Wind measurement lidar and wind measurement method

Abstract

The present application relates to a wind measurement laser radar and a wind measurement method. The laser radar comprises: a first light source, a beam splitter, a hybrid optical ring module, an adjustment module, a processing module, and a detection module. The laser radar of the present application, through the coordinated use of the hybrid optical ring module and the adjustment module, can perform two frequency modulations, two pulse modulations, and two power amplifications on the signal light of the target to be detected. Furthermore, the hybrid optical ring module design reduces the number of passive optical components, can improve the integration of the laser radar, and has low additional insertion loss.

Description

Technical Field

[0001] The present application relates to the field of laser radar technology, and in particular to a wind measurement laser radar and a wind measurement method. Background Art

[0002] With the development of lidar technology, lidar wind measurement technology has emerged. Wind measurement lidar measures the Doppler frequency shift of the backscattered signal of aerosol particles to obtain the inverted wind speed.

[0003] At present, the mainstream forms of short-range wind measurement lidar systems are nacelle-type and ground-based types. Among them, nacelle-type wind measurement lidar is used for wind turbine yaw calibration, wind power prediction, etc., and ground-based wind measurement lidar is used for wind turbine early site selection and wind power prediction, etc.

[0004] With the development of the wind power industry, higher requirements are placed on the cost, volume and power consumption of short-range wind measurement lidar. Summary of the Invention

[0005] Based on this, it is necessary to address the above technical issues and provide a more integrated wind measurement lidar and wind measurement method that can meet the low-cost, low-power and high-reliability requirements of the wind power industry.

[0006] In a first aspect, the present application provides a wind measurement laser radar, which includes: a first light source, which emits a first laser with a first wavelength; a beam splitter, which receives the first laser and splits the first laser into local oscillator light and a first signal light; a hybrid light ring module, which includes a first port and a second port; the hybrid light ring module receives the first signal light through the first port and outputs the first signal light from the second port; an adjustment module, which receives the first signal light from the second port and is used to perform two frequency modulations, two pulse modulations, and two power amplifications on the first signal light to obtain a second signal light; the hybrid light ring module also includes a third port, the second port of the hybrid light ring module also receives the second signal light and outputs the second signal light from the third port; a processing module, which receives the second signal light from the third port, transmits the second signal light to the target to be measured, and receives an echo signal reflected by the target to be measured; the hybrid light ring module also includes a detection port, the third port of the hybrid light ring module also receives the echo signal and transmits the echo signal to the detection port; the detection module, which receives the echo signal and the local oscillator light output by the detection port, thereby generating a wind speed signal of the target to be measured.

[0007] In one embodiment, the adjustment module includes: an acousto-optic module, which receives a first signal light and performs frequency modulation and pulse modulation on the first signal light to obtain a third signal light; a second light source, which emits a second laser with a second wavelength; an erbium-doped optical fiber, which receives and transmits the third signal light and the second laser, and the third signal light is transmitted and amplified along a first direction in the erbium-doped optical fiber under the action of the second laser to obtain a fourth signal light; a reflection module, which receives the fourth signal light and the second laser and reflects the fourth signal light and the second laser back to the erbium-doped optical fiber; the fourth signal light is transmitted and amplified again along a second direction in the erbium-doped optical fiber under the action of the second laser, and is incident on the acousto-optic module again, and is frequency modulated and pulse modulated by the acousto-optic module to obtain the second signal light; the second direction is opposite to the first direction.

[0008] In one embodiment, the second laser is transmitted along the second direction.

[0009] In one embodiment, the reflection module includes: a lens, receiving the fourth signal light and the second laser, and adjusting the fourth signal light and the second laser; a color filter, receiving the fourth signal light and the second laser adjusted by the lens, reflecting the second laser and transmitting the fourth signal light; the second laser is reflected to the lens, adjusted again by the lens, and then incident on the erbium-doped optical fiber; a polarization rotation unit, receiving the fourth signal light, rotating the polarization direction of the fourth signal light by 90 degrees, and then reflecting it to the color filter; the fourth signal light, after the polarization direction is rotated by 90 degrees, passes through the color filter and the lens again and is incident on the erbium-doped optical fiber.

[0010] In one embodiment, the hybrid optical ring module further includes a polarization beam splitter; the first signal light is received through the first port, deflected to the second port via the polarization beam splitter, and the first signal light is output from the second port; the second port of the hybrid optical ring module also receives the second signal light, the second signal light is deflected to the third port via the polarization beam splitter, and the second signal light is output from the third port.

[0011] In one embodiment, the repetition frequency of the first laser is between 1 kHz and 15 kHz.

[0012] In one embodiment, the repetition frequency of the first laser is 10 kHz.

[0013] In one embodiment, the polarization rotation unit includes: a Faraday rotator, configured to receive the fourth signal light and rotate the polarization direction of the fourth signal light by 45 degrees under the action of a magnetic field; a reflector, configured to receive the fourth signal light with its polarization direction rotated by 45 degrees and reflect the fourth signal light with its polarization direction rotated by 45 degrees back to the Faraday rotator; the fourth signal light with its polarization direction rotated by 45 degrees passes through the Faraday rotator again, and its polarization direction is rotated by another 45 degrees before being incident on the color filter.

[0014] In one embodiment, the reflection module further includes a dual-core pin, which includes: a first pin port, which receives the second laser and transmits the second laser to the reflection module; and a second pin port, which is connected to the erbium-doped optical fiber and is used to receive the fourth signal light and transmit the fourth signal light to the reflection module; and is also used to receive the second laser and the fourth signal light reflected by the reflection module, and transmit the second laser and the fourth signal light to the erbium-doped optical fiber.

[0015] In one embodiment, the first port, the second port, the third port, and the detection port of the hybrid optical ring module all use polarization-maintaining optical fibers, the slow axis of the polarization-maintaining optical fiber of the second port is aligned with the slow axis of the polarization-maintaining optical fiber of the first port, the fast axis of the polarization-maintaining optical fiber of the third port is aligned with the slow axis of the polarization-maintaining optical fiber of the second port, and the slow axis of the polarization-maintaining optical fiber of the detection port is aligned with the slow axis of the polarization-maintaining optical fiber of the third port.

[0016] In one embodiment, the processing module includes: an optical switch for switching the transmission channel and the receiving channel of the second signal light; a telescope for receiving the second signal light passing through the transmission channel opened by the optical switch and transmitting the second signal light to the target to be measured, receiving the echo signal reflected back by the target to be measured, and transmitting the echo signal to the receiving channel switched by the optical switch.

[0017] In one embodiment, the detection module includes: a coupler for coupling the echo signal and the local oscillator light to obtain a coupled optical signal; a balanced detector for receiving the coupled optical signal, beating the coupled optical signal, and converting the coupled optical signal after the beating into an electrical signal.

