Optical fiber laser, lidar and optical power adjustment method

Abstract

The application discloses an optical fiber laser, a laser radar and a light power adjusting method, which can be applied to the field of laser radars. The optical fiber laser comprises a plurality of seed light lasers with different powers and a fiber amplifier. The plurality of seed light lasers are the same type of lasers. One of the seed light lasers is configured to enter an excited state and emit a first seed light signal in response to a trigger event. The first seed light signal is coupled to the fiber amplifier. The other seed light lasers are configured to be in a standby excited state in response to the trigger event. The fiber amplifier is configured to be in a gain saturation state all the time and amplify the first seed light signal. In the application, the light power of the optical fiber laser is rapidly and dynamically adjusted by triggering the seed light lasers with different powers to emit seed light signals under the condition that the fiber amplifier is in the gain saturation state all the time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar, in particular to a fiber laser, a laser radar and a light power adjusting method. BACKGROUND

[0002] In recent years, with the rise of unmanned driving, laser radar, as the most core component of unmanned driving technology, has the advantages of long detection distance, high imaging accuracy, etc., and is the "eyes" of unmanned driving technology. The laser is an important component of the laser radar.

[0003] Generally, the fiber laser used in the laser radar is a master oscillator power-amplifier (MOPA) laser, which mainly consists of a seed source (which can also be described as a seed light signal) and a fiber amplifier. The seed source provides the pulse signal required by the radar, and the fiber amplifier is responsible for amplifying the pulse signal.

[0004] For the fiber laser, how to achieve rapid dynamic adjustment of the light power is a problem to be solved. SUMMARY

[0005] The present application provides a fiber laser, a laser radar and a light power adjusting method to achieve rapid dynamic adjustment of the light power of the fiber laser.

[0006] In a first aspect, the present application provides a fiber laser, comprising: a plurality of seed light lasers with different powers and a fiber amplifier; the plurality of seed light lasers are the same type of laser; one of the plurality of seed light lasers is configured to enter an excited state and emit a first seed light signal in response to a trigger event; the first seed light signal is coupled to the fiber amplifier; the other seed light lasers in the plurality of seed light lasers are configured to be in a standby excited state in response to the trigger event; and the fiber amplifier is configured to be in a gain saturation state at all times and amplify the first seed light signal.

[0007] In some possible implementation manners, the plurality of seed light lasers are coupled to the fiber amplifier by a beam combiner or spatial coupling.

[0008] In some possible implementation manners, the fiber amplifier comprises: a gain fiber and a pump light laser; one of the seed light lasers is configured to couple the first seed light signal to the gain fiber; the pump light laser is configured to emit a target pump light signal at all times and is coupled to the gain fiber; and the gain fiber is configured to be in a gain saturation state at all times in response to the target pump light signal and amplify the first seed light signal through the target pump light signal.

[0009] In some possible implementation, the seed laser with the largest power among the plurality of seed lasers is configured to emit a second seed light signal and couple to the fiber amplifier before one of the seed lasers enters the excited state in response to the trigger event; the seed lasers other than the seed laser with the largest power are configured to be in the standby excited state before one of the seed lasers enters the excited state in response to the trigger event; the fiber amplifier is further configured to amplify the second seed light signal before amplifying the first seed light signal, and adjust the pump power during the amplification of the second seed light signal until the gain saturation state is reached.

[0010] In some possible implementation, the fiber laser further comprises: a filter; the fiber amplifier is further configured to couple the amplified first seed light signal to the filter; the filter is configured to filter the amplified first seed light signal.

[0011] In the second aspect, the application provides a laser radar, comprising: the fiber laser according to any one of the first aspect and possible implementation thereof, and a controller; the controller is coupled to the plurality of seed lasers; the controller is configured to send a trigger signal to one of the seed lasers in response to a trigger event, the trigger signal being used to trigger one of the seed lasers to enter the excited state.

[0012] In the third aspect, the application provides a method for adjusting optical power, applied to the laser radar according to the second aspect; the method comprises: the controller obtains a trigger event, the trigger event being used to indicate one of the seed lasers to enter the excited state; the controller controls one of the seed lasers to enter the excited state and controls the other seed lasers to be in the standby excited state in response to the trigger event; one of the seed lasers emits a first seed light signal; the fiber amplifier amplifies the first seed light signal in the gain saturation state.

[0013] In some possible implementation, the fiber amplifier amplifies the first seed light signal in the gain saturation state, comprising: the fiber amplifier amplifies the first seed light signal by a target pump light signal, the target pump light signal being used to make the fiber amplifier in the gain saturation state.

[0014] In some possible implementation, before the trigger event is obtained, the method further comprises: the seed laser with the largest power among the plurality of seed lasers emits a second seed light signal; the fiber amplifier amplifies the second seed light signal; and the pump power is adjusted during the amplification of the second seed light signal until the gain saturation state is reached.

[0015] In some possible implementation manners, the method further includes filtering the amplified first seed light signal by a filter in the fiber laser.

