Rotation Doppler velocity measurement method and device based on Gaussian mode transmitting and multimode optical fiber receiving

Abstract

The invention discloses a rotating Doppler velocity measurement method and device based on Gaussian mode emission and multimode optical fiber receiving, belongs to the technical field of photoelectric detection and sensing, and aims to solve the technical problems of complex system, high cost and poor robustness caused by dependence on active orbital angular momentum modulation and filtering in the conventional rotating Doppler velocity measurement technology. The method comprises the following steps: emitting a single-mode Gaussian beam to a rotating target; a multimode optical fiber is used for receiving scattered echoes, and a plurality of OAM modes are excited; detecting an optical signal output by the multimode optical fiber to obtain a beat frequency time domain signal generated by multimode interference; and performing spectrum analysis on the signal to obtain a rotating Doppler spectrum containing spectrum peaks at equal intervals, and calculating the rotating speed according to the spectrum peak interval. The device comprises a laser emitting module, a light receiving and converting module and a signal processing module which are connected in sequence. According to the invention, active OAM modulation and filtering are not needed, and rotation speed measurement can be realized by using a conventional optical device.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection and sensing technology, specifically to a non-contact speed measurement method and device based on the rotating Doppler effect. Background Technology

[0002] The rotational Doppler effect refers to the phenomenon where rotational motion causes a shift in the frequency of received light; the magnitude of this frequency shift (…). The order of the orbital angular momentum (OAM) of the internal mode and rotational speed Size determines, that is Unlike the traditional linear Doppler effect, which can only detect the axial velocity of a target, the rotational Doppler effect can directly respond to the lateral rotational motion of a target, measuring not only the magnitude of the rotational speed but also the direction of rotation. Sensors based on this effect have advantages such as non-contact operation, fast response speed, wide measurement range, and high accuracy, demonstrating enormous application potential in fields such as deep space exploration, dynamic target identification, aerodynamic testing, turbulence monitoring, and industrial non-destructive testing.

[0003] Currently, the technical solutions for realizing rotating Doppler velocimetry mainly revolve around the generation and detection of OAM light, and can be mainly divided into two categories:

[0004] The first type is internal mode coherent detection. This method typically uses optical elements such as spatial light modulators, q-plates, or spiral phase plates to modulate the fundamental mode Gaussian light into an OAM beam with a specific topological charge at the transmitting end and illuminate the rotating target. The receiving end receives the beam modulated by the target, carrying the opposite OAM mode, and performs heterodyne interference with the reference light. The rotational speed is inverted by measuring the frequency shift of the beat frequency signal. This type of method requires precise phase modulation devices and a stable interference optical path.

[0005] The second type is mode-filtered detection. This method emits a Gaussian beam to a rotating target, and at the receiving end, a mode selection device (such as another spatial light modulator or mode diffraction grating) is used to filter out specific OAM mode components from the scattered echo. These components are then converted back to Gaussian mode and coupled into a single-mode fiber, where they are received by a photodetector and their intensity modulation frequency is analyzed. This type of method also relies on complex mode demodulation devices.

[0006] While the aforementioned existing technologies have verified the feasibility of rotating Doppler velocimetry, they all share common limitations: they rely heavily on active modulation or selective filtering of the OAM optical field. This necessitates the integration of expensive and optically path-calibration-sensitive optical components such as liquid crystal spatial light modulators and spiral phase plates, resulting in high cost, complex structure, and large size of the entire device. It also reduces its long-term stability and robustness under non-ideal environments such as vibration and temperature variations. Furthermore, the complex modulation and demodulation processes limit the real-time performance of measurements and the reliability of the system. Therefore, developing a rotating Doppler velocimetry method and device that requires no active OAM modulation / demodulation, has a simple structure, low cost, and robust performance is crucial for advancing this technology towards practical applications. Summary of the Invention

[0007] To address the technical problems of existing rotating Doppler velocimetry techniques, which rely on active orbital angular momentum modulation and filtering, resulting in complex systems, high costs, and poor robustness, this invention provides a rotating Doppler velocimetry method and apparatus that uses Gaussian mode transmission and multimode fiber reception.

