Train positioning and speed measurement system and method with meter-level resolution TGD-OFDR

Abstract

The application discloses a train positioning and speed measuring system and method with meter-level resolution TGD-OFDR, which comprises a TGD-OFDR optical path, a signal acquisition and demodulation module, a noise reduction module and a positioning and speed measuring module connected in sequence; the TGD-OFDR optical path couples the probe light with the local reference light; the signal acquisition and demodulation module processes the received optical signal to obtain real phase data; the noise reduction module uses the STAWDA algorithm to dynamically analyze the time-space correlation of the signal and the noise, enhances the effective vibration signal and suppresses random noise and interference; the positioning and speed measuring module calculates the differential phase curve based on the phase data after noise reduction, and determines the train position and speed through the time difference of the vibration position. The application effectively improves the train positioning accuracy and speed real-time monitoring, can acquire and process signals in real time, meets the positioning and speed measuring application requirements of the train in the actual scene, and provides reliable support for real-time monitoring and long-distance track train safe operation in the train operation process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of distributed optical fiber vibration acoustic sensing, in particular to a train positioning and speed measurement system and method of meter-level resolution TGD-OFDR. BACKGROUND

[0002] With the development of high-speed and intelligentization of railway transportation, real-time positioning and speed measurement of trains have become the core demand to ensure operation safety. Traditional technologies such as track circuit and satellite positioning have obvious limitations: track circuit is susceptible to electrical interference and has low spatial resolution (usually kilometer level), and satellite signals are easily blocked in tunnel, mountainous areas and other scenarios, resulting in failure.

[0003] Although distributed optical fiber sensing technology can realize monitoring by detecting fiber vibration, existing schemes based on phase-sensitive optical time domain reflection (Φ-OTDR) or optical frequency domain reflection (OFDR) face the following bottlenecks:

[0004] (1) The contradiction between spatial resolution and measurement distance is prominent, and it is difficult to balance meter-level positioning and long-distance coverage;

[0005] (2) Random noise (such as wind vibration and electromagnetic interference) in complex railway environment leads to sharp decline of signal-to-noise ratio (SNR) and difficulty in extracting vibration characteristics;

[0006] (3) Traditional demodulation algorithm relies on high sampling rate, and data processing delay is large, which cannot meet the real-time requirement. SUMMARY

[0007] Therefore, the present application provides a train positioning and speed measurement system and method of meter-level resolution TGD-OFDR, which can solve the problems of large amount of transmission data, high monitoring cost and other problems of traditional train monitoring technology, and cannot meet the actual positioning and speed measurement requirements.

[0008] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a train positioning and speed measurement system of meter-level resolution TGD-OFDR, comprising:

[0010] A TGD-OFDR optical path fusing intensity modulation and quadrature reception is buried beside the track to monitor vibration information when the train passes, and after coupling the probe light and the local reference light, backscattering Rayleigh scattering light signals containing vibration information are generated;

[0011] A signal acquisition and demodulation module integrated at the FPGA end is connected with the optical path, used for converting the optical signal into a digital signal and performing phase demodulation to output real phase data;

[0012] The noise reduction restoration module is connected with the signal acquisition and demodulation module, and adopts an STAWDA algorithm to perform time-space domain noise reduction processing on the phase data.

[0013] The positioning and speed measurement module calculates a differential phase curve based on the noise-reduced phase data, and determines the train position and speed through the time difference of the vibration position.

[0014] Further, the TGD-OFDR optical path comprises a narrow linewidth laser, a coupler, an intensity modulator, an erbium-doped fiber amplifier, a circulator, a 90° optical mixer, a polarization diversity device and a balanced detector.

[0015] The laser emitted by the narrow linewidth laser is divided into probe light and local reference light through the coupler, and the probe light generates a phase modulation signal after the intensity modulator.

[0016] The output end of the intensity modulator is connected with the erbium-doped fiber amplifier; the output end of the erbium-doped fiber amplifier is connected with the first port of the circulator; the second port of the circulator is connected with the optical cable laid beside the rail, and the third port is connected to the balanced detector through the 90° optical mixer and the polarization diversity device.

[0017] The Rayleigh scattering light and the local reference light enter the 90° optical mixer and the polarization diversity device to obtain four current signals, which are combined into complex signals and then pass through a matched filter for pulse compression.