[0018] In a second aspect, the present application further provides a wind measurement method using a wind laser radar, the method comprising:

[0019] Controlling the first light source to emit a first laser with a first wavelength, the first laser being split into a local oscillator light and a signal light by a beam splitter; transmitting the first signal light through the first port of the hybrid optical ring module to the second port of the hybrid optical ring module and being output from the second port;

[0020] The control and regulation module receives the first signal light from the second port, performs two frequency modulations, two pulse modulations, and two power amplifications on the first signal light to obtain a second signal light; the second signal light is incident on the hybrid optical ring module through the second port and is output from the third port of the hybrid optical ring module;

[0021] The processing module receives the second signal light from the third port, transmits the second signal light to the target to be measured, and receives the echo signal reflected back by the target to be measured; the echo signal is incident on the hybrid optical ring module through the third port and is output from the detection port of the hybrid optical ring module;

[0022] The detection module receives the echo signal and local oscillation light output from the detection port, thereby generating a wind speed signal of the target to be measured.

[0023] The above-mentioned wind measurement laser radar and wind measurement method include a first light source, a beam splitter, a hybrid optical ring module, an adjustment module, a processing module and a detection module. The above-mentioned laser radar emits a first laser with a first wavelength through the first light source; and splits the first laser into local oscillation light and a first signal light through the beam splitter; transmits the first signal light to the adjustment module through the hybrid optical ring module, and uses the adjustment module to perform two frequency modulations, two pulse modulations and two power amplifications on the first signal light to obtain a second signal light; and uses the hybrid optical ring module to transmit the second signal light to the processing module, thereby emitting the second signal light to the target to be measured, and receiving the echo signal reflected back by the target to be measured through the processing module; and, again transmits the echo signal to the detection module through the hybrid optical ring module, thereby generating the wind speed signal of the target to be measured. Therefore, through the coordinated use of the hybrid optical ring module and the adjustment module, the signal light of the target to be detected can be frequency modulated twice, pulse modulated twice and power amplified twice, and the hybrid optical ring module design reduces the number of passive optical components, can improve the integration of the laser radar, and has low additional insertion loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 is a schematic diagram of a wind measurement laser radar in one embodiment;

[0026] Figure 2 is a schematic diagram of a wind measurement laser radar in another embodiment;

[0027] Figure 3is a schematic diagram of a reflection module in one embodiment;

[0028] Figure 4 is a schematic diagram of a hybrid optical ring module according to one embodiment;

[0029] Figure 5 Schematic diagram of a flow chart of a wind measurement method using a wind laser radar in one embodiment.

[0030] Description of reference numerals:

[0031] 10. First light source; 20. Beam splitter; 30. Hybrid optical ring module; 31. First port; 32. Second port; 33. Third port; 34. Detection port; 40. Adjustment module; 50. Processing module; 60. Detection module; 51. Optical switch; 52. Telescope; 41. Acousto-optic module; 42. Erbium-doped fiber; 43. Second light source; 44. Reflection module; 61. Coupler; 62. Balanced detector; 441. Lens; 442. Color filter; 443. Polarization rotation unit; 4431. Faraday rotation unit; 4432. Reflector. DETAILED DESCRIPTION

[0032] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0035] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0036] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0037] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0038] Due to atmospheric loss and a small aerosol backscatter coefficient, the laser pulse emitted by the lidar returns a weak signal at the picowatt level. Therefore, to ensure the short-range detection range of the wind lidar while guaranteeing wind measurement accuracy, an embodiment of the present invention provides a short-range wind lidar.

[0039] See also Figure 1 , Figure 1A schematic diagram of a wind measurement laser radar in an embodiment of the present invention is shown. The laser radar provided in an embodiment of the present invention includes: a first light source 10, which emits a first laser with a first wavelength; a beam splitter 20, which receives the first laser and splits the first laser into a local oscillator light and a first signal light; a hybrid light ring module 30, which includes a first port 31 and a second port 32; the hybrid light ring module 30 receives the first signal light through the first port 31 and outputs the first signal light from the second port 32; an adjustment module 40, which receives the first signal light from the second port 32 and is used to perform two frequency modulations, two pulse modulations, and two power amplifications on the first signal light. , obtaining a second signal light; the hybrid optical ring module 30 also includes a third port 33, and the second port 32 of the hybrid optical ring module 30 further receives the second signal light and outputs the second signal light from the third port 33; the processing module 50 receives the second signal light from the third port 33, transmits the second signal light to the target to be measured, and receives an echo signal reflected by the target to be measured; the hybrid optical ring module 30 also includes a detection port 34, and the third port 33 of the hybrid optical ring module 30 further receives the echo signal and transmits the echo signal to the detection port 34; the detection module 60 receives the echo signal and the local oscillation light output by the detection port 34, thereby generating a wind speed signal of the target to be measured.

[0040] The beam splitter can be a polarization-maintaining fiber beam splitter. The beam splitter can split the first laser beam at a ratio of 5 / 95, 10 / 90, or 15 / 85. It is understood that the splitting ratio is affected by the power of the first light source, the amplifier's small-signal input requirements, and the optimal local oscillator optical power for balanced detection. The splitting ratio can be determined based on the power of the first light source, the amplifier's small-signal input requirements, and the optimal local oscillator optical power for balanced detection. Exemplarily, the splitting ratio is 5 / 95.

[0041] In one embodiment, the first laser light emitted by the first light source 10, such as a seed laser, is split into two beams by a beam splitter 20. One beam serves as the local oscillator light and is connected to the detection module 60. The other beam serves as the first signal light, which is transmitted to the first port 31 of the hybrid optical ring module 30, such as a four-port optical circulator, and is output from the second port 32 and transmitted to the adjustment module 40. The adjustment module 40 frequency-shifts the incident first laser light twice, chops it, and amplifies it to convert it into pulsed light of the second signal light, which is then reflected back to the second port 32. The second signal light is then emitted into the atmosphere through the processing module 50 through the third port 33. After receiving the aerosol backscatter signal, i.e., the echo signal, the processing module 50 transmits the echo signal to the third port 33 of the hybrid optical ring module 30. The echo signal is then emitted from the detection port 34 and transmitted to the detection module 60. The detection module 60 receives the echo signal and the local oscillator light output from the detection port 34, thereby generating a wind speed signal of the target to be measured.

[0042] In this embodiment, by using a hybrid optical ring module and an adjustment module in conjunction, the signal light of the target to be detected can be frequency modulated twice, pulse modulated twice, and power amplified twice. In addition, the hybrid optical ring module 30 is designed to reduce the number of passive optical components, thereby improving the integration of the laser radar and reducing the additional insertion loss.