[0016] The technical scheme provided in the application has the beneficial effects that:

[0017] In the application, when the fiber amplifier is in a gain saturation state, different seed light signals are emitted by triggering seed light lasers with different powers in the fiber laser, so that the amplitude of the amplified light signal output by the fiber amplifier changes synchronously with the power of the seed light signal, thereby realizing rapid dynamic adjustment of the optical power of the fiber laser.

[0018] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the protection scope of the application. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is a structural schematic diagram of a laser radar in the related art;

[0020] Figure 2 FIG. 2 is a structural schematic diagram of a fiber laser in the related art;

[0021] Figure 3 FIG. 3 is a schematic diagram of a seed light signal and an amplified light signal in the related art;

[0022] Figure 4 FIG. 4 is a structural schematic diagram of a fiber laser in an embodiment of the application;

[0023] Figure 5 FIG. 5 is another structural schematic diagram of a fiber laser in an embodiment of the application;

[0024] Figure 6 FIG. 6 is a schematic diagram of a seed light signal and an amplified light signal in an embodiment of the application;

[0025] Figure 7 FIG. 7 is a structural schematic diagram of a laser radar in an embodiment of the application;

[0026] Figure 8 FIG. 8 is another structural schematic diagram of a laser radar in an embodiment of the application;

[0027] Figure 9 FIG. 9 is an implementation flow schematic diagram of an optical power adjustment method in an embodiment of the application. DETAILED DESCRIPTION

[0028] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, technologies, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0029] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0030] In order to illustrate the technical solutions of the present application, the following will be described by specific embodiments.

[0031] Laser radar is a target detection technology. Laser radar emits a laser beam through a laser, the laser beam encounters a target object and is diffusely reflected, the reflected light beam is received by a detector, and the distance, direction, height, speed, attitude, shape, etc. of the target object are determined according to the emitted light beam and the reflected light beam.

[0032] The application field of laser radar is very wide. In addition to being used in the military field, it is also widely used in the field of life, including but not limited to: intelligent driving vehicles, intelligent driving aircrafts, three-dimensional (3D) printing, virtual reality, augmented reality, service robots, etc. For example, in the field of intelligent driving technology, a laser radar is arranged in an intelligent driving vehicle, which can scan the surrounding environment by rapidly and repeatedly emitting a laser beam to obtain point cloud data reflecting the shape, position, motion of one or more target objects in the surrounding environment, etc.

[0033] It should be noted that the above-mentioned intelligent driving technology can refer to unmanned driving, autonomous driving, assisted driving, etc.

[0034] Figure 1 A structure diagram of a laser radar in the related art is shown. Referring to Figure 1 As shown, the laser radar 10 can include a light emitting device 101, a light receiving device 102, and a processor 103. The light emitting device 101 and the light receiving device 102 are connected with the processor 103.

[0035] Among them, the connection relationship between the above-mentioned devices can be electrical connection, but also can be optical fiber connection. More specifically, in the light emitting device 101 and the light receiving device 102, there can be a plurality of optical devices respectively, and the connection relationship between these optical devices can also be spatial optical transmission connection.

[0036] The processor 103 is used to control the transmitting device 101 and the optical receiving device 102 so that the optical transmitting device 101 and the optical receiving device 102 can operate normally. For example, the processor 103 can provide driving voltages to the optical transmitting device 101 and the optical receiving device 102 respectively, and the processor 103 can also provide trigger signals to the optical transmitting device 101 and the optical receiving device 102.

[0037] For example, processor 103 can be a general-purpose processor, such as a central processing unit (CPU), a network processor (NP), etc.; processor 103 can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0038] The light emitting device 101 also includes a light source ( Figure 1 (Not shown). It is understood that the aforementioned light source can refer to a laser, and the number of lasers can be one or more. Optionally, the laser can specifically be a pulsed laser diode (PLD), a semiconductor laser, a fiber laser, etc. The aforementioned light source is used to emit a laser beam. Specifically, the processor 103 can send an emission trigger signal to the light source, thereby triggering the light source to emit a laser beam.

[0039] Understandably, the aforementioned laser beam can also be referred to as a laser pulse, laser, or emission beam, etc.

[0040] The following is combined with Figure 1 The structure of the lidar shown is briefly described, along with the detection process of the lidar on the target object 104.

[0041] See Figure 1 As shown, the laser beam propagates along the emission direction. When the laser beam encounters the target object 104, it is reflected from the surface of the target object 104, and the reflected beam is received by the laser radar's optical receiver 102. Here, the laser beam reflected back by the target object 104 can be called the echo beam. Figure 1 The laser beam and echo beam are indicated by solid lines.

[0042] After the light receiving device 102 receives the echo light beam, the echo light beam is photoelectrically converted, that is, the echo light beam is converted into an electrical signal, and the light receiving device 102 outputs the electrical signal corresponding to the echo light beam to the processor 103. The processor 103 can obtain point cloud data of the topography, position, and motion of the target object 104 according to the electrical signal of the echo light beam.

[0043] At present, the laser used by the laser radar is a 905nm wavelength semiconductor laser. However, the power of the semiconductor laser is limited, which affects the ranging of the laser radar. Although the power can be improved by using multiple lasers, the 905nm wavelength does not belong to the eye-safe wavelength band, and the power is too high to meet the requirements of the automotive standard, and the beam quality is far inferior to that of the fiber laser. Therefore, based on the factors of the eye-safe wavelength band, the automotive standard, and the beam quality, the high-power 1550nm fiber laser becomes the development direction of the laser in future laser radars.

