Laser speed and distance measurement integrated device based on optical frequency comb and working method of laser speed and distance measurement integrated device

Abstract

The invention relates to a laser speed measurement and distance measurement integrated device based on an optical frequency comb and a working method thereof, and belongs to the field of optical measurement. The laser speed measurement and distance measurement integrated device comprises an optical comb light source module, an amplification module, a filtering module, a light splitting coupling module and a speed measurement and distance measurement and state monitoring module; the optical comb light source module is used for outputting a plurality of wavelength signals; the amplification module adopts a two-stage amplification structure; the light splitting coupling module comprises a demultiplexer, a circulator, an optical antenna, a Faraday polarimeter and an optical fiber coupler; the speed and distance measurement and state monitoring module comprises a photoelectric detector, a data acquisition card and an FPGA signal processing unit, and the FPGA signal processing unit is used for calculating the speed and distance and counting the packet loss rate. According to the invention, error rate is eliminated by using redundancy in data, accuracy is improved, synchronous high-precision measurement of speed and distance is realized through multi-wavelength cooperative measurement and real-time monitoring of packet loss rate, and the system has the advantages of wide dynamic range, environmental interference resistance, high system integration level and the like.

Description

Technical Field

[0001] This invention relates to an integrated laser velocity and distance measurement device based on an optical frequency comb and its working method, belonging to the field of optical measurement technology. Background Technology

[0002] In the field of optical measurement, the synchronous measurement of the speed and distance of a target object is a core requirement, and it is widely used in intelligent transportation (real-time monitoring of vehicle speed and distance to ensure safety), industrial automation (accurate acquisition of workpiece movement speed and position to achieve closed-loop control), aerospace (long-distance monitoring of aircraft dynamic parameters to ensure mission stability) and other scenarios.

[0003] Traditional optical measurement techniques have significant limitations, often employing a single-function design: to simultaneously acquire velocity and distance information, two independent systems are typically required—one for laser velocimetry and the other for laser ranging. This separate approach has prominent drawbacks:

[0004] 1. Speed ​​measurement and distance measurement functions are often implemented separately, or although they are integrated, they lack a unified time reference, resulting in data asynchrony and affecting the correlation and reliability of measurement results;

[0005] 2. The signal processing link design is unreasonable. The single amplification or the structure of filtering before amplification is prone to signal loss or noise interference, which limits the improvement of accuracy. The speed measurement error of the existing solution is generally greater than 0.3m / s.

[0006] 3. It lacks the ability to adapt to environmental changes and has not established an effective state monitoring and feedback adjustment mechanism, making it prone to measurement failure in complex weather or dynamic target diffuse reflection scenarios;

[0007] In recent years, optical comb technology, with its highly stable multi-wavelength output and precise temporal coherence, has provided a new direction for overcoming bottlenecks. Its comb-shaped spectrum can provide multiple frequency-stable measurement "references," possessing the potential to support multi-parameter measurements. However, current optical comb measurement technology mainly focuses on high-precision spectral analysis or absolute distance measurement, and has not yet formed a mature solution that utilizes its multi-wavelength characteristics to deeply integrate velocity and distance measurement functions, thus failing to achieve synchronized, high-precision integrated measurement. Therefore, developing an integrated velocity and distance measurement device with high integration, excellent synchronization, high environmental adaptability, and reliable data has become a key issue that urgently needs to be addressed in the field of optical measurement. Summary of the Invention

[0008] To address the problems of low separation and integration of speed and distance measurement systems, poor environmental adaptability, and lack of data reliability in existing technologies, this invention proposes an integrated laser speed and distance measurement device and its working method based on an optical frequency comb. It utilizes data redundancy to eliminate bit error rate and improve accuracy. Through multi-wavelength collaborative measurement and real-time monitoring of packet loss rate, it achieves synchronous high-precision measurement of speed and distance. It also has advantages such as wide dynamic range, resistance to environmental interference, and high system integration.

[0009] The present invention adopts the following technical solution:

[0010] A laser velocity and distance measurement integrated device based on an optical frequency comb includes an optical comb light source module, an amplification module, a filtering module, a beam splitting coupling module, and a velocity and distance measurement and status monitoring module.

[0011] The optical comb light source module is used to output a spectrum containing multiple wavelengths ( , , ... The optical comb signal provides a stable multi-wavelength light source basis for speed and distance measurement. For the sake of simplicity, this invention uses only three wavelengths, but more wavelengths can actually be used for measurement. λ1 and λ2 are used as measurement wavelengths for coordinated speed and distance measurement, while λ3 is used as a reference wavelength for packet loss rate monitoring and system status assessment, and also as a time synchronization signal source.

[0012] The amplification module includes a first-stage amplifier and a second-stage amplifier. To compensate for signal losses during transmission and processing and ensure that the signal strength of all wavelengths meets the requirements for long-distance detection, this invention adopts a two-stage amplification structure of "amplification-filtering-amplification". The first-stage amplification provides sufficient signal strength for the subsequent filtering process, avoiding filtering losses that lead to an excessively weak effective signal. The second-stage amplification ensures that the optical signal still has a sufficient signal-to-noise ratio during long-distance transmission and in complex environments. This two-stage amplification design ensures that the reference signal λ3 and the measurement signals λ1 and λ2 have sufficient energy to reach the target and be reflected back, laying a solid foundation for subsequent packet loss rate calculation and accurate measurement.

[0013] The optical splitting and coupling module includes a demultiplexer, a circulator, an optical antenna, a Faraday rotator, and an optical fiber coupler. The demultiplexer separates the amplified optical signals into three paths. Two of these paths are reflected back to the circulator after hitting the target object via the circulator and the optical antenna, and then enter the optical fiber coupler. The third path changes the direction of the optical signal through the Faraday rotator and directly enters the optical fiber coupler. The optical fiber coupler efficiently couples the three optical signals λ1, λ2, and λ3 into a single composite optical signal with a coupling efficiency greater than 95%. The purpose is to allow the three wavelengths of optical signals to share the same optical transmission and reception link, ensuring that they experience the same transmission path and environmental influences (such as atmospheric scattering and temperature changes).

