Fiber laser amplifier for LiDAR system

Abstract

Various embodiments of a fiber laser amplifier are disclosed. In some embodiments, a gain fiber for a laser amplifier is provided in which a core of the gain fiber has one or more characteristics at a first end that differ from at a second end, including, for example, one or more of diameter, refractive index, and rare earth dopant concentration. In some embodiments, the residual pump laser reflecting element is positioned to reflect the residual pump laser back into the gain fiber to improve amplification efficiency. In some embodiments, a first cladding having a non-uniform thickness is disposed around a core of a gain fiber. These and other aspects of embodiments are more comprehensively disclosed herein.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 525,123, filed July 5, 2023, entitled "Fiber Laser Amplifier With Variable Characteristic Core for LiDAR System"; U.S. Provisional Patent Application Serial No. 63 / 530,688, filed August 3, 2023, entitled "LiDAR System With Gain Fiber Having Variable Thickness"; and U.S. Provisional Patent Application Serial No. 63 / 537,079, filed September 7, 2023, entitled "LiDAR System With Gain Fiber Having High Reflectivity for Pump Laser". The contents of these applications are incorporated herein by reference. Technical Field

[0002] This disclosure generally relates to fiber laser amplifiers. Background Technology

[0003] Light detection and ranging (LiDAR) systems use light pulses to create images or point clouds of the external environment. LiDAR systems can be scanning or non-scanning. Some typical scanning LiDAR systems include a light source, a light emitter, a light steering system, and a photodetector. The light source generates a light beam, which, when emitted from the LiDAR system, is guided in a specific direction by the light steering system. When the emitted beam is scattered or reflected by an object, a portion of the scattered or reflected light returns to the LiDAR system as a returned light pulse. The photodetector detects the returned light pulse. Using the difference between the time it takes to detect the returned light pulse and the time it takes for the corresponding light pulse in the beam to be emitted, the LiDAR system can determine the distance to an object based on the speed of light. This distance determination technique is called Time-of-Flight (ToF). The light steering system can guide the light beam along different paths to allow the LiDAR system to scan the surrounding environment and generate images or point clouds. Typical non-scanning LiDAR systems illuminate the entire field of view (FOV) rather than scanning it. An example of a non-scanning LiDAR system is a flash LiDAR, which can also use ToF technology to measure the distance to objects. The LiDAR system can also use techniques other than time-of-flight and scanning to measure the surrounding environment. Summary of the Invention

[0004] Existing fiber laser amplifiers suffer from various aspects that limit their efficiency. These amplifiers utilize gain fibers with essentially uniform core characteristics from one end to the other. Furthermore, a significant proportion of pump light power is typically dissipated in fiber laser systems and therefore not used for optical amplification, where the pump light power is an integral part of the fiber laser system. Additionally, when the core is located at the center of an inner cladding arranged uniformly and concentrically around it, some pump light may continue to reflect around the cladding without intersecting the core, and thus fail to excite rare-earth dopants in the core.

[0005] Embodiments of this disclosure address these problems in one or more different ways. In some embodiments of the fiber laser amplifier conforming to this disclosure, a gain fiber is provided, wherein the core diameter at a second end of the gain fiber is larger than the core diameter at a first end. In some embodiments, a gain fiber is provided, wherein the core refractive index of the gain fiber at the second end is greater than the core refractive index at the first end. In some embodiments, a gain fiber is provided, wherein the concentration of rare earth dopant in the core is greater at the second end of the gain fiber than at the first end. In some embodiments, two or more of these characteristics of the core differ at the first end from those at the second end. In some embodiments, a residual pump laser reflecting element is positioned to reflect residual pump laser back into the gain fiber to improve amplification efficiency. In some embodiments, a first cladding having a non-uniform thickness is provided around the core of the gain fiber. These and other aspects of the embodiments of this disclosure will be described in more detail below and in the context of the accompanying drawings. Attached Figure Description

[0006] This application can be best understood by referring to the embodiments described below in conjunction with the accompanying drawings, in which the same parts are indicated by the same reference numerals.

[0007] Figure 1 The illustration shows one or more exemplary LiDAR systems that are set up or included in a motor vehicle.

[0008] Figure 2 This is a block diagram illustrating the interaction between an exemplary LiDAR system and several other systems, including a vehicle perception and planning system.

[0009] Figure 3 This is a block diagram illustrating an exemplary LiDAR system.

[0010] Figure 4 This is a block diagram illustrating an exemplary fiber-optic-based laser source.

[0011] Figures 5A to 5C The illustration shows an exemplary LiDAR system that uses pulse signals to measure the distance to an object positioned in the field of view (FOV).

[0012] Figure 6 This is a block diagram illustrating exemplary apparatus for implementing systems, devices, and methods in various embodiments.

[0013] Figure 7 The illustration shows a fiber laser amplifier according to an embodiment.

[0014] Figure 8 The illustration shows a fiber laser amplifier with backpropagation pump according to an embodiment.

[0015] Figure 9 Details of the gain fiber according to an embodiment are illustrated.

[0016] Figure 10 The illustration shows a fiber laser amplifier according to another embodiment.

[0017] Figure 11 The illustration shows a fiber laser amplifier with backpropagation pump according to another embodiment.

[0018] Figure 12 Details of a gain fiber according to another embodiment are illustrated.

[0019] Figure 13 The illustration shows experimental results demonstrating the efficiency improvements provided by embodiments of the present disclosure.

[0020] Figure 14 The illustration shows a fiber laser amplifier with a residual pump laser reflection element according to an embodiment.

[0021] Figure 15 The illustration shows a fiber laser amplifier with a residual pump laser reflection element in backpropagation pumping according to an embodiment.

[0022] Figure 16 A schematic diagram of a residual pump laser reflector element according to an embodiment is shown.

[0023] Figure 17A The illustration shows a schematic diagram of a residual pumped laser reflective element having a passive side component according to an embodiment.

[0024] Figure 17B The illustration shows a schematic diagram of a residual pump laser reflection element having a passive side component in a backpropagation pump according to an embodiment.

[0025] Figure 18A The illustration shows a cross-section of a gain fiber with a circular inner cladding according to an embodiment.

[0026] Figures 18B to 18E The illustration shows a cross-section of a gain fiber with a non-circular or asymmetric inner cladding according to various embodiments. Detailed Implementation

[0027] To provide a more thorough understanding of the various embodiments of the present invention, numerous specific details, such as specific configurations, parameters, and examples, are set forth in the following description. However, it should be understood that this description is not intended to limit the scope of the invention, but rather to provide a better description of exemplary embodiments.

[0028] Throughout the specification and claims, unless the context clearly indicates otherwise, the following terms shall have the meaning explicitly associated herein: As used herein, the phrase "in one embodiment" does not necessarily refer to the same embodiment, although it may be the same embodiment. Therefore, as described below, various embodiments of the invention can be readily combined without departing from the scope or spirit of this disclosure.

[0029] As used herein, the term “or” is an inclusive “or” operator and is equivalent to the term “and / or”, unless the context clearly indicates otherwise.

[0030] The term "based on" is not exclusive and allows for the use of additional factors not described unless explicitly stated in the context.

[0031] As used herein, unless the context otherwise requires, the term "coupled to" is intended to include both direct coupling (where two coupled elements are in contact with each other) and indirect coupling (where at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. In the context of a networked environment where two or more components or devices are capable of exchanging data, the terms "coupled to" and "coupled with" are also used to indicate possible "communicable coupling" with via one or more intermediate devices. Components or devices can be optical, mechanical, and / or electrical.

[0032] Although the following description uses the terms "first," "second," etc., to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the examples in the various descriptions, a first sensor may be referred to as a second sensor, and similarly, a second sensor may be referred to as a first sensor. Both the first sensor and the second sensor can be sensors, and in some cases, they can be separate and distinct sensors.

[0033] Furthermore, throughout the specification, the meanings of “an,” “a,” and “the” include the plural, and the meaning of “in” can include both “in” and “on”.

[0034] While some embodiments given herein constitute a single combination of inventive elements, it should be understood that the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment includes elements A, B, and C, and another embodiment includes elements B and D, the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly discussed herein. Furthermore, the transitional term "comprising" means having a component or element, or those components or elements. As used herein, the transitional term "comprising" is inclusive or open-ended and does not exclude additional, unlisted elements or method steps.

[0035] As used in the description herein and throughout the claims thereafter, when a system, engine, server, device, module or other computing element is described as being configured to perform or execute functions on data in memory, the meaning of “configured to” or “programmed to” is defined as one or more processors or cores of the computing element being programmed with a set of software instructions stored in the memory of the computing element to perform that set of functions on target data or data objects stored in memory.

[0036] It should be noted that any language for computers should be understood to include any suitable combination of computing devices or network platforms, including servers, interfaces, systems, databases, agents, peers, engines, controllers, modules, or other types of computing devices, individually or in combination. It should be understood that computing devices include processors configured to execute software instructions stored on tangible, non-transitory computer-readable storage media, such as hard disk drives, FPGAs, PLAs, solid-state drives, RAM, flash memory, ROM, or any other volatile or non-volatile storage devices. These software instructions configure or program the computing device to provide roles, responsibilities, or other functions, as discussed below with respect to the disclosed apparatus. Furthermore, the disclosed technology can be embodied as a computer program product including a non-transitory computer-readable medium storing software instructions that cause a processor to perform the disclosed steps associated with the implementation of computer-based algorithms, processes, methods, or other instructions. In some embodiments, various servers, systems, databases, or interfaces exchange data using standardized protocols or algorithms, possibly based on HTTP, HTTPS, AES, public-key exchange, web service APIs, known financial transaction protocols, or other electronic information exchange methods. Data exchange between devices can be carried out through the following: packet-switched networks, the Internet, LAN, WAN, VPN or other types of packet-switched networks; circuit-switched networks; cell-switched networks; or other types of networks.

[0037] Fiber-based laser systems are suitable for LiDAR applications due to their high output power, low cost, good beam quality, and compactness. To achieve high output power from seed laser power less than 1mW, a preamplifier stage is typically used to amplify the signal to several mW. However, multi-stage fiber laser amplifiers increase the complexity and cost of the laser system. Therefore, improved fiber laser amplifiers are needed.

[0038] Embodiments of the present invention are described below. In various embodiments of the present invention, the fiber laser amplifier receiving input from a seed laser may include an optical fiber having a core and a cladding surrounding the core. A pump laser may be coupled to the cladding. The core may be connected to the seed laser at a first end and may generate output laser light with the same wavelength as the seed laser at a second end. The core may have different characteristics at the first end and the second end.

[0039] Figure 1 The illustration shows one or more exemplary LiDAR systems 110 set up or included in a motor vehicle 100. The vehicle 100 can be a car, SUV, truck, train, van, bicycle, motorcycle, tricycle, bus, motorized scooter, tram, ship, boat, underwater vehicle, airplane, helicopter, unmanned aerial vehicle (UAV), spacecraft, etc. The motor vehicle 100 can be a vehicle with any level of automation. For example, the motor vehicle 100 can be a partially automated vehicle, a highly automated vehicle, a fully automated vehicle, or a driverless vehicle. A partially automated vehicle can perform some driving functions without human driver intervention. For example, a partially automated vehicle can perform blind spot monitoring, lane keeping and / or lane changing operations, automatic emergency braking, intelligent cruise control and / or traffic following, etc. Some operations of a partially automated vehicle may be limited to specific applications or driving scenarios (e.g., limited to highway driving). A highly automated vehicle can generally perform all the operations of a partially automated vehicle, but with fewer limitations. Highly automated vehicles can also detect their own limits while operating the vehicle and, if necessary, request the driver to take over control. Fully automated vehicles can perform all vehicle operations without driver intervention, but can also detect their own limits and, if necessary, request driver intervention. Driverless vehicles can operate autonomously without any driver intervention.

[0040] In a typical configuration, the motor vehicle 100 includes one or more LiDAR systems 110 and 120A-120I. Each of the LiDAR systems 110 and 120A-120I can be a scanning-based LiDAR system and / or a non-scanning LiDAR system (e.g., a flash LiDAR). A scanning-based LiDAR system scans one or more beams in one or more directions (e.g., horizontal and vertical) to detect objects in the field of view (FOV). A non-scanning-based LiDAR system emits a laser to illuminate the FOV without scanning. For example, a flash LiDAR is a type of non-scanning-based LiDAR system. A flash LiDAR can emit a laser, illuminating the FOV simultaneously using a single light pulse or a beam of light.

[0041] LiDAR systems are commonly used sensors in at least partially automated vehicles. In one embodiment, such as... Figure 1 As shown, a motor vehicle 100 may include a single LiDAR system 110 (e.g., without LiDAR systems 120A-120I) positioned at the highest point of the vehicle (e.g., on the top of the vehicle). Positioning the LiDAR system 110 on the top of the vehicle facilitates 360-degree scanning around the vehicle 100. In some other embodiments, the motor vehicle 100 may include multiple LiDAR systems, including two or more of systems 110 and / or 120A-120I. Figure 1 As shown, in one embodiment, multiple LiDAR systems 110 and / or 120A-120I are attached to vehicle 100 at different locations on the vehicle. For example, LiDAR system 120A is attached to the front right corner of vehicle 100; LiDAR system 120B is attached to the front center of vehicle 100; LiDAR system 120C is attached to the front left corner of vehicle 100; LiDAR system 120D is attached to the right rearview mirror of vehicle 100; LiDAR system 120E is attached to the left rearview mirror of vehicle 100; LiDAR system 120F is attached to the rear center of vehicle 100; LiDAR system 120G is attached to the rear right corner of vehicle 100; and / or LiDAR system 120I is attached to the rear left corner of vehicle 100. It should be understood that one or more LiDAR systems can be distributed and attached to the vehicle in any desired manner, and Figure 1 Only one embodiment is illustrated. As another example, LiDAR systems 120D and 120E may be attached to the B-pillar of vehicle 100 instead of the rearview mirror. As another example, LiDAR system 120B may be attached to the windshield of vehicle 100 instead of the front bumper.