[0044] Figure 2 A structure diagram of a fiber laser in the related art is shown in FIG. 1. Figure 2 As shown in FIG. 1, the fiber laser in the laser radar is usually a MOPA fiber laser, which mainly consists of a seed light laser 21 (which can also be described as a seed source) and a fiber amplifier 22. The seed light laser 21 is used to provide a pulse signal (i.e., a seed light signal) required by the laser radar 10, and the fiber amplifier 22 is used to amplify the pulse signal and output an amplified light signal. Here, the fiber amplifier 22 can amplify the pulse signal by one or more stages. In the embodiments of the present application, the pulse signal is amplified by one stage as an example.

[0045] In an embodiment, the fiber amplifier 22 consists of a pump light laser 221 (which can also be described as a pump light source) and a gain fiber 222, wherein the pump light laser 221 is used to emit a pump light signal and couple the pump light signal to the gain fiber 222, and the gain fiber 222 amplifies the pulse signal by the pump light signal and outputs an amplified light signal, i.e., an amplified pulse signal or an amplified seed light signal.

[0046] Further, when the laser radar is working, it is necessary to dynamically adjust the optical power of the laser to ensure eye safety, protect the receiving end, and adapt to other emergency situations. Based on the structure of the above fiber laser, the most ideal dynamic adjustment is to realize it by adjusting the amplification factor of the fiber amplifier, of course, it can also be realized by adjusting the adjustable attenuator or the optical switch modulator.

[0047] However, to obtain more point clouds, lasers need to operate at high repetition rates, reaching up to the MHz (megahertz) level, meaning the interval between two pulse signals is less than 1 μs (microseconds). If the dynamic adjustment speed exceeds this time interval, it may result in lost points at distant locations or damage to the detector at close range, and could even cause eye injury. When the laser's optical power is dynamically adjusted by regulating the attenuator, the response speed is on the order of milliseconds (ms) due to the mechanical adjustment of the attenuator, which is completely insufficient for the requirements of rapid dynamic adjustment. When the laser's optical power is dynamically adjusted by regulating the optical switch modulator, the response speed of the optical switch modulator can range from several ps (picoseconds) to hundreds of ns (nanoseconds), which can fully meet the requirements of rapid dynamic adjustment. However, on the one hand, its high cost hinders the mass production of automotive LiDAR, and on the other hand, its large size results in a large LiDAR, which does not meet the small-volume design requirements of automotive radar. When the laser's optical power is dynamically adjusted by regulating the amplification factor of an fiber optic amplifier, the amplifier is essentially regulating the power of the pump signal (which can also be described as pump power), thereby changing the laser's optical power. However, Figure 3 The diagram illustrates the seed optical signal and amplified optical signal in related technologies. (See attached image.) Figure 3 As shown in (a), because the rare-earth ions doped in the gain fiber reach energy level saturation and the energy level lifetimes are on the order of hundreds of μs, the energy of the output amplified optical signal changes gradually during dynamic adjustment. In other words, the response of dynamic adjustment is not completely synchronous. Alternatively, the gain fiber can be pre-charged, i.e., the pump light signal can be coupled to the gain fiber in advance, allowing the gain fiber to reach gain saturation earlier. See [reference needed]. Figure 3 As shown in (b). However, during the power-charging period of the gain fiber, the pulse signal cannot be coupled to the gain fiber, otherwise the stored energy will be consumed. Therefore, for fiber lasers, how to achieve rapid dynamic adjustment of optical power is an urgent problem to be solved.

[0048] To address the aforementioned issues, this application provides a fiber laser that can be applied in a lidar system for radar ranging.

[0049] Figure 4 This is a schematic diagram of a fiber laser in one embodiment of this application. See also... Figure 4 As shown, the fiber laser 40 may include a plurality of seed lasers 41 arranged sequentially according to the optical signal amplification direction and an optical fiber amplifier 42.

[0050] Here, the plurality of seed light lasers 41 are lasers of different powers but same type, such as semiconductor lasers. Preferably, the seed light lasers 41 can be implemented by 1550 nm semiconductor lasers. Of course, the seed light lasers 41 can also be implemented by semiconductor lasers of other pulse widths, as long as the seed light emitted by the seed light lasers 41 is continuous and can be applied to a laser radar for radar ranging, and the present application does not make a specific limitation in this regard. In addition, the different powers of the seed light lasers can be understood as different peak powers or different average powers.

[0051] Optionally, the plurality of seed light lasers 41 are coupled to the fiber amplifier 42 by a beam combiner 43 or a spatial coupling manner. For example, when the seed light lasers 41 are two, the two seed light lasers 41 can be coupled to the fiber amplifier 42 by the beam combiner 43 or the spatial coupling manner; when the seed light lasers 41 are more than two, the seed light lasers 41 are coupled to the fiber amplifier 42 by the beam combiner 43. Of course, the seed light lasers 41 can also be coupled to the fiber amplifier 42 by other manners, and the present application does not make a specific limitation in this regard.