[0018] The main lobe half-width of the equivalent probe pulse after pulse compression is used as the spatial resolution of the TGD-OFDR, and the corresponding balanced detector realizes effective detection and conversion of the optical signal.

[0019] Further, the probe light generates a phase modulation signal after the intensity modulator, and the expression is as follows:

[0020]

[0021] Wherein, α RF is the modulation depth of the intensity modulator, α DC is the normalized bias voltage of the intensity modulator, f0 is the start frequency of the sweep, κ is the sweep speed, T p is the time length from the start to the end of the sweep pulse, t is the time within the period of 0 to T p , and represents the time of generating the phase modulation signal.

[0022] Further, the signal acquisition and demodulation module comprises:

[0023] The signal acquisition unit drives the high-speed ADC to perform analog-to-digital conversion on the optical signal to obtain a digital signal.

[0024] A demodulation unit extracts phase information from the digital signal, and performs time-space double unwrapping on the phase information to obtain real phase data.

[0025] A Rayleigh phase processing unit calculates differential phase data to obtain a phase curve to locate a vibration position, and generates a vibration waveform.

[0026] Further, in the noise reduction module, the STAWDA algorithm is used to perform time-space domain noise reduction processing on the phase data, including:

[0027] (a) performing mean removal and normalization preprocessing on the original signal matrix S(t, x);

[0028] (b) calculating the weighted difference value of the signals at adjacent time points, and the weight is dynamically allocated by the local signal-to-noise ratio;

[0029] (c) estimating the background noise based on the 3σ criterion, and setting a dynamic threshold to filter out random interference;

[0030] (d) performing time-space consistency moving average filtering on the accumulated results to eliminate isolated noise points.

[0031] Further, the positioning and speed measurement module is specifically configured to locate the vibration position according to the differential phase curve, calculate the time difference Δt of adjacent vibration positions, and combine the fiber laying sampling point vibration spacing Δx to calculate the real-time speed of the train through the formula v=Δx / Δt.

[0032] In a second aspect, the embodiments of the present application also provide a train positioning and speed measurement method with meter-level resolution TGD-OFDR, which applies the train positioning and speed measurement system with meter-level resolution TGD-OFDR as any one of the first aspect, and the method comprises:

[0033] S1. Through the TGD-OFDR optical path of fusion intensity modulation and quadrature reception, the backscattering Rayleigh scattering light signal containing vibration information is generated after coupling the probe light and the local reference light;

[0034] S2. Through the signal acquisition and demodulation module integrated on the FPGA end, the optical signal is converted into a digital signal and phase demodulated to output real phase data;

[0035] S3. The STAWDA algorithm is used to perform time-space domain noise reduction processing on the phase data;

[0036] S4. Based on the noise-reduced phase data, the differential phase curve is calculated, and the train position and speed are determined through the time difference of the vibration position.

[0037] Further, the step S2 comprises:

[0038] A high-speed ADC is driven to perform analog-to-digital conversion on the optical signal to obtain a digital signal;

[0039] extracting phase information from the digital signal; and performing space-time double unwrapping on the phase information to obtain real phase data;

[0040] calculating differential phase data to obtain a phase curve to locate a vibration position, and generating a vibration waveform.

[0041] Further, the step S3 comprises:

[0042] (a) performing mean removal and normalization preprocessing on the original signal matrix S(t, x);

[0043] (b) calculating a weighted difference value of signals at adjacent time points, the weight being dynamically allocated by a local signal-to-noise ratio;

[0044] (c) estimating background noise based on a 3σ criterion to set a dynamic threshold to filter out random interference;

[0045] (d) performing space-time consistent moving average filtering on the accumulated result to eliminate isolated noise points.

[0046] Further, the step S4 comprises:

[0047] locating a vibration position according to a differential phase curve, and calculating a time difference Δt of adjacent vibration positions;

[0048] combining a vibration interval Δx of a sampling point of fiber laying, and calculating a real-time speed of the train through a formula v = Δx / Δt.

