Turbulent water body profile flow velocity detection method and device based on laser Doppler effect

Abstract

The present invention relates to a method and device for detecting turbulent water bodies, and specifically relates to a method and device for detecting the cross-sectional flow velocity of turbulent water bodies based on the laser Doppler effect, which solves the deficiency in the prior art of having no means for detecting the cross-sectional flow velocity of deep-sea turbulent water bodies. The detection method provided by the present invention uses laser detection. The laser signal is divided into a measurement beam and a reference beam. The backscattered echo beam generated by the measurement beam at different cross-sections in the water body to be measured interferes with the reference beam to produce beat interference. The generated beat interference signal is converted into an electrical signal and then operated on to obtain the cross-sectional flow velocity of the turbulent water body. The present invention also provides a detection device for implementing the above detection method, including a laser, three laser beam splitters, a laser transmission optical path, a laser modulation system, a laser transceiver system, a photodetector, a signal processing system, and a data storage system. The present invention can be applied to the deep-sea environment and detect the flow velocity of small-scale turbulence, and has a higher horizontal resolution.

Description

Technical Field

[0001] The present invention relates to a method and device for detecting turbulent water bodies, and particularly to a method and device for detecting the profile flow velocity of turbulent water bodies based on the laser Doppler effect. Background Art

[0002] Turbulence is an important physical ocean phenomenon that can reflect the processes of ocean material circulation and energy transfer, and is of great significance for ocean research. Due to the high non-linearity and extreme asymmetry of turbulence, it is impossible to numerically simulate the complete and accurate turbulent motion process. Therefore, the research on turbulence is mainly based on a large amount of on-site observation data.

[0003] The intense mixing and diffusion processes of deep-sea turbulence play an important regulatory role in the global ocean material circulation, energy balance, global weather and climate change, and profoundly affect the ability of the ocean to absorb heat and carbon dioxide surplus in the atmosphere under the background of global warming. Therefore, the research on deep-sea turbulence activities has always been a hot topic in global ocean research.

[0004] At present, the turbulent kinetic energy - turbulent dissipation rate model (k-ε model) constructed based on the Reynolds averaging method is often used to approximately describe turbulence and its mixing and diffusion processes. The turbulent kinetic energy and turbulent dissipation rate characterizing the turbulent process are both determined by the turbulent flow velocity. Therefore, the flow velocity observation data is crucial for the research on turbulence.

[0005] Traditional turbulent observation instruments include turbulent profilers, point acoustic Doppler current meters, and acoustic Doppler profilers. Turbulent profilers can obtain the dissipation rate of turbulence by measuring the flow velocity shear, but cannot calculate the turbulent kinetic energy; point acoustic Doppler current meters can obtain the dissipation rate of turbulence through high-frequency repeated detection of a single point, but can only measure the flow velocity at a single point and cannot obtain the three-dimensional flow field information of turbulence, and the data validity is low.

[0006] Acoustic Doppler profilers can obtain the turbulent dissipation rate and turbulent kinetic energy by detecting the three-dimensional flow velocity of turbulence, and can not only observe the intensity of turbulent activities, but also explain to a certain extent the reasons for the strength of turbulent activities. Acoustic Doppler profilers detect the profile flow velocity by receiving the acoustic scattering echoes caused by plankton, suspended particulate matter, bubbles, etc. However, in deep-sea areas, the content of scatterers such as plankton and suspended particulate matter is extremely low, and the intensity of the acoustic scattering echo cannot meet the minimum signal-to-noise ratio requirements of high-frequency acoustic Doppler profilers. Therefore, acoustic Doppler profilers cannot be applied to the deep sea, which limits their research on deep-sea turbulence.

[0007] In view of the deficiencies in the observation capabilities of the above-mentioned instruments, it is necessary to propose a detection method and device that can effectively observe deep-sea turbulence activities. Summary of the Invention

[0008] The object of the present invention is to solve the technical problem in the prior art that there is no detection means for the profile flow velocity of deep - sea turbulent water bodies, and to provide a detection device and method for the profile flow velocity of turbulent water bodies based on the laser Doppler effect.

[0009] The design idea of the present invention is as follows:

[0010] Compared with large - scale physical oceanic effects such as ocean circulation and mesoscale eddies, the scale of turbulence is smaller, and some oceanic turbulence is even on the order of meters. Therefore, in order to achieve effective observation of turbulence, the observation equipment must have a high horizontal resolution. The back - scattering echo of laser in the deep sea is stronger. By receiving the back - scattering echo of the laser during forward transmission in the water body, and then extracting the Doppler frequency shift of the back - scattering echo signals of different profiles, the effective detection of the profile flow velocity can be realized.