[0014] The speed and distance measurement and status monitoring module includes a photodetector, a data acquisition card, and an FPGA signal processing unit. The photodetector is used to convert the received light signal into an electrical signal, and the FPGA signal processing unit is used for signal processing, including calculating speed and distance and calculating packet loss rate.

[0015] Preferably, it also includes a time synchronization module, which generates synchronization pulse signals and sends them to the data acquisition card of the speed and distance measurement and status monitoring modules through electrical signal transmission lines, providing a unified and accurate timestamp for the synchronous measurement of speed and distance and the time statistics of packet loss rate.

[0016] Preferably, if the target object is static, a plane mirror with high reflectivity is installed on the target object for reflection; if the target object is dynamic, the diffuse characteristics of the target object itself are used for reflection, and no additional reflection device is required.

[0017] Preferably, the optical comb light source module uses a fiber mode-locked laser as the light source, and more preferably an erbium-doped fiber mode-locked laser;

[0018] The filtering module employs a WSS filter. The core of the filtering module is the programmable wavelength selection switch (WSS), a key component for achieving "precise multi-wavelength selection," directly determining the purity of subsequent measurement signals and the system's anti-interference capability. The WSS filtering process is as follows:

[0019] First, the input receives the optical comb signal (containing approximately 1000 comb teeth in the 1520-1570nm range) after the first-stage amplification, equivalent to "multiple vehicles with different destinations (different wavelengths)". Then, based on the wavelength parameters preset by the host computer (specific wavelength values ​​of λ1, λ2, λ3, etc.), the optical control unit inside the WSS accurately identifies and filters the target wavelength while blocking all non-target wavelength clutter signals, much like "a traffic controller only allowing vehicles to pass to designated destinations". Finally, the filtered target wavelength signal maintains its original phase and polarization characteristics and is output to the subsequent second-stage amplification module in a low-loss form, ensuring that the signal quality is not affected by the control process. This guarantees that the optical signal entering the subsequent system is pure and meets the requirements.

[0020] Preferably, there are two circulators. For each circulator, 1, 2, and 3 are the three optical signal ports of the circulator. The arrows represent the unidirectional transmission path of the optical signal, that is, the optical signal can only be transmitted from port 1 to port 2 and port 2 to port 3, and cannot be transmitted in reverse. This can realize the separation of the optical paths of the emitted light and the reflected light, and avoid the emitted light from interfering with the reception of the reflected light.

[0021] A method for operating the aforementioned laser velocity and distance measurement integrated device based on an optical frequency comb includes:

[0022] S1, the optical comb light source module outputs an optical comb signal containing multiple wavelengths, where λ1 and λ2 are used as measurement wavelengths and λ3 is used as a reference wavelength; the optical comb signal passes through a first-stage amplifier and a filtering module in sequence, and finally enters the demultiplexer from the output of the second-stage amplifier.

[0023] S2, the demultiplexer separates the amplified optical signals λ1, λ2, and λ3 into three branches. The optical signals in the branches containing λ1 and λ2 enter the circulator, are reflected back to the circulator after hitting the target object by the optical antenna, and then enter the fiber coupler. The optical signal in the branch containing λ3 changes the direction of the optical signal through the Faraday rotator and enters the fiber coupler directly. The fiber coupler couples the three optical signals λ1, λ2, and λ3 into a composite optical signal, which is then detected by the photodetector.

[0024] S3, the photodetector converts the received optical signal into an electrical signal. The data acquisition card, triggered by the electrical pulse of the time synchronization module, synchronously acquires the electrical signal converted by the photodetector, ensuring that the acquisition action and the optical signal return timing are accurately matched.

[0025] S4, the FPGA signal processing unit, calculates speed and distance, and calculates packet loss rate.

[0026] Preferably, the process of calculating speed and distance in step S4 is as follows:

[0027] ① Calculation speed

[0028] Reference frequency calibration: The optical comb light source module is controlled to stably output wavelength signals λ1 and λ2 for speed measurement. After the signal is transmitted to the photodetector through the optical path, it is converted into an initial electrical signal. An FFT operation is performed on the initial electrical signal, and the characteristic frequencies corresponding to the λ1 and λ2 signals in the operation result are extracted as the initial reference frequency f0 (optical path noise interference needs to be eliminated, and the average value of 3 repeated measurements is taken to reduce the initial error).

[0029] Real-time frequency acquisition: After the target measurement is started, the λ1 and λ2 signals are transmitted through the optical path and focused onto the target object by the optical antenna. The signals reflected by the target return to the photodetector along the original optical path. The photodetector converts the reflected light signal into a real-time electrical signal and performs an FFT operation on the real-time electrical signal with parameters consistent with those in the reference frequency calibration stage to extract the real-time characteristic frequency f1 corresponding to the reflected signal.

[0030] The frequency change δf is calculated by taking f1 and f0 corresponding to the λ2 signal. The frequency change δf = f1 - f0. λ1 serves as a redundancy backup. When the λ2 signal is distorted, it can be switched to λ1 to ensure the continuity of velocity measurement. The sign corresponds to the target motion state: when the target approaches the measuring device, the reflected light produces a Doppler blue shift, the real-time frequency f1 is greater than the reference frequency f0, and δf is a positive value; when the target moves away from the measuring device, the reflected light produces a Doppler red shift, f1 is less than f0, and δf is a negative value. The final δf is directly related to the frequency offset caused by the target motion, providing a core parameter for subsequent velocity calculation.

[0031] It should be noted that the parameter settings for FFT operation must match the signal characteristics. For example, the sampling frequency must meet the Nyquist criterion (not less than twice the highest frequency of λ1 and λ2 signals), and the frequency resolution must be controlled within 1Hz to ensure the extraction accuracy of the reference frequency and real-time frequency and avoid the transmission of δf calculation errors to the speed result.