[0049] According to the technical solution, compared with the prior art, the present application has the following technical advantages:

[0050] By fusing intensity modulation and quadrature receiving optical path design, FPGA hardware accelerated signal processing and STAWDA (space-time adaptive weighted difference accumulation) denoising algorithm, the following breakthroughs are achieved:

[0051] (1) The spatial resolution is improved to the meter level by using frequency sweeping pulse compression technology, while maintaining long distance monitoring capability;

[0052] (2) The continuity of vibration signals is enhanced and isolated noise is suppressed by space-time domain joint analysis;

[0053] (3) Based on dynamic threshold adjustment and parallel pipeline architecture, millisecond-level real-time signal processing is realized, which significantly reduces the positioning error (≤1 meter) and speed error (≤1%). BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute a part of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings.

[0055] Figure 1 A train positioning and speed measuring system structure diagram of a meter-level resolution TGD-OFDR is provided.

[0056] Figure 2 A TGD-OFDR optical path schematic diagram is provided.

[0057] Figure 3 An STAWDA algorithm flow chart is provided.

[0058] Figure 4 A train positioning and speed measuring method flow chart of a meter-level resolution TGD-OFDR is provided. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0060] Referring to Figure 1 The embodiments of the present application disclose a train positioning and speed measuring system of a meter-level resolution TGD-OFDR, which is composed of a TGD-OFDR optical path fusing intensity modulation and quadrature reception, a signal acquisition and demodulation module integrated at an FPGA end, a noise reduction module, and a positioning and speed measuring module.

[0061] The TGD-OFDR optical path fusing intensity modulation and quadrature reception is buried beside a track and is used for monitoring vibration information to generate a scattered light signal when a train passes, coupling a probe light and a local reference light to generate a back Rayleigh scattering light signal containing vibration information.

[0062] The signal acquisition and demodulation module integrated at the FPGA end is connected with the TGD-OFDR optical path, is used for converting an optical signal into a digital signal and performing phase demodulation, and outputs real phase data.

[0063] The noise reduction module is connected with the signal acquisition and demodulation module, and uses an STAWDA algorithm to perform time-space domain noise reduction processing on the phase data.

[0064] A positioning and speed measurement module calculates a differential phase curve based on the denoised phase data and determines the train position and speed through the time difference of vibration positions.

[0065] Where TGD-OFDR is the detection of acoustic signals through optical fibers, and the characteristics of optical fibers are used to obtain vibration information along the optical fiber path. Through this technology, small changes along the optical fiber path can be monitored, including the vibration when the train passes, the state of the track, and external environmental disturbances. The advantage of this method is that it can achieve real-time monitoring of a wide area without the need to add additional sensors.

[0066] The principle of the present application mainly relies on laying optical fibers along the track and calculating the position of the train by measuring the time difference of acoustic wave propagation. The system can accurately determine the current position of the train by analyzing the acoustic signal changes at different positions in the optical fiber. TGD technology can accurately control and gate the optical signal. When combined with OFDR technology, it can more effectively suppress noise and interference. In complex railway environments, there are various electromagnetic and vibration interferences along the railway, and TGD technology can accurately gate the reflected light signal related to the train and exclude the influence of other interference signals, thereby improving the detection accuracy and spatial resolution of the signal. The system can accurately identify and locate the train, achieve meter-level resolution of train positioning and speed measurement, and meet the needs of modern railway intelligentization and high-precision operation.

[0067] The integration of TGD and OFDR technology makes up for the shortcomings of traditional train positioning and speed measurement technology. It no longer relies on electrical circuits that are easily affected by the environment, nor is it limited by satellite signal shielding, and it avoids errors caused by mechanical wear and tear. It provides a reliable and high-precision positioning and speed measurement solution for safe and efficient operation of railway trains, and adapts to the trend of intelligentization and digitization of the railway industry.

[0068] As shown in Figure 2 The TGD-OFDR optical path includes a narrow linewidth laser, a coupler, an intensity modulator, an erbium-doped fiber amplifier (EDFA), a circulator, a 90° optical mixer, and a polarization diversity and balanced detector BPD.