[0043] In one embodiment, the adjustment module 40 includes: an acousto-optic module 41, which receives the first signal light and performs frequency modulation and pulse modulation on the first signal light to obtain a third signal light; a second light source 43, which emits a second laser with a second wavelength; an erbium-doped fiber 42, which receives and transmits the third signal light and the second laser, and the third signal light is transmitted and amplified along the first direction in the erbium-doped fiber 42 under the action of the second laser to obtain a fourth signal light; a reflection module 44, which receives the fourth signal light and the second laser and reflects the fourth signal light and the second laser back to the erbium-doped fiber 42; the fourth signal light is transmitted and amplified again along the second direction in the erbium-doped fiber 42 under the action of the second laser, and is incident on the acousto-optic module 41 again, and is frequency modulated and pulse modulated by the acousto-optic module 41 to obtain a second signal light; the second direction is opposite to the first direction.

[0044] See also Figure 2 , Figure 2 A schematic diagram of a wind measurement laser radar in another embodiment of the present invention is shown.

[0045] Exemplarily, the first laser emitted by the first light source 10, such as a 1550nm single-frequency laser, is split into two beams by a beam splitter, such as a 5 / 95 optical beam splitter. The beam with 5% of the light intensity serves as the local oscillator light and is connected to the detection module 60. The beam with 95% of the light intensity serves as the signal light and is transmitted to the first port 31 of the hybrid optical ring module 30, output from the second port 32, and transmitted to the acousto-optic module 41. The acousto-optic module 41 shifts the frequency of the incident continuous light and chops it into a third signal light, i.e., pulsed light, which is then incident on the erbium-doped fiber 42. The second light source 43, such as a 974nm single-mode pump laser, transmits a second laser with a second wavelength, i.e., pump light, into the erbium-doped fiber 42. Under the action of the second laser, the third signal light is transmitted and amplified in the erbium-doped fiber 42 along the first direction to obtain a fourth signal light. After being reflected by the reflection module 44, the fourth signal light and the second laser are again amplified by the erbium-doped fiber 42. The light then passes through the acousto-optic module 41 again, using its shutdown function to shut down the ASE in the interval between adjacent pulses, generating a second signal light. This signal light is then transmitted to the third port 33 via the second port 32 of the hybrid optical ring module 30. The second signal light is then emitted into the atmosphere via the processing module 50. The processing module 50 receives the aerosol backscatter signal, i.e., the echo signal, and transmits the echo signal to the third port 33 of the hybrid optical ring module 30. The echo signal then exits from the detection port 34 and is then transmitted to the detection module 60. The detection module 60 receives the echo signal and the local oscillation light output from the detection port 34, thereby generating a wind speed signal of the target to be measured.

[0046] It is understood that the first light source, a 1550nm single-frequency laser, and the second light source, a 974nm single-mode pump laser, mentioned in this application are exemplary and non-restrictive. For example, the second light source may also include a 976nm pump laser. The frequency shift of the acousto-optic module, such as the acousto-optic modulator, is determined by the wind speed measurement range of the wind lidar system, with typical values ​​of 40MHz, 60MHz, 80MHz, etc.

[0047] Among them, inter-pulse ASE (Amplified Spontaneous Emission) refers to the amplified spontaneous emission generated between laser pulses.

[0048] In pulsed laser systems, especially high-power laser amplifiers, there is a certain time interval between pulses. During this time, the gain medium in the laser amplifier still generates gain, which leads to spontaneous emission (ASE) that is amplified and causes inter-pulse ASE. This inter-pulse ASE can interfere with system operation, reduce the signal-to-noise ratio, and affect measurement accuracy.

[0049] In this embodiment, a hybrid dual-pass optical path of acousto-optic and fiber amplification is used. The fiber-amplified dual-pass amplifier improves the amplifier's small-signal gain and slope efficiency by passing through the gain fiber twice, resulting in greater small-signal gain. The optical components in the hybrid dual-pass acousto-optic and amplifier link are streamlined, reducing optical additional loss and improving the laser slope efficiency. The amplified pulses are then chopped again through the acousto-optic module. This not only ensures the system's 100dB extinction ratio requirement (the typical value of a single acousto-optic dynamic extinction ratio is 50dB), but also acts as an optical switch, filtering out inter-pulse ASE, improving the laser output's side-mode suppression ratio (SMSR), and increasing the signal-to-noise ratio of the output pulsed optical signal. Furthermore, dual-pass amplification achieved through erbium-doped fiber allows the laser radar to achieve a wind measurement distance of hundreds of meters while maintaining a high level of integration in a single-stage amplification system.

[0050] In one embodiment, the repetition frequency of the first laser is between 1 kHz and 15 kHz.

[0051] Optionally, the repetition frequency of the first laser is 1 kHz, 2 kHz, 3 kHz, 4 kHz, 5 kHz, 6 kHz, 7 kHz, 8 kHz, 9 kHz, 10 kHz, 11 kHz, 12 kHz, 13 kHz, 14 kHz, or 15 kHz.

[0052] In one embodiment, the repetition frequency of the first laser is 10 kHz.

[0053] The wind lidar optical system must meet the radar system signal-to-noise ratio and accuracy requirements. Considering the system noise as shot noise, the lidar equation is shown in formula (1):

[0054] (1)

[0055] Where CNR is the carrier-to-noise ratio, is the optical system efficiency factor, is the laser single pulse energy, is the atmospheric backscattering coefficient, is the center wavelength of the emitted laser, is the atmospheric one-way loss coefficient, is the telescope aperture. is Planck's constant, is the circuit detection bandwidth, For the detection distance.

[0056] Under low carrier-to-noise ratio conditions, the wind lidar velocity measurement accuracy formula is shown in formula (2):

[0057] (2)

[0058] in is the speed standard deviation, is the signal spectrum bandwidth, is the number of pulse accumulation, is the number of sampling points within the range gate, and CNR is the carrier-to-noise ratio.

[0059] According to formula (1) and formula (2), the factors affecting the wind measurement accuracy in a single range gate are signal spectrum bandwidth, pulse accumulation times, sampling points, and signal-to-noise ratio. When only considering the influence of laser, the factors affecting wind measurement accuracy are pulse accumulation times. and laser single pulse energy .

[0060] Since the wind direction of the wind laser radar is synthesized from the radial wind speed vector, the pulse accumulation times are Limited by the integration time. The radial wind speed integration time is defined as . Pulse accumulation times and radial wind speed integration time and pulse repetition frequency The relationship is shown in formula (3):

[0061] (3)

[0062] The above formula can be defined Factor, through Factors are used to evaluate the correlation between laser parameters and wind measurement accuracy, as shown in formula (4):

[0063] (4)

[0064] From formula (4), we can see that when The larger the factor, the smaller the velocity measurement accuracy of the wind laser radar, that is, the higher the velocity measurement accuracy of the laser radar. and pulse output average power The relationship between the pulse repetition frequency is shown in formula (5):

[0065] (5)

[0066] Formula (6) can be obtained from formula (4) and formula (5):

[0067] (6)

[0068] Depend on The definition of the factor shows that when a low pulse repetition frequency is used and large laser single pulse energy The solution can also meet the needs of close-range wind measurement.