[0042] In some embodiments, LiDAR systems 110 and 120A-120I are independent LiDAR systems, each with its own laser source, control electronics, transmitter, receiver, and / or steering mechanism. In other embodiments, some of LiDAR systems 110 and 120A-120I may share one or more components, thereby forming a distributed sensor system. In one example, optical fiber is used to deliver laser light from a centralized laser source to all LiDAR systems. For example, system 110 (or another system located at the center of vehicle 100 or anywhere else) includes a light source, transmitter, and photodetector, but no steering mechanism. System 110 may distribute transmitted light to each of systems 120A-120I. The transmitted light may be distributed via optical fiber. Optical connectors may be used to couple optical fiber to each of systems 110 and 120A-120I. In some examples, one or more of systems 120A-120I include a steering mechanism, but no light source, transmitter, or photodetector. The steering mechanism may include one or more movable mirrors, such as one or more polygonal mirrors, one or more single-plane mirrors, one or more multi-plane mirrors, etc. Embodiments of the light source, emitter, steering mechanism, and photodetector will be described in more detail below. Via the steering mechanism, one or more systems in systems 120A-120I scan light into one or more corresponding fields of view (FOVs) and receive the corresponding return light. The return light is formed by the scattering or reflection of transmitted light by one or more objects in the FOV. Systems 120A-120I may also include collecting lenses and / or other optics to focus and / or guide the return light into an optical fiber, which delivers the received return light to system 110. System 110 includes one or more photodetectors for detecting the received return light. In some examples, system 110 is located inside a vehicle, thus placing it in a temperature-controlled environment, while one or more systems 120A-120I may be at least partially exposed to the external environment.

[0043] Figure 2 This is a block diagram 200 illustrating the interaction between an onboard LiDAR system 210 and several other systems, including a vehicle perception and planning system 220. The LiDAR system 210 can be mounted on or integrated into a vehicle. The LiDAR system 210 includes sensors that scan the surrounding environment with laser light to measure the distance, angle, and / or velocity of objects. Based on the scattered light returning to the LiDAR system 210, it can generate sensor data (e.g., image data or 3D point cloud data) representing the perceived external environment.

[0044] LiDAR system 210 may include one or more of short-range LiDAR sensors, mid-range LiDAR sensors, and long-range LiDAR sensors. Short-range LiDAR sensors measure objects at a distance of approximately 20-40 meters. They can be used, for example, to monitor nearby moving objects (e.g., pedestrians crossing the street in a school zone), parking assistance applications, etc. Mid-range LiDAR sensors measure objects at a distance of up to approximately 70-200 meters. They can be used, for example, to monitor road intersections, assist merging or exiting highways, etc. Long-range LiDAR sensors measure objects located at 200 meters and above. Long-range LiDAR sensors are typically used when vehicles are traveling at high speeds (e.g., on highways), allowing the vehicle's control system only a few seconds (e.g., 6-8 seconds) to respond to any event detected by the LiDAR sensor. Figure 2 As shown, in one embodiment, LiDAR sensor data can be provided to the vehicle perception and planning system 220 via communication path 213 for further processing and control of vehicle operation. Communication path 213 can be any wired or wireless communication link capable of transmitting data.

[0045] Still referencing Figure 2 In some embodiments, other vehicle sensors 230 are configured to provide additional sensor data, either alone or in conjunction with the LiDAR system 210. These other vehicle sensors 230 may include, for example, one or more cameras 232, one or more radars 234, one or more ultrasonic sensors 236, and / or other sensors 238. Cameras 232 may capture images and / or video of the vehicle's external environment. Cameras 232 may capture, for example, high-definition (HD) video with millions of pixels per frame. Cameras may include image sensors that facilitate the generation of monochrome or color images and videos. Color information may be important in interpreting data in certain situations (e.g., interpreting images of traffic lights). Color information may not be available from other sensors, such as LiDAR or radar sensors. Cameras 232 may include one or more of narrow-focal-length cameras, wide-focal-length cameras, side-view cameras, infrared cameras, fisheye cameras, etc. Image and / or video data generated by cameras 232 may also be provided to the vehicle perception and planning system 220 via communication path 233 for further processing and control of vehicle operation. The communication path 233 can be any wired or wireless communication link capable of transmitting data. The camera 232 can be mounted or integrated into the vehicle at any location (e.g., rearview mirror, pillar, front grille, and / or rear bumper).

[0046] Other vehicle-mounted sensors 230 may also include a radar sensor 234. The radar sensor 234 uses radio waves to determine the distance, angle, and speed of an object. The radar sensor 234 generates electromagnetic waves in the radio or microwave spectrum. These electromagnetic waves are reflected by the object, and some of the reflected waves return to the radar sensor, providing information about the object's position and speed. The radar sensor 234 may include one or more of short-range, medium-range, and long-range radars. Short-range radar measures objects at a distance of approximately 0.1–30 meters from the radar. Short-range radar is useful for detecting objects located near vehicles (such as other vehicles, buildings, walls, pedestrians, cyclists, etc.). Short-range radar can be used for blind spot detection, lane change assistance, providing rear-end collision warnings, parking assistance, and emergency braking. Medium-range radar measures objects at a distance of approximately 30–80 meters from the radar. Long-range radar measures objects located at approximately 80–200 meters. Medium-range and / or long-range radar can be used for, for example, traffic tracking, adaptive cruise control, and / or automatic braking on highways. Sensor data generated by radar sensor 234 can also be provided to vehicle perception and planning system 220 via communication path 233 for further processing and control of vehicle operation. Radar sensor 234 can be mounted or integrated into the vehicle at any location (e.g., rearview mirror, pillar, front grille and / or rear bumper, etc.).

[0047] Other onboard sensors 230 may also include ultrasonic sensors 236. Ultrasonic sensors 236 use sound waves or pulses to measure objects located outside the vehicle. Sound waves generated by ultrasonic sensors 236 are emitted into the surrounding environment. At least some of the emitted waves are reflected by objects and return to ultrasonic sensors 236. Based on the returned signals, the distance to the object can be calculated. Ultrasonic sensors 236 can be used, for example, to check blind spots, identify parking spaces, and provide lane change assistance in traffic. Sensor data generated by ultrasonic sensors 236 can also be provided via communication path 233 to the vehicle perception and planning system 220 for further processing and control of vehicle operation. Ultrasonic sensors 236 can be mounted or integrated into the vehicle at any location (e.g., rearview mirror, pillar, front grille, and / or rear bumper, etc.).

[0048] In some embodiments, one or more other sensors 238 may be attached to the vehicle and may also generate sensor data. Other sensors 238 may include, for example, a Global Positioning System (GPS), an Inertial Measurement Unit (IMU), etc. The sensor data generated by the other sensors 238 may also be provided to the vehicle perception and planning system 220 via communication path 233 for further processing and control of vehicle operation. It should be understood that communication path 233 may include one or more communication links for transmitting data between the various sensors 230 and the vehicle perception and planning system 220.

[0049] In some embodiments, such as Figure 2 As shown, sensor data from other vehicle-mounted sensors 230 can be provided to the vehicle-mounted LiDAR system 210 via communication path 231. The LiDAR system 210 can process the sensor data from the other vehicle-mounted sensors 230. For example, sensor data from camera 232, radar sensor 234, ultrasonic sensor 236, and / or other sensors 238 can be correlated or fused with the sensor data from the LiDAR system 210, thereby at least partially offloading the sensor fusion process performed by the vehicle perception and planning system 220. It should be understood that other configurations can also be implemented to transmit and process sensor data from various sensors (e.g., data can be transmitted to a cloud or edge computing service provider for processing, and the processing results can then be transmitted back to the vehicle perception and planning system 220 and / or the LiDAR system 210).

[0050] Still referencing Figure 2 In some embodiments, sensors on other vehicles 250 are used individually or in conjunction with the LiDAR system 210 to provide additional sensor data. For example, two or more nearby vehicles may have their own LiDAR sensors, cameras, radar sensors, ultrasonic sensors, etc. Nearby vehicles can transmit and share sensor data with each other. Communication between vehicles is also referred to as V2V (vehicle-to-vehicle) communication. For example, as... Figure 2 As shown, sensor data generated by other vehicles 250 can be transmitted to the vehicle perception and planning system 220 and / or the onboard LiDAR system 210 via communication path 253 and / or communication path 251, respectively. Communication paths 253 and 251 can be any wired or wireless communication links capable of transmitting data.

[0051] Sharing sensor data facilitates better perception of the external environment of a vehicle. For example, the first vehicle may not detect a pedestrian approaching it from behind a second vehicle. The second vehicle can share sensor data related to the pedestrian with the first vehicle, allowing the first vehicle additional reaction time to avoid a collision. In some embodiments, data generated by sensors on other vehicles 250, similar to data generated by sensor 230, can be correlated or fused with sensor data generated by LiDAR system 210 (or other LiDAR systems located in other vehicles), thereby at least partially offloading the sensor fusion process performed by vehicle perception and planning system 220.

[0052] In some embodiments, the intelligent infrastructure system 240 is used to provide sensor data, either alone or in conjunction with the LiDAR system 210. Certain infrastructure can be configured to communicate with vehicles to relay information, and vice versa. Communication between vehicles and infrastructure is generally referred to as V2I (vehicle-to-infrastructure) communication. For example, the intelligent infrastructure system 240 may include intelligent traffic lights that can communicate their status to approaching vehicles with messages such as "turns yellow in 5 seconds." The intelligent infrastructure system 240 may also include its own LiDAR system installed near an intersection, enabling it to transmit traffic monitoring information to vehicles. For example, a vehicle turning left at an intersection may not have sufficient sensing capabilities because some of its own sensors may be blocked by traffic from the opposite direction. In this case, the sensors of the intelligent infrastructure system 240 can provide useful data to the left-turning vehicle. This data may include, for example, traffic conditions, information about objects in the direction the vehicle is turning, traffic light status, and predictions. The sensor data generated by the intelligent infrastructure system 240 can be provided to the vehicle perception and planning system 220 and / or the onboard LiDAR system 210 via communication paths 243 and / or 241, respectively. Communication paths 243 and / or 241 can include any wired or wireless communication links capable of transmitting data. For example, sensor data from the intelligent infrastructure system 240 can be transmitted to the LiDAR system 210 and correlated or fused with the sensor data generated by the LiDAR system 210, thereby at least partially offloading the sensor fusion process performed by the vehicle perception and planning system 220. The above-described V2V and V2I communications are examples of vehicle-to-X (V2X) communications, where “X” represents any other device, system, sensor, infrastructure, etc., that can share data with the vehicle.

[0053] Still referencing Figure 2The vehicle perception and planning system 220 receives sensor data from one or more of the LiDAR system 210, other onboard sensors 230, other vehicles 250, and / or intelligent infrastructure systems 240 via various communication paths. In some embodiments, different types of sensor data are correlated and / or fused by a sensor fusion subsystem 222. For example, the sensor fusion subsystem 222 can generate a 360-degree model using multiple images or videos captured by multiple cameras located at different locations on the vehicle. The sensor fusion subsystem 222 obtains sensor data from different types of sensors and uses the combined data to perceive the environment more accurately. For example, the onboard camera 232 may not capture a clear image because it is directly facing the sun or a light source (e.g., the headlights of another vehicle at night). The LiDAR system 210 may not be significantly affected, and therefore the sensor fusion subsystem 222 can combine the sensor data provided by both the camera 232 and the LiDAR system 210, and use the sensor data provided by the LiDAR system 210 to compensate for the unclear image captured by the camera 232. As another example, in rainy or foggy weather, radar sensor 234 may perform better than camera 232 or LiDAR system 210. Accordingly, sensor fusion subsystem 222 can use sensor data provided by radar sensor 234 to compensate for sensor data provided by camera 232 or LiDAR system 210.

[0054] In other examples, sensor data generated by other onboard sensors 230 may have lower resolution (e.g., radar sensor data) and therefore may need to be correlated and verified by a LiDAR system 210, which typically has higher resolution. For example, radar sensor 234 may detect a manhole cover (also known as a maintenance hatch cover) as an object approaching a vehicle. Due to the low resolution of radar sensor 234, vehicle perception and planning system 220 may not be able to determine whether the object is an obstacle that the vehicle needs to avoid. Therefore, high-resolution sensor data generated by LiDAR system 210 can be used to correlate and verify that the object is a manhole cover and will not cause damage to the vehicle.

[0055] The vehicle perception and planning system 220 further includes an object classifier 223. Using raw sensor data and / or related / fused data provided by the sensor fusion subsystem 222, the object classifier 223 can use any computer vision technique to detect and classify objects and estimate their positions. In some embodiments, the object classifier 223 can use machine learning-based techniques to detect and classify objects. Examples of machine learning-based techniques include algorithms such as region-based convolutional neural networks (R-CNN), fast R-CNN, faster R-CNN, oriented gradient histogram (HOG), region-based fully convolutional networks (R-FCN), single-shot detectors (SSD), spatial pyramid pooling (SPP-net), and / or You Only Look Once (Yolo).

[0056] The vehicle perception and planning system 220 further includes a road detection subsystem 224. The road detection subsystem 224 locates the road and identifies objects and / or markings on the road. For example, based on raw or fused sensor data provided by radar sensor 234, camera 232, and / or LiDAR system 210, the road detection subsystem 224 can construct a 3D model of the road based on machine learning techniques (e.g., pattern recognition algorithms for lane identification). Using the 3D model of the road, the road detection subsystem 224 can identify objects (e.g., obstacles or debris) and / or markings (e.g., lane lines, turning signs, pedestrian crossing signs, etc.) on the road.

