Coherent signal combining with multiple-outputs for quasi-CW LIDAR operation

The present disclosure is directed to a coherent signal generator comprising an amplifier configured to receive a plurality of optical signals that are respectively associated with a plurality of phases, and generate a plurality of amplified optical signals using the plurality of optical signals; and a splitter network that is coupled to the amplifier. The splitter network is configured to receive the plurality of amplified optical signals, and generate a combined optical signal at an output of a plurality of outputs using the plurality of amplified optical signals.

BACKGROUND

Optical detection of range using lasers, often referenced by a mnemonic, LIDAR, for light detection and ranging, also sometimes called laser RADAR, is used for a variety of applications, from altimetry, to imaging, to collision avoidance. LIDAR provides finer scale range resolution with smaller beam sizes than conventional microwave ranging systems, such as radio-wave detection and ranging (RADAR). Optical detection of range can be accomplished with several different techniques, including direct ranging based on round trip travel time of an optical pulse to an object, and chirped detection based on a frequency difference between a transmitted chirped optical signal and a returned signal scattered from an object, and phase-encoded detection based on a sequence of single frequency phase changes that are distinguishable from natural signals.

SUMMARY

Aspects of the present disclosure relate generally to light detection and ranging (LIDAR) in the field of optics, and more particularly to systems and methods for coherent beam combining with multiple-outputs for quasi-CW LIDAR operation, to support the operation of a vehicle.

DETAILED DESCRIPTION

A LIDAR system may include a laser source for providing a light signal (sometimes referred to as, “beam”), one or more modulators for modulating a phase and/or a frequency of the light signal using Continuous Wave (CW) modulation or quasi-CW modulation, an amplifier for amplifying the modulated signal to send the signal up to a certain range, and/or optics (e.g., a mirror scanner) for steering the amplified signal to an environment within a given field of view.

In a LIDAR system that uses CW modulation, the modulator modulates the laser light continuously. For example, if a modulation cycle is 10 seconds, an input signal is modulated throughout the whole 10 seconds. Instead, in a LIDAR system that uses quasi-CW modulation, the modulator modulates the laser light to have both an active portion and an inactive portion. For example, for a 10 second cycle, the modulator modulates the laser light only for 8 seconds (sometimes referred to as, “the active portion”), but does not modulate the laser light for 2 seconds (sometimes referred to as, “the inactive portion”). By doing this, the LIDAR system may be able to reduce power consumption for the 2 seconds because the modulator does not have to provide a continuous signal.

In Frequency Modulated Continuous Wave (FMCW) LIDAR for automotive applications, it may be beneficial to operate the LIDAR system using quasi-CW modulation where FMCW measurement and signal processing methodologies are used, but the light signal is not in the on-state (e.g., enabled, powered, transmitting, etc.) all the time. In some implementations, Quasi-CW modulation can have a duty cycle that is equal to or greater than 1% and up to 50%. If the energy in the off-state (e.g., disabled, powered-down, etc.) can be expended during the actual measurement time then there may be a boost to signal-to-noise ratio (SNR) and/or a reduction in signal processing requirements to coherently integrate all the energy in the longer time scale.

In some implementations, an erbium-doped fiber amplifier (EDFA) may be used to implement a coherent signal generator (e.g., coherent signal generator206inFIG. 2A, coherent signal generator206inFIG. 2B). By using an EDFA for the coherent beam generator, for a system implementing quasi-CW modulation as the optical gain and/or energy can be stored and output signals from the EDFA can be provided in shorter bursts just by pulsing the input to the EDFA.

In some implementations, semiconductor optical amplifiers (SOAs) can be used to implement a coherent signal generator (e.g., coherent signal generator206inFIG. 2A, coherent signal generator206inFIG. 2B). By using SOAs for the coherent signal generator, a high level of integration may be achieved. For example, a large number of SOA's can be scaled-down and placed onto a single semiconductor chip, which may result in improvements in not only speed (e.g., less latency) and power consumption (e.g., the power may be more efficiently routed between the SOAs), but also improvements in the manufacturing process. That is, scaling down the coherent signal generator (sometimes referred to as, “signal processing system”) onto a single semiconductor chip means that the semiconductor chip (e.g., silicon) may be smaller in size, thereby decreasing the likelihood of a manufacturing defect affecting the performance of the coherent signal generator.

Accordingly, the present disclosure is directed to systems and methods for coherent signal generating (e.g., combining, merging, adding, mixing, etc.) with multiple-outputs for quasi-CW LIDAR operation, to support the operation of a LIDAR system for a vehicle.