[0052] In some possible embodiments, one of the plurality of seed light lasers 41 is configured to enter an excited state and emit a seed light signal A (i.e., a first seed light) in response to a trigger event, and couple the seed light signal A to the fiber amplifier 42; and the other seed light lasers 41 of the plurality of seed light lasers 41 are configured to enter a non-excited state in response to the trigger event; and the fiber amplifier 42 is configured to amplify the seed light signal A in a gain-saturated state.

[0053] Optionally, the different seed light lasers 41 can work at different currents, so that the powers of the different seed light lasers 41 are different, which can also be understood as the powers of the seed light signals emitted by the different seed light lasers 41 are different.

[0054] In an embodiment, each of the plurality of seed light lasers 41 is in the non-excited state on the premise that the fiber amplifier 42 is always in the gain-saturated state. In response to a trigger event, one of the plurality of seed light lasers 41 (i.e., the seed light laser 41 corresponding to the trigger event) enters the excited state and emits the seed light signal A, and the other seed light lasers 41 are in the non-excited state and do not emit the seed light signal.

[0055] In another embodiment, with the fiber amplifier 42 always in gain saturation, one of the seed lasers 41 is in an excited state, emitting seed light signal B, while the other seed lasers 41 are in a standby state. In response to a trigger event, another seed laser 41 (i.e., the seed laser 41 corresponding to the trigger event) enters the excited state and emits seed light signal A. Simultaneously, the seed laser 41 emitting seed light signal B returns to the standby state and stops emitting seed light signal B. This achieves the switching of the seed lasers. During the switching process, since the seed lasers are of the same type, only different seed lasers need to be triggered, without adaptively adjusting the relevant parameters of the fiber amplifier, thus improving the switching speed and enabling rapid dynamic adjustment of the fiber laser's optical power.

[0056] In this embodiment, a triggering event can be understood as saturation of the optical receiving device. For example, a change in the distance between the lidar and the target object, the appearance of a highly reflective object or a retroreflective object within the lidar's scanning range. In response to these triggering events, the fiber lidar needs to dynamically adjust its optical power. For instance, suppose the target object, such as a human body or other object, appears at close range within the lidar's scanning range. When the laser beam scans the target object, the shorter scanning distance enhances the echo beam, increasing the pulse peak value of the echo signal. When the optical receiving device receives a high-energy pulse, saturation occurs. At this time, the fiber laser needs to turn off the high-power seed laser and turn on the low-power seed laser. Alternatively, suppose a highly reflective object (such as a surface of water, an icy road, snow, or a glass obstacle) or a retroreflective object (such as a traffic sign) appears at mid-range within the lidar's scanning range. When the laser beam scans the reflective object, the strong reflection enhances the echo beam, increasing the pulse peak value of the echo signal. When the optical receiving device receives a high-energy pulse, saturation occurs. At this point, the fiber laser needs to turn off the high-power seed laser and turn on the low-power seed laser.

[0057] The following explanation uses two seed lasers 41 as examples to illustrate the fiber laser 40. Figure 5 This is another structural schematic diagram of the fiber laser in the embodiments of this application. See also... Figure 5 As shown, the fiber laser 40 includes a seed laser 41a for emitting seed light signal A and a seed laser 41b for emitting seed light signal B. The power of seed laser 41a is less than the power of seed laser 41b. In this case, seed laser 41b can be understood as the seed laser with the highest power among the multiple seed lasers 41.

[0058] If the trigger event is that a target object appears at the near range end of the lidar, then the seed light laser 41a enters the excited state from the standby state in response to the trigger event while the fiber amplifier 42 is in the gain saturated state, and emits the seed light signal A. The seed light laser 41b remains in the excited state or enters the standby state from the excited state in response to the trigger event, and does not emit (including remaining not to emit or stopping to emit) the seed light signal B.

[0059] In actual applications, when the lidar detects the above trigger event, which is used to indicate the control of the seed light laser 41a to enter the excited state, the seed light laser 41a receives a trigger signal in response to the trigger event, and enters the excited state in response to the trigger signal to emit the seed light signal A while the fiber amplifier 42 is in the gain saturated state. The other seed light laser 41b does not receive the above trigger signal, and thus is in the standby state and does not emit the seed signal.

[0060] In some possible embodiments, the structure of the fiber amplifier 42 can refer to the description of the structure of the fiber amplifier 22 in the above Figure 2 embodiments, which will not be described here again.

[0061] In an embodiment, during the use of the fiber laser 40, the seed light laser 41a (i.e., one seed light laser 41 entering the excited state) is configured to couple the seed light signal A to the gain fiber 222; the pump light laser 221 is configured to always emit the target pump light signal and is coupled to the gain fiber 222; and the gain fiber 222 is configured to always be in the gain saturated state in response to the target pump light signal, and amplify the seed light signal A by the target pump light signal.

[0062] It can be understood that the seed light laser 41a couples the seed light signal A to the gain fiber 222, and the pump light laser 221 always emits the target pump light signal so that the gain fiber 222 is always in the gain saturated state. The gain fiber 222 amplifies the seed light signal A by the target pump light signal while being in the gain saturated state. It should be noted that the gain fiber 222 being in the gain saturated state can also be understood as the fiber amplifier 42 being in the gain saturated state.