[0057] The vehicle perception and planning system 220 further includes a localization and vehicle attitude subsystem 225. Based on raw or fused sensor data, the localization and vehicle attitude subsystem 225 can determine the vehicle's position and attitude. For example, using sensor data from LiDAR system 210, camera 232, and / or GPS data, the localization and vehicle attitude subsystem 225 can determine the vehicle's precise location on the road and its six degrees of freedom (e.g., whether the vehicle is moving forward or backward, up or down, left or right). In some embodiments, a high-definition (HD) map is used for vehicle localization. The HD map can provide a very detailed three-dimensional computer map that accurately locates the vehicle's position. For example, using an HD map, the localization and vehicle attitude subsystem 225 can accurately determine the vehicle's current position (e.g., which lane the vehicle is currently in on the road, and how close it is to the curb or sidewalk) and predict the vehicle's future position.

[0058] The vehicle perception and planning system 220 further includes an obstacle predictor 226. Objects identified by the object classifier 223 can be stationary (e.g., lampposts, road signs) or dynamic (e.g., moving pedestrians, bicycles, another vehicle). For moving objects, predicting their movement paths or future positions is important for collision avoidance. The obstacle predictor 226 can predict obstacle trajectories and / or warn the driver or vehicle planning subsystem 228 of potential collisions. For example, if there is a high probability that the obstacle's trajectory will intersect with the vehicle's current movement path, the obstacle predictor 226 can generate such a warning. The obstacle predictor 226 can use various techniques to make such predictions. These techniques include, for example, constant speed or acceleration models, constant turning rate and speed / acceleration models, Kalman filter-based and extended Kalman filter-based models, recurrent neural network (RNN)-based models, long short-term memory (LSTM) neural network-based models, encoder-decoder RNN models, etc.

[0059] Still referencing Figure 2 In some embodiments, the vehicle perception and planning system 220 further includes a vehicle planning subsystem 228. The vehicle planning subsystem 228 may include one or more planners, such as a route planner, a driving behavior planner, and a motion planner. The route planner may plan a route for the vehicle based on the vehicle's current location data, target location data, traffic information, etc. The driving behavior planner uses obstacle prediction results provided by obstacle predictor 226 to adjust the timing and planned movement based on how other objects might move. The motion planner determines the specific actions the vehicle needs to follow. The planning results are then transmitted to the vehicle control system 280 via vehicle interface 270. Communication can be performed via communication paths 223 and 271, which include any wired or wireless communication links capable of transmitting data.

[0060] The vehicle control system 280 controls the vehicle's steering mechanism, throttle, brakes, etc., to operate the vehicle according to a planned route and movement. In some examples, the vehicle perception and planning system 220 may further include a user interface 260 that provides access to the vehicle control system 280 to a user (e.g., a driver) to, for example, overtake or take over control of the vehicle when necessary. The user interface 260 may also be separate from the vehicle perception and planning system 220. The user interface 260 may communicate with the vehicle perception and planning system 220, for example, to acquire and display raw or fused sensor data, identified objects, the vehicle's position / attitude, etc. This displayed data can help the user better operate the vehicle. The user interface 260 may communicate with the vehicle perception and planning system 220 and / or the vehicle control system 280 via communication paths 221 and 261, respectively, which include any wired or wireless communication links capable of transmitting data. It should be understood that... Figure 2 The various systems, sensors, communication links, and interfaces within can be configured in any desired manner, and are not limited to... Figure 2 The configuration shown.

[0061] Figure 3 This is a block diagram illustrating an exemplary LiDAR system 300. The LiDAR system 300 can be used to implement... Figure 1 and Figure 2 The LiDAR systems 110, 120A-120H, and / or 210 are shown. In one embodiment, LiDAR system 300 includes a light source 310, a transmitter 320, an optical receiver and photodetector 330, a steering system 340, and a control circuitry system 350. These components are coupled together using communication paths 312, 314, 322, 332, 342, 352, 362, and 372. These communication paths include communication links (wired or wireless, bidirectional or unidirectional) between various LiDAR system components, but do not necessarily have to be the physical components themselves. While communication paths can be implemented by one or more wires, buses, or optical fibers, they can also be wireless channels or free-space optical paths, thus eliminating the need for a physical communication medium. For example, in one embodiment of LiDAR system 300, communication path 314 between light source 310 and transmitter 320 can be implemented using one or more optical fibers. Communication paths 332 and 352 can represent optical paths implemented using free-space optical components and / or optical fibers. Furthermore, communication paths 312, 322, 342, and 362 can be implemented using one or more wires carrying electrical signals. The communication paths may also include one or more of the communication media of the types described above (for example, they may include optical fibers and free-space optical components, or include one or more optical fibers and one or more wires).

[0062] In some embodiments, LiDAR system 300 can be a coherent LiDAR system. Frequency-modulated continuous wave (FMCW) LiDAR is one example. Coherent LiDAR detects objects by mixing the reflected light from the object with light from a coherent laser emitter. Therefore, as... Figure 3 As shown, if the LiDAR system 300 is a coherent LiDAR, it may include a route 372 that provides a portion of the transmitted light from the transmitter 320 to the optical receiver and photodetector 330. The transmitted light provided by the transmitter 320 may be modulated light and may be split into two parts. One part is emitted to the field of view (FOV), while the second part is sent to the optical receiver and photodetector 330 of the LiDAR system 300. The second part is also referred to as light held locally (LO) within the LiDAR system 300. The transmitted light is scattered or reflected by various objects within the FOV, and at least a portion of it forms returned light. The returned light is then detected and interferes with and reconstitutes with the second part of the locally held transmitted light. A coherent LiDAR provides a mechanism for optically sensing the range of objects and their relative velocity along the line of sight (LOS).

[0063] The LiDAR system 300 may also include Figure 3 Other components not shown include power buses, power supplies, LED indicators, and switches. Additionally, other communication connections between components may exist, such as a direct connection between the light source 310 and the optical receiver and photodetector 330, to provide a reference signal that allows for accurate measurement of the time from the emission of a light pulse to detection and the return of the light pulse.

[0064] Light source 310 outputs laser light to illuminate objects within the field of view (FOV). The laser light can be infrared light with wavelengths ranging from 700 nm to 1 mm. Light source 310 can be, for example, a semiconductor-based laser (e.g., a diode laser) and / or a fiber-based laser. Semiconductor-based lasers can be, for example, edge-emitting lasers (EELs), vertical-cavity surface-emitting lasers (VCSELs), external-cavity diode lasers, vertical-external-cavity surface-emitting lasers, distributed feedback (DFB) lasers, distributed Bragg reflector (DBR) lasers, interband cascade lasers, quantum cascade lasers, quantum well lasers, dual heterostructure lasers, etc. Fiber-based lasers are lasers in which the active gain medium is an optical fiber doped with rare-earth elements such as erbium, ytterbium, neodymium, dysprosium, praseodymium, thulium, and / or holmium. In some embodiments, the fiber laser is based on double-clad fiber, wherein the gain medium forms the core of the fiber surrounded by two cladding layers. Double-clad fiber allows the fiber core to be pumped with a high-power beam, thus enabling the laser source to become a high-power fiber laser source.

[0065] In some embodiments, the light source 310 includes a master oscillator (also referred to as a seed laser) and a power amplifier (MOPA). The power amplifier amplifies the output power of the seed laser. The power amplifier can be an fiber amplifier, a bulk amplifier, or a semiconductor optical amplifier. The seed laser can be a diode laser (e.g., a Fabry-Perot cavity laser, a distributed feedback laser), a solid-state bulk laser, or an external cavity tunable diode laser. In some embodiments, the light source 310 can be an optically pumped microchip laser. A microchip laser is an alignment-free monolithic solid-state laser in which the laser crystal is in direct contact with the end mirror of the laser resonator. Microchip lasers are typically pumped by laser diodes (directly or using fiber) to obtain the desired output power. Microchip lasers can be based on neodymium-doped ytterbium aluminum garnet (Y3Al5O12) laser crystals (i.e., Nd:YAG) or neodymium-doped vanadate (i.e., ND:YVO4) laser crystals. In some examples, the light source 310 can have multiple amplification stages to achieve high power gain, allowing the laser output to have high power, thereby enabling the LiDAR system to have a long scan range. In some examples, the power amplifier of the light source 310 can be controlled, allowing the power gain to be changed to achieve any desired laser output power.

[0066] Figure 4 This is a block diagram illustrating an exemplary fiber-optic-based laser source 400, which includes a seed laser and one or more pumps (e.g., laser diodes) for pumping a desired output power. The fiber-optic-based laser source 400 is... Figure 3An example of light source 310 is shown. In some embodiments, the fiber-based laser source 400 includes a seed laser 402 configured to generate initial optical pulses of one or more wavelengths (e.g., infrared wavelengths such as 1550 nm), which are provided to a wavelength division multiplexer (WDM) 404 via fiber 403. The fiber-based laser source 400 further includes a pump 406 for providing laser power (e.g., different wavelengths, such as 980 nm) to the WDM 404 via fiber 405. The WDM 404 multiplexes the optical pulses provided by the seed laser 402 and the laser power provided by the pump 406 onto a single fiber 407. The output of the WDM 404 can then be provided to one or more preamplifiers 408 via fiber 407. The preamplifier 408 may be an optical amplifier that amplifies the optical signal (e.g., with a gain of about 10-30 dB). In some embodiments, the preamplifier 408 is a low-noise amplifier. The preamplifier 408 outputs to an optical combiner 410 via fiber 409. Combiner 410 combines the output laser from preamplifier 408 with laser power supplied by pump 412 via fiber optic 411. Combiner 410 can combine optical signals with the same or different wavelengths. An example of a combiner is a WDM. Combiner 410 provides the combined optical signal to boost amplifier 414, which generates an output optical pulse via fiber optic 410. Boost amplifier 414 provides further amplification of the optical signal (e.g., another 20-40 dB). The output optical pulse can then be transmitted to transmitter 320 and / or steering mechanism 340 (e.g., ...). Figure 3 (As shown). It should be understood that... Figure 4 The illustration shows an exemplary configuration of a fiber-optic laser source 400. The laser source 400 may have the following characteristics: Figure 4 One or more components shown and / or Figure 4 Many other configurations of different combinations of other components not shown (e.g., power supplies, lenses, filters, beam splitters, combiners, etc.).

[0067] In some variations, the fiber-based laser source 400 can be controlled (e.g., via control circuitry 350) to generate pulses of different amplitudes based on the fiber gain distribution of the fiber used in the fiber-based laser source 400. Communication path 312 couples the fiber-based laser source 400 to the control circuitry 350 (e.g., via control circuitry 350). Figure 3As shown, components of the fiber-based laser source 400 can be controlled by or otherwise communicate with the control circuitry system 350. Alternatively, the fiber-based laser source 400 may include its own dedicated controller. Instead of the control circuitry system 350 communicating directly with the components of the fiber-based laser source 400, the dedicated controller of the fiber-based laser source 400 communicates with and controls the components of the fiber-based laser source 400 and / or communicates with them. The fiber-based laser source 400 may also include other components not shown, such as one or more power connectors, power supplies, and / or transmission lines.

[0068] refer to Figure 3 Typical operating wavelengths of the light source 310 include, for example, approximately 850 nm, approximately 905 nm, approximately 940 nm, approximately 1064 nm, and approximately 1550 nm. For laser safety, the maximum usable laser power is capped by regulations set by the U.S. Food and Drug Administration (FDA). The optical power limit at 1550 nm is significantly higher than the power limits at the other wavelengths mentioned above. Furthermore, at 1550 nm, optical power loss in the fiber is very low. These characteristics of the 1550 nm wavelength make it more advantageous for long-range LiDAR applications. The amount of optical power output from the light source 310 can be characterized by its peak power, average power, pulse energy, and / or pulse energy density. Peak power is the ratio of pulse energy to pulse width (e.g., full width at half maximum or FWHM). Therefore, for a fixed amount of pulse energy, a smaller pulse width can provide a larger peak power. Pulse widths can range from nanoseconds to picoseconds. Average power is the product of pulse energy and pulse repetition rate (PRR). As described in more detail below, PRR represents the frequency of the pulsed laser. Generally, the smaller the time interval between pulses, the higher the PRR. PRR typically corresponds to the maximum range that a LiDAR system can measure. The light source 310 can be configured to generate pulses with a high PRR to meet the desired number of data points in the point cloud generated by the LiDAR system. The light source 310 can also be configured to generate pulses with a medium or low PRR to meet the desired maximum detection range. Wall insertion efficiency (WPE) is another factor for evaluating total power consumption and can be a useful metric for assessing laser efficiency. For example, as... Figure 1 As shown, multiple LiDAR systems can be attached to vehicles, which can be electric vehicles or vehicles with limited fuel or battery power. Therefore, high WPE and intelligent methods of using laser power are often important considerations when selecting and configuring the light source 310 and / or designing laser delivery systems for vehicle-mounted LiDAR applications.

[0069] It should be understood that the above description provides a non-limiting example of light source 310. Light source 310 can be configured to include many other types of light sources (e.g., laser diodes, short-cavity fiber lasers, solid-state lasers, and / or external-cavity tunable diode lasers) configured to generate one or more optical signals of various wavelengths. In some examples, light source 310 includes amplifiers (e.g., preamplifiers and / or boost amplifiers), which can be doped fiber amplifiers, solid-state amplifiers, and / or semiconductor optical amplifiers. The amplifiers are configured to receive and amplify the optical signals at a desired gain.