In various example implementations, as described in the below passages, a coherent signal generator may include one or more phase shifters, and/or one or more splitters (e.g., 50/50 splitters). The coherent signal generator may include an amplifier containing multiple sub-amplifiers, such as SOAs, that are each coupled to one or more output channels of the coherent signal generator via one or more beam splitters (e.g., a 50/50 beam splitter, etc.). Each sub-amplifier may provide a continuous wave (e.g., up to 95% duty cycle) having a fixed output power. The coherent signal generator may coherently combine (using the one or more splitters) the output powers of some or all of the sub-amplifiers into a combined output power, and send the combined output power to one of the output channels. For example, if the coherent signal generator includes 8 sub-amplifiers that each produce 100 milliwatts (mW) of output power, then the coherent signal generator would combine the output power from the 8 sub-amplifiers to generate a combined output power of 800 mW, and send the combined output power to one of the output channels.

The power combining may be controlled by specific settings of the optical phase relationships among all the sub-amplifiers. The phases may be set (e.g., configured, programmed, initialized, etc.) to provide a combined output power from all the sub-amplifiers in the coherent signal generator to one output channel (e.g., 800 mW of output power that is generated/combined from 8 sub-amplifiers that each produce 100 mW), a combined output power from some of the sub-amplifiers in the coherent signal generator to one output channel (e.g., 200 mW of output power that is generated/combined from 2 of the 8 sub-amplifiers in the coherent signal generator that each produce 100 mW), or any combination in-between. The phases may be set to provide the output power (e.g., 100 mW) of any of the sub-amplifiers to any of the output channels.

As the phase settings can be changed rapidly, in some implementations, the architecture of the CNC network allows the full combined output power (e.g., 800 mW in an 8 sub-amplifier network) from all the sub-amplifiers to be sent to each of the output channels (e.g., 8 channels) sequentially, thereby producing a series of pulses in time provided from each output channel. In some implementations, the total average power provided from all the output channels of the coherent signal generator remains constant, but the distribution of power among the output channels may vary in time.

Various example implementations described herein may include one or more of the following features: (1) some or all paths (from input to output) of the coherent signal generator may be length-matched to ensure stable operation over temperature; (2) the output powers of some or all of the sub-amplifiers of the one or more splitters may be close to identical to get high contrast on one or more output channels of the coherent signal generator; (3) the one or more splitters may have a low-loss and/or very close to a 50/50 split ratio; (4) the coherent signal generator may include one or more waveguide crossings, where the coupling to the wrong path is minimized; the coherent signal generator may include one or more slow static phase shifters on half the branches of each layer to maintain stable operation; (5) the coherent signal generator may include a tap photodiode on the output channels and/or selected points along the branches of the one or more splitters for development purposes and/or to ensure stable operation; (6) the coherent signal generator may include a tap from a laser source before the one or more modulators for coherent detection; (7) the coherent signal generator may include one or more phase shifters before the one or more sub-amplifiers; (8) the coherent signal generator may include one or more phase shifters after the one or more sub-amplifiers; and (9) the coherent signal generator may include one or more phase shifters after the one or more sub-amplifiers that are fast enough to implement the switching efficiently and rapidly (e.g., rise time less than 100 ns), to produce the benefit of losses being compensated by the sub-amplifier gain.

The one or more splitters, in some implementations, may be replaced with a multi-mode interference (MMI) structure or coupler. A binary switch network, in some implementations, after the one or more splitters (or the MIM structure or coupler) may be used to split the outputs to even more output channels.

1. System Environment for Autonomous Vehicles

FIG. 1is a block diagram illustrating an example of a system environment for autonomous vehicles according to some implementations.

Referring toFIG. 1, an example autonomous vehicle100within which the various techniques disclosed herein may be implemented. The vehicle100, for example, may include a powertrain102including a prime mover104powered by an energy source106and capable of providing power to a drivetrain108, as well as a control system110including a direction control112, a powertrain control114, and a brake control116. The vehicle100may be implemented as any number of different types of vehicles, including vehicles capable of transporting people and/or cargo, and capable of traveling in various environments, and it will be appreciated that the aforementioned components102-116can vary widely based upon the type of vehicle within which these components are utilized.

For simplicity, the implementations discussed hereinafter will focus on a wheeled land vehicle such as a car, van, truck, bus, etc. In such implementations, the prime mover104may include one or more electric motors and/or an internal combustion engine (among others). The energy source may include, for example, a fuel system (e.g., providing gasoline, diesel, hydrogen, etc.), a battery system, solar panels or other renewable energy source, and/or a fuel cell system. The drivetrain108can include wheels and/or tires along with a transmission and/or any other mechanical drive components to convert the output of the prime mover104into vehicular motion, as well as one or more brakes configured to controllably stop or slow the vehicle100and direction or steering components suitable for controlling the trajectory of the vehicle100(e.g., a rack and pinion steering linkage enabling one or more wheels of the vehicle100to pivot about a generally vertical axis to vary an angle of the rotational planes of the wheels relative to the longitudinal axis of the vehicle). In some implementations, combinations of powertrains and energy sources may be used (e.g., in the case of electric/gas hybrid vehicles), and in some instances multiple electric motors (e.g., dedicated to individual wheels or axles) may be used as a prime mover.

