fig. 9) can be followed. The 1D steering model can include a phase-shifter-specific phase offset term, determined from the transfer function of the passive NxN coupler and a measured calibration offset term, to calculate the appropriate actuation signals for each emission angle and optical input source channel.

[0059] Fig. Figure 9 shows an exemplary 1D steering model 902 that can be implemented by a digital beamforming control system. Compared to the one in Fig. The 1D steering model 602 shown in Figure 6 includes a phase shift term in the 1D steering model 902 to support time-division multiplexing, with the output from an NxN coupler being taken as input to an OPA (e.g., the one shown in Figure 6). Fig. The OPA 828 shown in Figure 8C is used. In this example, the 1D steering model 902 takes an input tilt angle θ of an OPA as an input. The 1D steering model 902 calculates the tangent of the input tilt angle θ (e.g., using a lookup table) and multiplies the result by the wavenumber and the antenna spacing (i.e., the distance between adjacent antenna elements) to determine an adjacent antenna phase difference 904. To calculate a phase for each antenna, the adjacent antenna phase difference 904 is multiplied by the antenna position, and the resulting product is summed with both (1) a calibration offset for the antenna and (2) the output of an AND gate that receives a phase offset and an offset release signal as inputs. The phase mod 2π is provided as input for a phase DAC input code converter 906, which generates a DAC input code 908 corresponding to the antenna under consideration.

[0060] Fig. Figure 10A shows an exemplary implementation of the additional phase shift logic, which is described in Fig. Figure 9 shows the 1D steering model 902 as it is applied to an exemplary time-division multiplexed SOS that includes a passive 2x2 coupler. In this example, the phase offset is held at a constant value and is only released by the offset enable signal for the relevant phase shifters.

[0061] Fig. Figure 10B shows an exemplary implementation of the additional phase shift logic, which is described in Fig. Figure 9 shows the 1D steering model 902 as it is applied to an exemplary time-division multiplexed SOS that includes a passive 4x4 coupler. In this example, the phase shift can be updated to apply the correct signal to all phase shifters in the array of phase shifters. For example, the phase shift can be varied during a given laser band (i.e., a duration for which a given laser is active).

[0062] An additional advantage of time-division multiplexed SOS is that a laser in an inactive channel is given extra time to stabilize its wavelength before being activated. This can be particularly useful for a coherent LiDAR system, where it may be desirable to have good control over the laser's frequency during operation. To allow for this extra settling time, the active lasers can be switched between the two bands instead of traversing an entire band before switching to the other. An example timing diagram is shown in Fig. Figure 11 shows that while one channel is active, the laser from the other channel tunes to the desired wavelength and settles into a steady state. An implementation of this timing diagram in a time-division multiplexed SOS is shown in Fig. Figure 12 is shown to demonstrate how the emitted wavelengths switch between the two channels.

[0063] Fig. Figure 11 shows an exemplary timing diagram for time-division multiplexing (TDM) that includes alternating wavelength bands to allow for additional settling time of the optical source in an exemplary TDM system comprising two optical sources and two amplifiers. In this example, a first optical source tunes to and settles at an output frequency while a second optical source is amplified by a second amplifier. The amplifiers switch on and off to enable TDM between the first and second optical sources.

[0064] Fig. Figure 12 shows an exemplary time-division multiplexed SOS 1200 comprising a passive coupler 1201. A first optical source 1202A is optically coupled to a first amplifier 1204A, which amplifies the optical power it receives from the first optical source 1202A based at least partially on one or more control signals provided by a first current driver 1206A. A second optical source 1202B is optically coupled to a second amplifier 1204B, which amplifies the optical power it receives from the second optical source 1202B based at least partially on one or more control signals provided by a second current driver 1206B. The first amplifier 1204A and the second amplifier 1204B are each optically coupled to the passive coupler 1201 through their respective optical source terminals.In this example, the passive coupler 1201 is a passive 2x2 coupler that optically couples light at its two input terminals to two output terminals of the passive coupler 1202, which are optically coupled via an ODN 1210 into an OPA 1208. The time-division multiplexed SOS 1200 can be configured to emit multiple wavelengths 1212 over time (e.g., according to the one in ). Fig. (11 shown in the time diagram). The different wavelengths 1212, which are emitted at different times, can have different emission inclination angles.