[0070] Return to reference Figure 3 The LiDAR system 300 further includes a transmitter 320. A light source 310 supplies laser light (e.g., in the form of a laser beam) to the transmitter 320. The laser light supplied by the light source 310 may be an amplified laser with a predetermined or controlled wavelength, pulse repetition rate, and / or power level. The transmitter 320 receives the laser light from the light source 310 and transmits the laser light to a steering mechanism 340 with low divergence. In some embodiments, the transmitter 320 may include, for example, optical components (e.g., lenses, optical fibers, mirrors, etc.) for transmitting one or more laser beams directly or via the steering mechanism 340 to the field of view (FOV). Although Figure 3 The transmitter 320 and the steering mechanism 340 are illustrated as separate components, but in some embodiments, they may be combined or integrated into a system. The steering mechanism 340 will be described in more detail below.

[0071] The laser beam supplied by light source 310 may diverge as it propagates to emitter 320. Therefore, emitter 320 typically includes a collimating lens or lens group configured to collect the diverging laser beam and produce a more parallel beam with reduced or minimal divergence. The collimated beam can then be further guided through various optics, such as mirrors and lenses. The collimating lens can be, for example, a single plano-convex lens or a lens group. The collimating lens can be configured to achieve any desired characteristics, such as beam diameter, divergence, numerical aperture, focal length, etc. The beam propagation ratio, or beam quality factor (also known as the M² factor), is used to measure the quality of the laser beam. In many LiDAR applications, good laser beam quality is important in the generated emitted laser beam. The M² factor represents the degree of variation of the beam relative to an ideal Gaussian beam. Therefore, the M² factor reflects how well a collimated laser beam can be focused on a small point, or how well a diverging laser beam can be collimated. Therefore, the light source 310 and / or emitter 320 can be configured to meet, for example, scanning resolution requirements while maintaining the desired M2 factor.

[0072] One or more beams of light provided by transmitter 320 are scanned onto the field of view (FOV) by steering mechanism 340. Steering mechanism 340 scans the beams in multiple dimensions (e.g., horizontal and vertical) to allow LiDAR system 300 to map the environment by generating a 3D point cloud. The horizontal dimension may be parallel to the horizon or a surface associated with the LiDAR system or vehicle (e.g., a road surface). The vertical dimension is perpendicular to the horizontal dimension (i.e., the vertical dimension forms a 90-degree angle with the horizontal dimension). Steering mechanism 340 will be described in more detail below. The laser light scanned onto the FOV may be scattered or reflected by objects within the FOV. At least a portion of the scattered or reflected light forms a return beam that returns to LiDAR system 300. Figure 3 Further illustration shows an optical receiver and photodetector 330 configured to receive returned light. The optical receiver and photodetector 330 include an optical receiver configured to collect returned light from the field of view (FOV). The optical receiver may include optics (e.g., lenses, optical fibers, mirrors, etc.) for receiving, redirecting, focusing, amplifying, and / or filtering the returned light from the FOV. For example, the optical receiver typically includes a collecting lens (e.g., a single plano-convex lens or a group of lenses) to collect the returned light and / or focus the collected returned light onto the photodetector.

[0073] A photodetector detects the returned light focused by an optical receiver and generates a current and / or voltage signal proportional to the incident intensity of the returned light. Based on such current and / or voltage signals, depth information of the object within the field of view (FOV) can be derived. An exemplary method for deriving this depth information is based on direct time-of-flight (TOF), which will be described in more detail below. A photodetector can be characterized by its detection sensitivity, quantum efficiency, detector bandwidth, linearity, signal-to-noise ratio (SNR), overload immunity, interference immunity, etc. Depending on the application, a photodetector can be configured or customized to have any desired characteristics. For example, the optical receiver and photodetector 330 can be configured such that the photodetector has a large dynamic range while maintaining good linearity. Photodetector linearity indicates the detector's ability to maintain a linear relationship between the input optical signal power and the detector output. A detector with good linearity can maintain a linear relationship over a large dynamic range of input optical signals.

[0074] To achieve the desired detector characteristics, the structure and / or material system of the photodetector can be configured or customized. Various detector structures can be used for photodetectors. For example, a photodetector structure can be a PIN-based structure with an undoped intrinsic semiconductor region (i.e., the "I" region) between the p-type and n-type semiconductor regions. Other photodetector structures include, for example, APD (avalanche photodiode) based structures, PMT (photomultiplier tube) based structures, SiPM (silicon photomultiplier tube) based structures, SPAD (single-photon avalanche diode) based structures, and / or quantum wires. For the material system used in the photodetector, Si, InGaAs, and / or Si / Ge-based materials can be used. It should be understood that many other detector structures and / or material systems can be used in the optical receiver and photodetector 330.

[0075] Photodetectors (e.g., APD-based detectors) can have internal gain, amplifying the input signal when an output signal is generated. However, noise can also be amplified due to the photodetector's internal gain. Common noise types include signal shot noise, dark current shot noise, thermal noise, and amplifier noise. In some embodiments, the optical receiver and photodetector 330 may include a preamplifier for a low-noise amplifier (LNA). In some embodiments, the preamplifier may also include a transimpedance amplifier (TIA) that converts a current signal into a voltage signal. For linear detector systems, input equivalent noise or noise equivalent power (NEP) measures the photodetector's sensitivity to weak signals. Therefore, they can be used as indicators of overall system performance. For example, the photodetector's NEP specifies the power of the weakest signal that can be detected, and thus it specifies the maximum range of the LiDAR system. It should be understood that various photodetector optimization techniques can be used to meet the requirements of the LiDAR system 300. Such optimization techniques may include selecting different detector structures, materials, and / or implementing signal processing techniques (e.g., filtering, noise reduction, amplification, etc.). For example, coherent detection can be used in photodetectors in addition to or instead of direct detection using a returned signal (e.g., by using Time-of-Flight). Coherent detection allows the detection of the amplitude and phase information of received light by interfering the received light with a local oscillator. Coherent detection can improve detection sensitivity and noise immunity.

[0076] Figure 3Further illustration shows the LiDAR system 300 including a steering mechanism 340. As described above, the steering mechanism 340 guides the beam from the transmitter 320 to scan the field of view (FOV) in multiple dimensions. The steering mechanism is also referred to as a grating mechanism, a scanning mechanism, or simply a light scanner. Scanning the beam in multiple directions (e.g., horizontal and vertical) facilitates the LiDAR system in mapping the environment by generating images or 3D point clouds. The steering mechanism can be based on mechanical scanning and / or solid-state scanning. Mechanical scanning uses rotating mirrors to steer the laser beam or physically rotates the LiDAR transmitter and receiver (collectively referred to as transceivers) to scan the laser beam. Solid-state scanning guides the laser beam to various locations within the FOV without mechanically moving any macroscopic components, such as transceivers. Solid-state scanning mechanisms include, for example, steering based on optical phased arrays and steering based on flash LiDAR. In some embodiments, steering performed by a solid-state scanning mechanism can be referred to as effective steering because the solid-state scanning mechanism does not physically move macroscopic components. LiDAR systems using solid-state scanning can also be referred to as non-mechanical scanning or simple non-scanning LiDAR systems (flash LiDAR systems are exemplary non-scanning LiDAR systems).

[0077] The steering mechanism 340 can be used with transceivers (e.g., transmitter 320 and optical receiver and photodetector 330) to scan the field of view (FOV) for generating images or 3D point clouds. As an example, to implement the steering mechanism 340, a 2D mechanical scanner can be used with a single-point or several single-point transceivers. The single-point transceivers transmit a single beam or a small number of beams (e.g., 2-8 beams) to the steering mechanism. 2D mechanical steering mechanisms include, for example, polygonal mirrors, oscillating mirrors, rotating prisms, rotating tilting mirrors, single-plane or multi-plane mirrors, or combinations thereof. In some embodiments, the steering mechanism 340 can include a non-mechanical steering mechanism, such as a solid-state steering mechanism. For example, the steering mechanism 340 can be based on the tuned wavelength of a laser incorporating refractive effects, and / or on a reconfigurable grating / phase array. In some embodiments, the steering mechanism 340 can implement 2D scanning using a single scanning device or by using a combination of multiple scanning devices.

[0078] As another example, to implement steering mechanism 340, a one-dimensional mechanical scanner can be used in conjunction with an array or a large number of single-point transceivers. Specifically, the transceiver array can be mounted on a rotating platform to achieve a 360-degree horizontal field of view. Alternatively, a static transceiver array can be combined with a one-dimensional mechanical scanner. One-dimensional mechanical scanners include polygonal mirrors, oscillating mirrors, rotating prisms, rotating tilting mirrors, or combinations thereof, for obtaining a forward-looking horizontal field of view. Steering mechanisms using mechanical scanners can provide robustness and reliability in mass production for automotive applications.

[0079] As another example, to implement the steering mechanism 340, a two-dimensional transceiver can be used to directly generate scanned images or 3D point clouds. In some embodiments, stitching or micro-displacement methods can be used to improve the resolution of the scanned image or the scanned field of view. For example, using a two-dimensional transceiver, signals generated in one direction (e.g., horizontal) and signals generated in another direction (e.g., vertical) can be integrated, interleaved, and / or matched to generate a higher or full-resolution image or 3D point cloud representing the scanned FOV.

[0080] Some implementations of the redirection mechanism 340 include one or more optical redirection elements (e.g., mirrors or lenses) that redirect the returning optical signal along the receiving path (e.g., by rotation, vibration, or guidance) to direct the returning optical signal to the optical receiver and photodetector 330. The optical redirection elements that guide the optical signal along the transmission and receiving paths can be identical components (e.g., shared), separate components (e.g., dedicated), and / or a combination of shared and separate components. This means that in some cases, the transmission and receiving paths are different, although they may partially overlap (or in some cases, substantially overlap or completely overlap).

[0081] Still referencing Figure 3 The LiDAR system 300 further includes a control circuitry system 350. The control circuitry system 350 can be configured and / or programmed to control various parts of the LiDAR system 300 and / or perform signal processing. In a typical system, the control circuitry system 350 can be configured and / or programmed to perform one or more control operations, including, for example, controlling the light source 310 to obtain desired laser pulse timing, pulse repetition rate, and power; controlling the steering mechanism 340 (e.g., controlling speed, direction, and / or other parameters) to scan the field of view (FOV) and maintain pixel registration and / or alignment; controlling the optical receiver and photodetector 330 (e.g., controlling sensitivity, noise reduction, filtering, and / or other parameters) to optimize their operation; and monitoring the overall system health / functional safety status (e.g., monitoring the laser output power and / or the safety of the steering mechanism's operating status).

[0082] The control circuit system 350 can also be configured and / or programmed to perform signal processing on the raw data generated by the optical receiver and photodetector 330 to obtain distance and reflectivity information, and to perform data packaging and communication with the vehicle perception and planning system 220 (such as...). Figure 2The communication (as shown) involves, for example, the control circuitry 350 determining the time taken from the transmission of a light pulse to the receipt of a corresponding return light pulse; determining when a return light pulse is not received for the transmitted light pulse; determining the direction of the transmitted / return light pulse (e.g., horizontal and / or vertical information); determining an estimated range in a specific direction; deriving the reflectivity of objects in the field of view (FOV); and / or determining any other types of data relevant to the LiDAR system 300.

[0083] The LiDAR system 300 can be incorporated into a vehicle that operates in a variety of environments, including hot or cold weather, rough road conditions that may cause severe vibrations, high or low humidity, dusty areas, etc. Therefore, in some embodiments, the optical and / or electronic components of the LiDAR system 300 (e.g., the optics, optical receivers, and photodetectors 330 in the transmitter 320, and the steering mechanism 340) are positioned and / or configured to maintain long-term mechanical and optical stability. For example, components in the LiDAR system 300 can be secured and sealed so that they can operate under all conditions the vehicle may encounter. As an example, moisture-proof coatings and / or hermetic seals can be applied to the optical components, optical receivers, and photodetectors 330, and the steering mechanism 340 of the transmitter 320 (as well as other components susceptible to moisture). As another example, housings, enclosures, fairings, and / or windows can be used in the LiDAR system 300 to provide desired properties such as hardness, foreign object protection rating (IP), self-cleaning capability, chemical resistance, and impact resistance. In addition, the efficient and economical method for assembling the LiDAR system 300 can be used to meet the operational requirements of LiDAR while maintaining low cost.

[0084] Those skilled in the art should understand that Figure 3 The above description is for illustrative purposes only, and a LiDAR system may include other functional units, blocks, or segments, and may include variations or combinations of these functional units, blocks, or segments. For example, LiDAR system 300 may also include Figure 3 Other components not shown include power buses, power supplies, LED indicators, and switches. Additionally, other connections between components may exist, such as direct connections between the light source 310 and the optical receiver and photodetector 330, allowing the photodetector 330 to accurately measure the time from the emission of a light pulse by the light source 310 to the detection of the returning light pulse by the photodetector 330.

[0085] Figure 3The components shown are coupled together using communication paths 312, 314, 322, 332, 342, 352, 362, and 372. These communication paths represent communication (bidirectional or unidirectional) between various LiDAR system components, but do not necessarily involve the physical components themselves. While communication paths can be implemented using one or more wires, buses, or optical fibers, they can also be wireless channels or exposed optical paths, thus eliminating the need for a physical communication medium. For example, in an exemplary LiDAR system, communication path 314 includes one or more optical fibers; communication path 352 represents an optical path; and communication paths 312, 322, 342, and 362 are all wires carrying electrical signals. Communication paths can also include more than one of the communication media of the types described above (e.g., they can include optical fibers and optical paths, or one or more optical fibers and one or more wires).