[0011] To achieve the above - mentioned invention object and complete the above - mentioned invention idea, the technical solution adopted by the present invention is as follows:

[0012] A method for detecting the profile flow velocity of turbulent water bodies based on the laser Doppler effect, which is characterized in that it includes the following steps:

[0013] Step 1: Divide the continuous laser signal emitted by the laser 1 into two beams, one beam is denoted as the measurement beam, and the other beam is denoted as the reference beam;

[0014] Step 2: Modulate the measurement beam into a pulsed beam, and irradiate the pulsed beam towards the water body 8 to be measured;

[0015] Step 3: The pulsed beam generates back - scattering echo beams at different profiles in the water body 8 to be measured. Receive the back - scattering echo beams and make them undergo beat interference with the reference beam to generate beat interference signals;

[0016] Step 4: Convert the beat interference signal into an analog electrical signal, and transmit the analog electrical signal to the signal processing system 6;

[0017] Step 5: Use the signal processing system 6 to extract the Doppler frequency shift of the analog electrical signal, and calculate through the following formula to obtain the flow velocity of each profile of the water body 8 to be measured:

[0018]

[0019] where v is the flow velocity of each profile;

[0020] f is the Doppler frequency shift of each profile;

[0021] λ is the wavelength of the continuous laser signal emitted by the laser 1.

[0022] Furthermore, in the above - mentioned step 1, the wavelength of the continuous laser signal emitted by the laser 1 is 460nm - 550nm.

[0023] Furthermore, it also includes:

[0024] Step 6: The flow velocity v of each section of the water body 8 to be measured calculated by the signal processing system 6 is transmitted to the data storage system 7 for storage.

[0025] The present invention also provides a turbulent water body profile velocity detection device based on the laser Doppler effect, which is used to implement the above-mentioned turbulent water body profile velocity detection method based on the laser Doppler effect, and its special features are:

[0026] It includes a laser 1, a first laser beam splitter 121, a second laser beam splitter 122, a third laser beam splitter 123, a laser transmission optical path 13, a laser modulation system 2, a laser transceiver system 4, a photodetector 5, a signal processing system 6 and a data storage system 7;

[0027] The first laser beam splitter 121 is arranged on the laser transmission optical path 13 of the continuous laser signal emitted by the laser 1, and divides the continuous laser signal into two beams, one of which is recorded as a measuring beam and the other is recorded as a reference beam; the laser modulation system 2 is located on the laser transmission optical path 13 of the measuring beam, and modulates the measuring beam into a pulsed beam; the third laser beam splitter 123 is located on the laser transmission optical path 13 of the reference beam;

[0028] The second laser beam splitter 122 and the laser transceiver system 4 are sequentially located on the laser transmission optical path 13 of the pulsed light beam. The laser transceiver system 4 sends the pulsed light beam to the water body 8 to be measured, and receives the backscattered echo light beams generated by different sections of the water body 8 to be measured, and then transmits the backscattered echo light beams to the third laser beam splitter 123 via the second laser beam splitter 122.

[0029] The reference beam passing through the third laser beam splitter 123 and the backscattered echo beam transmitted to the third laser beam splitter 123 via the second laser beam splitter 122 undergo beat frequency interference, generating a beat frequency interference signal; the photodetector 5 is located on the laser transmission optical path 13 of the third laser beam splitter 123, and converts the detected beat frequency interference signal into an analog electrical signal and transmits it to the signal processing system 6;

[0030] The data storage system 7 and the signal processing system 6 are connected via an electrical signal transmission line 14 and are used to store the calculated turbulent water body profile velocity information.

[0031] Further, the laser modulation system 2 comprises a signal source 9, a radio frequency signal amplifier 10 and a laser modulator 11 which are sequentially connected via an electrical signal transmission line 14;

[0032] The laser modulator 11 is located on the laser transmission optical path 13 of the measuring light beam, and modulates the measuring light beam into a pulse light beam.

[0033] Further, the first laser beam splitter 121, the second laser beam splitter 122, and the third laser beam splitter 123 are composed of a spatial optical component or a fiber optical component, and the beam splitting ratio is from 1:99 to 99:1.