[0069] To achieve the effect of traditional two-stage amplification with single-stage double-pass amplification, the laser repetition frequency operates at a low repetition frequency, typically below 15kHz. Specifically, the pulse duty cycle and the number of pulse accumulations of the radar system need to be considered. In this embodiment, the repetition frequency of the first laser is designed to be 10kHz. Typical pulse widths are 200ns, 300ns, 400ns, etc., and the blind spots and measurement distance of the wind-measuring lidar system need to be comprehensively considered. In one embodiment, the pulse width is 300ns. Due to the high small-signal gain and high slope efficiency characteristics of double-pass amplification and its operation at a low repetition frequency, the single pulse energy output by the light source is large, and the peak power of the laser output pulse is also large, which easily reaches the stimulated Brillouin scattering (SBS) threshold, thereby causing pulse trailing edge jitter that affects wind measurement accuracy.

[0070] In this embodiment, by designing the repetition frequency of the first laser to 10 kHz, the single-pulse energy is increased under a certain average power condition, so that the single-pulse energy of the single-stage amplification reaches the level of the traditional two-stage amplification, eliminating the second-stage amplifier and reducing the cost and power consumption of the radar system. In addition, in this embodiment, based on the lidar equation and wind measurement accuracy, the single-stage fiber amplifier design is optimized by optimizing the relationship between the number of pulse accumulations and the single-pulse energy, so that the amplifier operates in a low-repetition-rate, high-pulse-energy mode, reducing one amplifier stage, that is, reducing the number of optical amplification stages, while reducing cost, power consumption, and size.

[0071] In one embodiment, the reflection module 44 includes: a lens 441, which receives the fourth signal light and the second laser, and adjusts the fourth signal light and the second laser; a color filter 442, which receives the fourth signal light and the second laser adjusted by the lens 441, reflects the second laser and transmits the fourth signal light; the second laser is reflected to the lens 441, adjusted again by the lens 441, and then incident on the erbium-doped optical fiber 42; a polarization rotation unit 443, which receives the fourth signal light, rotates the polarization direction of the fourth signal light by 90 degrees, and then reflects it to the color filter 442; the fourth signal light, after the polarization direction is rotated by 90 degrees, passes through the color filter 442 and the lens 441 again and is incident on the erbium-doped optical fiber 42.

[0072] When the first signal light enters the acousto-optic module, since the acousto-optic module includes a first surface and a second surface, both the first surface and the second surface will reflect the first signal light, and the reflected light will beat with the echo signal, thereby making the detection result inaccurate.

[0073] To solve the above problem, in one embodiment, the hybrid optical ring module further includes a polarization beam splitter; the first signal light is received through the first port, deflected to the second port via the polarization beam splitter, and the first signal light is output from the second port; the second port of the hybrid optical ring module also receives the second signal light, the second signal light is deflected to the third port via the polarization beam splitter, and the second signal light is output from the third port.

[0074] For example, when the first signal light received by the hybrid optical ring module through the first port is in a first polarization state, for example, P light, the polarization beam splitter can reflect the first signal light in the first polarization state to the second port and emit it from the second port. After the first signal light is processed by the adjustment module, the polarization state changes by 90 degrees and becomes the second signal light in a second polarization state, for example, S light. The second signal light is again incident on the hybrid optical ring module from the second port and is transmitted to the third port through the polarization beam splitter and emitted from the third port. The adjustment module includes an acousto-optic module. It is understandable that the polarization state of the first signal light can also be the second polarization state, for example, S light, and thus the polarization state of the second signal light can also be the first polarization state, for example, P light. It is further understandable that the polarization beam splitter can transmit light in the first polarization state and reflect light in the second polarization state, and this application does not limit this.

[0075] When the first signal light passes through the acousto-optic module for the first time, most of the light will enter the subsequent amplification from the output fiber collimator after diffraction by the acousto-optic module, but a small amount of light will return to the incident fiber collimator of the acousto-optic module after a single frequency shift, and then be transmitted to the first port of the hybrid optical ring module. Without special treatment, the secondary frequency-shifted amplified signal light and the stray light after the single frequency shift will interfere with each other, causing envelope modulation of the output pulse, affecting the wind measurement accuracy. In this embodiment, by providing a polarization beam splitter in the hybrid optical ring module, the polarization state of the first signal light reflected by the first or second surface of the acousto-optic module and the echo signal can be different when passing through the acousto-optic module. Therefore, the light reflected by the first or second surface of the acousto-optic module will not form a beat frequency with the echo signal on the surface of the detector, thereby reducing noise interference and improving the accuracy of laser radar detection.

[0076] In one embodiment, the second laser is transmitted along the second direction.

[0077] For example, see Figure 3 , Figure 3This is a schematic diagram of a reflection module 44 in one embodiment, in which the first laser emitted by the first light source 10 is split into two beams by the beam splitter 20. For example, the light beam with 5% of the light intensity is used as the local oscillator light and is connected to the detection module 60. The light beam with 95% of the light intensity is used as the signal light, which is transmitted to the first port 31 of the hybrid optical ring module 30, output from the second port 32, and transmitted to the acousto-optic module 41. The acousto-optic module 41 shifts the frequency of the incident continuous light and chops it into a third signal light, i.e., pulsed light, which is then incident on the erbium-doped fiber 42. The second light source 43, such as a 974nm single-mode pump laser, transmits a second laser with a second wavelength, i.e., pump light, to the reflection module 44. The lens 441 of the reflection module 44 receives the fourth signal light and the second laser, and after adjusting the fourth signal light and the second laser, they are incident on the color filter 442. Color filter 442 receives the fourth signal light and the second laser light modulated by lens 441, reflects the second laser light, and transmits the fourth signal light. The second laser light is then reflected by lens 441, modulated again by lens 441, and incident on erbium-doped fiber 42. The fourth signal light that passes through color filter 442 is incident on polarization rotation unit 443. Polarization rotation unit 443 receives the fourth signal light, rotates its polarization direction by 90 degrees, and then reflects it back to color filter 442. After passing through color filter 442 and lens 441 again, it is incident on erbium-doped fiber 42. Consequently, the fourth signal light, obtained after amplification of the third signal light, is reflected by reflection module 44, its polarization state rotated by 90 degrees, and then passes through erbium-doped fiber 42 for a second amplification. It then passes through acousto-optic module 41 again, where its shutdown function disables ASE in the interval between adjacent pulses, generating the second signal light. The second signal light is then transmitted through second port 32 of hybrid optical ring module 30 to third port 33. The signal light is then emitted into the atmosphere through the processing module 50. After receiving the aerosol backscatter signal, i.e., the echo signal, the processing module 50 transmits the echo signal to the third port 33 of the hybrid light ring module 30, and then emits it from the detection port 34 and is then transmitted to the detection module 60. The detection module 60 receives the echo signal and the local oscillation light outputted from the detection port 34, thereby generating a wind speed signal of the target to be measured.