[0069] The laser emitted by the narrow linewidth laser is divided into probe light and local reference light through a coupler, the probe light generates a phase modulation signal after passing through an intensity modulator; the output end of the intensity modulator is connected to an erbium-doped fiber amplifier; the output end of the erbium-doped fiber amplifier is connected to the first port of a circulator; the second port of the circulator is connected to an optical cable laid beside the rail, and the third port is connected to a balanced detector through a 90° optical mixer and a polarization diversity device; the Rayleigh scattering light and the local reference light enter the 90° optical mixer and the polarization diversity device to obtain four current signals, which are combined into a complex signal and then pass through a matched filter for pulse compression; the full width at half maximum of the main lobe of the equivalent probe pulse after pulse compression serves as the spatial resolution of the TGD-OFDR, and the corresponding balanced detector realizes effective detection and conversion of the optical signal.

[0070] Specifically, the laser emitted by the narrow linewidth laser is divided into probe light and local reference light through a coupler, the probe light drives a Mach-Zehnder interferometer structure intensity modulator by a linear sweep electric pulse generated by an arbitrary waveform generator, the linear sweep electric pulse changes according to a specific rule, changes the working state of the modulator, and then modulates the pulsed light. After the probe light emitted by the laser passes through the intensity modulator, the phase change of the laser is

[0071]

[0072] In the formula, α RF is the modulation depth of the intensity modulator, α DC is the normalized bias voltage of the intensity modulator, f0 is the starting frequency of the sweep, κ is the sweep speed, T p is the time length experienced from the beginning to the end of the sweep pulse, and t indicates that the phase modulation signal is generated within 0 to T p The 2πf0t+πκt 2 is simply written as The optical field expression of the light passing through the intensity modulator is:

[0073]

[0074] The local light, that is, the optical field expression of the light without modulation, is

[0075]

[0076] In the formula, P0 is the input light power, ω c is the center angular frequency of the laser. The amplitudes of the electric fields are normalized to 1. In the X polarization state, the total scattering light of each scattering point is:

[0077]

[0078] In the formula, i represents the i-th scattering point in the optical fiber; τ ithe round-trip time of light from the input section of the fiber to the scattering point; i the electric field amplitude of the scattered light from the scattering point into the intensity modulator, determined by the scattering rate of the point and the fiber attenuation along the way; i the angle between the scattered light from the point and the X-polarization axis. After the probe light and the local reference light enter the 90° optical mixer and the polarization diversity, they are divided into four paths, and four current signals are obtained, i IX , i QX , i IY , and i QY . i IX and i QX have the same polarization state, but the phases are orthogonal to each other, i IY and i QY are the same. We combine two orthogonal current signals with the same polarization state into a complex signal, and the signal of the X-polarization state is:

[0079]

[0080] wherein a(τ)cos[θ(τ)] represents the parameters related to the scattering point in the fiber, a(τ) is related to the electric field amplitude of the scattered light from the scattering point into the intensity modulator, determined by the scattering rate of the point and the fiber attenuation along the way, and cos[θ(τ)] is related to the angle between the scattered light from the point and the X-polarization axis; τ represents the round-trip time of light from the input section of the fiber to the scattering point; s(t) is the phase modulation signal generated by the probe light after the intensity modulator, represents the convolution symbol; represents the impulse response of the fiber. By adjusting α RF and α DC , the high-order harmonics are suppressed, and cos[s(t)] is expanded as:

[0081]

[0082] wherein J n is the n-order Bessel function. The linear sweep pulse generated by the intensity modulator has many harmonics, but we only need the first-order positive and negative frequency components, because the bandwidth of the high-order sidebands exceeds the receiving bandwidth of the BPD. Since contains both positive and negative frequency components, using two different matched filters to process can obtain Rayleigh signals at two different frequencies:

[0083]

[0084] wherein

[0085]

[0086] and

[0087]

[0088] where τ p represents the round-trip time of light from the fiber launch section to the pth scattering location, defines the time interval in which the equivalent probe pulse exists, and f'0 is the processed equivalent start frequency of the sweep, and is the equivalent probe pulse after pulse compression. They are no longer sweep pulses, but are compressed into single-frequency pulses, and the pulse shape is the same, that is, |W(t)|. |W(t)| is the product of a sinc function and a triangular window, and the full width at half maximum of the main lobe is taken as the spatial resolution of the TGD-OFDR.