[0063] In some possible embodiments, before the fiber laser 40 is put into use (e.g., one of the seed lasers enters the excited state in response to a trigger event as described above), the fiber laser 40 also needs to be debugged so that the fiber amplifier 42 reaches and remains in the gain saturation state (which can also be understood as the amplification multiple of the seed signal being maintained at a specific value). Then, the seed laser 41 with the maximum power among the plurality of seed lasers 41 (e.g., the fiber laser 41b) is configured to emit the seed signal B (i.e., the second seed signal) and be coupled to the fiber amplifier 42; the other seed lasers 41 (e.g., the seed laser 41a) except the seed laser 41 with the maximum power are configured to be in the standby state; and the fiber amplifier 42 is further configured to amplify the seed signal B and adjust the pump power (i.e., the power of the pump signal) during the amplification of the seed signal B until the gain saturation state is reached.

[0064] Optionally, after the fiber amplifier 42 reaches the gain saturation state, the plurality of seed lasers 41 enter the standby state and wait for the fiber laser 40 to be put into use. Alternatively, after the fiber amplifier 42 reaches the gain saturation state, the seed laser 41 with the maximum power can still remain in the excited state and continuously emit the seed signal B until one of the seed lasers 41 enters the excited state in response to a trigger event, and the seed laser 41 with the maximum power returns to the standby state. The other seed lasers 41 remain in the standby state.

[0065] In an embodiment, if the above-mentioned one of the seed lasers 41 is a seed laser 41 other than the seed laser 41 with the maximum power, after the fiber amplifier 42 reaches the gain saturation state, one of the seed lasers 41 enters the excited state in response to a trigger event and emits the seed signal A, at which time the seed laser 41 with the maximum power enters the standby state and stops emitting the seed signal B. The other seed lasers 41 remain in the standby state. If the above-mentioned one of the seed lasers 41 is the seed laser 41 with the maximum power, after the fiber amplifier 42 reaches the gain saturation state, the seed laser 41 with the maximum power can still remain in the excited state and continuously emit the seed signal B in response to a trigger event, at which time the seed signal B is the seed signal A. The other seed lasers 41 remain in the standby state.

[0066] It can be understood that, during the debugging process of the fiber laser 40, the seed light laser 41b can generate the seed light signal B and couple to the fiber amplifier 42; the fiber amplifier 42 amplifies the seed light signal B. During the amplification of the seed light signal B, the fiber amplifier 42 adjusts the pump power (i.e. the power of the pump light signal) until the fiber amplifier 42 reaches the gain saturation state, at which time the pump light signal in the fiber amplifier 42 is the target pump light signal. Further, the fiber amplifier 42 remains in the gain saturation state after reaching the gain saturation state.

[0067] For example, during the debugging process of the fiber laser 40, the seed light laser 41b first generates the seed light signal B. At this time, the seed light signal B serves as an auxiliary signal to assist in the debugging of the fiber amplifier 42. The gain fiber 222 amplifies the seed light signal B using the pump light signal emitted by the pump light laser 221. During the amplification of the seed light signal B, the pump light laser 221 adjusts the pump power to emit pump light signals of different powers. When the pump light signal is adjusted to the target pump light signal, the gain fiber 222 reaches the gain saturation state and remains in the gain saturation state.

[0068] It should be noted that, when the gain fiber 222 is in the gain saturation state, the power of the amplified light signal output by the gain fiber 222 further increases with the increase of the power of the seed light signal. Further, the gain fiber 222 amplifies the seed light signal while remaining in the gain saturation state. At this time, the input seed light signal and the output amplified light signal are monotonically related (which can also be understood as being positively or negatively related).

[0069] In some possible embodiments, since a seed light signal with low power (which can also be described as a small signal) cannot completely take away the energy of the pump light signal in the fiber amplifier 42, the excess pump light signal energy is emitted as amplified spontaneous emission (ASE). Therefore, in order to eliminate the ASE, retain the amplified light signal and improve the signal-to-noise ratio of the laser, still referring to Figure 4 As shown in the figure, the fiber laser 40 can further include a filter 44 arranged after the fiber amplifier 42 according to the direction of light signal amplification.

[0070] In an embodiment, the fiber amplifier 42 is further configured to couple the amplified seed light signal A (i.e. the amplified light signal) to the filter 44; the filter 44 is configured to filter the amplified seed light signal A. In this way, the amplified light signal can be obtained.

[0071] In some possible embodiments, the fiber laser 40 can further include an isolator, one or more other combiners, etc. Figure 4An isolator can be disposed at the output end of the seed laser 41 for ensuring unidirectional propagation of the seed signal and protecting the seed laser 41. One or more combiners can be disposed at the output end of the pump laser 221 for coupling the pump signal to the gain fiber 222.

[0072] The above fiber laser 40 is described in detail below with specific examples.