[0008] In a first aspect, the present invention provides a rotating Doppler velocimetry method for Gaussian mode transmission and multimode fiber reception, comprising the following steps:

[0009] S1. Light emission and scattering steps: A single-mode Gaussian beam is emitted toward the rotating target surface. The single-mode Gaussian beam is scattered by the target surface to form a scattered light field carrying target rotation information.

[0010] S2. Multimode reception and coupling steps: The scattered light field is received using a multimode fiber, and the scattered light field is coupled into the multimode fiber to excite multiple transmission modes with different orbital angular momentum orders.

[0011] S3. Signal detection and acquisition steps: Detect the optical signal output by the multimode fiber to obtain the beat frequency time-domain signal generated by the pairwise interference between the multiple transmission modes;

[0012] S4. Spectrum analysis and velocity measurement steps: Perform spectrum analysis on the beat frequency time domain signal to obtain a rotating Doppler spectrum containing a series of equally spaced spectral peaks, and calculate the rotation speed of the rotating target based on the frequency interval between adjacent spectral peaks.

[0013] Preferably, the step S1 of emitting a single-mode Gaussian beam toward the rotating target surface specifically includes:

[0014] A narrow-linewidth laser is generated; the narrow-linewidth laser is coupled into a single-mode fiber for transmission; the Gaussian beam output from the single-mode fiber is sequentially expanded, collimated, and polarized to form a linearly polarized single-mode Gaussian beam with controllable parameters, which is then irradiated onto the surface of the rotating target.

[0015] Preferably, step S2, which involves receiving the scattered light field using a multimode fiber, specifically includes:

[0016] The echo light scattered by the target surface is collected using a receiving optical system; a bandpass filter is set in the optical path of the receiving optical system to filter out stray light other than the laser wavelength in the echo light; the filtered echo light is coupled into the input end face of a multimode optical fiber.

[0017] Preferably, in step S4, the rotating Doppler spectrum... for:

[0018]

[0019] In the formula, For frequency, This represents the difference in orbital angular momentum order between adjacent pairs of modes. For rotational speed, For amplitude, This is the Dirac function.

[0020] Preferably, step S4, which calculates the rotational speed of the rotating target based on the frequency interval between adjacent spectral peaks, specifically includes:

[0021] Obtain the frequency interval between adjacent spectral peaks in the rotating Doppler spectrum. According to the formula Calculate the rotational speed of the rotating target. .

[0022] In a second aspect, the present invention provides a rotating Doppler velocimetry device for Gaussian mode transmission and multimode fiber reception, comprising:

[0023] The laser emission module is used to generate and shape a single-mode Gaussian beam and illuminate it onto the surface of the rotating target 12;

[0024] The optical receiving and conversion module is used to receive the scattered echo light from the surface of target 12 and convert it into an electrical signal;

[0025] A signal processing module is used to process the electrical signal to obtain the rotation speed of the rotating target;

[0026] The optical receiving and conversion module includes a multimode fiber 8, which is used to receive the scattered echo light and excite multiple transmission modes therein. The electrical signal is a beat frequency signal generated by the interference between the multiple transmission modes.

[0027] Preferably, the laser emitting module includes:

[0028] Narrow linewidth laser 1, used to generate Gaussian mode beams;

[0029] Single-mode fiber 2, whose input end is connected to the output end of the narrow linewidth laser 1, is used to transmit single-mode Gaussian light;

[0030] The beam expander collimator 3 is connected to the output end of the single-mode fiber 2 and is used to modulate the radius and divergence angle of the output single-mode Gaussian light.

[0031] A polarization modulation component is disposed in the output optical path of the beam expander collimator 3 and is used to modulate the polarization state of the output beam.

[0032] Preferably, the polarization modulation component includes:

[0033] Half-wave plate 4 is placed in the optical path behind beam expander collimator 3 to adjust the ratio of horizontal and vertical polarization components;

[0034] A linear polarizer 5 is disposed in the optical path behind the half-wave plate 4 to control the output light to be linearly polarized light.

[0035] Preferably, the optical receiving and conversion module includes:

[0036] Bandpass filter 6 is used to filter out rotating Doppler echo signals of a specific wavelength;

[0037] The receiving optical system 7 is placed in the scattered echo optical path after the bandpass filter 6, and is used to collect the echo light signal scattered by the target. The echo light signal scattered by the target is a multimode optical signal.