[0078] In this embodiment, by transmitting the pump light in reverse, the integration of optical devices such as wavelength division multiplexers and reflection modules is facilitated, the transmission fiber length is shortened, and the nonlinear effect caused by stimulated Brillouin scattering (SBS) is reduced.

[0079] In one embodiment, the polarization rotation unit 443 includes: a Faraday rotation unit 4431, which is used to receive the fourth signal light and rotate the polarization direction of the fourth signal light by 45 degrees under the action of a magnetic field; a reflector 4432, which receives the fourth signal light with a polarization direction rotated by 45 degrees and reflects the fourth signal light with a polarization direction rotated by 45 degrees back to the Faraday rotation unit 4431; the fourth signal light with a polarization direction rotated by 45 degrees passes through the Faraday rotation unit again, and the polarization direction is rotated by another 45 degrees before being incident on the color filter 442.

[0080] For example, please refer again Figure 3 , Figure 3This is a schematic diagram of a reflection module 44 in one embodiment, in which the first laser emitted by the first light source 10 is split into two beams by the beam splitter 20. For example, the light beam with 5% of the light intensity is used as the local oscillator light and is connected to the detection module 60. The light beam with 95% of the light intensity is used as the signal light, which is transmitted to the first port 31 of the hybrid optical ring module 30, output from the second port 32, and transmitted to the acousto-optic module 41. The acousto-optic module 41 shifts the frequency of the incident continuous light and chops it into a third signal light, i.e., pulsed light, which is then incident on the erbium-doped fiber 42. The second light source 43, such as a 974nm single-mode pump laser, transmits a second laser with a second wavelength, i.e., pump light, to the reflection module 44. The lens 441 of the reflection module 44 receives the fourth signal light and the second laser, and after adjusting the fourth signal light and the second laser, they are incident on the color filter 442. Color filter 442 receives the fourth signal light and the second laser light modulated by lens 441, reflects the second laser light, and transmits the fourth signal light. The second laser light is reflected by lens 441, modulated again by lens 441, and then incident on erbium-doped fiber 42. The fourth signal light that passes through color filter 442 is incident on polarization rotation unit 443. Faraday rotator 4431 of polarization rotation unit 443 receives the fourth signal light and rotates its polarization direction by 45 degrees under the action of a magnetic field. Reflector 4432 receives the fourth signal light with its polarization rotated by 45 degrees and reflects the fourth signal light with its polarization rotated by 45 degrees back to Faraday rotator 4431. The fourth signal light with its polarization rotated by 45 degrees passes through the Faraday rotator again, where its polarization direction is rotated by 45 degrees again, before entering color filter 442, passing through color filter 442 and lens 441 again, and then entering erbium-doped fiber 42. As a result, the fourth signal light obtained after amplifying the third signal light is reflected by the reflection module 44, its polarization state rotated 90°, and then passed through the erbium-doped fiber 42 for secondary amplification. It then passes through the acousto-optic module 41 again, and the acousto-optic module 41's shutdown function is used to shut down the ASE in the adjacent pulse interval to obtain the second signal light. The second signal light is then transmitted through the second port 32 of the hybrid optical ring module 30 to the third port 33. The signal light is then emitted into the atmosphere through the processing module 50. After receiving the aerosol backscatter signal, i.e., the echo signal, the processing module 50 transmits the echo signal to the third port 33 of the hybrid optical ring module 30. The echo signal is then emitted from the detection port 34 and transmitted to the detection module 60. The detection module 60 receives the echo signal and local oscillation light output from the detection port 34, thereby generating a wind speed signal of the target to be measured.

[0081] As the single pulse energy increases, the pulse peak power increases and the stimulated Brillouin scattering (SBS) effect intensifies, which intensifies the pulse trailing edge jitter and affects the wind measurement accuracy. The stimulated Brillouin scattering threshold (SBST) is shown in formula (7):

[0082] (7)

[0083] in is the stimulated Brillouin scattering threshold, and is the pulse peak power. is the fiber mode field area, is the Brillouin gain value. is the effective fiber length. For gain fiber, this value is the path integral, for ordinary transmission fiber, this value is equivalent to the physical length of the transmission fiber Optimizing the gain fiber length to reduce SBS will also affect the amplifier gain. Therefore, from an engineering perspective, the most effective way to suppress SBS is to reduce the length of the transmission fiber. .

[0084] Exemplarily, the reflection module 44 also includes a dual-core pin, which includes: a first pin port 31, which receives the second laser and transmits the second laser to the reflection module 44; and a second pin port 32, which is connected to the erbium-doped optical fiber 42, for receiving the fourth signal light and transmitting the fourth signal light to the reflection module 44; and is also used to receive the second laser and the fourth signal light reflected by the reflection module 44, and transmit the second laser and the fourth signal light to the erbium-doped optical fiber 42.

[0085] The backward-pumped, double-pass amplified optical path proposed in this application facilitates the integration of wavelength division multiplexers and Faraday rotator optical devices. Considering device loss and splicer operability, we assume that each optical fiber pigtail is 10 cm long. Considering the double-pass optical path, the optical path length saved after device integration is 40 cm. The 980° pump light, or the second laser, passes through the first port of the connector and is focused by a self-focusing collimator onto filter 442. Filter 442 reflects the second laser light, or pump light, to the common port (COM), the second port of the connector. Signal light is input through the COM port, reflected by the Faraday rotator and reflector, and then returned to the common port along the original path for output.

[0086] In this embodiment, the second port 32 of the hybrid optical ring module 30 and the Faraday rotator 4431 form a polarization switch, which can effectively isolate stray light from a single optical path within the acousto-optic modulator. By adopting a dual-pass structure of a polarization beam splitter and a Faraday rotator, the polarization state of the secondarily frequency-shifted signal light changes by 90° after passing through the Faraday rotator. However, the single-frequency-shifted stray light caused by reflection from the internal surface of the acousto-optic modulator does not pass through the Faraday rotator and has a polarization state that differs by 90° from the signal light. Thus, the principle of polarization separation is utilized to separate the signal light from the stray light, avoiding the problem of pulse envelope modulation caused by interference between the two. Furthermore, by ensuring that the pump light, i.e., the second laser, propagates in the opposite direction to the first laser, the integration of the wavelength division multiplexer and the Faraday rotator is facilitated, the transmission fiber length is shortened, and the nonlinear effect caused by SBS is reduced.