[0065] Although the disclosure has been described in connection with certain embodiments, it is understood that the disclosure is not intended to be limited to the disclosed embodiments, but on the contrary is intended to cover various modifications and equivalent arrangements that are included within the scope of protection of the attached claims, the scope of protection being to be interpreted in the broadest possible way in order to encompass all such modifications and equivalent structures as is permissible under the law. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 462,606

[0001]

Claims

[1] A device comprising: a multitude of optical source connections, each configured to provide a specific optical wave tuned over different respective wavelengths and provided within different respective time slots; at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grid antennas, including two or more optical grid antennas, each coupled to a different optical phase shifter; at least one optical distribution network (ODN) that includes the following: a variety of ODN input ports and a variety of ODN output ports, including two or more ODN output ports, each coupled to a different optical phase shifter, wherein each of the two or more ODN output ports is coupled to one of the plurality of ODN input ports; and at least one passive multiport optical coupler (PMOC) comprising the following: a variety of PMOC input ports, including two or more PMOC input ports, each coupled to a different optical source port, and a variety of PMOC output ports, including two or more PMOC output ports, each coupled to a different variety of ODN input ports, where one of the two or more PMOC input terminals is connected to a first and a second of the two or more PMOC output terminals is coupled via different respective propagation paths that have a first relative optical phase shift, and a second of the two or more PMOC input terminals is coupled to the first and the second of the two or more PMOC output terminals via the different respective propagation paths that have a second relative optical phase shift that differs from the first relative optical phase shift. [2] Device according to claim 1, further comprising a circuit configured to provide a control signal to at least one of the optical phase shifters for controlling an optical phase shift imposed by the first of the optical phase shifters. [3] The device according to claim 2, wherein the control signal is based at least partially on the first relative optical phase shift and the second relative optical phase shift. [4] The device according to claim 2, wherein the control signal is based at least partially on the first relative optical phase shift during a first of the time slots associated with a first of the optical source terminals, and at least partially on the second relative optical phase shift during a second of the time slots associated with a second of the optical source terminals. [5] The device according to claim 1, wherein each of the two or more PMOC input terminals is coupled to all of the two or more PMOC output terminals. [6] The device according to claim 1, wherein each of the two or more PMOC input ports is coupled to at least one of the two or more PMOC output ports with an optical loss of less than 50%. [7] The device according to claim 6, wherein each of the two or more PMOC input ports is coupled to at least one of the two or more PMOC output ports with an optical loss of less than 20%. [8] The device according to claim 1, wherein the different respective wavelengths for different optical source connections do not overlap. [9] The device according to claim 1, wherein the different respective time slots for different optical source connections do not overlap. [10] The device according to claim 1, further comprising a plurality of optical sources coupled to different of the plurality of optical source connections, each optical source being configured to provide one of the respective optical waves. [11] A method for directing light, comprising the following: Providing, from a multitude of optical source connections, a respective optical wave tuned over different respective wavelengths within different respective time slots; Emitting at least a portion of the light from at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grid antennas, including two or more optical grid antennas, each coupled to a different optical phase shifter; Distribute at least a portion of the light using at least one optical distribution network (ODN) comprising the following: a variety of ODN input ports and a variety of ODN output ports, including two or more ODN output ports, each coupled to a different optical phase shifter, wherein each of the two or more ODN output ports is coupled to one of the plurality of ODN input ports; and Coupling at least part of the light using at least one passive multiport optical coupler (PMOC) comprising the following: a variety of PMOC input ports, including two or more PMOC input ports, each coupled to a different optical source port, and a variety of PMOC output ports, including two or more PMOC output ports, each coupled to a different variety of ODN input ports, wherein a first of the two or more PMOC input terminals is coupled to a first and a second of the two or more PMOC output terminals via different respective propagation paths that have a first relative optical phase shift, and a second of the two or more PMOC input terminals is coupled to the first and the second of the two or more PMOC output terminals via the different respective propagation paths that have a second relative optical phase shift that differs from the first relative optical phase shift. [12] The method according to claim 11, further comprising providing a control signal to at least one first of the optical phase shifters to control an optical phase shift imposed by the first of the optical phase shifters. [13] The method according to claim 12, wherein the control signal is based