[0073] Still referring to Figure 5 As shown, the fiber laser 40 includes a seed laser 41a and a seed laser 41b. The seed laser 41a is configured to emit a seed signal A, and the seed laser 41b is configured to emit a seed signal B. For example, the power of the seed laser 41a is less than the power of the seed laser 41b, and the seed laser 41b can be understood as the seed laser with the largest power among the seed lasers.

[0074] First, during the debugging process of the fiber laser 40, the seed laser 41b is excited to emit the seed signal B. The other seed lasers, i.e., the seed laser 41a, do not emit the seed signal A because they are not excited. The seed signal B is coupled to the gain fiber 222 by the seed laser 41b. The gain fiber 222 amplifies the seed signal B. During the amplification of the seed signal B, the pump laser 221 adjusts the pump power until the gain fiber 222 reaches a gain saturation state, at which time the pump laser 221 emits a target pump signal. After the gain fiber amplifier 42 reaches the gain saturation state, the pump laser 221 continues to emit the target pump signal so that the gain fiber 222 is always in the gain saturation state. Optionally, the seed laser 41b returns to the standby state after the gain fiber amplifier 42 reaches the gain saturation state. At this time, the seed lasers 41a and 41b are both in the standby state.

[0075] Next, during the use of the fiber laser 40, when the laser radar detects a trigger event corresponding to the seed laser 41a, the seed laser 41a is excited by the trigger event and emits the seed signal A in response to the trigger event. The other seed lasers, i.e., the seed laser 41b, do not emit the seed signal B because they are not excited by the trigger event. The seed laser 41a couples the seed signal A to the gain fiber 222. The gain fiber 222 is always in the gain saturation state and amplifies the seed signal A by the target pump signal to obtain an amplified light signal. At this time, Figure 6 A schematic diagram of the seed signal and the amplified light signal in the embodiment of the present application is shown in FIG. 1.Figure 6 As shown, the adjustment of the seed light signal is synchronized with the adjustment of the amplified light signal, and the fiber laser 40 is capable of achieving fast dynamic adjustment of the optical power.

[0076] Thus, the fast dynamic adjustment of the optical power of the fiber laser is achieved.

[0077] In the embodiment of the present application, in the case that the fiber amplifier is always in gain saturation, different seed light signals are emitted by triggering different seed light lasers with different powers in the fiber laser, so that the amplitude of the amplified light signal output by the fiber laser changes synchronously with the power of the seed light signal, thereby realizing fast dynamic adjustment of the optical power of the fiber laser. In addition, since the multiple seed light lasers are of the same type, when adjusting the seed light signal, only different seed light lasers need to be triggered, and other parts such as the fiber amplifier do not need to be adjusted, further accelerating the dynamic adjustment of the optical power of the fiber laser.

[0078] Based on the same inventive concept, the embodiment of the present application also provides a laser radar, which is consistent with the laser radar in the above Figure 2 embodiment.

[0079] Figure 7 FIG. 7 is a structural schematic diagram of the laser radar in the embodiment of the present application, as shown in the figure, the laser radar 70 can include a controller 71 and a fiber laser 72. Figure 7

[0080] The controller 71 can be the processor 103 or a part of the processor 103. Of course, the controller 71 can also be an independently arranged device. Optionally, the controller 71 can be implemented by a CPU, a DSP, an ASIC, an FPGA, other programmable logic devices, etc. Preferably, the controller 71 is implemented by an FPGA. The fiber laser 72 is consistent with the fiber laser 40 described above, and the specific description of the fiber laser 72 can be referred to the description of the fiber laser 40 in the above Figure 4 to Figure 6 , which will not be repeated here. Further, the controller 71 is coupled with the multiple seed light lasers 41. That is, different seed light lasers 41 are triggered by the controller 71 to achieve fast dynamic adjustment of the power and ensure the continuity of the seed light signal.

[0081] ​It can be understood that the controller 71 is configured to send a trigger signal to the seed laser 41a corresponding to the trigger event in response to a trigger event, and the trigger signal is used to trigger the seed laser 41a to enter the excitation. The seed laser 41a is configured to enter the excitation state in response to the trigger signal and emit the seed light signal A; the other seed lasers 41 are configured to be in the standby excitation state in response to the trigger signal; and the fiber amplifier 42 is configured to be in the gain saturation state all the time and amplify the seed light signal A.

[0082] In actual application, the trigger signal emitted by the controller 71 is an electrical signal, which is used to stimulate the seed laser 41 to work to emit the seed light signal.

[0083] In some possible embodiments, in the case that the fiber amplifier 42 is in the gain saturation state all the time, the controller 71 can also send another trigger signal (e.g., trigger signal B) to the seed laser 41b in response to another trigger event before sending the trigger signal (e.g., trigger signal A) to the seed laser 41a, and the seed laser 41b enters the excitation state in response to the trigger signal B and emits the seed light signal B. Then, when the controller 71 sends the trigger signal A to the seed laser 41a, the controller 71 stops sending the trigger signal B to the seed laser 41b, so that the seed laser 41b returns to the standby excitation state. In this process, the controller 71 realizes the switching of the trigger signal, and then triggers the seed lasers with different powers to realize the rapid dynamic adjustment of the optical power of the fiber laser.