[0087] In one embodiment, the first port 31, the second port 32, the third port 33, and the detection port 34 of the hybrid optical ring module 30 all use polarization-maintaining fibers. The slow axis of the polarization-maintaining fiber of the second port 32 is aligned with the slow axis of the polarization-maintaining fiber of the first port 31. The fast axis of the polarization-maintaining fiber of the third port 33 is aligned with the slow axis of the polarization-maintaining fiber of the second port 32. The slow axis of the polarization-maintaining fiber of the detection port 34 is aligned with the slow axis of the polarization-maintaining fiber of the third port 33.

[0088] For example, please refer to Figure 4 , Figure 4 Schematic diagram of a hybrid optical ring module in one embodiment. The first port 31, second port 32, third port 33, and detection port 34 of the hybrid optical ring module 30 all use polarization-maintaining fibers. The slow axis of the polarization-maintaining fiber at the second port 32 is aligned with the slow axis of the polarization-maintaining fiber at the first port 31, the fast axis of the polarization-maintaining fiber at the third port 33 is aligned with the slow axis of the polarization-maintaining fiber at the second port 32, and the slow axis of the polarization-maintaining fiber at the detection port 34 is aligned with the slow axis of the polarization-maintaining fiber at the third port 33.

[0089] In one embodiment, the polarization state of the first signal light output by the beam splitter 20 is input along the slow axis direction of the first port 31 of the hybrid optical ring module 30, and then output to the acousto-optic module 41 along the slow axis direction of the second port 32. After being chopped and frequency-shifted by the acousto-optic module 41, it is amplified by the erbium-doped fiber 42, passes through the lens 441 and the color filter 442 to reach the polarization rotation unit 443 and then reflected back to the erbium-doped fiber 42. At this time, the polarization state changes by 90° and is transmitted along the fast axis of the polarization-maintaining fiber. After secondary amplification and a second pass through the acousto-optic module 41, it is transmitted along the fast axis direction of the second port 32 to the hybrid optical ring module 30, and then output from the third port 33. After passing through the rotating axis, it is output along the slow axis of the third port 33, and then emitted into the atmosphere through the processing module 50. Ignoring the atmospheric depolarization effect, the polarization state of the scattered return light received by the processing module 50 is still transmitted along the slow axis of the polarization-maintaining fiber, passes through the optical switch, reaches the third port 33 of the hybrid optical ring module 30, is then transmitted to the hybrid optical ring module 30 along the slow axis direction of the third port 33, and is finally output to the detection module 60 along the slow axis direction of the detection port 34.

[0090] After the laser passes through the gain fiber a second time, the energy of the single pulse is further amplified, exacerbating the SBS effect. At this point, the length of the transmission fiber after the output from the gain fiber has a greater impact. In this embodiment, by combining a polarization beam splitter (PBS) with the four ports of the hybrid optical ring module 30 and designing the transmission characteristics of each port to ensure the polarization separation effect of the PBS + Faraday rotator, 20 cm of fiber length can be saved, reducing the SBS effect.

[0091] In one embodiment, the processing module 50 includes: an optical switch 51, which is used to switch the transmission channel and the receiving channel of the second signal light; a telescope 52, which receives the second signal light through the transmission channel opened by the optical switch 51 and transmits the second signal light to the target to be measured, receives the echo signal reflected back by the target to be measured, and transmits the echo signal to the receiving channel switched by the optical switch 51.

[0092] Exemplarily, the first laser light emitted by the first light source 10, such as a seed laser, is split into two beams by the beam splitter 20. One beam serves as the local oscillator light and is connected to the detection module 60. The other beam serves as the first signal light, which is transmitted to the first port 31 of the hybrid optical ring module 30, such as a four-port optical circulator, and is output from the second port 32 and transmitted to the adjustment module 40. The adjustment module 40 frequency-shifts the incident first laser light twice, chops it, and amplifies it to convert it into pulsed light of the second signal light, which is then reflected back to the second port 32. The second signal light then passes through the third port 33, passes through the optical switch 51, and is emitted into the atmosphere through the telescope 52. The scattered return light signal carrying Doppler frequency shift information, i.e., the echo signal, is received by the telescope 52 and transmitted to the third port 33 of the hybrid optical ring module 30. It is then emitted from the detection port 34 and transmitted to the detection module 60. The detection module 60 receives the echo signal and the local oscillator light output from the detection port 34, thereby generating a wind speed signal of the target to be measured.

[0093] Optionally, the processing module may be a time-division transceiver module, which first switches the second signal light by time-division using an optical switch, then transmits the second signal light through a telescope, and then receives an echo signal through the time-division transceiver module.

[0094] In one embodiment, the detection module 60 includes: a coupler 61 for coupling the echo signal and the local oscillator light to obtain a coupled optical signal; a balanced detector 62 for receiving the coupled optical signal, beating the coupled optical signal, and converting the coupled optical signal after beating into an electrical signal.

[0095] Exemplarily, the coupler 61 can be a 50 / 50 optical coupler. When coherent detection is possible, the coherent laser signal and the local oscillator signal are incident on the photosensitive surface of the balanced detector 62 together under the condition of wavefront matching, generating a beat frequency or coherent superposition, so that the output electrical signal of the balanced detector 62 is proportional to the square of the sum of the echo signal (backscattered signal light) and the local oscillator light.

[0096] Furthermore, the slow axis of the detection port 34 of the hybrid optical ring module 30 and the slow axis of the local oscillator light of the beam splitter 20 are respectively connected to the slow axis of the input end of the coupler 61, for example, a 50 / 50 optical coupler. The signal light and the local oscillator light are both transmitted along the slow axis of the input end of the 50 / 50 optical coupler, and the vibration directions of the two are consistent, thereby ensuring the coherence efficiency of the subsequent beat frequency between the local oscillator light and the echo signal scattered by the aerosol surface.

[0097] Based on the same inventive concept, the embodiment of the present application also provides a wind measurement method using a wind laser radar. The solution provided by this method is similar to the solution described in the above-mentioned wind laser radar. Therefore, the specific limitations of the wind measurement method embodiments of one or more wind laser radars provided below can be found in the above-mentioned limitations on wind laser radars, and will not be repeated here. Figure 5 , Figure 5 FIG. 5 is a flow chart of a wind measurement method using a wind laser radar according to an embodiment of the present invention. The method includes:

[0098] Step 502: Control a first light source to emit a first laser having a first wavelength. The first laser is split into a local oscillator light and a first signal light by a beam splitter. The first signal light is transmitted through a first port of the hybrid optical ring module to a second port of the hybrid optical ring module and is output from the second port.

[0099] In step 504 , the control and regulation module receives the first signal light from the second port, performs two frequency modulations, two pulse modulations, and two power amplifications on the first signal light to obtain a second signal light. The second signal light is incident on the hybrid optical ring module through the second port and is output from the third port of the hybrid optical ring module.

[0100] Step 506: The processing module receives the second signal light from the third port, transmits the second signal light to the target to be measured, and receives an echo signal reflected by the target to be measured; the echo signal is incident on the hybrid optical ring module through the third port and is output from the detection port of the hybrid optical ring module.