[0086] As mentioned above, some LiDAR systems use the time-of-flight (ToF) of an optical signal (e.g., a light pulse) to determine the distance to an object in the optical path. For example, reference... Figure 5A An exemplary LiDAR system 500 includes a laser source (e.g., a fiber laser), a steering mechanism (e.g., a system with one or more moving mirrors), and a photodetector (e.g., a photodetector with one or more optics). The LiDAR system 500 can be implemented using, for example, the LiDAR system 300 described above. The LiDAR system 500 emits light pulses 502 along an optical path 504 defined by the steering mechanism of the LiDAR system 500. In the depicted example, the light pulses 502 generated by the laser source are short pulses of laser light. Furthermore, the signal manipulation mechanism of the LiDAR system 500 is a pulse signal steering mechanism. However, it should be understood that LiDAR systems can operate by generating, emitting, and detecting non-pulsed light signals and using techniques other than time-of-flight to derive the distance to objects in the surrounding environment. For example, some LiDAR systems use frequency-modulated continuous wave (i.e., "FMCW"). It should also be understood that any techniques described herein for time-of-flight based systems using pulsed signals can also be applied to LiDAR systems that do not use one or both of these techniques.

[0087] Return to reference Figure 5A(For example, a time-of-flight LiDAR system using light pulses is illustrated.) When light pulse 502 reaches object 506, it is scattered or reflected to form a returning light pulse 508. The returning light pulse 508 can return to system 500 along optical path 510. The time from when the emitted light pulse 502 leaves LiDAR system 500 to when the returning light pulse 508 returns to LiDAR system 500 can be measured (e.g., via a processor or other electronic device within the LiDAR system, such as control circuitry system 350). This time-of-flight, combined with knowledge of the speed of light, can be used to determine the distance / range from LiDAR system 500 to the portion of object 506 where the light pulse 502 is scattered or reflected.

[0088] By guiding many light pulses, such as Figure 5B As depicted, the LiDAR system 500 scans the external environment (e.g., by guiding optical pulses 502, 522, 526, and 530 along optical paths 504, 524, 528, and 532, respectively). Figure 5C As depicted, the LiDAR system 500 receives returned light pulses 508, 542, and 548 (corresponding to emitted light pulses 502, 522, and 530, respectively). The returned light pulses 508, 542, and 548 are formed by scattering or reflecting the emitted light pulses by one of objects 506 and 514. The returned light pulses 508, 542, and 548 can return to the LiDAR system 500 along optical paths 510, 544, and 546, respectively. Based on the direction of the emitted light pulses (as determined by the LiDAR system 500) and the calculated distance from the LiDAR system 500 to the portion of the object scattering or reflecting the light pulses (e.g., portions of objects 506 and 514), the external environment within the detectable range (e.g., the field of view between paths 504 and 532, included) can be precisely mapped or plotted (e.g., by generating a 3D point cloud or image).

[0089] If no corresponding light pulse is received for a specific emitted light pulse, the LiDAR system 500 can determine that there is no object within its detectable range (e.g., the object is beyond the maximum scanning distance of the LiDAR system 500). For example, in Figure 5B In the middle, optical pulse 526 may not have a corresponding return optical pulse (e.g. Figure 5C As illustrated, the light pulse 526 may not generate a scattering event along its transmission path 528 within a predetermined detection range. The LiDAR system 500 or an external system (e.g., a cloud system or service) communicating with the LiDAR system 500 may interpret the lack of a returning light pulse as the absence of an object positioned along the light path 528 within the detectable range of the LiDAR system 500.

[0090] exist Figure 5B In this process, optical pulses 502, 522, 526, and 530 can be emitted in any order, serially, in parallel, or based on other timing relative to each other. Additionally, although... Figure 5B The emitted light pulse can be depicted as being guided in one dimension or one plane (e.g., the plane of paper), but the LiDAR system 500 can also guide the emitted light pulse along other dimensions or planes. For example, the LiDAR system 500 can also guide the emitted light pulse perpendicular to... Figure 5B The emitted light pulse is guided in the dimension or plane shown, thereby forming a 2D transmission of the light pulse. This 2D transmission of the light pulse can be point-by-point, line-by-line, one-time, or otherwise. That is, the LiDAR system 500 can be configured to perform point scans, line scans, single scans without scanning, or combinations thereof. Point clouds or images (e.g., a single horizontal line) from 1D transmissions of the light pulse can generate 2D data (e.g., (1) data from the horizontal transmission direction and (2) the extent or distance to the object). Similarly, point clouds or images from 2D transmissions of the light pulse can generate 3D data (e.g., (1) data from the horizontal transmission direction, (2) data from the vertical transmission direction, and (3) the extent or distance to the object). Typically, a LiDAR system performing an n-dimensional transmission of the light pulse generates (n+1)-dimensional data. This is because the LiDAR system can measure the depth of an object or the distance to an object, which provides an additional dimension of data. Therefore, 2D scanning performed by the LiDAR system can generate 3D point clouds for mapping the external environment of the LiDAR system.

[0091] Point cloud density refers to the number of measurements (data points) performed by a LiDAR system for each region. Point cloud density is related to the LiDAR scan resolution. Generally, at least for the region of interest (ROI), a higher point cloud density is desired, and therefore a higher resolution is required. The point density in a point cloud or image generated by a LiDAR system is equal to the number of pulses divided by the field of view. In some embodiments, the field of view can be fixed. Therefore, to increase the density of points generated by a set of transmit-receive optics (or transceiver optics), a LiDAR system may need to generate pulses more frequently. In other words, the light source in a LiDAR system can have a higher pulse repetition rate (PRR). On the other hand, by generating and transmitting pulses more frequently, the maximum distance that a LiDAR system can detect may be limited. For example, if a return signal from a distant object is received after the system transmits the next pulse, the return signal may be detected in a different order than the corresponding transmitted signal, resulting in ambiguity if the system cannot correctly correlate the return signal with the transmitted signal.

[0092] To illustrate, consider an exemplary LiDAR system capable of emitting laser pulses with repetition rates between 500 kHz and 1 MHz. Based on the time it takes for the pulse to return to the LiDAR system, and to avoid confusion between return pulses from continuous pulses in a typical LiDAR design, the maximum detection range of the LiDAR system could be 300 meters for 500 kHz and 150 meters for 1 MHz. The point density of a LiDAR system with a repetition rate of 500 kHz is half that of a 1 MHz system. Therefore, this example shows that increasing the repetition rate from 500 kHz to 1 MHz (and thus increasing the point density) may reduce the system's detection range if the system cannot properly correlate out-of-order arriving return signals. Various techniques are used to mitigate the trade-off between a higher PRR and limited detection range. For example, multiple wavelengths can be used to detect objects within different ranges. Optical and / or signal processing techniques (e.g., pulse coding techniques) are also used to correlate the emitted and returned optical signals.

[0093] The various systems, apparatuses, and methods described herein can be implemented using digital circuitry or using one or more computers that utilize well-known computer processors, memory units, storage devices, computer software, and other components. Typically, a computer includes a processor for executing instructions and one or more memories for storing instructions and data. A computer may also include or be coupled to one or more mass storage devices, such as one or more disks, internal hard disks and removable disks, magneto-optical disks, optical disks, etc.

[0094] The various systems, apparatuses, and methods described herein can be implemented using computers operating in a client-server relationship. Typically, in such a system, the client computer is located remotely from the server computer and interacts via a network. The client-server relationship can be defined and controlled by computer programs running on the respective client and server computers. Examples of client computers may include desktop computers, workstations, laptops, cellular smartphones, tablets, or other types of computing devices.

[0095] The various systems, apparatuses, and methods described herein can be implemented using computer program products tangibly contained in an information carrier, such as a non-transitory machine-readable storage device, for execution by a programmable processor; and the method processes and steps can be implemented using one or more computer programs executable by such a processor. A computer program is a set of computer program instructions that can be used directly or indirectly in a computer to perform a specific activity or produce a specific result. Computer programs can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0096] Figure 6 A simplified block diagram of an exemplary apparatus that can be used to implement the systems, devices, and methods described herein is illustrated. Apparatus 600 includes a processor 610 operatively coupled to persistent storage device 620 and main memory device 630. Processor 610 controls the overall operation of apparatus 600 by executing computer program instructions that define these operations. The computer program instructions may be stored in persistent storage device 620 or other computer-readable medium and loaded into main memory device 630 when execution of the computer program instructions is desired. For example, processor 610 may be used to implement one or more components and systems described herein, such as control circuitry system 350 (… Figure 3 As shown), the vehicle perception and planning system 220 ( Figure 2 (as shown) and vehicle control system 280 ( Figure 2 (As shown). Therefore, Figures 1 to 10 At least some of the method steps described herein can be defined by computer program instructions stored in main memory device 630 and / or persistent storage device 620, and controlled by processor 610 executing the computer program instructions. For example, the computer program instructions can be implemented as computer-executable code programmed by someone skilled in the art to execute the algorithm defined by the method steps discussed herein. Accordingly, by executing the computer program instructions, processor 610 executes the algorithm defined herein. Figures 1 to 10 The method steps define the algorithm. Device 600 also includes one or more network interfaces 680 for communicating with other devices via a network. Device 600 may also include one or more input / output devices 690 that enable a user to interact with device 600 (e.g., a display, keyboard, mouse, speaker, buttons, etc.).

[0097] Processor 610 may include both general-purpose microprocessors and special-purpose microprocessors, and may be the sole processor of device 600 or one of multiple processors. Processor 610 may include one or more central processing units (CPUs) and one or more graphics processing units (GPUs), the GPUs of which may, for example, operate independently of one or more CPUs and / or perform multitasking with one or more CPUs to accelerate processing, for example, for the various image processing applications described herein. Processor 610, persistent storage device 620, and / or main memory device 630 may include one or more application-specific integrated circuits (ASICs) and / or one or more field-programmable gate arrays (FPGAs), or be supplemented by one or more ASICs and / or one or more FPGAs, or incorporated into one or more ASICs and / or one or more FPGAs.

[0098] Persistent storage device 620 and main memory device 630 each include a tangible, non-transitory computer-readable storage medium. Persistent storage device 620 and main memory device 630 may each include high-speed random access memory, such as dynamic random access memory (DRAM), static random access memory (SRAM), double-data-rate synchronous dynamic random access memory (DDR RAM), or other random access solid-state memory devices, and may include non-volatile memory, such as one or more disk storage devices, such as internal hard disks and removable disks, magneto-optical disk storage devices, optical disk storage devices, flash memory devices, semiconductor storage devices (such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), optical disc read-only memory (CD-ROM), digital universal optical disc read-only memory (DVD-ROM), or other non-volatile solid-state storage devices.

[0099] Input / output device 690 may include peripheral devices such as printers, scanners, displays, etc. For example, input / output device 690 may include display devices for displaying information to a user (such as cathode ray tube (CRT), plasma or liquid crystal display (LCD) monitors, keyboards) and pointing devices (such as mice or trackballs) that a user can use to provide input to device 600.

[0100] Any or all of the functions of the systems and apparatuses discussed herein may be executed by processor 610 and / or incorporated into an apparatus or system such as LiDAR system 300. Furthermore, LiDAR system 300 and / or apparatus 600 may utilize one or more neural networks or other deep learning techniques executed by processor 610 or other systems or apparatuses discussed herein.

[0101] Those skilled in the art will recognize that actual computer or computer system implementations may have other structures and may include other components, and Figure 6 This is a brief representation of some of the components of this computer for illustrative purposes.

[0102] Figure 7 A laser amplifier 700 according to an embodiment of the present disclosure is illustrated. The laser amplifier 700 includes a combiner 704, one or more pump laser sources 703 (e.g., laser diodes), a gain fiber 707, and a residual pump stripper 705. The "gain" fiber may also be referred to as an "active" fiber.

[0103] In the illustrated embodiment, the laser amplifier 700 receives signal light from the seed laser source 701 via isolator 702 and provides amplified output light to isolator 706.

[0104] In the illustrated embodiment, combiner 704 (pump signal combiner) combines the pump light from laser diode 703 and the signal light from seed laser 701. Various known optical combiners can be used. The pump light from laser diode 703 excites rare-earth dopants (e.g., erbium and / or ytterbium ions and / or other rare-earth dopants, such as thulium, neodymium, and / or holmium) in the core of gain fiber 707, resulting in the emission of photons at a frequency that amplifies the signal light received at the first end 707-1 of gain fiber 707, to provide amplified light at the second end 707-2 of gain fiber 707. Because the pump light propagates in the same direction as the signal light, this configuration is referred to as collinear pumping or co-directional propagation.

[0105] If in Figure 9 As further described in the context, the core of the gain fiber 707 has one or more characteristics at the first end 707-1 that differ from those at the second end 707-2. In a particular embodiment, one or more of the core diameter, core refractive index, and core rare earth dopant concentration at the second end 707-2 are greater than one or more of the core diameter, core refractive index, and core rare earth dopant concentration at the first end 707-1.

[0106] In various embodiments, the seed laser input and amplified output can be at a wavelength of approximately 1500-1600 nm. In some embodiments, the seed laser can be generated by a diode laser with an average power of 20µW-100µW. In some embodiments, the pump laser can have a wavelength of approximately 900-1000 nm and can be a high-power multimode fiber-coupled laser diode.

[0107] Figure 8A laser amplifier 800 according to another embodiment of the present disclosure is illustrated. The laser amplifier 800 includes a combiner 804 (pump signal combiner), one or more pump laser sources 803 (e.g., laser diodes), a gain fiber 807, and a residual pump stripper 805. Figure 8 The embodiments implement a reverse pumping (sometimes referred to as "reverse propagation" or "reverse pumping") arrangement in which the pump light is introduced from the second end of the gain fiber, while the signal light is introduced through the first end.