[0032] Velocity v = (δf × λ2) / (2 × f0);

[0033] This invention is based on a redundant design of multiple velocity measurement wavelengths (λ1, λ2, ...) using a single optical comb. The frequency change δf is obtained by performing FFT analysis on the reflected λ1, λ2, ... electrical signals. The velocity is directly calculated by combining the Doppler effect formula v = (δf×λ2) / (2×f2). The redundancy of λ1, λ2, ... data can avoid the influence of single-channel signal distortion and reduce false alarms in the system. If a velocity signal is lost, other channels can be switched immediately.

[0034] ② Calculate the distance

[0035] Reference template signal storage: First, the wavelength of λ3 is fixed by temperature control calibration of the FP standard etalon (stabilized to 25.00℃±0.01℃) to keep the frequency and waveform of the λ3 signal output by the optical comb light source module stable. This λ3 signal serves as a time synchronization reference signal. After being converted into an electrical signal by a photodetector, waveform data within its complete cycle is collected. After removing the initial transmission noise, a standard template signal S0(t) is generated and stored in the algorithm cache module. The template signal includes key features such as waveform peak value and rising edge slope to ensure matching accuracy.

[0036] Reflected signal waveform acquisition and cross-correlation calculation:

[0037] During target measurement, the velocity signals λ1 and λ2 are reflected back to the photodetector after being reflected by the target object. The real-time electrical signal waveforms converted from the two reflected signals are simultaneously acquired and denoted as S1(t) (λ1 reflected signal) and S2(t) (λ2 reflected signal), respectively. Then, S1(t) and S2(t) are substituted with the standard template signal S0(t) into the cross-correlation function for calculation, i.e. , During the operation, the waveforms of the two signals are aligned by iteratively adjusting the τ value.

[0038] Round-trip time extraction and Δt calculation: The core characteristic of cross-correlation function operation is that "the function value reaches its peak when the two signal waveforms are most similar". The τ value corresponding to the peak value is the round-trip flight time of a single signal from the device to the target object after reflection. τ1 (round-trip time of λ1 signal) corresponding to the peak value of R2(τ) and τ2 (round-trip time of λ2 signal) corresponding to the peak value of R2(τ) are extracted respectively. Considering that the single signal may have time deviation caused by reflection interference, the arithmetic mean of τ1 and τ2 is taken to obtain a stable round-trip flight time difference Δt, which provides accurate time parameters for distance calculation.

[0039] Distance d = c·Δt / 2.

[0040] It should be noted that S1(t) and S2(t) need to be preprocessed (such as DC component removal and low-pass filtering) before cross-correlation calculation to filter out environmental noise and optical path interference introduced during reflection, so as to avoid noise causing cross-correlation peak shift. At the same time, the iteration step size needs to be controlled within 1ns to match the high-speed transmission characteristics of optical signals and ensure the accuracy of round-trip time extraction.

[0041] This invention employs a single optical comb with multi-wavelength collaborative design, selecting a specific reference wavelength λ. n As a benchmark, λ1, λ2, ... and λ are measured respectively using a cross-correlation algorithm. n The round-trip flight time differences Δt1, Δt2, ... are used to calculate the distance using the formula d = c·Δt / 2; λ is also utilized simultaneously. nReal-time monitoring of packet loss rate and coordinated adjustment of system parameters to compensate for environmental interference, along with multi-beam laser velocimetry, provide sufficient data redundancy and further reduce errors.

[0042] Preferably, the process of calculating the packet loss rate in step S4 is as follows:

[0043] Using the period set by the time synchronization module as the statistical unit, the system periodically checks whether the λ3 signal has been successfully received (based on the detection of a valid rising edge of the λ3 signal). The total number of transmitted pulses within the period is determined based on the repetition frequency of the light source, and the number of valid rising edges of the λ3 signal detected within the period is taken as the number of successfully received pulses.

[0044] Packet loss rate = (Total number of transmitted pulses - Number of successfully received pulses) / Total number of transmitted pulses × 100%.

[0045] Preferably, the present invention dynamically adjusts and remeasures based on the packet loss rate to ensure the reliability of the output results.

[0046] The status is assessed based on the packet loss rate. When the packet loss rate is lower than the system's preset 1% threshold, it indicates that the current measurement environment is excellent, the optical link is unobstructed, and the measurement results are highly reliable.

[0047] When the packet loss rate exceeds the system's preset 1% threshold, the system immediately determines that the current measurement environment has deteriorated, the optical signal-to-noise ratio is too low, and the reliability of the recently measured set of speed and distance data is questionable. The FPGA signal processing unit automatically triggers the dynamic calibration program.

[0048] Preferably, the dynamic calibration procedure includes:

[0049] (1) Send a calibration command to the amplification module to increase the gain of the secondary amplifier and offset the signal attenuation caused by the rainstorm by increasing the power of the transmitter;

[0050] At the same time, a parameter adjustment command is sent to the data acquisition card to extend the sampling time from 20ns to 50ns;

[0051] (2) After the instruction is issued, the system enters a 100ms temporary verification period to continuously monitor the packet loss rate. If the packet loss rate decreases within 100ms but does not reach the threshold, the FPGA signal processing unit will further increase the gain of the first-stage amplifier to provide a higher initial power basis for the second-stage amplifier.

[0052] (3) If the packet loss rate drops below the threshold within 100ms, or if the packet loss rate drops below the threshold after another 100ms verification, the system determines that the current optical link has recovered to a reliable state and restarts the normal measurement process with the current parameters; at this time, the FPGA signal processing unit will mark the status of the previously questionable data and package the first set of valid data after calibration (such as speed 10.2m / s, distance 14.98km, packet loss rate 0.8%) together with the calibration parameters (amplifier gain, integration time) to ensure data traceability;

[0053] (4) If the packet loss rate remains below 0.5 times the threshold within the next 10 minutes, the system determines that the deteriorating environment (rainstorm) has weakened or stopped, and automatically resets each parameter (amplifier gain, integration time, temperature control accuracy) to the initial value to avoid module wear caused by long-term high-power operation and balance measurement performance and equipment life.

[0054] For any details not covered in this invention, please refer to the prior art.