[0084] Preferably, in order to shorten the time length of the controller switching the trigger signal, the controller 71 can use an FPGA with a working frequency of 200 MHz. Then, the switching time length of the trigger signal can reach 5 ns (nanoseconds), which is much lower than the pulse interval of the seed light signal, so that the seed light signal and the amplified light signal are synchronized to adjust, and the rapid dynamic adjustment of the optical power is realized.

[0085] In some possible embodiments, still referring to Figure 7 The pump light laser 221 can be coupled with the controller 71. The controller 71 can adjust the power of the pump light signal. Of course, the power of the pump light signal can also be adjusted by other controllers, which are not limited in the embodiments of the present application.

[0086] The above laser radar 70 is specifically described below with specific examples.

[0087] Figure 8 Another structure of the laser radar in the embodiments of the present application is shown in FIG. 8. As shown in FIG. 8, the laser radar 70 includes a seed laser 41, a fiber amplifier 42, a controller 71, a pump light laser 221, and a light receiving device 222. Figure 8As shown, the fiber laser 72 includes a seed light laser 41a for emitting a seed light signal A and a seed light laser 41b for emitting a seed light signal B, the power of the seed light laser 41a is less than the power of the seed light laser 41b. At this time, the seed light laser 41b can be understood as the seed light laser with the largest power in the plurality of seed light lasers 41.

[0088] First, during the debugging process of the fiber laser 72, the controller 41 can output a trigger signal to the seed light laser 41b. The seed light laser 41b is excited by the trigger signal, and in response to the trigger signal, enters an excited state and emits a seed light signal B. Other seed light lasers, i.e. the seed light laser 41a, will not emit a seed light signal A because they are not excited by the trigger event. The seed light signal B is coupled to the gain fiber 222 by the seed light laser 41b. The gain fiber 222 amplifies the seed light signal B. And during the amplification of the seed light signal B, the pump light laser 221 adjusts the pump power until the gain fiber 222 reaches a gain saturation state, at which time the pump light laser 221 emits a target pump light signal. After the gain saturation state is reached, the pump light laser 221 always emits the target pump light signal so that the gain fiber 222 is always in the gain saturation state. Optionally, the seed light laser 41b returns to the standby state after the gain saturation state of the fiber amplifier 42 is reached. At this time, the seed light lasers 41a and 41b are both in the standby state.

[0089] Next, during the use of the fiber laser 72, when the lidar detects a trigger event corresponding to the seed light laser 41a while the gain fiber 222 is always in the gain saturation state, the controller 41 outputs a corresponding trigger signal to the seed light laser 41a in response to the trigger event. The seed light laser 41a is excited by the trigger signal, and in response to the trigger signal, enters an excited state and emits a seed light signal A. Other seed light lasers, i.e. the seed light laser 41b, will not emit a seed light signal B because they are not excited by the trigger event. The seed light laser 41a couples the seed light signal A to the gain fiber 222. The gain fiber 222 is always in the gain saturation state, and the seed light signal A is amplified by the target pump light signal to obtain an amplified light signal. At this time, referring to Figure 6 As shown, the adjustment of the seed light signal is synchronized with the adjustment of the amplified light signal, and the fiber laser 72 can achieve fast dynamic adjustment of the optical power.

[0090] At this point, the optical power of the lidar is achieved by fast dynamic adjustment.

[0091] In the embodiment of the present application, when the optical fiber amplifier is always in gain saturation, different seed light signals are emitted by triggering seed light lasers with different powers in the optical fiber laser, so that the amplitude of the amplified light signal output by the optical fiber laser changes synchronously with the power of the seed light signal, thereby realizing fast dynamic adjustment of the optical power of the optical fiber laser, and further realizing fast dynamic adjustment of the optical power of the laser radar. In addition, since the multiple seed light lasers are of the same type, when adjusting the seed light signal, only different seed light lasers need to be triggered, and other parts such as the optical fiber amplifier do not need to be adjusted, further speeding up the dynamic adjustment of the optical power of the optical fiber laser.

[0092] Based on the same inventive concept, the embodiment of the present application provides an optical power adjustment method, which is applied to the laser radar of one or more of the above embodiments.

[0093] Figure 9 For an implementation flowchart of the optical power adjustment method in the embodiment of the present application, refer to the figure, the method can include:

[0094] S901, the controller obtains a trigger event.

[0095] In the embodiment of the present application, the trigger event can be understood as saturation of the light receiving device. For example, the distance between the laser radar and the target object changes, a reflection object with high reflectivity, a retroreflective object, etc. appears in the scanning range of the laser radar. Then, in response to these trigger events, the optical fiber laser radar needs to dynamically adjust its optical power. For example, it is assumed that a target object, such as a human body or an object, appears at the near distance end of the scanning range of the laser radar. When the laser beam scans the target object, the scanning distance becomes shorter, the return light beam is enhanced, the pulse peak of the return signal is increased, and the light receiving device receives a high-energy pulse, which is saturated. At this time, the optical fiber laser needs to turn off the high-power seed laser and turn on the low-power seed laser. Or, it is assumed that a reflection object with high reflectivity (such as the surface of accumulated water, icy road surface, snow ground, glass barrier, etc.), a retroreflective object (such as a traffic sign), etc. appears at the middle distance end of the scanning range of the laser radar. When the laser beam scans the reflection object, the reflection is strong, the return light beam is enhanced, the pulse peak of the return signal is increased, and the light receiving device receives a high-energy pulse, which is saturated. At this time, the optical fiber laser needs to turn off the high-power seed laser and turn on the low-power seed laser.