[0034] Further, a reflecting mirror 3 is further included;

[0035] The reflecting mirror 3 is located on the laser transmission optical path 13 of the reference beam and is used to reflect the reference beam to the third laser beam splitter 123;

[0036] The first laser beam splitter 121, the second laser beam splitter 122, and the third laser beam splitter 123 are a flat beam splitter, a beam splitting cube, or a beam splitting prism;

[0037] The laser transmission optical path 13 is the transmission path of the laser in space.

[0038] Further, the first laser beam splitter 121, the second laser beam splitter 122, and the third laser beam splitter 123 are a fiber coupler or a fiber circulator;

[0039] The laser transmission optical path 13 is the transmission path of the laser in the optical fiber;

[0040] The carrier of the laser transmission optical path 13 is a single-mode optical fiber.

[0041] Further, the photodetector 5 is a photodetector, a photodiode, a photomultiplier tube, a streak camera, or a digital camera based on CCD and CMOS;

[0042] The signal processing system 6 is a signal processing circuit system developed based on a single-chip microcomputer, FPGA, DPS, or ARM, or a data acquisition card, an oscilloscope, or a computer;

[0043] The signal source 9 is a commercial or industrial signal generator, or a circuit system with signal output ability developed based on a single-chip microcomputer, FPGA, DSP, or ARM;

[0044] The radio frequency signal amplifier 10 is a separate module or circuit board, or an integrated system integrated with the signal source;

[0045] The laser modulator 11 is an electro-optic, acousto-optic, or liquid crystal modulator, or a semiconductor optical switch, a mechanical optical switch, or a MEMS optical switch.

[0046] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0047] 1. It can detect the velocity of small-scale turbulent flow: The collimation of the laser is good. The detection beam width will be effectively compressed and there is no side-wave interference, enabling a higher horizontal resolution, and thus effective observation of turbulence can be achieved.

[0048] 2. It can be applied to the deep-sea environment: The wavelength of the laser is shorter. Its echo signal includes not only the Mie scattering echo caused by suspended particulate matter but also the Rayleigh scattering echo caused by water molecules. Even when the concentration of suspended particulate matter in the deep sea is extremely low, the scattered echo signal can still be received, enabling effective detection of the velocity of the turbulent water body profile in the deep sea. Description of the Drawings

[0049] Figure 1 It is the structural schematic diagram of the first embodiment of the device for detecting the velocity of the turbulent water body profile based on the laser Doppler effect of the present invention;

[0050] The descriptions of the reference numerals are as follows:

[0051] 1 - Laser, 2 - Laser modulation system, 3 - Reflector, 4 - Laser transceiver system, 5 - Photoelectric detector, 6 - Signal processing system, 7 - Data storage system, 8 - Water body to be measured, 9 - Signal source, 10 - RF signal amplifier, 11 - Laser modulator, 121 - First laser beam splitter, 122 - Second laser beam splitter, 123 - Third laser beam splitter, 13 - Laser transmission optical path, 14 - Electrical signal transmission line. Detailed Embodiment

[0052] The following further elaborates in detail on a method and device for detecting the velocity of the turbulent water body profile based on the laser Doppler effect proposed by the present invention in conjunction with the drawings and specific embodiments. In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0053] Embodiment 1

[0054] A device for detecting the velocity of the turbulent water body profile based on the laser Doppler effect, as Figure 1 , includes a laser 1, a first laser beam splitter 121, a second laser beam splitter 122, a third laser beam splitter 123, a laser transmission optical path 13, a signal source 9, an RF signal amplifier 10, a laser modulator 11, a reflector 3, a laser transceiver system 4, a photoelectric detector 5, a signal processing system 6, and a data storage system 7.

[0055] Among them, the splitting ratios of the first laser beam splitter 121, the second laser beam splitter 122, and the third laser beam splitter 123 are from 1:99 to 99:1. The first laser beam splitter 121, the second laser beam splitter 122, and the third laser beam splitter 123 can be a flat beam splitter, or a beam splitting cube or a beam splitting prism. At this time, the laser transmission optical path 13 is the transmission path of the laser in space.

[0056] The first laser beam splitter 121 is arranged on the laser transmission optical path 13 of the continuous laser signal emitted by the laser 1, and divides the continuous laser signal into two beams. One beam is recorded as the measurement beam, which is transmitted to the laser modulator 11 and modulated into a pulsed beam; the other reflected beam is recorded as the reference beam, which is transmitted to the mirror 3; the mirror 3 is located on the transmission optical path of the reflected light of the first laser beam splitter 121, and reflects the reference beam to the third laser beam splitter 123.