[0055] The beneficial effects of this invention are as follows:

[0056] 1. Significantly Improved Measurement Accuracy: This invention employs a graded amplification system adapted to a high signal-to-noise ratio, coupled with a "first amplification - then filtering - then amplification" architecture. This ensures sufficient power for the speed measurement signal even at long distances and in diffuse reflection scenarios, avoiding signal loss caused by traditional single amplification and expanding the applicable distance for high-speed target speed measurement (supporting speed measurement at a distance of 15km). This invention utilizes two-stage amplification + FP etalon wavelength fine-tuning, combined with a high-precision algorithm, achieving a speed measurement error of <0.1m / s and a ranging accuracy of 0.15m, superior to traditional single-measurement schemes.

[0057] 2. Integrated design for high efficiency and collaboration: The single optical comb architecture of this invention integrates speed measurement, distance measurement, and status monitoring (packet loss rate). It is equipped with an independent time synchronization module to provide a unified time reference, ensuring data synchronization without delay. It eliminates the need for multiple systems to be spliced ​​together, enabling speed measurement, distance measurement, and status monitoring to be performed simultaneously without splitting the measurement process, thus improving work efficiency.

[0058] 3. Enhanced environmental adaptability: This invention uses λ3 packet loss rate as a real-time feedback indicator, which can dynamically adjust amplifier gain and signal processing parameters. It can cope with signal attenuation in complex environments such as heavy rain and diffuse reflection, ensuring data reliability.

[0059] 4. Superior system stability and compatibility: This invention adopts a highly stable core component (mode-locked laser), with strong adaptability between modules, taking into account both laboratory calibration and dynamic scene (vehicle, train) measurement needs; speed measurement adopts λ1 and λ2 data redundancy, and distance measurement relies on the reference wavelength benchmark. If any single signal is abnormal, backup data can be switched to eliminate the bit error rate.

[0060] 5. Lower system complexity and cost: This invention adopts a single optical comb + simplified module design, which eliminates the need for dual optical comb repetition frequency calibration or multi-phase meter coordination, resulting in a compact structure that is easy to miniaturize. Attached Figure Description

[0061] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0062] Figure 1 This is a schematic diagram of the integrated laser velocity and distance measurement device based on an optical frequency comb according to the present invention. Detailed Implementation

[0063] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. However, this is not the only description; all aspects not described in detail herein are based on conventional techniques in the art.

[0064] Example 1

[0065] A laser velocity and distance measurement integrated device based on an optical frequency comb, such as Figure 1 As shown, it includes an optical comb light source module, an amplification module, a filtering module, a beam splitting coupling module, and a speed and distance measurement and status monitoring module; each module is connected through a single-mode optical fiber or a high-precision circuit to form a compact and efficient integrated measurement system.

[0066] The optical comb light source module uses an erbium-doped fiber mode-locked laser to output multiple wavelengths ( , , ... The optical comb signal from this laser model provides ample available wavelength resources for subsequent multi-wavelength collaborative measurements. For simplicity, this system selects only three specific wavelengths: λ1: as the main velocity measurement signal, its frequency variation will be used to calculate the target velocity; λ2: also as the main velocity measurement signal, its frequency variation will be used to calculate the target velocity, providing data redundancy; λ3: as a reference signal, providing time synchronization information and a reference frequency.

[0067] The amplification module includes a primary amplifier and a secondary amplifier. To compensate for optical signal losses during transmission and processing, and to avoid the problem of weak signals after filtering being difficult to amplify, this embodiment adopts a two-stage amplification structure of "amplification-filtering-amplification" to precisely control the optical signal power and ensure wavelength selection efficiency: The first-stage amplification (before filtering) uses an erbium-doped fiber amplifier (EDFA). After wavelength selection (filtering), the signal passes through another fiber amplifier. After the filtering module selects the three target optical signals λ1, λ2, and λ3, these three beams enter the high-power fiber amplifier together. This step ensures that the optical signal still has a sufficient signal-to-noise ratio in scenarios such as long-distance transmission (e.g., 15km) and target diffuse reflection, providing stable optical energy support for speed measurement, ranging, and packet loss rate monitoring.

[0068] The core of the filtering module is the programmable wavelength selective switch (WSS), which selects three target wavelengths λ1, λ2, and λ3 from the multi-wavelength optical signal after the first stage amplification. It can ensure the purity of the output optical signal while maintaining signal power.

[0069] The optical splitting and coupling module includes a demultiplexer, a circulator, an optical antenna (lens group), a Faraday rotator, and an optical fiber coupler. The demultiplexer is used to separate the two-stage amplified optical signals and distribute them to three paths. Two of the paths are reflected back to the circulator after hitting the target object via the circulator and the optical antenna, and then enter the optical fiber coupler. The third path changes the direction of the optical signal through the Faraday rotator and directly enters the optical fiber coupler. The optical fiber coupler efficiently couples the three optical signals λ1, λ2, and λ3 into a single composite optical signal.

[0070] Optical antennas (lens groups) can focus emitted light signals, increase light energy density, extend measurement distance (such as supporting long-distance measurement of 15km), and enhance the ability to converge reflected echo light signals, thereby improving signal reception efficiency.

[0071] The circulator isolates the emitted and reflected light paths, preventing strong signals from the emitter from directly entering the detector and causing damage. This ensures the detector only receives the reflected light signal carrying the target parameters, guaranteeing accurate signal detection. In this embodiment, the emitted light signals can share the same optical transmit and receive links, ensuring they undergo identical transmission paths and environmental influences.

[0072] The speed and distance measurement and status monitoring module includes a photodetector, a data acquisition card, and an FPGA signal processing unit. The photodetector is used to convert the received light signal into an electrical signal. The data acquisition card can simultaneously acquire analog signals from the detector and trigger signals from the time synchronization module. The FPGA signal processing unit is used for signal processing, including calculating speed and distance and calculating packet loss rate.

[0073] The FPGA signal processing unit is responsible for the following three core tasks:

[0074] (1) Speed ​​calculation: The received λ2 signal is subjected to fast Fourier transform (FFT) in real time to detect the frequency change δf.