[0089] The signal acquisition and demodulation module integrated on the FPGA end comprises:

[0090] a signal acquisition unit configured to drive a high-speed ADC to perform analog-to-digital conversion on the optical signal to obtain a digital signal;

[0091] a demodulation unit configured to extract phase information from the digital signal, and to perform time-space double unwrapping on the phase information to obtain real phase data;

[0092] a Rayleigh phase processing unit configured to calculate the differential phase data to obtain a phase curve and locate a vibration position, and to generate a vibration waveform.

[0093] The signal acquisition unit is configured to acquire the optical signal by using an AD and convert the optical signal into a digital signal, the demodulation unit is configured to obtain phase data by performing IQ demodulation on the digital signal, the real phase information is obtained by performing time-space double unwrapping on the phase data, the differential phase data is obtained by the Rayleigh phase processing unit from the real phase information, and the vibration waveform data is obtained by calculating the differential phase curve from the differential phase data to locate the vibration linearity.

[0094] Referring to Figure 3 , an STAWDA denoising algorithm composed of time-space domain signal modeling, adaptive differential accumulation, noise level estimation and dynamic threshold adjustment, and time-space consistency enhancement is adopted. The signal is regarded as a two-dimensional matrix S(t,x), t is the time dimension, and x is the fiber position. The effective vibration signal appears as a continuous region in the time-space domain, and the noise is randomly distributed. The amplitudes of adjacent time points are adaptively differentially superimposed, the noise level is estimated and the threshold is dynamically adjusted, the accumulated results are time-space smoothed by using the time-space continuity of train vibration (such as moving average or median filtering), and the isolated noise points are eliminated.

[0095] Specifically as follows: the vibration waveform data is first preprocessed by STAWDA algorithm in the noise reduction module, the original amplitude signal matrix collected by the system is input, the baseline drift is eliminated, the data range is standardized, and the preprocessed signal matrix is output; then adaptive differential accumulation is performed, the vibration signal is enhanced, and random noise is suppressed, the difference algorithm of adjacent time points is performed, the field weighting and weighted accumulation are performed, and the weighted accumulated signal is obtained; that is, the difference value of adjacent time points in time and space domain is calculated, and the neighborhood weight is dynamically allocated based on the local signal-to-noise ratio, and the continuity of the vibration signal is enhanced.

[0096] Then noise estimation and dynamic threshold adjustment are performed, and the update of the accumulator is related to whether the signal exceeds the dynamic threshold. When the signal intensity ΔS(t i x) collected is greater than the dynamic threshold T(x), it is considered that the signal is an effective signal, and the accumulator needs to be updated at this time, and the effective signal is included in the accumulation calculation. This is because the effective signal contains information related to train vibration, which is important for determining the position and speed of the train, and by continuously updating the accumulator, the signal can be more accurately analyzed, and the monitoring accuracy of the system can be improved. If the signal intensity is less than or equal to the dynamic threshold, the signal is identified as noise and will not trigger the accumulator update, avoiding the interference of noise on the accumulation result. Background noise estimation is performed by collecting data during the period without the train, the noise standard deviation of each spatial point X is calculated, the dynamic threshold setting and threshold triggering accumulation are performed; that is, based on the 3σ criterion of background noise, combined with dynamic threshold adjustment, only the effective signal is retained for accumulation, and random noise is suppressed.

[0097] Finally, time sliding average and spatial dimension median filtering are performed according to the accumulation result to eliminate isolated noise points and enhance continuous vibration regions, and the noise-reduced signal is output. That is, isolated noise points are eliminated by enhancing the consistency of time and space, and high signal-to-noise ratio signals are output. The algorithm is realized in real time on FPGA through parallel pipeline architecture, experiments show that it can reduce the train positioning error from 3 meters to 1 meter, and the speed error from 4% to 1%, especially suitable for long-distance high-precision railway monitoring scenarios, with anti-interference, real-time and high efficiency of hardware deployment. Finally, the difference phase curve is calculated and the vibration is positioned according to the change amount, and the vibration waveform is linearly obtained. The results of adjacent multiple data are obtained, and input into the positioning and speed measurement module.