[0057] The second laser beam splitter 122 and the laser transceiver system 4 are successively arranged on the laser transmission optical path 13 of the pulsed beam. The laser transceiver system 4 sends the pulsed beam transmitted by the second laser beam splitter 122 to the water body to be measured 8, and receives the backscattered echo beam generated by different profiles of the water body to be measured 8, and then reflects the backscattered echo beam to the third laser beam splitter 123 through the second laser beam splitter 122.

[0058] The reference beam reflected by the mirror 3 to the third laser beam splitter 123 and the backscattered echo beam reflected by the second laser beam splitter 122 to the third laser beam splitter 123 undergo beat interference to generate a beat interference signal. The photodetector 5 is arranged on the laser transmission optical path 13 of the third laser beam splitter 123, and converts the detected beat interference signal into an analog electrical signal and transmits it to the signal processing system 6. The data storage system 7 and the signal processing system 6 are connected by an electrical signal transmission line 14, and are used to store the calculated turbulent water body profile flow velocity information.

[0059] The signal source 9, the radio frequency signal amplifier 10, and the laser modulator 11 form a laser modulation system 2, which are successively connected by an electrical signal transmission line 14. The laser modulation system 2 is used to modulate the measurement beam into a pulsed form.

[0060] The signal source 9 is used to generate a modulation signal for the normal operation of the laser modulator. It is a mature commercial or industrial-grade signal generator, or a circuit system with signal output capabilities developed based on single-chip microcomputers, FPGAs, DSPs, ARMs, etc.; the radio frequency signal amplifier 10 is used to amplify the signal power sent by the signal source 9 to meet the usage requirements of the laser modulator 11. It is a separate module or circuit board, or an integrated system integrated with the signal source; the laser modulator 11 is used to modulate the continuous laser signal so that it operates in a pulsed form. The laser modulator 11 can select electro-optic, acousto-optic, and liquid crystal modulators, or semiconductor optical switches, mechanical optical switches, and MEMS optical switches, etc. In this embodiment, an electro-optic modulator and a mechanical optical switch are selected.

[0061] The photodetector 5, the signal processing system 6, and the data storage system 7 are connected in sequence through the electrical signal transmission line 14. The photodetector 5 is used to receive the beat interference signal generated by the backscattered light of the water body received by the laser transceiver system 4 and the continuous signal transmitted within the system, and convert the beat interference signal into an analog electrical signal. It is a device such as a photodiode, a photomultiplier tube, a streak camera, or a digital camera based on CCD and CMOS that can convert optical signals into electrical signals. In this embodiment, a photodetector or a photomultiplier tube is selected. The signal processing system 6 is used to receive the analog electrical signal output by the photodetector 5 and obtain the flow velocity of each water body profile by extracting the Doppler frequency shift. It is a signal processing circuit system developed based on single-chip microcomputers, FPGAs, DPSs, ARMs, etc., or a device such as an oscilloscope or a computer that can perform digital signal acquisition and processing. In this embodiment, an embedded programmable system based on FPGA and DSP, or a data acquisition card and an oscilloscope are selected. The data storage system 7 is used to store the water body profile flow velocity information calculated by the signal processing system 6.

[0062] The working principle of the detection device provided in this embodiment is as follows:

[0063] The laser 1 emits a beam of continuous laser signal, which is split into two beams by the first laser beam splitter 121. The beam passing through the laser modulation system 2 is denoted as the measurement beam, and the other beam is denoted as the reference beam. The laser modulator 11 modulates the measurement beam into a pulsed beam. The pulsed beam is split by the second laser beam splitter 122 and then emitted by the laser transceiver system 4, irradiating the water body 8 to be measured; the reference beam is reflected by the mirror 3 to the third laser beam splitter 123.

[0064] The pulsed beam generates backscattered echo beams at different profiles in the water body 8 to be measured, which are received by the laser transceiver system 4 and transmitted through the second laser beam splitter 122 to the third laser beam splitter 123, where they interfere with the reference beam passing through the third laser beam splitter 123 to generate a beat interference signal, and the beat interference signal is received by the photodetector 5.

[0065] The photodetector 5 converts the received beat interference signal into an analog electrical signal and transmits the analog electrical signal to the signal processing system 6. The signal processing system 6 extracts the Doppler frequency shift of the analog electrical signal formed after the interference of the backward scattering echo beam generated by each profile of the water body 8 to be measured and the reference beam, and the flow velocity of each profile of the water body 8 to be measured can be obtained through calculation, and the flow velocity detection data is transmitted to the data storage system 7 for storage.