[0075] (2) Distance calculation: The round-trip flight time difference Δt of the signals λ1, λ2 and λ3 is accurately measured by cross-correlation algorithm.

[0076] (3) Packet loss rate statistics: Under the pulse control of the time synchronization module, the λ3 signal is periodically checked to see if it is successfully received.

[0077] Example 2

[0078] An integrated laser speed and distance measurement device based on an optical frequency comb, as described in Embodiment 1, differs in that it also includes a time synchronization module for generating synchronization pulse signals, which are transmitted via electrical signal transmission lines to the data acquisition cards of the speed and distance measurement and status monitoring modules, providing a unified and accurate timestamp for the synchronous measurement of speed and distance and the time statistics of packet loss rate.

[0079] Example 3

[0080] An integrated laser velocity and distance measurement device based on an optical frequency comb, as described in Example 2, differs in that if the target object is static, a high-reflectivity plane mirror is set on the target object for reflection; if the target object is dynamic, the diffuse characteristics of the target object itself are used for reflection.

[0081] Example 4

[0082] A laser velocity and distance measurement integrated device based on an optical frequency comb, as described in Example 3, except that the number of circulators is two.

[0083] Example 5

[0084] A working method for an integrated laser speed and distance measurement device based on an optical frequency comb is described below. The following embodiment takes the measurement of the speed and distance of a high-speed train as an example to illustrate the working process and key parameter settings of the device in detail. The entire process is divided into four stages: system initialization, optical signal processing and transmission, signal reception and multi-parameter measurement, and data processing and intelligent output.

[0085] System initialization phase (0-100ms):

[0086] First, start and preheat the light source. Turn on the optical comb light source module, set its output power to 20mW and repetition frequency to 100MHz, and start the preheating program for 100ms. After the output power, center wavelength, and repetition frequency of the light source stabilize (power fluctuation < ±0.1mW, wavelength drift < ±1pm), proceed to the next stage.

[0087] Then, the module parameters are configured using the host computer software.

[0088] For the amplification module: set the first-stage EDFA gain to 23dB (input 20mW → output 100mW), and the second-stage high-power amplifier gain to 7dB (filtered input approximately 50mW → output 500mW).

[0089] For the filter module (WSS): Configure three target wavelength channels with center wavelengths of 1530nm (λ1), 1545nm (λ2), and 1560nm (λ3), respectively, and set the filtering bandwidth of each channel to 10GHz.

[0090] For the speed measurement, distance measurement, and status monitoring module: configure the data acquisition card to have a sampling rate of 10GS / s, a sampling depth of 1M points, and set the trigger mode to "external trigger".

[0091] The FPGA loads the pre-compiled algorithm firmware, sets the frequency detection resolution to 1kHz, the time measurement resolution to 10ps, and the packet loss rate statistics period to 100ms.

[0092] Optical signal processing and transmission phase (100ms-100.1ms):

[0093] Multi-wavelength optical signal generation: The stabilized optical comb light source output contains multi-wavelength optical signals from approximately 1000 comb teeth in the range of 1520-1570nm, with a comb tooth spacing of 100MHz and an initial power of 20mW.

[0094] First stage amplification (before filtering): The optical signal first enters the first stage EDFA, where the power is amplified from 20mW to 100mW, providing sufficient signal strength for subsequent filtering;

[0095] Filtering and screening target wavelengths: The amplified optical signal enters the WSS filtering module, which filters out the three target optical signals λ1, λ2, and λ3. The total power after filtering is about 50mW (the power of a single signal is about 16-17mW, minus 3dB insertion loss).

[0096] Second-stage amplification (after filtering): The filtered λ1, λ2, and λ3 signals enter the second-stage high-power amplifier together, increasing the total power from 50mW to 500mW (the power of a single signal is about 160-170mW).

[0097] The mixed optical signal is separated and distributed to three branches:

[0098] For the branches containing λ1 and λ2: the original signal state is maintained, and they both enter the reflection module. FFT frequency analysis is used for velocity measurement.

[0099] Signal reception and multi-parameter measurement phase (100.1ms-100.1002ms):

[0100] Signal conversion and acquisition: The optical signal from the fiber optic coupler is first received by the high-speed photodetector and converted into a corresponding electrical signal.

[0101] The data acquisition card begins to acquire the electrical signal output by the photodetector when triggered by a 10ns pulse signal from the time synchronization module. The sampling duration is 200ns, and a total of 2000 sampling points are acquired.

[0102] Multi-parameter synchronous measurement: The FPGA signal processing unit and the data acquisition card work synchronously, executing three tasks in parallel:

[0103] ① Velocity Measurement: Perform Fast Fourier Transform (FFT) on the electrical signals corresponding to λ1 and λ2 to extract their frequency change δf. The FFT calculation accuracy can reach 1kHz, ensuring that the velocity measurement error is less than 0.1m / s. Specifically:

[0104] Reference frequency calibration: The optical comb light source module is controlled to stably output wavelength signals λ1 and λ2 for speed measurement. The signals are transmitted to the photodetector through the optical path and converted into initial electrical signals. FFT operation is performed on the initial electrical signals, and the characteristic frequencies corresponding to the λ1 and λ2 signals in the operation results are extracted as the initial reference frequency f0.

[0105] Real-time frequency acquisition: After the target measurement is started, the λ1 and λ2 signals are transmitted through the optical path and focused onto the target object by the optical antenna. The signals reflected by the target return to the photodetector along the original optical path. The photodetector converts the reflected light signal into a real-time electrical signal and performs an FFT operation on the real-time electrical signal with parameters consistent with those in the reference frequency calibration stage to extract the real-time characteristic frequency f1 corresponding to the reflected signal.

[0106] The frequency change is calculated by taking f1 and f0 corresponding to the λ2 signal. The frequency change δf = f1 - f0. λ1 serves as a redundancy backup. When the λ2 signal is distorted, it can be switched to λ1 to ensure the continuity of speed measurement.

[0107] Velocity v = (δf × λ2) / (2 × f0).