The direction control112may include one or more actuators and/or sensors for controlling and receiving feedback from the direction or steering components to enable the vehicle100to follow a desired trajectory. The powertrain control114may be configured to control the output of the powertrain102, e.g., to control the output power of the prime mover104, to control a gear of a transmission in the drivetrain108, etc., thereby controlling a speed and/or direction of the vehicle100. The brake control116may be configured to control one or more brakes that slow or stop vehicle100, e.g., disk or drum brakes coupled to the wheels of the vehicle.

Other vehicle types, including but not limited to off-road vehicles, all-terrain or tracked vehicles, construction equipment etc., will necessarily utilize different powertrains, drivetrains, energy sources, direction controls, powertrain controls and brake controls. Moreover, in some implementations, some of the components can be combined, e.g., where directional control of a vehicle is primarily handled by varying an output of one or more prime movers. Therefore, implementations disclosed herein are not limited to the particular application of the herein-described techniques in an autonomous wheeled land vehicle.

Various levels of autonomous control over the vehicle100can be implemented in a vehicle control system120, which may include one or more processors122and one or more memories124, with each processor122configured to execute program code instructions126stored in a memory124. The processors(s) can include, for example, graphics processing unit(s) (“GPU(s)”)) and/or central processing unit(s) (“CPU(s)”).

Sensors130may include various sensors suitable for collecting information from a vehicle's surrounding environment for use in controlling the operation of the vehicle. For example, sensors130can include radar sensor134, LIDAR (Light Detection and Ranging) sensor136, a 3D positioning sensors138, e.g., any of an accelerometer, a gyroscope, a magnetometer, or a satellite navigation system such as GPS (Global Positioning System), GLONASS (Globalnaya Navigazionnaya Sputnikovaya Sistema, or Global Navigation Satellite System), BeiDou Navigation Satellite System (BDS), Galileo, Compass, etc. The 3D positioning sensors138can be used to determine the location of the vehicle on the Earth using satellite signals. The sensors130can include a camera140and/or an IMU (inertial measurement unit)142. The camera140can be a monographic or stereographic camera and can record still and/or video images. The IMU142can include multiple gyroscopes and accelerometers capable of detecting linear and rotational motion of the vehicle in three directions. One or more encoders (not illustrated), such as wheel encoders may be used to monitor the rotation of one or more wheels of vehicle100. Each sensor130can output sensor data at various data rates, which may be different than the data rates of other sensors130.

The outputs of sensors130may be provided to a set of control subsystems150, including, a localization subsystem152, a planning subsystem156, a perception subsystem154, and a control subsystem158. The localization subsystem152can perform functions such as precisely determining the location and orientation (also sometimes referred to as “pose”) of the vehicle100within its surrounding environment, and generally within some frame of reference. The location of an autonomous vehicle can be compared with the location of an additional vehicle in the same environment as part of generating labeled autonomous vehicle data. The perception subsystem154can perform functions such as detecting, tracking, determining, and/or identifying objects within the environment surrounding vehicle100. A machine learning model in accordance with some implementations can be utilized in tracking objects. The planning subsystem156can perform functions such as planning a trajectory for vehicle100over some timeframe given a desired destination as well as the static and moving objects within the environment. A machine learning model in accordance with some implementations can be utilized in planning a vehicle trajectory. The control subsystem158can perform functions such as generating suitable control signals for controlling the various controls in the vehicle control system120in order to implement the planned trajectory of the vehicle100. A machine learning model can be utilized to generate one or more signals to control an autonomous vehicle to implement the planned trajectory.

It will be appreciated that the collection of components illustrated inFIG. 1for the vehicle control system120is merely exemplary in nature. Individual sensors may be omitted in some implementations. Additionally or alternatively, in some implementations, multiple sensors of types illustrated inFIG. 1may be used for redundancy and/or to cover different regions around a vehicle, and other types of sensors may be used. Likewise, different types and/or combinations of control subsystems may be used in other implementations. Further, while subsystems152-158are illustrated as being separate from processor122and memory124, it will be appreciated that in some implementations, some or all of the functionality of a subsystem152-158may be implemented with program code instructions126resident in one or more memories124and executed by one or more processors122, and that these subsystems152-158may in some instances be implemented using the same processor(s) and/or memory. Subsystems may be implemented at least in part using various dedicated circuit logic, various processors, various field programmable gate arrays (“FPGA”), various application-specific integrated circuits (“ASIC”), various real time controllers, and the like, as noted above, multiple subsystems may utilize circuitry, processors, sensors, and/or other components. Further, the various components in the vehicle control system120may be networked in various manners.