[0101] Step 508: Receive the echo signal and local oscillation light outputted from the detection port through the detection module, thereby generating a wind speed signal of the target to be measured.

[0102] In this embodiment, by using a hybrid optical ring module and an adjustment module in conjunction, the signal light of the target to be detected can be frequency modulated twice, pulse modulated twice, and power amplified twice. The hybrid optical ring module design reduces the number of passive optical components, improves the integration of the laser radar, and reduces the additional insertion loss.

[0103] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0104] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A wind measurement laser radar, characterized in that: The laser radar includes: a first light source, emitting a first laser having a first wavelength; a beam splitter, receiving the first laser and splitting the first laser into a local oscillator light and a first signal light; A hybrid optical ring module includes a first port and a second port; the hybrid optical ring module receives the first signal light through the first port and outputs the first signal light from the second port; an adjustment module, receiving the first signal light from the second port, and being configured to perform two frequency modulations, two pulse modulations, and two power amplifications on the first signal light to obtain a second signal light; the hybrid optical ring module further includes a third port, the second port of the hybrid optical ring module further receives the second signal light, and outputs the second signal light from the third port; wherein the adjustment module includes: an acousto-optic module, receiving the first signal light, and performing frequency modulation and pulse modulation on the first signal light to obtain a third signal light; a second light source, the second light source emitting a second laser having a second wavelength; the second laser being a pump light; an erbium-doped optical fiber, receiving and transmitting the third signal light and the second laser, wherein the third signal light is transmitted and amplified in the erbium-doped optical fiber along a first direction under the action of the second laser to obtain a fourth signal light; A reflection module receives the fourth signal light and the second laser, and reflects the fourth signal light and the second laser back to the erbium-doped optical fiber; the fourth signal light is again transmitted and amplified along the second direction in the erbium-doped optical fiber under the action of the second laser, and is again incident on the acousto-optic module, and is frequency modulated and pulse modulated by the acousto-optic module to obtain a second signal light of amplified spontaneous emission of adjacent pulse intervals by using the shutdown function of the acousto-optic module; wherein the reflection module includes: a lens, receiving the fourth signal light and the second laser, and adjusting the fourth signal light and the second laser; a color filter receiving the fourth signal light and the second laser light regulated by the lens, reflecting the second laser light and transmitting the fourth signal light; the second laser light is reflected to the lens, regulated again by the lens, and then incident on the erbium-doped optical fiber; a polarization rotation unit, receiving the fourth signal light, rotating the polarization direction of the fourth signal light by 90 degrees, and then reflecting the fourth signal light to the color filter; after the polarization direction is rotated by 90 degrees, the fourth signal light passes through the color filter and the lens again and is incident on the erbium-doped optical fiber; wherein the polarization rotation unit includes: a Faraday rotation unit, configured to receive the fourth signal light and rotate the polarization direction of the fourth signal light by 45 degrees under the action of a magnetic field; a reflector, receiving the fourth signal light with a polarization direction rotated by 45 degrees, and reflecting the fourth signal light with a polarization direction rotated by 45 degrees back to the Faraday rotator; the fourth signal light with a polarization direction rotated by 45 degrees passes through the Faraday rotator again, and the polarization direction is rotated by another 45 degrees before being incident on the color filter; a processing module, receiving the second signal light from the third port, emitting the second signal light to the target to be measured, and receiving an echo signal reflected back by the target to be measured; the hybrid optical ring module further includes a detection port, the third port of the hybrid optical ring module further receiving the echo signal, and transmitting the echo signal to the detection port; a detection module, receiving the echo signal and the local oscillation light output by the detection port, thereby generating a wind speed signal of the target to be measured; The hybrid optical ring module also includes a polarization beam splitter; the first signal light is received through the first port and deflected to the second port via the polarization beam splitter, and the first signal light is output from the second port; the second port of the hybrid optical ring module also receives the second signal light, the second signal light is deflected to the third port via the polarization beam splitter, and the second signal light is output from the third port; the first port, the second port, the third port and the detection port of the hybrid optical ring module all use polarization-maintaining optical fibers, the slow axis of the polarization-maintaining optical fiber of the second port is aligned with the slow axis of the polarization-maintaining optical fiber of the first port, the fast axis of the polarization-maintaining optical fiber of the third port is aligned with the slow axis of the polarization-maintaining optical fiber of the second port, and the slow axis of the polarization-maintaining optical fiber of the detection port is aligned with the slow axis of the polarization-maintaining optical fiber of the third port; Among them, the wind measurement lidar optical system needs to meet the radar system signal-to-noise ratio and accuracy requirements; considering that the system noise is shot noise, the lidar equation is shown in formula (1): （1） in, CNR is the carrier-to-noise ratio, η is the optical system efficiency factor, E p represents the laser single pulse energy, β is the atmospheric backscattering coefficient, λ is the center wavelength of the emitted laser, T is the atmospheric one-way loss coefficient, D is the telescope aperture, h is Planck's constant, B is the circuit detection bandwidth, R is the detection distance; Under low carrier-to-noise ratio conditions, the wind measurement accuracy formula of the wind laser radar is shown in formula (2): （2） Among them, σ υ is the velocity standard deviation, δ υ is the signal spectrum bandwidth, N p is the number of pulse accumulations, N g is the number of sampling points within the range gate; According to formula (1) and formula (2), the factors affecting the wind measurement accuracy in a single range gate are signal spectrum bandwidth, pulse accumulation times, number of sampling points and signal-to-noise ratio. When only considering the influence of laser, the factors affecting the wind measurement accuracy are pulse accumulation times. N p and laser single pulse energy E p ; Since the wind direction of the wind laser radar is synthesized from the radial wind speed vector, the pulse accumulation times are N p Limited by the integration time; the radial wind speed integration time is defined as T 积分 ; Pulse accumulation times N p and radial wind speed integration time and pulse repetition frequency f p The relationship is shown in formula (3): N p =T 积分 × f p （3） The F factor can be defined by the above formula, and the F factor can be used to evaluate the correlation between laser parameters and wind measurement accuracy, as shown in formula (4): （4） From formula (4), we can see that when the F factor is larger, it means that the wind laser radar velocity measurement accuracy value σ υ The smaller the laser radar is, the higher the speed measurement accuracy is. The laser single pulse energy is E p and pulse output average power P avg The relationship between the pulse repetition frequency is shown in formula (5): （5） Formula (6) can be obtained from formula (4) and formula (5): （6） From the definition of F factor, we know that when using low pulse repetition frequency f p and large laser single pulse energy E p The solution can also meet the needs of close-range wind measurement; The repetition frequency of the first laser is set to 10 kHz.