[0108] ② Distance measurement: Perform cross-correlation on the electrical signal corresponding to λ3 to calculate the round-trip flight time difference Δt between signals λ1, λ2, and λ3. Specifically:

[0109] Reference template signal storage: First, the wavelength of λ3 is fixed by temperature control calibration of the FP standard etalon (stabilized to 25.00℃±0.01℃) to keep the frequency and waveform of the λ3 signal output by the optical comb light source module stable. This λ3 signal serves as a time synchronization reference signal. After being converted into an electrical signal by a photodetector, waveform data within its complete cycle is collected. After removing the initial transmission noise, a standard template signal S0(t) is generated and stored in the algorithm cache module. The template signal includes key features such as waveform peak value and rising edge slope to ensure matching accuracy.

[0110] Reflected signal waveform acquisition and cross-correlation calculation:

[0111] During target measurement, the velocity signals λ1 and λ2 are reflected back to the photodetector after being reflected by the target object. The real-time electrical signal waveforms converted from the two reflected signals are simultaneously acquired and denoted as S1(t) (λ1 reflected signal) and S2(t) (λ2 reflected signal), respectively. Then, S1(t) and S2(t) are substituted with the standard template signal S0(t) into the cross-correlation function for calculation, i.e. , During the operation, the waveforms of the two signals are aligned by iteratively adjusting the τ value.

[0112] Round-trip time extraction and Δt calculation: The core characteristic of cross-correlation function operation is that "the function value reaches its peak when the two signal waveforms are most similar". The τ value corresponding to the peak value is the round-trip flight time of a single signal from the device to the target object after reflection. τ1 (round-trip time of λ1 signal) corresponding to the peak value of R2(τ) and τ2 (round-trip time of λ2 signal) corresponding to the peak value of R2(τ) are extracted respectively. Considering that the single signal may have time deviation caused by reflection interference, the arithmetic mean of τ1 and τ2 is taken to obtain a stable round-trip flight time difference Δt, which provides accurate time parameters for distance calculation.

[0113] Distance d = c·Δt / 2.

[0114] ③ Packet loss rate statistics: Check whether the rising edge of the λ3 signal is successfully detected within the current 100ms statistical period.

[0115] Using the period set by the time synchronization module as the statistical unit, the system periodically checks whether the λ3 signal has been successfully received. The total number of transmitted pulses within the period is determined based on the repetition frequency of the light source. The number of valid rising edges of the λ3 signal within the period is used as the number of successfully received pulses.

[0116] Packet loss rate = (Total number of transmitted pulses - Number of successfully received pulses) / Total number of transmitted pulses × 100%.

[0117] Data processing and intelligent output phase (100.1002ms-100.101ms):

[0118] Speed ​​calculation (based on Doppler effect): The FPGA algorithm detected the frequency change δf = 20MHz of the λ1 and λ2 signals in the reflected light through FFT analysis.

[0119] As the train moves toward the device, the frequency increases, and δf becomes a positive value.

[0120] According to the Doppler effect formula: v = (δf × λ²) / (2 × f²), where f² is the center frequency of λ² (approximately 193.9 THz), substituting the values, we get: v = (20 × 10⁻⁶ THz). 6 Hz × 1545×10 -9 m) / (2 × 193.9×10 12 Hz) ≈10.0m / s (i.e. 36km / h).

[0121] Distance calculation (based on time-of-flight method): The FPGA algorithm accurately measures the round-trip time difference Δt = 100 μs of the λ3 signal through cross-correlation analysis.

[0122] Combining the speed of light c = 3 × 10 8 The distance is calculated using the formula d = c·Δt / 2 (m / s).

[0123] d = (3×10 8 m / s × 100×10 -6 s) / 2 = 15,000m (i.e. 15km).

[0124] Packet loss rate calculation and status assessment: Within the current statistical period of 100ms, the system transmitted a total of 10,000 λ1 signal pulses (calculated from a repetition frequency of 100MHz).

[0125] The FPGA successfully detected 9,995 valid pulses, so the packet loss rate = (10,000 - 9,995) / 10,000 × 100% = 0.05%.

[0126] The packet loss rate is far below the system's preset 1% threshold, indicating that the current measurement environment is excellent, the optical link is unobstructed, and the measurement results are highly reliable.

[0127] Results output and storage: The FPGA packages the calculated speed v (10.0m / s), distance d (15km), packet loss rate (0.05%), and corresponding timestamps into data frames.

[0128] The data is transmitted to the host computer via the PCIe bus; the host computer software parses and displays the data, and stores the raw data and processing results to the hard disk.

[0129] The data is in CSV format and includes information such as timestamp, speed, distance, packet loss rate, and signal strength, completing a full measurement process.

[0130] One of the core advantages of this invention lies in its intelligent adaptability to complex environments, which is mainly achieved through real-time monitoring and feedback control of packet loss rate.

[0131] Suppose that during the measurement process, the weather suddenly changes and a heavy rain begins. Raindrops will cause strong scattering and attenuation of the light signal, resulting in a significant decrease in signal strength across all wavelengths.

[0132] At this point, the system will initiate the following intelligent response process:

[0133] 1. Increased packet loss rate: The FPGA detected that the packet loss rate of λ1 surged from 0.05% to 8% in a short period of time, exceeding the warning threshold of 1%;

[0134] 2. Status Judgment: The system immediately determines that the current measurement environment has deteriorated, the optical signal-to-noise ratio is too low, and the reliability of the just measured set of speed and distance data is questionable;

[0135] 3. Automatic calibration (matching two-stage amplification structure): The FPGA automatically triggers a dynamic calibration program.

[0136] (1) Send a command to the amplification module to increase the gain of the second-stage high-power amplifier from 7dB to 10dB (the output power is increased from 500mW to about 1000mW, and the single-beam signal power is increased to 320-340mW simultaneously) to offset the signal attenuation caused by the rainstorm by increasing the power of the transmitting end;

[0137] At the same time, a parameter adjustment command is sent to the data acquisition card to extend the sampling integration time from 20ns to 50ns, while reducing the signal detection threshold level (from the original 0.5μW to 0.2μW) to enhance the ability to capture weak reflection signals.