In some implementations, the vehicle100may also include a secondary vehicle control system (not illustrated), which may be used as a redundant or backup control system for the vehicle100. In some implementations, the secondary vehicle control system may be capable of fully operating the autonomous vehicle100in the event of an adverse event in the vehicle control system120, while in other implementations, the secondary vehicle control system may only have limited functionality, e.g., to perform a controlled stop of the vehicle100in response to an adverse event detected in the primary vehicle control system120. In still other implementations, the secondary vehicle control system may be omitted.

In general, an innumerable number of different architectures, including various combinations of software, hardware, circuit logic, sensors, networks, etc. may be used to implement the various components illustrated inFIG. 1. Each processor may be implemented, for example, as a microprocessor and each memory may represent the random access memory (“RAM”) devices comprising a main storage, as well as any supplemental levels of memory, e.g., cache memories, non-volatile or backup memories (e.g., programmable or flash memories), read-only memories, etc. In addition, each memory may be considered to include memory storage physically located elsewhere in the vehicle100, e.g., any cache memory in a processor, as well as any storage capacity used as a virtual memory, e.g., as stored on a mass storage device or another computer controller. One or more processors illustrated inFIG. 1, or entirely separate processors, may be used to implement additional functionality in the vehicle100outside of the purposes of autonomous control, e.g., to control entertainment systems, to operate doors, lights, convenience features, etc.

In addition, for additional storage, the vehicle100may include one or more mass storage devices, e.g., a removable disk drive, a hard disk drive, a direct access storage device (“DASD”), an optical drive (e.g., a CD drive, a DVD drive, etc.), a solid state storage drive (“SSD”), network attached storage, a storage area network, and/or a tape drive, among others.

Furthermore, the vehicle100may include a user interface164to enable vehicle100to receive a number of inputs from and generate outputs for a user or operator, e.g., one or more displays, touchscreens, voice and/or gesture interfaces, buttons and other tactile controls, etc. Otherwise, user input may be received via another computer or electronic device, e.g., via an app on a mobile device or via a web interface.

Moreover, the vehicle100may include one or more network interfaces, e.g., network interface162, suitable for communicating with one or more networks170(e.g., a Local Area Network (“LAN”), a wide area network (“WAN”), a wireless network, and/or the Internet, among others) to permit the communication of information with other computers and electronic device, including, for example, a central service, such as a cloud service, from which the vehicle100receives environmental and other data for use in autonomous control thereof. Data collected by the one or more sensors130can be uploaded to a computing system172via the network170for additional processing. In some implementations, a time stamp can be added to each instance of vehicle data prior to uploading.

Each processor illustrated inFIG. 1, as well as various additional controllers and subsystems disclosed herein, generally operates under the control of an operating system and executes or otherwise relies upon various computer software applications, components, programs, objects, modules, data structures, etc., as will be described in greater detail below. Moreover, various applications, components, programs, objects, modules, etc. may also execute on one or more processors in another computer coupled to vehicle100via network170, e.g., in a distributed, cloud-based, or client-server computing environment, whereby the processing required to implement the functions of a computer program may be allocated to multiple computers and/or services over a network.

In general, the routines executed to implement the various implementations described herein, whether implemented as part of an operating system or a specific application, component, program, object, module or sequence of instructions, or even a subset thereof, will be referred to herein as “program code”. Program code can include one or more instructions that are resident at various times in various memory and storage devices, and that, when read and executed by one or more processors, perform the steps necessary to execute steps or elements embodying the various aspects of the present disclosure. Moreover, while implementations have and hereinafter will be described in the context of fully functioning computers and systems, it will be appreciated that the various implementations described herein are capable of being distributed as a program product in a variety of forms, and that implementations can be implemented regardless of the particular type of computer readable media used to actually carry out the distribution.

Examples of computer readable media include tangible, non-transitory media such as volatile and non-volatile memory devices, floppy and other removable disks, solid state drives, hard disk drives, magnetic tape, and optical disks (e.g., CD-ROMs, DVDs, etc.) among others.

The environment illustrated inFIG. 1is not intended to limit implementations disclosed herein. Indeed, other alternative hardware and/or software environments may be used without departing from the scope of implementations disclosed herein.

2. Coherent Signal Combining with Multiple-Outputs

FIG. 2Ais a block diagram depicting an example quasi-CW LIDAR system for operating of a vehicle, according to some implementations. The quasi-CW LIDAR system200aincludes a laser source202for providing a light signal (sometimes referred to as, “beam”).

The quasi-CW LIDAR system200aincludes a modulator204for modulating the light signal and a coherent signal generator206(sometimes referred to as, “signal processing system”) for coherent signal generating (e.g., combining, merging, adding, mixing, etc.) with multiple-outputs for quasi-CW LIDAR operation. That is, the modulator204receives the light signal from the laser source202, modulates a phase and/or a frequency of the light signal using Continuous Wave (CW) modulation or quasi-CW modulation, and provides the modulated signal to one or more input channels of the coherent signal generator206.