2. The laser radar according to claim 1, wherein: The second direction is opposite to the first direction.

3. The laser radar according to claim 1, wherein The second laser is transmitted along a second direction.

4. The laser radar according to claim 1, wherein The processing modules include: an optical switch, configured to switch a transmitting channel and a receiving channel of the second signal light; The telescope receives the second signal light passing through the transmitting channel opened by the optical switch and transmits the second signal light to the target to be measured, receives the echo signal reflected back by the target to be measured, and transmits the echo signal to the receiving channel switched by the optical switch.

5. The laser radar according to claim 1, characterized in that The detection module includes: a coupler, configured to couple the echo signal and the local oscillator light to obtain a coupled optical signal; The balanced detector receives the coupled optical signal, performs beat frequency on the coupled optical signal, and converts the coupled optical signal after the beat frequency into an electrical signal.

6. A wind measurement method using a wind laser radar, characterized in that: The method comprises: Controlling a first light source to emit a first laser having a first wavelength, wherein the first laser is split into a local oscillator light and a first signal light by a beam splitter; transmitting the first signal light through a first port of the hybrid optical ring module to a second port of the hybrid optical ring module, and outputting from the second port; The control and adjustment module receives the first signal light from the second port, performs two frequency modulations, two pulse modulations, and two power amplifications on the first signal light to obtain a second signal light; the second signal light is incident on the hybrid optical ring module through the second port and is output from the third port of the hybrid optical ring module; wherein controlling the adjustment module includes: The acousto-optic module is controlled to receive the first signal light and frequency-modulate and pulse-modulate the first signal light to obtain a third signal light; the second light source is controlled to emit a second laser with a second wavelength; the second laser is a pump light; the erbium-doped optical fiber receives and transmits the third signal light and the second laser, and the third signal light is amplified along the first direction in the erbium-doped optical fiber under the action of the second laser to obtain a fourth signal light; the reflection module receives the fourth signal light and the second laser and reflects the fourth signal light and the second laser back to the erbium-doped optical fiber; the fourth signal light is amplified again along the second direction in the erbium-doped optical fiber under the action of the second laser and is incident on the acousto-optic module again, and is frequency-modulated and pulse-modulated by the acousto-optic module to obtain a second signal light of amplified spontaneous emission of adjacent pulse intervals by using the shutdown function of the acousto-optic module; wherein the reflection module includes: a lens, which receives the fourth signal light and the second laser, and amplifies the fourth signal light. the fourth signal light and the second laser light adjusted by the lens; a color filter receiving the fourth signal light and the second laser light adjusted by the lens, reflecting the second laser light and transmitting the fourth signal light; the second laser light being reflected to the lens, adjusted again by the lens, and incident on the erbium-doped optical fiber; a polarization rotation unit receiving the fourth signal light, rotating the polarization direction of the fourth signal light by 90 degrees, and then reflecting it to the color filter; the fourth signal light after the polarization direction is rotated by 90 degrees passes through the color filter and the lens again, and then incident on the erbium-doped optical fiber; wherein the polarization rotation unit includes: a Faraday rotator for receiving the fourth signal light and rotating the polarization direction of the fourth signal light by 45 degrees under the action of a magnetic field; a reflector receiving the fourth signal light with the polarization direction rotated by 45 degrees, and reflecting the fourth signal light with the polarization direction rotated by 45 degrees back to the Faraday rotator; the fourth signal light with the polarization direction rotated by 45 degrees passes through the Faraday rotator again, and then rotates the polarization direction by 45 degrees again, and then incident on the color filter; receiving the second signal light from the third port through the processing module, emitting the second signal light to the target to be measured, and receiving an echo signal reflected back by the target to be measured; the echo signal is incident on the hybrid optical ring module through the third port, and is output from the detection port of the hybrid optical ring module; Receiving the echo signal and the local oscillation light outputted by the detection port through a detection module, thereby generating a wind speed signal of the target to be measured; Wherein the hybrid optical ring module further includes a polarization beam splitter; the first signal light passes through the first port of the hybrid optical ring module, is deflected to the second port via the polarization beam splitter, and is output from the second port; the second signal light is incident on the hybrid optical ring module through the second port, is deflected to the third port via the polarization beam splitter, and is output from the third port; the first port, the second port, the third port and the detection port of the hybrid optical ring module all use polarization-maintaining optical fibers, the slow axis of the polarization-maintaining optical fiber of the second port is aligned with the slow axis of the polarization-maintaining optical fiber of the first port, the fast axis of the polarization-maintaining optical fiber of the third port is aligned with the slow axis of the polarization-maintaining optical fiber of the second port, and the slow axis of the polarization-maintaining optical fiber of the detection port is aligned with the slow axis of the polarization-maintaining optical fiber of the third port; Among them, the wind measurement lidar optical system needs to meet the radar system signal-to-noise ratio and accuracy requirements; considering that the system noise is shot noise, the lidar equation is shown in formula (1): （1） in, CNR is the carrier-to-noise ratio, η is the optical system efficiency factor, E p represents the laser single pulse energy, β is the atmospheric backscattering coefficient, λ is the center wavelength of the emitted laser, T is the atmospheric one-way loss coefficient, D is the telescope aperture, h is Planck's constant, B is the circuit detection bandwidth, R is the detection distance; Under low carrier-to-noise ratio conditions, the wind measurement accuracy formula of the wind laser radar is shown in formula (2): （2） Among them, σ υ is the velocity standard deviation, δ υ is the signal spectrum bandwidth, N p is the number of pulse accumulations, N g is the number of sampling points within the range gate; According to formula (1) and formula (2), the factors affecting the wind measurement accuracy in a single range gate are signal spectrum bandwidth, pulse accumulation times, number of sampling points and signal-to-noise ratio. When only considering the influence of laser, the factors affecting the wind measurement accuracy are pulse accumulation times. N p and laser single pulse energy E p ; Since the wind direction of the wind laser radar is synthesized from the radial wind speed vector, the pulse accumulation times are N p Limited by the integration time; the radial wind speed integration time is defined as T 积分 ; Pulse accumulation times N p and radial wind speed integration time and pulse repetition frequency f p The relationship is shown in formula (3): N p = T 积分 × f p （3） The F factor can be defined by the above formula, and the F factor can be used to evaluate the correlation between laser parameters and wind measurement accuracy, as shown in formula (4): （4） From formula (4), we can see that when the F factor is larger, it means that the wind laser radar velocity measurement accuracy value σ υ The smaller the laser radar is, the higher the speed measurement accuracy is. The laser single pulse energy is E p and pulse output average power P avg The relationship between the pulse repetition frequency is shown in formula (5): （5） Formula (6) can be obtained from formula (4) and formula (5): （6） From the definition of F factor, we know that when using low pulse repetition frequency f p and large laser single pulse energy E p The solution can also meet the needs of close-range wind measurement; The repetition frequency of the first laser is set to 10 kHz.

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