[0108] In the illustrated embodiment, the signal light from the seed laser source 801 propagates through isolator 802 and residual pump stripper 805, and is introduced into gain fiber 807 via first end 807-1. Pump light from pump laser diode 803 propagates through combiner 804 and is introduced into gain fiber 807 via second end 807-2. Therefore, the pump light propagates in the opposite direction to the signal light (reverse propagation). The amplified output light is provided to isolator 806.

[0109] However, the gain fiber 807 is similar to the above. Figure 7 The gain fiber 707 in this embodiment operates in a manner that is described in detail below. Specifically, and as will be explained in the following... Figure 9 As further described in the context, the core of the gain fiber 807 has one or more characteristics at the first end 807-1 that are different from those at the second end 807-2. In a particular embodiment, one or more of the core diameter, core refractive index, and core rare earth dopant concentration at the second end 807-2 are greater than one or more of the core diameter, core refractive index, and core rare earth dopant concentration at the first end 807-1.

[0110] Figure 9 The illustration shows a gain fiber 907 according to an embodiment of the present disclosure. Gain fibers such as gain fiber 907 can be used as… Figure 7 and Figure 8 The illustrated laser amplifier embodiment shows a gain fiber. Gain fiber 907 is illustrated as a double-clad implementation. However, embodiments of the inventive principles disclosed herein are not necessarily limited to double-clad fibers, but can be applied to single-clad fibers or fibers with more than two clads.

[0111] like Figure 9 As illustrated, the gain fiber 907 includes a tapered core 901, an inner cladding 902, and an outer cladding 903. The core 901 is doped with a rare earth dopant 912. In some examples, the rare earth dopant can be ions of rare earth elements, such as erbium (Eb), ytterbium (Yb), thulium (Tm), neodymium (Nd), and / or holmium (Ho) and / or other rare earth elements.

[0112] The tapered fiber core 901 has a diameter d1 at or near the first end 907-1 and a diameter d2 at or near the second end 907-2. In the illustrated embodiment, d2 > d1. The fiber core 901 has a refractive index n1 at or near the first end 907-1 and a refractive index n2 at or near the second end 907-2. In the illustrated embodiment, n2 > n1. The fiber core 901 has a higher concentration of rare earth dopant 912 at or near the second end 907-2 than at or near the first end 907-1.

[0113] In summary, the fiber core 901 has one or more characteristics, including a different diameter, refractive index, and / or rare-earth dopant concentration at the second end 907-2 than at the first end 907-1. In various embodiments, one or more of these characteristics are greater at or near the second end 907-2 than at or near the first end 907-1. When implemented as part of a laser amplifier including a pump laser source providing pump light, the signal light injected at the first end 907-1 of the gain fiber core 907-1 is amplified, resulting in a greater intensity (photon number) of the output light at the second end 907-2 at the signal light frequency. In various embodiments, a difference in any one of these core characteristics, or any combination of two or three of these core characteristics, from the first end receiving the signal light to the second end outputting the amplified light can provide enhanced amplification relative to prior art fiber amplifiers lacking such differences in these characteristics.

[0114] The inner cladding 902 has a refractive index n3 greater than n2. The outer cladding 903 has a refractive index n4 greater than n3.

[0115] Figures 10 to 12 The illustration shows an alternative embodiment in which the gain fiber is implemented using two or more gain fiber segments spliced ​​together.

[0116] Figure 10 A laser amplifier 1000 according to an embodiment of the present disclosure is illustrated. The laser amplifier 1000 includes a combiner 1004, one or more pump laser sources 1003 (e.g., laser diodes), a gain fiber 1007, and a residual pump stripper 1005. As shown, the gain fiber 1007 includes a first gain fiber segment 1007a and a second gain fiber segment 1007b. In this embodiment, the two gain fiber segments are spliced ​​together at a splice location 1008.

[0117] In the illustrated embodiment, the laser amplifier 1000 receives signal light from the seed laser source 1001 via the isolator 1002 and provides amplified output light to the isolator 1006.

[0118] In the illustrated embodiment, combiner 1004 combines pump light from laser diode 1003 and signal light from seed laser 1001. The pump light from laser diode 1003 excites rare-earth dopants in the core of gain fiber 1007, causing photons to be emitted at a frequency that amplifies the signal light received at the first end 1007-1 of gain fiber 1007, thereby providing amplified light at the second end 1007-2 of gain fiber 1007.

[0119] If in Figure 12 As further described in the context, the core of the first gain fiber segment 1007a of the gain fiber 1007 has one or more characteristics different from the core of the second gain fiber segment 1007b. In a particular embodiment, one or more of the core diameter, core refractive index, and core rare earth dopant concentration in the core of the second gain fiber segment 1007b are greater than one or more of the core diameter, core refractive index, and core rare earth dopant concentration in the core of the first gain fiber segment 1007a.

[0120] Figure 11 A laser amplifier 1100 according to another embodiment of the present disclosure is illustrated. The laser amplifier 1100 includes a combiner 1104, one or more pump laser sources 1103 (e.g., laser diodes), a gain fiber 1107, and a residual pump stripper 1105. As shown, the gain fiber 1107 includes a first gain fiber segment 1107a and a second gain fiber segment 1107b. In this embodiment, the two gain fiber segments are spliced ​​together at a splice position 1108.

[0121] Figure 11 The embodiments implement a reverse pumping (or "reverse" pumping) arrangement in which the pump light is introduced from the second end of the gain fiber, while the signal light is introduced through the first end.

[0122] In the illustrated embodiment, signal light from seed laser source 1101 propagates through isolator 1102 and residual pump stripper 1105, and is introduced into gain fiber 1107 via first end 1107-1. Pump light from pump laser diode 1103 propagates through combiner 1104 and is introduced into gain fiber 1107 via second end 1107-2. Therefore, the pump light propagates in the opposite direction to the signal light (“reverse propagation”). Amplified output light is provided to isolator 1106.

[0123] However, the gain fiber 1107 is similar to the above. Figure 10 The gain fiber 1007 of the embodiment operates in a manner that is described below. Specifically, and as will be explained in the following... Figure 12As further described in the context, the core of the first gain fiber segment 1107a of the gain fiber 1107 has one or more characteristics different from the core of the second gain fiber segment 1107b. In a particular embodiment, one or more of the core diameter, core refractive index, and core rare earth dopant concentration in the core of the second gain fiber segment 1107b are greater than one or more of the core diameter, core refractive index, and core rare earth dopant concentration in the core of the first gain fiber segment 1107a.

[0124] Figure 12 The illustration shows a gain fiber 1207 according to an embodiment of the present disclosure. Gain fibers, such as gain fiber 1207, can be used as… Figure 10 and Figure 11 The illustrated laser amplifier embodiment shows a gain fiber. Gain fiber 1207 is illustrated with a double-clad implementation. However, embodiments of the inventive principles disclosed herein are not necessarily limited to double-clad fibers, but can be applied to single-clad fibers or fibers with more than two clads (e.g., triple-clad fibers).

[0125] like Figure 12 As illustrated, the gain fiber 1207 comprises multiple segments spliced ​​together or otherwise connected together. Figure 12 The diagram shows a first segment 1207a, a second segment 1207b, and an Nth segment 1203N, illustrating that the number of segments may be two, three, or more than three. Each segment includes a core, an inner cladding, and an outer cladding. Specifically, the first segment 1207a includes a core 1201a, an inner cladding 1202a, and an outer cladding 1203a. The second segment 1207b includes a core 1201b, an inner cladding 1202b, and an outer cladding 1203b. The nth segment 1207N includes a core 1201N, an inner cladding 1202N, and an outer cladding 1203N. Each segment (i.e., 1201a, 1202b...1201N) is doped with a rare-earth dopant 1212, which in some examples may be rare-earth elements such as Eb, Yb, Tm, Nd, and / or Ho, and / or ions of other rare-earth elements.

[0126] In some embodiments, the refractive index of each inner cladding segment may be n3, and the refractive index of each outer cladding segment may be n4, where n3 > n4. In alternative embodiments, the refractive index of the inner cladding may differ from one segment to another, and the refractive index of the outer cladding may also differ from one segment to another. However, in either case, within each segment, the refractive index of the core is typically greater than that of the inner cladding, and the refractive index of the inner cladding is typically greater than that of the outer cladding.

[0127] In the illustrated embodiment, the chip segments have different characteristics from one segment to another, including one or more of different diameters, different refractive indices, and different rare-earth dopant concentrations. Specifically, chip segment 1201a has a diameter D1; chip segment 1201b has a diameter d2, and chip segment 1201N has a diameter dN. As shown, the diameter increases from one segment to another, such that dN > d2 > d1. Chip segment 1201a has a refractive index n1; chip segment 1201b has a refractive index n2, and chip segment 1201N has a refractive index nN. The refractive index increases from one segment to another, such that nN > n2 > n1. Furthermore, as shown, the concentration of rare-earth dopant 1212 increases from one segment to another, such that chip segment 1201N has a larger rare-earth dopant concentration than chip segment 1201b, which in turn has a larger rare-earth dopant concentration than chip segment 1201a.

[0128] Manufacturing a single continuous optical fiber with similar core properties from one end to the other may be more likely than manufacturing a single continuous optical fiber such as... Figure 9 The single continuous optical fiber shown is easier to use, in Figure 9 In this process, the characteristics of the fiber core vary from one end to the other (diameter, refractive index, and / or rare-earth dopant concentration). Therefore, Figures 10 to 12 The embodiments provided offer practical implementations of some of the inventive principles of this disclosure. Within a segment, each segment has similar core characteristics, but these characteristics vary from one segment to another, such that when these segments are spliced ​​together, they collectively provide a gain fiber with varying characteristics, thereby improving amplification efficiency.

[0129] Figure 13 The figures illustrate experimental results demonstrating the efficiency improvements provided by embodiments of the present disclosure. The data graphs show the relationship between pump power and output power. A reverse pumping arrangement was used in the experiments illustrating the results. Data graph 1301 was generated using 3.5-meter-long Er / Yb co-doped gain fiber, specifically Coractive DCF-EY-6 / 128 gain fiber with a core diameter of 5.5 ± 0.5 μm. Data graph 1302 was generated using 3.5-meter-long Er / Yb co-doped gain fiber, specifically Coractive DCF-EY-10 / 128 gain fiber with a core diameter of 10 ± 1 μm. Data graph 1303 was generated using a 3.5-meter-long gain fiber fabricated by splicing two gain fiber segments together: the first segment is a 1.5-meter-long Coractive DCF-EY-6 / 128 gain fiber segment, and the second segment is a 2.0-meter-long Coractive DCF-EY-10 / 128 gain fiber segment.

[0130] Data curve 1301 shows a slope efficiency of 13%. Data curve 1302 shows a slope efficiency of 18.7%. Data curve 1303 shows a slope efficiency of 22.3%. In summary, these results demonstrate that using gain fiber made by splicing together two segments with different core diameters (a smaller diameter at the end introducing the signal light from the seed source and a larger diameter at the output end) yields higher efficiency (curve 1303) compared to the efficiency achieved using fiber with the same core diameter at both ends (curves 1301 and 1302). This is true even when the total gain fiber length is the same in all three cases (3.5 meters in this case).

[0131] Figure 14 A laser amplifier 1400 with a residual pump laser reflecting element is illustrated according to an embodiment of the present disclosure. The laser amplifier 1400 includes a combiner 1404, one or more pump laser sources 1403 (e.g., laser diodes), a gain fiber 1407, and a residual pump laser reflecting element 1405. The term "residual pump laser reflecting element" is sometimes referred to as a "reflecting element" in this disclosure. Figure 14 Similar to Figure 7 The main difference is Figure 7 The residual pump stripper 705 in the middle is Figure 14 The reflective element 1405 is replaced in the middle.

[0132] In the illustrated embodiment, the laser amplifier 1400 receives signal light from the seed laser source 1401 via isolator 1402 and provides amplified output light to isolator 1406. Figure 14 The diagram illustrates a collinear pump arrangement.

[0133] In the illustrated embodiment, combiner 1404 combines pump light from laser diode 1403 and signal light from seed laser 1401. The pump light from laser diode 1403 excites rare-earth dopant in the core of gain fiber 1407, causing photons to be emitted at a frequency that amplifies the signal light received at the first end 1407-1 of gain fiber 1407, providing amplified light at the second end 1407-2 of gain fiber 1407. During the amplification process, although most of the pump light is absorbed by the rare-earth dopant in the core, some residual pump light remains in gain fiber 1407. This residual pump light appears at the second end 1407-2 of gain fiber 1407 as the pump light propagates in the same direction as the signal light (from the first end 1407-1 to the second end 1407-2). In one embodiment, the power of the residual pump light accounts for approximately 10% of the total pump light power.

[0134] The presence of residual pump light at the second end 1407-2 of the gain fiber 1407 poses several challenges to LiDAR systems. First, it may interfere with the signal light. Second, it may damage downstream optical components. To remove the residual pump light at the second end 1407-2 of the gain fiber 1407, one solution is to use... Figure 7 The illustration shows a residual pump stripper 705. However, removing residual pump light reduces the efficiency of a LiDAR system because residual pump light, which may account for up to 10% of the total pump light power, is discarded. Furthermore, using a residual pump stripper introduces unnecessary heat dissipation into the LiDAR system. It may also increase the system complexity and overall cost of the LiDAR system.