The coherent signal generator206combines the received modulated signals to generate a continuous wave signal across the plurality of outputs (e.g., output channels312a-312dinFIG. 3) of the coherent signal generator206, and provide the continuous wave signal to a scanner208(e.g., an oscillatory scanner, a unidirectional scanner, a Risley prism, etc.). In some implementations, the coherent signal generator206generates the continuous wave signal by operating a plurality of sub-amplifiers (e.g., SOAs308a-dinFIG. 3) on different duty cycles.

Based on the received continuous signal, the scanner208generates one or more scanning signals to drive one or more optical elements for the optical detection of an object210.

As shown inFIG. 2A, the modulator204may be separate from the coherent signal generator206.

Any of the components (e.g., laser source202, modulator204, coherent signal generator206, and scanner208) of the quasi-CW LIDAR system200amay be included in one or more semiconductor packages. For example, the laser202may be in a first semiconductor package, the coherent signal generator204may be in a second semiconductor package, and the scanner206may be in a third semiconductor package. As another example, a semiconductor package may include the laser202, the modulator204, the coherent signal generator206, and the scanner208.

FIG. 2Bis a block diagram depicting an example quasi-CW LIDAR system for operating of a vehicle, according to some implementations. The quasi-CW LIDAR system200bincludes the laser source202, the coherent signal generator206, and the scanner208for the optical detection of the object210. The coherent signal generator206inFIG. 2Bincludes the features and/or functionality of the modulator204inFIG. 2A.

Any of the components (e.g., laser source202, coherent signal generator206, and scanner208) of the quasi-CW LIDAR system200bmay be included in one or more semiconductor packages.

FIG. 3is a block diagram depicting an example environment of a coherent signal generator architecture (e.g., coherent signal generator206inFIG. 2A, coherent signal generator206inFIG. 2B) for coherent signal combining with multiple-outputs for quasi-CW LIDAR operation, according to some implementations. The environment300includes a laser source202for providing a light signal (sometimes referred to as, “beam”). The environment300includes a modulator204for modulating the phase and/or the frequency of the light signal using Continuous Wave (CW) modulation or quasi-CW modulation to generate a modulated signal.

The environment300includes a phase shifter network306for adjusting the phase of the modulated signal and providing the modulated signal to an amplifier308. The phase shifter306contains a phase shifter306a, a phase shifter306b, a phase shifter306c, and a phase shifter306d; collectively referred to as, “phase shifters306a-d”.

The amplifier308includes sub-amplifiers, such as an SOA308a, an SOA308b, an SOA308c, and an SOA308d; collectively referred to as, “SOAs308a-d”. Each of the sub-amplifiers produces an amplified signal.

The environment300includes a beam splitter network310(sometimes referred to as, “splitter310”) that produces output waveforms by combining some or all of the amplified signals based on constructive and destructive interference principles. The beam splitter network310includes a beam splitter310a(shown inFIG. 3as, “50/50310a”), a beam splitter310b(shown inFIG. 3as, “50/50310b”), a beam splitter310c(shown inFIG. 3as, “50/50310c”), and a beam splitter310d(shown inFIG. 3as, “50/50310d”); collectively referred to as, “beam splitters310a-d”.

The environment300includes output channel312a, output channel312b, output channel312c, and output channel312d; collectively referred to as, “output channels312a-d”. AlthoughFIG. 3shows only a select number of components (e.g., laser source202, modulator204, phase shifters306a-d, SOAs308a-d, and beam splitters310a-d) and output channels312a-d; it will be appreciated by those skilled in the art that the environment300may include any number of components and/or output channels (in any combination) that are interconnected in any arrangement to facilitate coherent signal combining for quasi-CW LIDAR operation. For example, an 8-channel coherent signal generator architecture (e.g., as shown inFIG. 8) would include 8 phase shifters, 8 SOAs, 8 output channels, and 13 splitters. As another example, a 16-channel coherent signal generator would include 16 phase-shifters, 16 SOAs, 16 output channels, and 26 splitters.

The laser source202couples to an input terminal of the modulator204, whose output couples to an input terminal of the phase shifter306a, an input terminal of the phase shifter306b, an input terminal of the phase shifter306c, and an input terminal of the phase shifter306d.

An output terminal of the phase shifter306acouples to an input terminal of the SOA308a, whose output terminal couples to a first input terminal of the beam splitter310b. An output terminal of the phase shifter306bcouples to an input terminal of the SOA308b, whose output terminal couples to a first input terminal of the beam splitter310a. An output terminal of the phase shifter306ccouples to an input terminal of the SOA308c, whose output terminal couples to a second input terminal of the beam splitter310a. An output terminal of the phase shifter306dcouples to an input terminal of the SOA308d, whose output terminal couples to a second input terminal of the beam splitter310b.