[0066] Based on the above detection device, this embodiment also provides a method for detecting the profile flow velocity of a turbulent water body based on the laser Doppler effect, including the following steps:

[0067] Step 1: The laser 1 emits a continuous laser signal with a wavelength of 460 nm - 550 nm, which is divided into two beams by the first laser beam splitter 121. The beam passing through the laser modulator 11 is denoted as the measurement beam, and the other beam is denoted as the reference beam;

[0068] Step 2: The laser modulator 11 modulates the measurement beam into a pulsed beam. After being split by the second laser beam splitter 122, the pulsed beam is emitted by the laser transceiver system 4 and irradiated onto the water body 8 to be measured;

[0069] Step 3: The pulsed beam generates backward scattering echo beams at different profiles in the water body 8 to be measured, which are received by the laser transceiver system 4 and transmitted to the third laser beam splitter 123 via the second laser beam splitter 122, and beat interference occurs with the reference beam passing through the third laser beam splitter 123 to generate a beat interference signal;

[0070] Step 4: The photodetector 5 receives the beat interference signal, converts it into an analog electrical signal and transmits it to the signal processing system 6;

[0071] Step 5: The signal processing system 6 extracts the Doppler frequency shift of the analog electrical signal, and through the following formula calculation, the flow velocity of each profile of the water body 8 to be measured is obtained:

[0072]

[0073] where, v is the flow velocity of each profile;

[0074] f is the Doppler frequency shift of each profile;

[0075] λ is the wavelength of the continuous laser signal emitted by the laser 1;

[0076] Step 6: After the signal processing system 6 calculates the flow velocity v of each profile of the water body 8 to be measured, the flow velocity detection data is transmitted to the data storage system 7 for storage.

[0077] Embodiment 2

[0078] Compared with the detection device provided in the first embodiment, the detection device provided in this embodiment does not include the mirror 3. The first laser beam splitter 121, the second laser beam splitter 122, and the third laser beam splitter 123 can be selected as fiber couplers or fiber circulators. At this time, the laser transmission optical path 13 is the transmission path of the laser in the optical fiber, and its carrier is a single-mode optical fiber.

[0079] The first laser beam splitter 121 is arranged on the laser transmission optical path 13 of the continuous laser signal emitted by the laser 1, and divides the continuous laser signal into two beams, one beam is denoted as the measurement beam, and the other beam is denoted as the reference beam.

[0080] The measurement beam is transmitted to the laser modulator 11 through a single-mode optical fiber, modulated into a pulsed beam, and then sent to the water body to be measured 8 by the laser transceiver system 4 through the second laser beam splitter 122; the reference beam is directly transmitted to the third laser beam splitter 123 through a single-mode optical fiber.

[0081] The laser transceiver system 4 receives the backward scattered echo beam generated by different profiles of the water body to be measured 8, and then transmits the backward scattered echo beam to the second laser beam splitter 122. The second laser beam splitter 122 splits the backward scattered echo beam and then transmits it to the third laser beam splitter 123. The reference beam and the backward scattered echo beam undergo beat interference to generate a beat interference signal.

[0082] The structures, working principles, and detection methods of other parts of this embodiment are the same as those of the first embodiment.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for detecting the cross-sectional flow velocity of turbulent water based on the laser Doppler effect, characterized in that, it includes the following steps: Step 1: Divide the continuous laser signal with a wavelength of 460nm - 550nm emitted by the laser (1) into two beams, one beam is denoted as the measurement beam, and the other beam is denoted as the reference beam; Step 2: Modulate the measurement beam into a pulsed beam and irradiate the pulsed beam towards the water body to be measured (8); Step 3: The pulsed beam generates a backward scattered echo beam at different cross-sections in the water body to be measured (8). Receive the backward scattered echo beam and make it undergo beat interference with the reference beam to generate a beat interference signal; Step 4: Convert the beat interference signal into an analog electrical signal and transmit the analog electrical signal to the signal processing system (6); Step 5: Use the signal processing system (6) to extract the Doppler frequency shift of the analog electrical signal and calculate through the following formula to obtain the cross-sectional flow velocity of each cross-section of the water body to be measured (8): where, v is the cross-sectional flow velocity of each cross-section; f is the Doppler frequency shift of each cross-section; λ is the wavelength of the continuous laser signal emitted by the laser (1).