[0038] The multimode optical fiber 8 has its input end face located at the image plane or conjugate plane of the receiving optical system 7, and is used to transmit the received multimode optical signal.

[0039] The photodetector 9 is connected to the output end of the multimode fiber 8 and is used to convert the multimode interference light signal output by the multimode fiber 8 into a beat frequency time-domain electrical signal.

[0040] Preferably, the signal processing module includes:

[0041] Data acquisition card 10 is connected to photodetector 9 and is used to convert the beat frequency time-domain electrical signal into a digital signal;

[0042] The host 11 is connected to the data acquisition card 10 and is used to perform spectrum analysis on the digitized time-domain signal, identify spectral peaks with equal intervals in the spectrum and calculate the frequency intervals, and then calculate the rotation speed based on the frequency intervals.

[0043] The beneficial effects of this invention are:

[0044] This invention eliminates the need for modulation or filtering of the orbital angular momentum beam; it extracts the velocity signal solely through Gaussian beam scattering and mode interference received by multimode fiber, greatly simplifying the system architecture.

[0045] All the components used are low-cost conventional components such as narrow linewidth lasers, conventional optical fibers, basic optical elements and standard detectors, eliminating expensive special components such as spatial light modulators, which significantly reduces hardware costs and assembly difficulty.

[0046] The system is based on the intrinsic interferometry mechanism of multimode fiber, which is insensitive to changes in target surface characteristics and rotational attitude, and has strong environmental adaptability and measurement stability.

[0047] The generated beat frequency spectrum exhibits equally spaced discrete peaks, the intervals of which satisfy a definite relationship with the rotational angular velocity. The characteristics are clear and easy to extract accurately using standard algorithms, thus ensuring measurement accuracy.

[0048] With a highly fiber-optic optical path and a compact structure, combined with an integrated electrical processing unit, the system is easy to miniaturize and port, making it suitable for field applications and integrated deployment. Attached Figure Description

[0049] Figure 1 This is a schematic diagram illustrating the principle of the method provided by the present invention.

[0050] Figure 2 This is a schematic diagram of the device structure according to an embodiment of the present invention.

[0051] Figure 3 A typical rotating Doppler spectrum obtained by measuring using the method and apparatus of the present invention.

[0052] Figure 4 This diagram illustrates the effect of using multimode optical fibers with different core diameters on the relative error of velocity measurement.

[0053] In the diagram, 1-narrow linewidth laser, 2-single-mode fiber, 3-beam expander collimator, 4-half-wave plate, 5-linear polarizer, 6-bandpass filter, 7-receiving optical system, 8-multimode fiber, 9-photodetector, 10-data acquisition card, 11-host computer, 12-rotating target. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0056] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0057] Specific Implementation Method 1: The following is combined with... Figures 1 to 4 This implementation method is described below.

[0058] 1. System Construction

[0059] Reference Figure 2 The rotating Doppler velocimeter device of this invention was constructed. The device mainly includes a laser emission module, an optical receiving and conversion module, and a signal processing module.

[0060] The laser emission module consists of a narrow-linewidth laser 1, a single-mode fiber 2, a beam expander / collimator 3, a half-wave plate 4, and a linear polarizer 5 connected sequentially. The output end of the narrow-linewidth laser 1 is connected to the input end of the single-mode fiber 2 via a fiber optic flange. The output end of the single-mode fiber 2 is connected to the beam expander / collimator 3 to expand and collimate the beam. In the output optical path of the beam expander / collimator 3, the half-wave plate 4 and the linear polarizer 5 are placed sequentially to adjust and fix the output beam as linearly polarized light in a specific direction, thereby improving the efficiency of interaction with the target.

[0061] The optical receiving and conversion module consists of a bandpass filter 6, a receiving system 7, a multimode fiber 8, and a photodetector 9. The bandpass filter 6 strongly suppresses ambient stray light. The receiving system 7 comprises one or more achromatic lenses for efficiently collecting scattered echo light from the surface of the rotating target 12. The filtered light spot is precisely coupled into the input end face of a section of multimode fiber 8. The output end of the multimode fiber 8 is directly aligned with the photosensitive surface of the photodetector 9. The photodetector 9 converts the multimode interference light signal output from the multimode fiber 8 into a beat frequency time-domain electrical signal.