A first output terminal of the beam splitter310acouples to a first input terminal of the beam splitter310c, whose first output terminal couples to an output channel312a(shown inFIG. 3as, “output312a”) and second output terminal couples to an output channel312b(shown inFIG. 3as, “output312b”).

A second output terminal of the beam splitter310acouples to a second input terminal of the beam splitter310d, whose first output terminal couples to an output channel312c(shown inFIG. 3as, “output312c”) and second output terminal couples to an output channel312d(shown inFIG. 3as, “output312d”).

A first output terminal of the beam splitter310bcouples to a second input terminal of the beam splitter310cand a second output terminal of the beam splitter310bcouples to a first input terminal of the beam splitter310d.

A semiconductor packaging (not shown inFIG. 3), in some implementations, may include some or all of the components (e.g., laser source202, modulator204, phase shifters306a-d, SOAs308a-d, and beam splitters310a-d) of environment300. For example, a first semiconductor packaging may include the components of the modulator204; and a second semiconductor packaging may include the components of the phase shifter306(e.g., phase shifters306a-d), the components of the amplifier308(e.g., SOAs308a-d), and/or the components of the beam splitter network310(e.g., beam splitters310a-d). In this arrangement, one or more outputs of the first semiconductor packaging may be coupled to the one or more inputs of the second semiconductor packaging.

As another example, a semiconductor packaging may include the components of the modulator204, the components of the phase shifter306(e.g., phase shifters306a-d), the components of the amplifier308(e.g., SOAs308a-d), and/or the components of the beam splitter network310(e.g., beam splitters310a-d). In this arrangement, the laser202may be coupled to the one or more inputs of the semiconductor packaging.

The output channels312a-312d, in some implementations, may correspond to outputs on a semiconductor packaging.

Still referring toFIG. 3, by operating the sub-amplifiers (e.g., SOAs308a-d) on different duty cycles, the amplifier308and the beam splitter network310may produce a continuous output waveform (e.g., output waveforms402a-dinFIG. 4) across the output channels312a-312dof the coherent signal generator. That is, the continuous wave power from each SOA308a-dmay be summed (based on the constructive and destructive interference principles) coherently in the beam splitter network310to ideally increase the output power to a single output channel at a time by N where N is the number of sub-amplifiers. This increased output power may be directed (e.g., routed, focused, etc.) at different times to different outputs providing switching to increase the effective number of available channels. The difficulty comes in the control of the phases in the beam splitter network310which depend on the optical path lengths of waveguides. In some implementations, some or all of the paths between the beam splitters310a-310dmay be matched. In some implementations, with good design and/or process control the number of phase shifters (e.g., phase shifters306a-d) needed for control of the output may be reduced.

FIG. 4is a time-based graph400depicting quasi-CW waveforms as measured at the output channels312a-312dof the coherent signal generator inFIG. 3, in accordance with an illustrative implementation. The time-base graph includes output waveform402a, output waveform402b, output waveform402c, and output waveform402b; each of which are quasi-CW waveforms resulting from operating the components of the coherent signal generator (e.g., laser source202, modulator204, phase shifters306a-d, SOAs308a-d, and beam splitters310a-d) under a set of operating conditions.

For example, referring toFIG. 3, the laser202drives the modulator with a 400 mW continuous wave (e.g., up to 95% duty cycle). The modulator204modulates a phase and/or a frequency of the received light signal using quasi-CW modulation to produce a modulated light signal and sends the modulated light signal to each of the input terminals of the phase shifters306a-d. Each of the phase shifters306a-d, as controlled by a processor (not shown inFIG. 3), shifts (e.g., adjusts, modifies, etc.) the phase of the modulated signal that it receives to produce a shifted modulated signal and sends the shifted modulated signal to the amplifier308. The amplifier308amplifies each of the shifted modulated signals (four copies) that it receives from the phase shifter306, to produce a first amplified signal that measures 100 mW at tap309a, a second amplified signal that measures 100 mW at tap309b, a third amplified signal that measures 100 mW at tap309c, and a fourth amplified signal that measures 100 mW at tap309d. The amplifier308sends the amplified signals (e.g., the first amplified signal, the second amplified signal, the third amplified signal, and the fourth amplified signal) to the beam splitter network310, which produces output waveform402aat output channel312a, output waveform402bat output channel312b, output waveform402cat output channel312c, and output waveform402dat output channel312d.

The beam splitter network310produces each of the output waveforms412a-412dby combining some or all of the amplified signals based on constructive and destructive interference principles.

In constructive interference, the beam splitter network310combines two waveforms to produce a resultant waveform having an amplitude that is higher than each of the two waveforms. For example, if the beam splitter network310combines two waveforms that have the same amplitude, then the resultant waveform would have a maximum amplitude that is twice the amplitude of the two waveforms. The region where the amplitude is between the original amplitude and the maximum amplitude is referred as the constructive interference. The constructive interference occurs when the waveforms are in-phase with each other.