[0098] The application utilizes Rayleigh phase method to process the initial phase data: since the phase change of back Rayleigh scattering light in the optical fiber is related to train vibration, temperature change and other external factors, in an ideal case, based on Rayleigh scattering principle, the phase of the scattering light has a specific relationship with the fiber length, light propagation characteristics and the like. In the system, the phase change related to train vibration is mainly concerned, the initial phase data at different times and different positions are compared and analyzed, for example, the phase difference of adjacent sampling points is calculated, combined with the known fiber parameters and the system set sampling time interval and the like information, a phase change model is constructed. According to the model, the phase change part caused by train vibration can be accurately extracted from the initial phase data, so that the differential phase data is obtained.

[0099] And the positioning and speed measurement module is used for positioning the vibration position according to the differential phase curve, calculating the time difference Δt of adjacent vibration positions; combined with the vibration interval Δx of the fiber laying sampling point, the real-time speed of the train is calculated through the formula v=Δx / Δt.

[0100] The train positioning and speed measurement system with meter-level resolution TGD-OFDR provided by the application has the working principle as follows:

[0101] With the help of the meter-level resolution TGD-OFDR optical path, the basic TGD-OFDR optical path is used to fuse intensity modulation and quadrature reception, and the returned back Rayleigh scattering light is received by the balance detector; the signal acquisition unit drives the high-speed ADC chip to perform analog-to-digital conversion on the returned Rayleigh scattering signal in the optical path, and transmits the digital signal to the FPGA for subsequent processing, the electrical signal is digitized through the signal acquisition unit, and the analog-to-digital conversion of the Rayleigh scattering signal is completed; the above is demodulated by the demodulation unit, the demodulation signal is obtained, the phase information is extracted from the high-frequency digital signal, and the real phase information is obtained by phase unwrapping; the real phase information is obtained by the Rayleigh phase processing unit to obtain the differential phase curve, so that the vibration can be positioned according to the change amount, and the vibration waveform can be linearly obtained; the STAWDA algorithm is adopted in the noise reduction and restoration module, and the obtained signal, i.e. the vibration data of the track along the line, is denoised through time-space domain joint analysis and adaptive strategy, which improves the noise resistance and monitoring accuracy of the TGD-OFDR system in the complex railway environment. The system locates the vibration position according to the differential phase curve through the positioning and speed measurement module, calculates the time difference Δt of adjacent vibration positions; combined with the vibration interval Δx of the fiber laying sampling point, the real-time speed of the train is calculated through the formula v=Δx / Δt. Through the analysis of the positioning data along the railway line, the position of the train is determined, and the corresponding position time difference is calculated, and the position and speed of the train are monitored.

[0102] Based on the same inventive concept, the application also provides a train positioning and speed measuring method of the meter-level resolution TGD-OFDR, which is applied to the train positioning and speed measuring system of the meter-level resolution TGD-OFDR as described above. Since the principle of the problem solved by the method is similar to the train positioning and speed measuring system of the meter-level resolution TGD-OFDR as described above, the implementation of the method can be referred to the implementation of the system, and the repeated parts will not be described here. Refer to Figure 4 The method comprises the following steps of:

[0103] S1. The TGD-OFDR optical path of fused intensity modulation and quadrature reception is used to couple the probe light and the local reference light to generate the back Rayleigh scattering light signal containing vibration information;

[0104] S2. The signal acquisition and demodulation module integrated at the FPGA end is used to convert the optical signal into a digital signal and perform phase demodulation to output real phase data;

[0105] S3. The STAWDA algorithm is used to perform time-space domain noise reduction processing on the phase data;

[0106] S4. The differential phase curve is calculated based on the noise-reduced phase data, and the train position and speed are determined through the time difference of the vibration position.

[0107] The method emits laser pulses to the optical fiber laid beside the track to detect the back Rayleigh scattering light. When the train passes, the vibration of the track is transmitted to the optical fiber, causing the local refractive index or length of the optical fiber to change, resulting in changes in the amplitude or phase of the scattered light. The vibration source is positioned by analyzing the amplitude change of the back Rayleigh scattering light of the optical fiber, and the speed measurement is realized through dynamic calibration and time difference calculation.