[0138] (2) After the calibration command is issued, the system enters a 100ms temporary verification period to continuously monitor the packet loss rate of λ1. If the packet loss rate drops from 8% to 1.2% within 100ms (still slightly higher than the threshold), the FPGA will further fine-tune the first-stage EDFA gain from 23dB to 25dB (input 20mW → output 158mW) to provide a higher initial power basis for the second-stage amplification;

[0139] (3) Result Confirmation and Output: After another 100ms verification, the packet loss rate of λ1 stabilized and dropped to 0.8% (below the 1% threshold). The system determined that the current optical link had recovered to a reliable state and restarted the normal measurement process. At this time, the FPGA would mark the status of the previously "questionable data" and package the first set of valid data after calibration (such as speed 10.2m / s, distance 14.98km, packet loss rate 0.8%) together with the calibration parameters (amplifier gain, integration time) to ensure data traceability;

[0140] (4) Reset after environmental recovery: If the packet loss rate remains below 0.5% for the next 10 minutes, the system will determine that the rainstorm has weakened or stopped and will automatically reset the parameters of each module (amplifier gain, integration time, temperature control accuracy) to the initial optimized value to avoid module wear caused by long-term high-power operation and balance measurement performance and equipment life.

[0141] In summary, the advantages of this invention are as follows:

[0142] Improve accuracy and eliminate error rate by using data redundancy: When packet loss occurs when measuring speed or distance in one channel, other backup optical links are immediately used to eliminate the adverse effects of error rate and packet loss rate by using data redundancy.

[0143] Hierarchical amplification architecture design: Breaking through the traditional amplification logic, it adopts a two-stage structure of "amplification-filtering-amplification". Before filtering, the signal power is increased to avoid noise interference after weak signal filtering; after filtering, it is amplified a second time to ensure that the signal meets the signal-to-noise ratio requirements of long-distance transmission and diffuse reflection scenarios, thus solving the performance bottleneck of single amplification schemes.

[0144] Multi-wavelength coordination and self-calibration mechanism: Different wavelengths are assigned "reference, velocity measurement, and distance measurement" functions respectively, and the same optical link is used to ensure consistency in environmental impact; the packet loss rate of the reference wavelength is used as the core feedback indicator, and the amplifier, data acquisition, temperature control and other module parameters are automatically adjusted when the environment deteriorates, so as to achieve stable all-weather measurement without manual intervention.

[0145] Multi-parameter parallel real-time processing solution: The core processing unit is built based on a high-performance FPGA, integrating algorithms such as frequency analysis, time measurement, and packet loss rate statistics to achieve multi-parameter parallel operation, which greatly improves the system response speed and meets the real-time monitoring requirements of high-speed moving targets.

[0146] The performance indicators of this invention have been verified as follows:

[0147] Laboratory static verification: the speed measurement error is controlled within a very small range, the fluctuation is small when repeated measurements are taken over a distance of 15km, the packet loss rate is stable during continuous 24-hour operation, and the accuracy and reliability of the core performance indicators meet the standards.

[0148] Verification in complex environments: In heavy rain scenarios, the self-calibration function can quickly bring the packet loss rate and velocity measurement error back to a reliable range; in long-distance diffuse reflection scenarios, the reflected echo signal can be captured stably; in wide temperature range environments, the ranging accuracy fluctuates little and has strong environmental adaptability.

[0149] System integration verification: The time stamp deviation between speed measurement and distance measurement data is extremely small, and the synchronization is excellent; the system power consumption and size are reasonably controlled, meeting the needs of outdoor mobile deployment; it supports real-time data storage and traceability, and complies with industrial-grade application standards.

[0150] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A laser velocimetry and ranging integrated device based on an optical frequency comb, characterized in that, It includes an optical comb light source module, an amplification module, a filtering module, a beam splitting coupling module, and a speed and distance measurement and status monitoring module; The optical comb light source module is used to output an optical comb signal containing multiple wavelengths, where λ1 and λ2 are used as measurement wavelengths for coordinated measurement of speed and distance, and λ3 is used as a reference wavelength for packet loss rate monitoring and system status assessment, and also as a time synchronization signal source. The amplification module includes a first-stage amplifier and a second-stage amplifier, employing a two-stage amplification structure of "amplification-filtering-amplification". The optical splitting and coupling module includes a demultiplexer, a circulator, an optical antenna, a Faraday rotator, and an optical fiber coupler. The demultiplexer is used to separate the two-stage amplified optical signals and distribute them to three paths. Two of the paths are reflected back to the circulator after hitting the target object via the circulator and the optical antenna, and then enter the optical fiber coupler. The third path changes the direction of the optical signal through the Faraday rotator and directly enters the optical fiber coupler. The optical fiber coupler efficiently couples the three optical signals into a single composite optical signal. The speed and distance measurement and status monitoring module includes a photodetector, a data acquisition card, and an FPGA signal processing unit. The photodetector is used to convert the received light signal into an electrical signal, and the FPGA signal processing unit is used for signal processing, including calculating speed and distance and calculating packet loss rate.

2. The integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 2, characterized in that, It also includes a time synchronization module, which generates synchronization pulse signals and sends them to the data acquisition cards of the speed and distance measurement and status monitoring modules via electrical signal transmission lines, providing a unified and accurate timestamp for the synchronous measurement of speed and distance and the time statistics of packet loss rate.

3. The integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 2, characterized in that, If the target object is static, a plane mirror is placed on the target object for reflection; if the target object is dynamic, the diffuse properties of the target object itself are used for reflection.

4. The integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 3, characterized in that, The optical comb light source module uses a fiber mode-locked laser as the light source, preferably an erbium-doped fiber mode-locked laser; The filtering module uses WSS filtering.