In destructive interference, the beam splitter network310combines two waveforms to produce a resultant waveform having an amplitude that is lower than each of the two waveforms. For example, if the beam splitter network310combines two waveforms that have the same amplitude, then the resultant waveform would have a minimum amplitude that is zero. In this case, the resultant waveform would completely disappears at some places. The region between the original amplitude and the minimum amplitude is known as the region of destructive interference. Destructive interference occurs when the waveforms are out-of-phase with each other.

FIG. 5is a time-based graph depicting the summation of the output powers from the SOAs308a-308dof the coherent signal generator inFIG. 3, in accordance with an illustrative implementation. The time-base graph500depicts the relationship between the output waveform402aat the output channel312a(shown inFIG. 5as, “Ch1”), the output waveform402bat the output channel312b(shown inFIG. 5as, “Ch2”), the output waveform402cat the output channel312c(shown inFIG. 5as, “Ch3”), and the output waveform402dat the output channel312d(shown inFIG. 5as, “Ch4”).

With the beam splitter network310including beam splitters310a-d(e.g., 50:50 2×2 splitters), it is straightforward to determine the phases of the light after the SOAs308a-dthat are needed to direct the light into a particular output channel312a-312d. Each beam splitter310a-dmay be parameterized as a 2×2 scattering matrix according to Equation (1):

The full network may be scaled-up. For example, the coherent signal generator (e.g., a 4×4 network) inFIG. 3may be parameterized as two layers of 4×4 scattering matrices each of which are made up of 2×2 sub-matrices describing the 2×2 splitters in each layer. The final matrix for the 4×4 network shown inFIG. 3may be based on Equation (2):

This scattering matrix may then be inverted to find the phases of the input fields that result in all the power being directed to a single output channel312a-d, according to Equation (3):
Ein→=M−1Eout→(3)

If Eout→=[2,0,0,0]Tis desired representing 4 times the light of one individual channel being provided out of the upper most output channel (e.g., output channel112a). The phases, in some implementations, on the input channels are φ=[0, π/2, π/2]Tor [0 deg., 90 deg., 180 deg., 90 deg.] as illustrated inFIG. 6.

FIG. 6is a block diagram depicting the example environment of the coherent signal generator architecture inFIG. 3when configured to direct all the light onto an output channel, according to some implementations. The environment600shows the amplitude and phases for directing all of the light onto the output channel312a, assuming all the paths from input into the beam splitter network310to all the output channels312a-dhave the same length. The phases are relative, so any rotation of all the phases by the same amount lead to all of the light remaining in the same output channel.

As shown inFIG. 6, the phase shifter306ais configured to 0 degrees, the phase shifter306bis configured to 90 degrees, the phase shifter306cis configured to 180 degrees, the phase shifter306dis configured to 90 degrees, the amplified signal at tap309ais 100 mW, the amplified signal at tap309bis 100 mW, the amplified signal at tap309cis 100 mW, and the amplified signal at tap309dis 100 mW. Under these conditions, the coherent signal generator produces a 400 mW waveform (100 mW+100 mW+100 mW+100 mW=400 mW) at the output channel312aand 0 mW at output channels312b,312c,312d.

FIG. 7is a block diagram depicting the example environment of the coherent signal generator architecture inFIG. 3when configured to direct all the light onto an output channel, according to some implementations. The environment700shows the amplitude and phases for directing all of the light onto the output channel312b, assuming all the paths from input into the beam splitter network310to all the output channels312a-dhave the same length. The phases are relative, so any rotation of all the phases by the same amount lead to all of the light remaining in the same output channel.

As shown inFIG. 7, the phase shifter306ais configured to 90 degrees, the phase shifter306bis configured to 0 degrees, the phase shifter306cis configured to 90 degrees, the phase shifter306dis configured to 180 degrees, the amplified signal at tap309ais 100 mW, the amplified signal at tap309bis 100 mW, the amplified signal at tap309cis 100 mW, and the amplified signal at tap309dis 100 mW. Under these conditions, the coherent signal generator produces a 400 mW waveform (100 mW+100 mW+100 mW+100 mW=400 mW) at the output channel312band 0 mW at output channels112a,112c,112d.

FIG. 8is a block diagram depicting the example environment of the coherent signal generator architecture inFIG. 3when configured to direct all the light onto an output channel, according to some implementations. The environment800shows the amplitude and phases for directing all of the light onto the output channel312c, assuming all the paths from input into the beam splitter network310to all the output channels312a-dhave the same length. The phases are relative, so any rotation of all the phases by the same amount lead to all of the light remaining in the same output channel.

As shown inFIG. 8, the phase shifter306ais configured to 180 degrees, the phase shifter306bis configured to 90 degrees, the phase shifter306cis configured to 0 degrees, the phase shifter306dis configured to 90 degrees, the amplified signal at tap309ais 100 mW, the amplified signal at tap309bis 100 mW, the amplified signal at tap309cis 100 mW, and the amplified signal at tap309dis 100 mW. Under these conditions, the coherent signal generator produces a 400 mW waveform (100 mW+100 mW+100 mW+100 mW=400 mW) at the output channel312cand 0 mW at output channels312a,312b,312d.