[0062] The signal processing module consists of a data acquisition card 10 and a host computer 11. The analog beat frequency electrical signal output by the photodetector 9 is input to the high-speed data acquisition card 10 via a coaxial cable. The data acquisition card 10 converts the beat frequency time-domain electrical signal into a digital signal and sends it to the host computer 11. The host computer 11 performs spectral analysis on the digitized time-domain signal, identifies equally spaced spectral peaks in the spectrum and calculates the frequency intervals, and then calculates the rotational speed based on the frequency intervals.

[0063] 2. Measurement Process

[0064] The first step is system calibration and target setup. Turn on the narrow-linewidth laser 1 and adjust the emitted optical path so that the collimated linearly polarized Gaussian beam is incident squarely on the test area of ​​the rotating target 12. The rotating target 12 can be a motor-driven turntable with a rough tin foil adhered to its surface or a diffuse reflection coating sprayed onto it to simulate an actual diffuse reflector. Adjust the position and angle of the receiving system 7 to ensure it can effectively collect the scattered echoes from the light spot area and optimize the optical power coupled to the multimode fiber 8.

[0065] The second step is data acquisition. The rotating target 12 is controlled to rotate at a preset stable speed. Rotate. Start the data acquisition card 10 and acquire the beat frequency time-domain electrical signal output by the photodetector 9 at the set high sampling rate. After continuous acquisition for a period of time, transmit the data to the host 11.

[0066] The third step is signal processing and speed calculation. The processing software in host 11 performs a fast Fourier transform on the acquired beat frequency time-domain electrical signal to obtain its power spectral density map, i.e., the rotating Doppler spectrum. .like Figure 3 As shown, the spectrum exhibits a series of equally spaced discrete spectral peaks. The software automatically identifies these peaks using a peak detection algorithm and calculates the frequency interval between adjacent peaks. .

[0067] Step four, velocity calculation and output. Based on the core physical relationship of this invention: rotational angular velocity. Frequency spacing between adjacent spectral peaks satisfy The calculated Substitute the values ​​into the equation to obtain the target's rotational speed. (Unit: rad / s). The software displays and stores the final speed result on the interface.

[0068] The principle of the speed measurement method will be explained below.

[0069] like Figure 1 As shown. When the fundamental Gaussian light is emitted onto the surface of a rotating target, the amplitude of the echo field scattered in free space can be expressed as:

[0070] (1)

[0071] definition Represents a cylindrical coordinate system. express polar coordinates on the receiving plane Indicates radial distance. Indicates the polar angle;

[0072] Formula (1) is used to describe the situation in the receiving plane (i.e. On the plane, the complex amplitude of the scattered light field changes with time. and polar coordinates on the plane The changing relationship.

[0073] In formula (1), The fundamental Gaussian light field distribution:

[0074] (2)

[0075] In the formula, The normalized amplitude of the Gaussian light. Let be the radius of the Gaussian waist.

[0076] In formula (1), Modulation function for rotating target surface:

[0077] (3)

[0078] in For rotational speed, For the first The complex amplitude of the modulation factor. Then the scattered light field of formula (1) can be rewritten, and the amplitude of the echo light field. for:

[0079] (4)

[0080] When the scattered light field is coupled into the input end face of a multimode fiber, the field in the fiber can be unfolded into a superposition of fiber modes:

[0081] (5)

[0082] in, For superposition fields, It is a normalized fiber optic mode. and These represent the OAM order and radial order, respectively. Complex exponential mode basis vectors are used. The mode coefficients are then given by the overlap integral:

[0083] (6)

[0084] In the formula, is For fiber optic mode, it is the conjugate complex number.

[0085] Substituting equation (6) into the scattered light field equation (4), and considering the angular integral relationship... We can obtain:

[0086] (7)

[0087] Among them, the weighting coefficient (8)

[0088] In the formula, For the first The complex amplitude of the first modulation factor; The complex amplitude of the basis vector is related to the radial position r.