2. The method for detecting the cross-sectional flow velocity of turbulent water based on the laser Doppler effect according to claim 1, characterized in that, it further includes: Step 6: Transmit the cross-sectional flow velocity v of each cross-section of the water body to be measured (8) calculated by the signal processing system (6) to the data storage system (7) for storage.

3. A device for detecting the cross-sectional flow velocity of turbulent water based on the laser Doppler effect, which is used to implement the method for detecting the cross-sectional flow velocity of turbulent water based on the laser Doppler effect according to claim 1 or 2, characterized in that: It includes a laser (1), a first laser beam splitter (121), a second laser beam splitter (122), a third laser beam splitter (123), a laser transmission optical path (13), a laser modulation system (2), a laser transceiver system (4), a photodetector (5), a signal processing system (6) and a data storage system (7); The first laser beam splitter (121) is arranged on the laser transmission optical path (13) of the continuous laser signal emitted by the laser (1) to divide the continuous laser signal into two beams, one beam is denoted as the measurement beam, and the other beam is denoted as the reference beam; the wavelength of the continuous laser signal emitted by the laser (1) is 460nm - 550nm; the laser modulation system (2) is located on the laser transmission optical path (13) of the measurement beam to modulate the measurement beam into a pulsed beam; the third laser beam splitter (123) is located on the laser transmission optical path (13) of the reference beam; The second laser beam splitter (122) and the laser transceiver system (4) are successively located on the laser transmission optical path (13) of the pulsed beam. The laser transceiver system (4) sends the pulsed beam to the water body to be measured (8), receives the backward scattered echo beam generated by different cross-sections of the water body to be measured (8), and then transmits the backward scattered echo beam to the third laser beam splitter (123) via the second laser beam splitter (122); The reference beam passing through the third laser beam splitter (123) and the backscattered echo beam transmitted to the third laser beam splitter (123) via the second laser beam splitter (122) undergo beat frequency interference to generate a beat frequency interference signal; the photodetector (5) is located on the laser transmission optical path (13) of the third laser beam splitter (123), and converts the detected beat frequency interference signal into an analog electrical signal and transmits it to the signal processing system (6); The data storage system (7) and the signal processing system (6) are connected by an electrical signal transmission line (14) and are used to store the calculated turbulent water body profile flow velocity information.

4. The turbulent water body profile flow velocity detection device based on the laser Doppler effect according to claim 3, characterized in that: The laser modulation system (2) includes a signal source (9), a radio frequency signal amplifier (10), and a laser modulator (11) that are sequentially connected by an electrical signal transmission line (14); The laser modulator (11) is located on the laser transmission optical path (13) of the measurement beam and modulates the measurement beam into a pulsed beam.

5. The turbulent water body profile flow velocity detection device based on the laser Doppler effect according to claim 4, characterized in that: The first laser beam splitter (121), the second laser beam splitter (122), and the third laser beam splitter (123) are spatial optical components or fiber optical components, and the splitting ratio is from 1:99 to 99:

1.

6. The turbulent water body profile flow velocity detection device based on the laser Doppler effect according to claim 5, characterized in that: It further includes a reflector (3); The reflector (3) is located on the laser transmission optical path (13) of the reference beam and is used to reflect the reference beam to the third laser beam splitter (123); The first laser beam splitter (121), the second laser beam splitter (122), and the third laser beam splitter (123) are flat beam splitters, beam splitting cubes, or beam splitting prisms; The laser transmission optical path (13) is the transmission path of the laser in space.

7. The turbulent water body profile flow velocity detection device based on the laser Doppler effect according to claim 5, characterized in that: The first laser beam splitter (121), the second laser beam splitter (122), and the third laser beam splitter (123) are fiber couplers or fiber circulators; The laser transmission optical path (13) is the transmission path of the laser in the fiber; The carrier of the laser transmission optical path (13) is a single-mode fiber.

8. The turbulent water body profile flow velocity detection device based on the laser Doppler effect according to any one of claims 4-7, characterized in that: The photodetector (5) is a photodetector or a photomultiplier tube; The signal processing system (6) is an embedded programmable system based on FPGA or DSP, or a data acquisition card or an oscilloscope; The signal source (9) is a signal generator or an embedded programmable system with a signal output function; The radio frequency signal amplifier (10) is a separate module or circuit board, or an integrated system integrated with the signal source; The laser modulator (11) is an electro-optic modulator and a mechanical optical switch.

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