FIG. 9is a block diagram depicting the example environment of the coherent signal generator architecture inFIG. 3when configured to direct all the light onto an output channel, according to some implementations. The environment900shows the amplitude and phases for directing all of the light onto the output channel312d, assuming all the paths from input into the beam splitter network310to all the output channels312a-dhave the same length. The phases are relative, so any rotation of all the phases by the same amount lead to all of the light remaining in the same output channel.

As shown inFIG. 9, the phase shifter306ais configured to 90 degrees, the phase shifter306bis configured to 180 degrees, the phase shifter306cis configured to 90 degrees, the phase shifter306dis configured to 0 degrees, the amplified signal at tap309ais 100 mW, the amplified signal at tap309bis 100 mW, the amplified signal at tap309cis 100 mW, and the amplified signal at tap309dis 100 mW. Under these conditions, the coherent signal generator produces a 400 mW waveform (100 mW+100 mW+100 mW+100 mW=400 mW) at the output channel312dand 0 mW at output channels312a,312b,312c.

FIG. 10is a block diagram depicting an example environment of a coherent signal generator architecture for coherent signal combining with multiple-outputs for quasi-CW LIDAR operation, according to some implementations. The environment1000includes a laser source202for providing a light signal. The environment1000includes a modulator204for modulating a phase and/or a frequency of the light signal using Continuous Wave (CW) modulation or quasi-CW modulation to generate a modulated signal.

The environment1000includes a phase shifter network for adjusting the phase of the modulated signal and providing the modulated signal to an amplifier. The phase shifter network contains a phase shifter1006a, a phase shifter1006b, a phase shifter1006c, a phase shifter1006d, a phase shifter1006e, a phase shifter1006f, a phase shifter1006g, and a phase shifter1006h; collectively referred to as, “phase shifters1006a-h”.

The amplifier includes sub-amplifiers, such as an SOA1008a, an SOA1008b, an SOA1008c, an SOA1008d, an SOA1008e, an SOA1008f, an SOA1008g, and an SOA1008h; collectively referred to as, “SOAs1008a-h”. Each of the sub-amplifiers produces an amplified signal.

The environment1000includes output channel1012a, output channel1012b, output channel1012c, output channel1012d, output channel1012e, output channel1012f, output channel1012g, and output channel1012h; collectively referred to as, “output channels1012a-h”. AlthoughFIG. 10shows only a select number of components (e.g., laser source202, modulator204, phase shifters1006a-h, SOAs1008a-h, and beam splitters1010a-m) and output channels1012a-h; it will be appreciated by those skilled in the art that the environment1000may include any number of components and/or output channels (in any combination) that are interconnected in any arrangement to facilitate coherent signal combining for quasi-CW LIDAR operation.

It is understood that the specific order or hierarchy of blocks in the processes disclosed is an example of illustrative approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes may be rearranged while remaining within the scope of the previous description. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The previous description of the disclosed implementations is provided to enable any person skilled in the art to make or use the disclosed subject matter. Various modifications to these implementations will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of the previous description. Thus, the previous description is not intended to be limited to the implementations shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The various examples illustrated and described are provided merely as examples to illustrate various features of the claims. However, features shown and described with respect to any given example are not necessarily limited to the associated example and may be used or combined with other examples that are shown and described. Further, the claims are not intended to be limited by any one example.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope are approximations, the numerical values set forth in specific non-limiting examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements at the time of this writing. Furthermore, unless otherwise clear from the context, a numerical value presented herein has an implied precision given by the least significant digit. Thus a value 1.1 implies a value from 1.05 to 1.15. The term “about” is used to indicate a broader range centered on the given value, and unless otherwise clear from the context implies a broader range around the least significant digit, such as “about 1.1” implies a range from 1.0 to 1.2. If the least significant digit is unclear, then the term “about” implies a factor of two, e.g., “about X” implies a value in the range from 0.5X to 2X, for example, about 100 implies a value in a range from 50 to 200. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” for a positive only parameter can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10 (e.g., 1 to 4).

Some implementations of the present disclosure are described below in the context of one or more hi-res Doppler LIDAR systems that are mounted onto an area (e.g., front, back, side, top, and/or bottom) of a personal automobile; but, implementations are not limited to this context. In other implementations, one or multiple systems of the same type or other high resolution LIDAR, with or without Doppler components, with overlapping or non-overlapping fields of view or one or more such systems mounted on smaller or larger land, sea or air vehicles, piloted or autonomous, are employed. In other implementations, the scanning hi-res LIDAR is mounted at temporary or permanent fixed positions on land or sea.