[0089] In multimode fiber, the echo laser mode propagates at a constant propagation time. Propagation, therefore the total field at position z for:

[0090] (9)

[0091] The beat frequency signal strength detected by the photodetector is ,Right now:

[0092] (10)

[0093] In the formula, The complex conjugate of the weighting coefficients. The complex amplitude of the basis vectors related to the radial position of the scattered light signal. The propagation constant of the scattered light signal is given by the time oscillation term. Corresponding mode and The beat frequency between them. Ignoring the DC component, the beat frequency signal can be represented as a superposition of a series of harmonics:

[0094] (11)

[0095] in, This indicates the complex conjugate of the preceding term;

[0096] coefficient And satisfy , The weighting coefficients of the scattered light signal are complex conjugates. The difference in orbital angular momentum order between adjacent pairs of modes. ,right Perform Fourier transform:

[0097] (12)

[0098] In the formula, The laser's circular frequency, due to It is a real signal, and its spectrum exhibits Hermitian symmetry, satisfying... Taking only the positive frequency portion, we get:

[0099] (13)

[0100] This equation shows that the spectrum consists of a series of frequencies located at... The discrete spectral lines at the location are composed of amplitudes of The frequency shift magnitude is The frequency interval between adjacent spectral peaks is:

[0101] (14)

[0102] Therefore, it can be concluded that by measuring the frequency interval between adjacent spectral peaks... The magnitude of the rotational speed can then be determined as: .

[0103] The following two embodiments briefly describe a rotating Doppler velocimetry method and apparatus for Gaussian mode transmission and multimode fiber reception according to the present invention.

[0104] Example 1: Measuring the rotational Doppler spectrum and velocity measurement accuracy of a target under different preset rotational speeds and attitudes.

[0105] In this embodiment, based on the rotating Doppler velocimetry method and apparatus for Gaussian mode transmission and multimode fiber reception of the present invention, the rotation speed is first preset. The frequency was set to 70Hz, and then the rotating Doppler spectrum and frequency shift interval velocity measurement accuracy were measured. Figure 3 The experimentally measured rotating Doppler spectrum distribution is presented. From the spectral intervals, it can be calculated that the measurement accuracy of the method and apparatus of this invention reaches 0.8%.

[0106] Example 2: Influence of different multimode fiber core diameters on velocity measurement accuracy

[0107] In this embodiment, we change the core diameter of the multimode fiber, and then, based on the rotating Doppler velocimetry method and apparatus of the present invention for Gaussian mode transmission and multimode fiber reception, we measure the rotating Doppler spectral distribution and relative velocity measurement error under the same target rotation speed and attitude. Figure 4 The relative error measurement results for different multimode fiber core diameters are presented. The measurement results are in good agreement with the preset values, further proving the effectiveness and practicality of the present invention.

[0108] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A rotating Doppler velocimeter method for Gaussian mode transmission and multimode fiber reception, characterized in that, Includes the following steps: S1. Light emission and scattering steps: A single-mode Gaussian beam is emitted toward the rotating target surface. The single-mode Gaussian beam is scattered by the target surface to form a scattered light field carrying target rotation information. S2. Multimode reception and coupling steps: The scattered light field is received using a multimode fiber, and the scattered light field is coupled into the multimode fiber to excite multiple transmission modes with different orbital angular momentum orders. S3. Signal detection and acquisition steps: Detect the optical signal output by the multimode fiber to obtain the beat frequency time-domain signal generated by the pairwise interference between the multiple transmission modes; S4. Spectrum analysis and velocity measurement steps: Perform spectrum analysis on the beat frequency time domain signal to obtain a rotating Doppler spectrum containing a series of equally spaced spectral peaks, and calculate the rotation speed of the rotating target based on the frequency interval between adjacent spectral peaks.

2. The rotating Doppler velocimetry method for Gaussian mode transmission and multimode fiber reception according to claim 1, characterized in that, The step S1 of emitting a single-mode Gaussian beam toward the rotating target surface specifically includes: A narrow-linewidth laser is generated; the narrow-linewidth laser is coupled into a single-mode fiber for transmission; the Gaussian beam output from the single-mode fiber is sequentially expanded, collimated, and polarized to form a linearly polarized single-mode Gaussian beam with controllable parameters, which is then irradiated onto the surface of the rotating target.