5. The integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 4, characterized in that, There are two circulators.

6. A method for operating the integrated laser velocity and distance measurement device based on an optical frequency comb as described in any one of claims 1-5, characterized in that, include: S1, the optical comb light source module outputs an optical comb signal containing multiple wavelengths, where λ1 and λ2 are used as measurement wavelengths and λ3 is used as a reference wavelength; The optical comb signal passes through a first-stage amplifier and a filtering module in sequence, and finally enters the demultiplexer from the output of the second-stage amplifier; S2, the demultiplexer separates the amplified optical signals λ1, λ2, and λ3 into three branches. The optical signals in the branches containing λ1 and λ2 enter the circulator, are reflected back to the circulator after hitting the target object by the optical antenna, and then enter the fiber coupler. The optical signal in the branch containing λ3 changes the direction of the optical signal through the Faraday rotator and enters the fiber coupler directly. The fiber coupler couples the three optical signals λ1, λ2, and λ3 into a composite optical signal, which is then detected by the photodetector. S3, the photodetector converts the received optical signal into an electrical signal. The data acquisition card, triggered by the electrical pulse of the time synchronization module, synchronously acquires the electrical signal converted by the photodetector, ensuring that the acquisition action and the optical signal return timing are accurately matched. S4, the FPGA signal processing unit, calculates speed and distance, and calculates packet loss rate.

7. The working method of the integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 6, characterized in that, The process of calculating speed and distance in step S4 is as follows: ① Calculation speed Reference frequency calibration: The optical comb light source module is controlled to stably output wavelength signals λ1 and λ2 for speed measurement. The signals are transmitted to the photodetector through the optical path and converted into initial electrical signals. FFT operation is performed on the initial electrical signals, and the characteristic frequencies corresponding to the λ1 and λ2 signals in the operation results are extracted as the initial reference frequency f0. Real-time frequency acquisition: After the target measurement is started, the λ1 and λ2 signals are transmitted through the optical path and focused onto the target object by the optical antenna. The signals reflected by the target return to the photodetector along the original optical path. The photodetector converts the reflected light signal into a real-time electrical signal and performs an FFT operation on the real-time electrical signal with parameters consistent with those in the reference frequency calibration stage to extract the real-time characteristic frequency f1 corresponding to the reflected signal. Calculate the frequency change by taking f1 and f0 corresponding to the λ2 signal, where the frequency change δf = f1 - f0; Velocity v = (δf × λ2) / (2 × f0); ② Calculate the distance Reference template signal storage: First, the wavelength of λ3 is fixed by temperature control calibration of the FP standard etalon (stabilized to 25.00℃±0.01℃) to keep the frequency and waveform of the λ3 signal output by the optical comb light source module stable. This λ3 signal serves as a time synchronization reference signal. After being converted into an electrical signal by a photodetector, waveform data within its complete cycle is collected. After removing the initial transmission noise, a standard template signal S0(t) is generated and stored. The template signal includes the waveform peak value and rising edge slope to ensure matching accuracy. Reflected signal waveform acquisition and cross-correlation calculation: During target measurement, the velocity signals λ1 and λ2 are reflected back to the photodetector after being reflected by the target object. The real-time electrical signal waveforms converted from the two reflected signals are simultaneously acquired and denoted as S1(t) and S2(t), respectively. Then, S1(t) and S2(t) are substituted with the standard template signal S0(t) into the cross-correlation function for calculation, i.e. , During the operation, the waveforms of the two signals are aligned by iteratively adjusting the τ value. Round-trip time extraction and Δt calculation: The core characteristic of cross-correlation function operation is that "the function value reaches its peak when the two signal waveforms are most similar". The τ value corresponding to the peak value is the round-trip flight time of a single signal from the device to the target object and back. Extract τ1 corresponding to the peak value of R2(τ) and τ2 corresponding to the peak value of R2(τ) respectively, and take the arithmetic mean of τ1 and τ2 to obtain the round-trip flight time difference Δt. Distance d = c·Δt / 2.

8. The working method of the integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 7, characterized in that, The process of calculating the packet loss rate in step S4 is as follows: Using the period set by the time synchronization module as the statistical unit, the system periodically checks whether the λ3 signal has been successfully received. The total number of transmitted pulses within the period is determined based on the repetition frequency of the light source. The number of valid rising edges of the λ3 signal within the period is used as the number of successfully received pulses. Packet loss rate = (Total number of transmitted pulses - Number of successfully received pulses) / Total number of transmitted pulses × 100%.

9. The working method of the integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 8, characterized in that, The status is assessed based on the packet loss rate. When the packet loss rate is lower than the system's preset threshold of 1%, it indicates that the current measurement environment is excellent, the optical link is unobstructed, and the measurement results are highly reliable. When the packet loss rate exceeds the system's preset 1% threshold, the system immediately determines that the current measurement environment has deteriorated, the optical signal-to-noise ratio is low, and the reliability of the recently measured set of speed and distance data is questionable. The FPGA signal processing unit automatically triggers the dynamic calibration program.

10. The working method of the integrated laser velocimetry and ranging device based on an optical frequency comb according to claim 9, characterized in that, The dynamic calibration procedure includes: (1) Send a calibration command to the amplification module to increase the gain of the secondary amplifier and offset the signal attenuation by increasing the power of the transmitting end; At the same time, a parameter adjustment command is sent to the data acquisition card to extend the sampling time from 20ns to 50ns; (2) After the instruction is issued, the system enters a 100ms temporary verification period to continuously monitor the packet loss rate. If the packet loss rate decreases within 100ms but does not reach the threshold, the FPGA signal processing unit will further increase the gain of the first-stage amplifier. (3) If the packet loss rate drops below the threshold within 100ms, or if the packet loss rate drops below the threshold after another 100ms verification, the system determines that the current optical link has been restored to a reliable state and restarts the normal measurement process with the current parameters. At this time, the FPGA signal processing unit will mark the status of the previously questionable data and package the first set of valid data after calibration together with the calibration parameters to ensure data traceability. (4) If the packet loss rate remains below 0.5 times the threshold for the next 10 minutes, the system determines that the deterioration of the environment has weakened or stopped, and automatically resets each parameter to its initial value.

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