[0096] S902, the controller responds to the trigger event, controls one seed light laser to enter an excited state, and controls other seed light lasers to be in a standby excited state.

[0097] S903, the seed light laser in the excited state emits a first seed light signal;

[0098] S904, the fiber amplifier amplifies the first seed light signal in a state of being always in gain saturation.

[0099] In some possible implementation manners, S904 can include that the fiber amplifier amplifies the first seed light signal by a target pump light signal, the target pump light signal being used to make the fiber amplifier in the state of being in gain saturation.

[0100] In some possible implementation manners, referring to FIG. 1, before S901, the control method can further include: Figure 9

[0101] S905, the seed light laser with the maximum power emits a second seed light signal.

[0102] S906, the fiber amplifier amplifies the second seed light signal, and adjusts the pump power in the process of amplifying the second seed light signal until the state of gain saturation is reached. Here, the fiber amplifier is in the state of gain saturation after reaching the state of gain saturation.

[0103] In some possible implementation manners, after S904, the control method further includes that a filter filters the amplified first seed light signal.

[0104] It should be noted that the specific implementation process of the light power adjustment method can be referred to the description of the working process of the laser radar 70 and the fiber laser 40 in the Figure 4 to Figure 8 embodiments, and will not be described here again.

[0105] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or replace some technical features. The modification or replacement does not make the essence of the corresponding technical solution deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.​

Claims

1. A fiber laser, characterized in that, include: Multiple seed lasers with different powers and fiber amplifiers; The multiple seed lasers are of the same type; One of the plurality of seed lasers is configured to enter an excited state and emit a first seed light signal in response to a triggering event; the first seed light signal is coupled to the fiber amplifier; the triggering event is that the optical receiver of the lidar becomes saturated; The other seed lasers among the plurality of seed lasers are configured to be in a state of waiting to be excited in response to the triggering event; The fiber amplifier is configured to always be in a gain saturation state and amplify the first seed optical signal, wherein the first seed optical signal input to the fiber amplifier is monotonically correlated with the amplified optical signal output by the fiber amplifier. The fiber amplifier includes a gain fiber and a pump laser; the seed laser is configured to couple a first seed light signal to the gain fiber; the pump laser is configured to continuously emit a target pump light signal and couple it to the gain fiber; the gain fiber is configured to remain in gain saturation in response to the target pump light signal and amplify the first seed light signal through the target pump light signal. The seed laser with the highest power among the plurality of seed lasers is configured to emit a second seed laser signal and couple it to the fiber amplifier before the seed laser enters the excitation state in response to the triggering event. Other seed lasers, except for the seed laser with the highest power, are configured to be in a state of waiting to be excited before one of the seed lasers enters the excited state in response to the triggering event; The fiber amplifier is also configured to amplify the second seed optical signal and, during the amplification of the second seed optical signal, adjust the pump power until gain saturation is achieved.

2. The fiber laser according to claim 1, characterized in that, The plurality of seed lasers are coupled to the fiber amplifier via a beam combiner or spatial coupling.

3. The fiber laser according to claim 1, characterized in that, The fiber laser also includes: a filter; The fiber amplifier is also configured to couple the amplified first seed optical signal to the filter; The filter is configured to filter the amplified first seed optical signal.

4. A lidar, characterized in that, include: The fiber laser and controller as described in any one of claims 1 to 3; the controller is coupled to the plurality of seed lasers; The controller is configured to send a trigger signal to the seed laser in response to a trigger event, the trigger signal being used to trigger the seed laser to enter an excitation state; the trigger event being saturation of the laser radar's optical receiving device.

5. A method for adjusting optical power, characterized in that, Applied to the lidar as described in claim 4; the method includes: The controller receives a trigger event, which indicates that the seed laser enters an excitation state; the trigger event is that the light receiving device of the lidar becomes saturated. In response to the triggering event, the controller controls one seed laser to enter the excitation state and controls the other seed lasers to be in the quiescent state. The seed laser emits a first seed light signal; The fiber amplifier amplifies the first seed optical signal while it is always in a gain saturation state, wherein the first seed optical signal input to the fiber amplifier is monotonically correlated with the amplified optical signal output by the fiber amplifier. The method further includes, prior to the controller receiving a trigger event: The seed laser with the highest power among the plurality of seed lasers emits a second seed laser signal; The fiber amplifier amplifies the second seed optical signal, and during the amplification process, the pump power is adjusted until gain saturation is achieved.

6. The method according to claim 5, characterized in that, The fiber amplifier amplifies the first seed optical signal while remaining in a gain saturation state, including: The fiber amplifier amplifies the first seed light signal using a target pump light signal, which keeps the fiber amplifier in gain saturation.

7. The method according to claim 5, characterized in that, The method further includes: The filter in the fiber laser filters the amplified first seed light signal.

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