3. The rotating Doppler velocimetry method for Gaussian mode transmission and multimode fiber reception according to claim 1, characterized in that, Step S2, which involves receiving the scattered light field using a multimode fiber, specifically includes: The echo light scattered by the target surface is collected using a receiving optical system; a bandpass filter is set in the optical path of the receiving optical system to filter out stray light other than the laser wavelength in the echo light; the filtered echo light is coupled into the input end face of a multimode optical fiber.

4. The rotating Doppler velocimetry method for Gaussian mode transmission and multimode fiber reception according to claim 1, characterized in that, In step S4, the rotating Doppler spectrum for: In the formula, For frequency, This represents the difference in orbital angular momentum order between adjacent pairs of modes. For rotational speed, For amplitude, This is the Dirac function.

5. The rotating Doppler velocimetry method for Gaussian mode transmission and multimode fiber reception according to claim 4, characterized in that, Step S4, which calculates the rotational speed of the rotating target based on the frequency interval between adjacent spectral peaks, specifically includes: Obtain the frequency interval between adjacent spectral peaks in the rotating Doppler spectrum. According to the formula Calculate the rotational speed of the rotating target. .

6. The rotating Doppler velocimetry device for Gaussian mode transmission and multimode fiber reception according to claim 1, used to implement the method of any one of claims 1 to 5, characterized in that, include: A laser emission module is used to generate and shape a single-mode Gaussian beam and irradiate it onto the surface of a rotating target (12); The light receiving and conversion module is used to receive the scattered echo light from the surface of the target (12) and convert it into an electrical signal; A signal processing module is used to process the electrical signal to obtain the rotation speed of the rotating target; The optical receiving and conversion module includes a multimode optical fiber (8) for receiving the scattered echo light and exciting multiple transmission modes therein, wherein the electrical signal is a beat frequency signal generated by interference between the multiple transmission modes.

7. The rotating Doppler velocimetry device for Gaussian mode transmission and multimode fiber reception according to claim 6, characterized in that, The laser emitting module includes: Narrow linewidth laser (1) is used to generate Gaussian mode beams; A single-mode fiber (2) is connected at its input end to the output end of the narrow linewidth laser (1) for transmitting single-mode Gaussian light; A beam expander collimator (3) is connected to the output end of the single-mode fiber (2) and is used to modulate the radius and divergence angle of the output single-mode Gaussian light. A polarization modulation component is disposed in the outgoing optical path of the beam expander collimator (3) and is used to modulate the polarization state of the output beam.

8. The rotating Doppler velocimetry device for Gaussian mode transmission and multimode fiber reception according to claim 7, characterized in that, The polarization modulation component includes: A half-wave plate (4) is placed in the optical path behind the beam expander collimator (3) to adjust the ratio of horizontal and vertical polarization components; A linear polarizer (5) is placed in the optical path behind the half-wave plate (4) to control the output light to be linearly polarized.

9. The rotating Doppler velocimeter device for Gaussian mode transmission and multimode fiber reception according to claim 8, characterized in that, The optical receiving and conversion module includes: A bandpass filter (6) is used to filter out rotating Doppler echo signals of a specific wavelength; The receiving optical system (7) is placed in the scattered echo optical path behind the bandpass filter (6) to collect the echo light signal scattered by the target, wherein the echo light signal scattered by the target is a multimode optical signal; The multimode optical fiber (8) has its input end face located at the image plane or conjugate plane of the receiving optical system (7) for transmitting the received multimode optical signal; A photodetector (9) is connected to the output end of the multimode fiber (8) and is used to convert the multimode interference light signal output by the multimode fiber (8) into a beat frequency time-domain electrical signal.

10. The rotating Doppler velocimetry device for Gaussian mode transmission and multimode fiber reception according to claim 9, characterized in that, The signal processing module includes: The data acquisition card (10) is connected to the photodetector (9) and is used to convert the beat frequency time-domain electrical signal into a digital signal. The host (11) is connected to the data acquisition card (10) and is used to perform spectrum analysis on the digitized time-domain signal, identify the spectral peaks with equal intervals in the spectrum and calculate the frequency intervals, and then calculate the rotation speed based on the frequency intervals.

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