[0135] In some embodiments, efficiency improvements allow fiber lasers in LiDAR systems or other medium- to high-power systems to have a single amplification stage instead of two (or several amplification stages that would otherwise be required). For example, Figure 4 The illustrated fiber laser system can be modified to use with Figures 7 to 12 One or more embodiments of a consistent fiber laser amplifier (shown as including associated pump diodes and combiners) are used to replace preamplifier 408, pump 406, and WDM404 to provide sufficiently efficient amplification, so that no additional fiber laser amplifier is required. Figure 4 The second-stage amplification components shown are specifically the pump 412, combiner 410, and boost amplifier 414. This can reduce the cost and complexity of implementing fiber laser sources in LiDAR or other systems with comparable power requirements.

[0136] exist Figure 14 In this process, the residual pump light is reflected back into the gain fiber 1407 by the residual pump laser reflecting element 1405. This allows the residual pump light to be reused within the gain fiber 1407. Reusing the residual pump light has several advantages compared to discarding it. It improves the efficiency of the LiDAR system and reduces heat dissipation. It can reduce overall system complexity and cost.

[0137] Figure 15 The illustration shows a laser amplifier 1500 having a residual pump laser reflector element in a backpropagation pumping arrangement according to another embodiment of the present disclosure. The laser amplifier 1500 includes a combiner 1504, one or more pump laser sources 1503 (e.g., laser diodes), a gain fiber 1507, and a residual pump laser reflector element 1505. Figure 15 Similar to Figure 8 The main difference is Figure 8 The residual pump stripper 805 in the middle is Figure 15 The reflective element 1505 is replaced in the middle.

[0138] In the illustrated embodiment, signal light from seed laser source 1501 propagates through isolator 1502 and reflector 1505, and is introduced into gain fiber 1507 via first end 1507-1. Pump light from pump laser diode 1503 propagates through combiner 1504 and enters gain fiber 1507 via second end 1507-2. The signal light is amplified in gain fiber 1507, and the amplified output light exits at second end 1507-2 of gain fiber 1507. The amplified light is supplied to isolator 1506. As the pump light propagates in the opposite direction to the signal light (“reverse propagation”), residual pump light appears at first end 1507-1 of gain fiber 1507.

[0139] Similar to Figure 14 The explanation provided is that residual pump light can interfere with the signal light and may damage downstream optical components. To remove residual pump light at the first end 1507-1 of the gain fiber 1507, methods such as... Figure 8 The illustration shows a residual pump stripper 805. However, as previously mentioned, removing residual pump light reduces the efficiency of the LiDAR system, introduces unnecessary heat, and increases the system complexity and overall cost of the LiDAR system.

[0140] exist Figure 15 In this process, the residual pump light is reflected back into the gain fiber 1507 by the residual pump laser reflecting element 1505. This allows the residual pump light to be reused within the gain fiber 1507. As... Figure 14 The embodiment shown in the diagram increases the efficiency of the LiDAR system by reusing residual pump light, reduces the overall system complexity and cost, and minimizes heat dissipation within the LiDAR system.

[0141] Figure 16 A schematic diagram of a residual pump laser reflective element 1600 according to an embodiment of the present disclosure is illustrated. The reflective element 1600 includes a reflective coating 1603, which, in a preferred embodiment, is a high-reflectivity coating. In some embodiments, the reflective element 1600 includes an optical fiber sleeve 1602. In some embodiments, it further includes a collimator package 1604, which may include a collimator lens 1605. The reflective element 1600 can be used as... Figure 14 The reflective element 1405 shown can also be used as... Figure 15 The reflective element 1505 is shown.

[0142] The reflective element 1600 is connected to one end of the active optical fiber 1601. For Figure 14 In the co-propagation configuration, the reflector element 1600 is connected to the second end (1407-2) of the active optical fiber. For Figure 15The reverse propagation configuration is connected to the first end (1507-1) of the active fiber. Arrow 1611 indicates the direction of the residual pump light. Arrow 1612 indicates the direction of the reflected residual pump light, which is reflected back into the gain fiber 1601 by the reflective element 1600.

[0143] In some embodiments, the reflective coating 1603 includes a dichroic mirror that selectively reflects certain wavelengths of light while transmitting other wavelengths. As previously described, the signal light may have a wavelength of approximately 1500-1600 nm, while the pump light may have a wavelength of approximately 900-1000 nm. The dichroic mirror is designed to reflect light with wavelengths in the 900-1000 nm range and transmit light with wavelengths in the 1500-1600 nm range. This configuration allows residual pump light to be reflected back into the gain fiber 1601 along direction 1612, while the signal light can pass through the dichroic mirror to the next stage. In some embodiments, the reflective coating 1603 may include a grating and / or a multilayer optical film.

[0144] In some embodiments, the fiber optic sleeve 1602 is used to connect and align the active fiber 1601 with the reflective element 1600. One end of the fiber optic sleeve 1602 is coupled to the active fiber 1601, while the other end is coupled to the reflective coating 1603.

[0145] In some embodiments, the reflective element 1600 includes a collimator package 1604 that houses an optical fiber sleeve 1602 and a reflective coating 1603. Additionally, the collimator package 1604 may include a collimator lens 1605. The collimator package 1604 aligns the collimator lens 1605 with the active optical fiber 1601. The collimator lens 1605 collimates the signal light from the active optical fiber 1601 into a parallel beam, which is then guided to the next stage.

[0146] Figure 17A A schematic diagram of a residual pumped laser reflective element 1700 having a passive side component according to an embodiment of the present disclosure is shown. Figure 17A The component on the left side of the optical isolator 1709 and Figure 16 The same as shown. In one embodiment, the reflective element 1700 includes an optical fiber sleeve 1702, a reflective coating 1703, a collimator package 1704, and a collimator lens 1705. To the left of the reflective element 1700, it is connected to the active optical fiber 1701. Arrow 1711 indicates the direction of the residual pump light. Arrow 1712 indicates the direction of the reflected residual pump light, which is reflected back into the gain optical fiber 1701 by the reflective element 1700.

[0147] On the right side of the reflective element 1700, it is optically coupled to the passive-side optical components via an optical isolator 1709. The passive-side optical components include a passive-side collimator lens 1706, a passive-side collimator package 1707, a passive-side fiber optic sleeve 1708, and a passive fiber optic cable 1710. The passive-side fiber optic sleeve 1708 connects and aligns the passive fiber optic cable 1710 with the passive-side collimator package 1707. The passive-side collimator package 1707 houses the passive-side collimator lens 1706, which collimates the signal light from the reflective element 1700 into a parallel beam, which is then guided into the passive fiber optic cable 1710.

[0148] Optical isolator 1709 is a device that allows light to pass in one direction, as indicated by arrow 1713 at the top of the isolator, while blocking light from propagating in the opposite direction. It can be placed between active optical fiber 1701 and passive optical fiber 1710. Figure 17A This illustrates a co-directional propagation configuration where light travels from the active fiber 1701 through an isolator to the passive fiber 1710. This arrangement ensures that any light reflected back from the passive fiber 1710 does not enter the active fiber 1701.

[0149] Figure 17B The illustration shows a schematic diagram of a residual pump laser reflection element having a passive side component in a backpropagation pump according to an embodiment of the present disclosure. Figure 17B Similar to Figure 17A The difference is Figure 17B The direction of the middle arrow 1714 (which indicates the direction in which the light can pass through the isolator 1709) and Figure 17A The direction of the middle arrow 1713 is opposite. Figure 17B This illustrates a reverse propagation configuration where light travels from passive fiber 1710 through isolator 1709 to active fiber 1701. This arrangement ensures that any light reflected back from active fiber 1701 does not enter passive fiber 1710. Although in Figure 17A and Figure 17B The seed laser providing the signal light is not shown separately, but those skilled in the art will understand that it is assumed that the signal light comes from... Figure 17A Seeds spread from the left side of the middle, and from... Figure 17B Seed source propagation on the right side of the middle.

[0150] Figure 18A The illustration shows a cross-section of a gain fiber 1801 with a circular inner cladding according to an embodiment of the present disclosure. Gain fibers such as gain fiber 1801 can be used as… Figures 7 to 12 as well as Figures 14 to 1The gain fiber of the laser amplifier embodiment illustrated in Figure 7. Gain fiber 1801 is illustrated as a double-clad implementation. However, embodiments of the inventive principles disclosed herein are not necessarily limited to double-clad fibers, but can be applied to single-clad fibers or fibers with more than two clads.

[0151] The gain fiber 1801 includes a core 1811, an inner cladding 1812, and an outer cladding 1813. The inner cladding 1812 is circular and symmetrical, with the core 1811 located at its center. The core 1801 is doped with rare earth ions, such as erbium (Eb), ytterbium (Yb), thulium (Tm), neodymium (Nd), and / or holmium (Ho) and / or other rare earth elements. The core 1801 is surrounded by the inner cladding 1812, which has a circular shape and a lower refractive index than the core 1811. Because the inner cladding 1812 is circular and symmetrical, with the core 1811 located at its center, the inner cladding 1812 has a uniform thickness around the core 1811. The inner cladding 1812 is surrounded by the outer cladding 1813, which has a lower refractive index than the inner cladding 1812. This ensures that the pump light remains confined within the inner cladding 1812.

[0152] During the amplification process, signal light is injected into the fiber core 1811, and pump light is injected into the inner cladding 1812. As the pump light propagates through the inner cladding 1812, it may pass through the fiber core 1811 multiple times due to reflections within the cladding. The pump light passing through the fiber core 1811 excites the rare-earth dopant, causing photon emission, which in turn amplifies the signal light propagating in the fiber core 1811.

[0153] During the amplification process, when the pump light is reflected within the inner cladding 1812, some of the pump light may never pass through the core 1811 because it propagates along the entire length of the gain fiber 1801. This can happen if the pump beam is injected at a specific angle relative to the periphery of the inner cladding 1812. Figure 18A As shown, due to the circular shape of the inner cladding 1812 and / or the symmetrical structure of the core 1811 and the inner cladding 1812, the pump beam 1814 is reflected around the core 1811 but never intersects with it. This phenomenon is sometimes referred to as the "skewed ray" problem. Due to the skewed ray, the pump light is not completely absorbed by the core. The efficiency of the amplification process is reduced.

[0154] The problem of slanted light can be mitigated by changing the circular and / or symmetrical shape of the inner cladding 1812. Figures 18B to 18E The illustration shows a cross-section of a gain fiber with a non-circular or asymmetric inner cladding according to an embodiment of the present disclosure. In these embodiments, the inner cladding 1812 is non-circular or asymmetric, wherein the fiber core 1811 is off-center. The inner cladding 1812 has a uniform thickness around the fiber core 1811. Figure 10 Compared to A, in Figures 18B to 18EIn this structure, the inner cladding 1812 has a non-uniform thickness around the fiber core 1811. Therefore, it can alleviate the problem of skewing light and improve the efficiency of the amplification process.

[0155] exist Figure 18B In the fiber 1802, the gain fiber includes an inner cladding 1812, which is a basic circle with one or more flat edges. As shown, the pump beam 1815 is reflected around the core 1811, but may intersect the core 1811 due to reflections from the flat edges.

[0156] exist Figure 18C In the middle, the gain fiber 1803 includes a core 1811 that is not located at the center of the inner cladding 1812. As shown in the figure, with Figure 18A Pump beam 1816 with the same angle as pump beam 1814 can intersect with core 1811 because core 1811 is not located at the center of inner cladding 1812.

[0157] exist Figure 18D In the fiber 1804, the gain fiber includes an inner cladding 1812 shaped as a polygon. As shown, the pump beam 1817 is reflected around the core 1811, but can intersect the core 1811 due to reflections from the edges of the polygon.

[0158] exist Figure 18E In this fiber, the gain fiber 1805 includes an irregularly shaped inner cladding 1812. The inner cladding 1812 can have various configurations, such as a petal-like shape, or it can include one or more convex corners, concave corners, convex curved edges, concave curved edges, or flat edges. Alternatively, the shape can be completely irregular and random. As shown, the pump beam 1817 can intersect with the core 1811 because the inner cladding 1812 has an irregular shape.

[0159] To further improve the efficiency of the laser amplifier, such as Figure 9 The gain fiber 907 shown can also have an inner cladding with a non-uniform thickness around the fiber core. For example, in Figure 9 In the embodiments, although one or more characteristics of the core 901 (such as diameter, refractive index, and / or rare earth dopant concentration) differ from the first end to the second end of the gain fiber 907, the inner cladding of the gain fiber 907 can have a non-circular or asymmetrical shape, such as... Figures 18B to 18E As shown. Similarly, in Figure 12 In some embodiments, each inner cladding segment may have a non-circular or asymmetrical shape, such as Figures 18B to 18E As shown.

[0160] in addition, Figures 14 to 1The residual pump laser reflector illustrated in Figure 7 can be used in conjunction with a gain fiber having a non-circular and / or asymmetric inner cladding. For example, in one embodiment, Figure 14 The fiber laser amplifier 1400 shown may further include a gain fiber with an inner cladding having a non-uniform thickness around the fiber core, such as... Figures 18B to 18E As shown.

[0161] Additional Examples Example 1: A fiber laser amplifier that receives input from a seed laser, the fiber laser amplifier comprising: an optical fiber having a core and a cladding surrounding the core; and a pump laser connected to the cladding, wherein the core is connected to the seed laser at a first end and generates an output laser with the same wavelength as the seed laser at a second end, and wherein the core has different characteristics at the first end than at the second end.

[0162] Example 2: The fiber laser amplifier according to Example 1, wherein the fiber core has a smaller diameter at the first end than at the second end.

[0163] Example 3: A fiber laser amplifier according to any one of Examples 1 to 2, wherein the fiber core has a lower refractive index at the first end than at the second end.

[0164] Example 4: A fiber laser amplifier according to any one of Examples 1 to 3, wherein the fiber core comprises a plurality of fiber chip segments connected in series, wherein the plurality of fiber chip segments have an increasing diameter from the first end to the second end.