at least partially on the first relative optical phase shift and the second relative optical phase shift. [14] The method according to claim 12, wherein the control signal is based at least partially on the first relative optical phase shift during a first of the time slots associated with a first of the optical source terminals, and at least partially on the second relative optical phase shift during a second of the time slots associated with a second of the optical source terminals. [15] The method according to claim 11, wherein the different respective time slots for different optical source connections do not overlap. [16] A device comprising: a multitude of optical source connections, each configured to provide a respective optical wave tuned over different respective wavelengths and provided within different respective time slots of a multitude of time slots; at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grid antennas, including two or more optical grid antennas, each coupled to a different optical phase shifter; at least one optical distribution network (ODN) that includes the following: one or more ODN input ports and a variety of ODN output ports, including two or more ODN output ports, each coupled to a different optical phase shifter; and at least one optical coupler (OC) comprising the following: one or more OC input ports, including at least one OC input port coupled to one of the optical source ports, and one or more OC output ports, including at least one OC output port coupled to one of the one or more ODN input ports; wherein a single period of a repeating pattern of wavelengths is provided by the plurality of optical source connections in the plurality of time slots, the plurality of time slots comprising the following: a first time slot in which a first of the multitude of optical source connections provides an optical wave tuned to a first wavelength, a second time slot, beginning at or after an end of the first time slot, in which a second of the plurality of optical source connections provides an optical wave tuned to a second wavelength different from the first wavelength, and a third time slot beginning at or after the end of the second time slot, in which the first of the plurality of optical source connections provides an optical wave tuned to a third wavelength between the first wavelength and the second wavelength. [17] The device according to claim 16, wherein the at least one optical coupler comprises two or more optical couplers, the at least one optical distribution network comprises two or more optical distribution networks, and the at least one optical phased array comprises two or more optical phased arrays, wherein The two or more optical phased arrays include the following: a first optical phased array (OPA) and a second optical phased array (OPA); the two or more optical distribution networks include the following: a first optical distribution network (ODN) coupled with the first OPA, and a second optical distribution network (ODN) coupled to the second OPA; and The two or more optical couplers include the following: a first optical coupler comprising a first waveguide that couples the first of the multitude of optical source connections to the first ODN, and a second optical coupler comprising a second waveguide that couples the second of the multiple optical source connections to the second ODN. [18] The device according to claim 16, wherein the at least one optical coupler comprises an optical switch which switches the at least one OC output terminal between different ones of the one or more OC input terminals, including an OC input terminal coupled to the first of the plurality of optical source terminals and an OC input terminal coupled to the second of the plurality of optical source terminals. [19] The device according to claim 16, wherein the at least one optical coupler comprises a passive optical multiport coupler comprising a plurality of OC input ports and a plurality of OC output ports. [20] A method for directing light, comprising the following: Providing, from a multitude of optical source connections, a respective optical wave tuned over different respective wavelengths, within different respective time slots of a multitude of time slots; Emitting at least a portion of the light from at least one optical phased array comprising a plurality of optical phase shifters and a plurality of optical grid antennas, including two or more optical grid antennas, each coupled to a different optical phase shifter; Distribute at least a portion of the light using at least one optical distribution network (ODN) comprising the following: one or more ODN input ports and a variety of ODN output ports, including two or more ODN output ports, each coupled to a different optical phase shifter; and Coupling at least part of the light using at least one optical coupler (OC) comprising the following: one or more OC input ports, including at least one OC input port coupled to one of the optical source ports, and one or more OC output ports, including at least one OC output port coupled to one of the one or more ODN input ports; wherein a single period of a repeating pattern of wavelengths is provided by the plurality of optical source connections in the plurality of time slots, the plurality of time slots comprising the following: a first time slot in which a first of the multitude of optical source connections provides an optical wave tuned to a first wavelength, a second time slot, beginning at or after an end of the first time slot, in which a second of the plurality of optical source connections provides an optical wave tuned to a second wavelength different from the first wavelength, and a third time slot beginning at or after the end of the second time slot, in which the first of the plurality of optical source connections provides an optical wave tuned to a third wavelength between the first wavelength and the second wavelength.

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