[0165] Example 5: A fiber laser amplifier according to any one of claims 1 to 4, wherein the fiber core comprises a plurality of fiber chip segments connected in series, wherein the plurality of fiber chip segments have an increasing refractive index from the first end to the second end.

[0166] Example 6: A system for optical ranging and detection (LiDAR), the system comprising: a laser source having a fiber laser amplifier according to any one of Examples 1 to 5; a scanner; a receiver; and a controller.

[0167] Example 7: A vehicle including the system according to Example 6.

[0168] Example 8: A system for optical ranging and detection (LiDAR), the system comprising: a scanner; a receiver; a controller; and a laser source, the laser source including a fiber laser amplifier receiving input from a seed laser, wherein the fiber laser amplifier further includes an optical fiber and a pump laser, the optical fiber having a core and a cladding surrounding the core, the pump laser being connected to the cladding, wherein the core is connected to the seed laser at a first end and generates an output laser having the same wavelength as the seed laser at a second end, and the cladding having a non-uniform thickness around the core.

[0169] Example 9: According to the system of Example 8, wherein the cladding has a radial cross-section, and the centroid of the radial cross-section of the cladding is aligned with the centroid of the radial cross-section of the fiber core.

[0170] Example 10: The system according to Example 8, wherein the cladding has a radial cross-section, the centroid of the radial cross-section of the cladding is not aligned with the centroid of the radial cross-section of the fiber core.

[0171] Example 11: The system according to Example 8, wherein the cladding has a radial cross-section with a convex polygonal shape.

[0172] Example 12: The system according to Example 8, wherein the cladding has a concave polygonal radial cross section.

[0173] Example 13: The system according to Example 8, wherein the cladding has a circular radial cross-section.

[0174] Example 14: The system according to Example 8, wherein the cladding has a radial cross-section, the radial cross-section being a circular shape with one or more flat sides.

[0175] Example 15: The system according to Example 8, wherein the cladding has a radial cross-section with one or more convex corners, one or more concave corners, one or more convex curved edges, one or more concave curved edges, or one or more flat edges.

[0176] Example 16: A vehicle comprising the system according to any one of Examples 8 to 15.

[0177] Example 17: A laser amplifier comprising: a gain fiber; a seed laser that transmits a first laser of a first frequency to the core of the gain fiber; a pump laser that transmits a second laser of a second frequency to the cladding of the gain fiber at a first end of the gain fiber; and a residual pump laser reflecting element located at a second end of the gain fiber that reflects a residual portion of the second laser of the second frequency.

[0178] Example 18: The laser amplifier according to Example 17, wherein the residual pump laser reflecting element selectively reflects light of the second frequency.

[0179] Example 19: A laser amplifier according to any one of Examples 17 to 18, wherein the residual pump laser reflecting element transmits light of the first frequency.

[0180] Example 20: A laser amplifier according to any one of Examples 17 to 19, wherein the residual pump laser reflecting element comprises a grating.

[0181] Example 21: A laser amplifier according to any one of Examples 17 to 20, wherein the residual pump laser reflecting element includes a wavelength selective mirror.

[0182] Example 22: A laser amplifier according to any one of Examples 17 to 21, wherein the residual pump laser reflecting element comprises a multilayer optical film.

[0183] Example 23: A system for optical ranging and detection (LiDAR), the system comprising: a scanner; a receiver; a controller; and a laser amplifier according to any one of Examples 17 to 22.

[0184] Example 24: A vehicle including the system according to Example 23.

[0185] The appended claims cover various embodiments of LiDAR systems including fiber laser amplifiers consistent with those of this disclosure. However, this disclosure, in its broadest sense, also covers fiber laser amplifiers consistent with the principles and embodiments described herein, whether such fiber laser amplifiers are part of a LiDAR system, part of a different type of system, or separate from any larger system.

[0186] The foregoing description should be understood as illustrative and exemplary in all respects, not restrictive, and the scope of the invention disclosed herein is not determined by the description, but by the claims as interpreted in the fullest extent permitted by patent law. It should be understood that the embodiments shown and described herein are merely illustrative of the principles of the invention, and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. Various other combinations of features can be implemented by those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. A system for optical ranging and detection (LiDAR), the system comprising a fiber laser amplifier, wherein the fiber laser amplifier comprises: The core of the gain fiber; The first cladding of the gain fiber is disposed around the fiber core; and One or more pump laser sources are coupled to provide optical pumping to the gain fiber; wherein: One or more of the refractive index, diameter, and rare earth dopant concentration of the fiber core differ at the first end of the gain fiber from that at the second end of the gain fiber.

2. The system according to claim 1, The diameter of the core at the second end of the gain fiber is greater than the diameter of the core at the first end of the gain fiber.

3. The system according to any one of claims 1 to 2, wherein the rare earth dopant concentration of the core at the second end of the gain fiber is greater than the rare earth dopant concentration of the core at the first end of the gain fiber.

4. The system according to any one of claims 1 to 3, wherein the refractive index of the core at the second end of the gain fiber is greater than the refractive index of the core at the first end of the gain fiber.

5. The system according to any one of claims 1 to 4, wherein the gain fiber is coupled to receive seed light at the first end.

6. The system according to any one of claims 1 to 5, wherein the gain fiber is coupled to receive pump light from the one or more pump laser sources at the first end.

7. The system according to any one of claims 1 to 5, wherein the gain fiber is coupled to receive pump light from the one or more pump laser sources at the second end.

8. The system according to any one of claims 1 to 7, the system further comprising a second cladding of the gain fiber disposed around the first cladding.

9. A system for optical ranging and detection (LiDAR), the system comprising a fiber laser amplifier, wherein the fiber laser amplifier comprises: Gain fiber, the gain fiber comprising a plurality of gain fiber segments coupled together, each gain fiber segment comprising a chip segment and a first cladding segment surrounding the chip segment; and One or more pump laser sources are coupled to provide optical pumping to the gain fiber; wherein: One or more of the diameter, rare earth dopant concentration, and refractive index of the fiber segment at the first end of the gain fiber are different from one or more of the diameter, rare earth dopant concentration, and refractive index of the fiber segment at the second end of the gain fiber.

10. The system of claim 9, wherein the plurality of gain fiber segments are spliced ​​together.

11. The system according to any one of claims 9 to 10: The diameter of the fiber segment at the second end of the gain fiber is larger than the diameter of the fiber segment at the first end of the gain fiber.

12. The system according to any one of claims 9 to 11, wherein the core diameter increases from the first end of the gain fiber to the second end of the gain fiber from one gain fiber segment to the next gain fiber segment.

13. The system according to any one of claims 9 to 12, wherein the rare earth dopant concentration of the fiber segment at the second end of the gain fiber is greater than the rare earth dopant concentration of the fiber segment at the first end of the gain fiber.

14. The system according to any one of claims 9 to 13, wherein the rare earth dopant concentration increases from one gain fiber segment to the next gain fiber segment from the first end of the gain fiber to the second end of the gain fiber.

15. The system according to any one of claims 9 to 14, wherein the refractive index of the fiber segment at the second end of the gain fiber is greater than the refractive index of the fiber segment at the first end of the gain fiber.

16. The system according to any one of claims 9 to 15, wherein the refractive index increases from the first end of the gain fiber to the second end of the gain fiber from one gain fiber segment to the next gain fiber segment.

17. The system according to any one of claims 9 to 16, wherein the gain fiber is coupled to receive seed light at the first end.

18. The system according to any one of claims 9 to 16, wherein the gain fiber is coupled to receive pump light from the one or more pump laser sources at the first end.

19. The system according to any one of claims 9 to 15, wherein the gain fiber is coupled to receive pump light from the one or more pump laser sources at the second end.

20. The system according to any one of claims 9 to 19, wherein each gain fiber segment includes a second cladding segment disposed around the first cladding segment.

21. A system for optical ranging and detection (LiDAR), the system comprising a fiber laser amplifier, wherein the fiber laser amplifier comprises: The core of the gain fiber; The first cladding of the gain fiber is disposed around the fiber core; and One or more pump laser sources are coupled to provide optical pumping to the gain fiber; wherein: The first cladding has a non-uniform thickness around the fiber core.

22. The system of claim 21, wherein the centroid of the cross section of the first cladding is aligned with the centroid of the cross section of the fiber core.

23. The system of claim 21, wherein the centroid of the cross-section of the first cladding is not aligned with the centroid of the cross-section of the fiber core.

24. The system according to any one of claims 21 to 23, wherein the cross-section of the first cladding is circular.

25. The system according to any one of claims 21 to 23, wherein the cross-section of the first cladding is non-circular.

26. The system of claim 25, wherein the cross-section of the first cladding layer is polygonal.

27. The system according to any one of claims 25 to 26, wherein the cross-section of the first cladding is a substantially circular shape having one or more flat edges.

28. The system according to any one of claims 25 to 27, wherein the cross-section of the first cladding layer has a petal-like shape.

29. The system according to any one of claims 25 to 28, wherein the cross-section of the first cladding layer has an irregular shape.

30. The system according to any one of claims 25 to 29, wherein the cross-section of the first cladding layer has one or more convex corners, one or more concave corners, one or more convex curved edges, one or more concave curved edges, or one or more flat edges.

31. The system according to any one of claims 21 to 30, the system further comprising a second cladding of the gain fiber disposed around the first cladding.

32. A system for optical ranging and detection (LiDAR), the system comprising a fiber laser amplifier, wherein the fiber laser amplifier comprises: Gain fiber; One or more seed laser sources are coupled to provide a first laser to the gain fiber, wherein the first laser has a wavelength corresponding to a first frequency; One or more pump laser sources are coupled to provide a second laser for optical pumping to the gain fiber at one end of the gain fiber, wherein the second laser has a wavelength corresponding to a second frequency; and A residual pump laser reflector is positioned at the other end of the gain fiber, wherein the residual pump laser reflector includes a reflective coating configured to reflect a residual portion of the second laser back into the gain fiber.

33. The system of claim 32, wherein the gain fiber comprises a core and a first cladding surrounding the core, wherein the first laser is provided to the core and the second laser is provided to the first cladding.

34. The system according to any one of claims 32 to 33, wherein the reflective coating selectively reflects light with a wavelength corresponding to the second frequency.

35. The system according to any one of claims 32 to 34, wherein the reflective coating selectively transmits light with a wavelength corresponding to the first frequency.

36. The system according to any one of claims 32 to 35, the system further comprising an optical combiner located at one end of the gain fiber, wherein the optical combiner is configured to combine the first laser and the second laser.

37. The system according to any one of claims 32 to 36, wherein the residual pump laser reflecting element further comprises a first fiber optic sleeve, wherein a first end of the first fiber optic sleeve is coupled to the other end of the gain fiber, and a second end of the first fiber optic sleeve is coupled to the reflective coating.

38. The system of claim 37, wherein the residual pump laser reflective element further comprises a first collimator package surrounding the first fiber optic sleeve and the reflective coating.

39. The system according to claim 38, wherein, The first collimator package is optically coupled to the second collimator package of the passive optical fiber.

40. The system according to claim 39, wherein, The second collimator package of the passive optical fiber includes a second optical fiber sleeve.

41. The system according to any one of claims 32 to 40, the system further comprising an isolator optically coupled between the other end of the gain fiber and the first end of the passive fiber, wherein the isolator is configured to allow light to travel from the gain fiber to the passive fiber and to prevent light from traveling from the passive fiber to the gain fiber.

42. The system according to any one of claims 32 to 40, the system further comprising an isolator optically coupled between the second end of the gain fiber and the first end of the passive fiber, wherein the isolator is configured to allow light to travel from the passive fiber to the gain fiber and to prevent light from traveling from the gain fiber to the passive fiber.

43. The system according to any one of claims 32 to 42, wherein the residual pump laser reflecting element comprises at least one of a grating, a wavelength selective mirror, and a multilayer optical film.

44. A system for optical ranging and detection (LiDAR), the system comprising a fiber laser amplifier, wherein the fiber laser amplifier comprises: A gain fiber, the gain fiber comprising a core and a first cladding surrounding the core, wherein the first cladding has a non-uniform thickness around the core; One or more seed laser sources are coupled to provide a first laser to the gain fiber, wherein the first laser has a wavelength corresponding to a first frequency; One or more pump laser sources are coupled to provide a second laser for optical pumping to the gain fiber at one end of the gain fiber, wherein the second laser has a wavelength corresponding to a second frequency; and A residual pump laser reflector is positioned at the other end of the gain fiber, wherein the residual pump laser reflector includes a reflective coating configured to reflect a residual portion of the second laser back into the gain fiber.

45. The system of claim 44, wherein one or more of the refractive index, diameter, and rare earth dopant concentration of the core at one end of the gain fiber are different from one or more of the refractive index, diameter, and rare earth dopant concentration of the core at the other end of the gain fiber.

46. ​​The system of claims 44 to 45, wherein the cross-section of the first cladding is a substantially circular shape having one or more flat edges, and wherein the reflective coating selectively reflects light with a wavelength corresponding to the second frequency.

47. A system for optical ranging and detection (LiDAR), the system comprising a fiber laser amplifier, wherein the fiber laser amplifier comprises: Gain fiber, the gain fiber comprising a plurality of gain fiber segments coupled together, each gain fiber segment comprising a chip segment and a first cladding segment surrounding the chip segment, wherein the first cladding segment has a non-uniform thickness around the chip segment; and One or more pump laser sources are coupled to provide optical pumping to the gain fiber; wherein: One or more of the diameter, rare earth dopant concentration, and refractive index of the fiber segment at the first end of the gain fiber are different from one or more of the diameter, rare earth dopant concentration, and refractive index of the fiber segment at the second end of the gain fiber.

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