[0108] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0109] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A train positioning and speed measurement system of a meter resolution TGD-OFDR, characterized in that, The application relates to a train positioning and speed measuring system based on a meter-level resolution TGD-OFDR. The TGD-OFDR optical path integrating intensity modulation and quadrature reception is buried beside a track to monitor vibration information when a train passes, and back Rayleigh scattering light signals containing the vibration information are generated after coupling of probe light and local reference light; the TGD-OFDR optical path comprises a narrow-line-width laser, a coupler, an intensity modulator, an erbium-doped fiber amplifier, a circulator, a 90-degree optical mixer and a polarization diversity device and a balanced detector; laser emitted by the narrow-line-width laser is divided into probe light and local reference light through the coupler, and the probe light generates a phase modulation signal after the intensity modulator; the expression is as follows: wherein α RF is a modulation depth of the intensity modulator, α DC is a normalized bias voltage of the intensity modulator, f0is a start frequency of the sweep, κ is a sweep speed, T p is a length of time elapsed from the start to the end of the sweep pulse, t is a time within the 0 to T p time period, and represents a time at which the phase modulation signal is generated; A signal acquisition and demodulation module integrated at an FPGA end is connected with the optical path and is used for converting the optical signal into a digital signal and performing phase demodulation to output real phase data; A noise reduction and restoration module is connected with the signal acquisition and demodulation module, adopts an STAWDA algorithm to perform time-space domain noise reduction processing on the phase data, and comprises the following steps: (a) performing mean value removal and normalization pretreatment on an original signal matrix S(t, x); (b) calculating a weighted difference value of signals at adjacent time points, and dynamically allocating a weight according to a local signal-to-noise ratio; (c) estimating background noise based on a 3sigma criterion, and setting a dynamic threshold to filter out random interference; (d) performing time-space consistency sliding average filtering on an accumulated result to eliminate isolated noise points; A positioning and speed measuring module is used for calculating a differential phase curve based on the phase data after noise reduction, determining a train position and speed through a time difference of vibration positions, and specifically used for positioning vibration positions according to the differential phase curve, calculating a time difference Delta t of adjacent vibration positions, combining a vibration interval Delta x of a sampling point of the optical fiber, and calculating a real-time speed of the train through a formula v=Delta x / Delta t.

2. The train positioning and speed measurement system of claim 1, wherein, The laser emitted by the narrow-line-width laser is divided into probe light and local reference light through the coupler, and the probe light generates a phase modulation signal after the intensity modulator; An output end of the intensity modulator is connected with the erbium-doped fiber amplifier; an output end of the erbium-doped fiber amplifier is connected with a first port of the circulator; a second port of the circulator is connected with an optical cable laid beside the track, and a third port is connected to the balanced detector through the 90-degree optical mixer and the polarization diversity device; The Rayleigh scattering light and the local reference light enter the 90-degree optical mixer and the polarization diversity device to obtain four current signals, the four current signals are combined into complex signals, and the complex signals pass through a matching filter to perform pulse compression; A main lobe half-width full-width of an equivalent probe pulse after pulse compression is used as a spatial resolution of the TGD-OFDR, and the corresponding balanced detector realizes effective detection and conversion of the optical signal. The signal acquisition and demodulation module comprises:

3. The train positioning and speed measurement system of claim 1, wherein, A signal acquisition unit drives a high-speed ADC to convert the optical signal into a digital signal through analog-digital conversion; A demodulation unit extracts phase information by processing the digital signal, and performs time-space double unwrapping on the phase information to obtain real phase data; A Rayleigh phase processing unit calculates differential phase data to obtain a phase curve for positioning vibration positions and generates a vibration waveform. The application relates to a train positioning and speed measuring system based on a meter-level resolution TGD-OFDR.

4. A train positioning and speed measurement method of a meter-resolution TGD-OFDR, characterized by, ​ S1. Through the TGD-OFDR optical path of fusion intensity modulation and quadrature reception, the back Rayleigh scattering light signal containing vibration information is generated after coupling the probe light and the local reference light; S2. Through the signal acquisition and demodulation module integrated at the FPGA end, the optical signal is converted into a digital signal and phase demodulated to output real phase data; S3. The STAWDA algorithm is used to perform time-space domain noise reduction processing on the phase data; S4. Based on the phase data after noise reduction, the differential phase curve is calculated, and the train position and speed are determined through the time difference of the vibration position; Wherein, the step S3 comprises: (a) The original signal matrix S(t, x) is preprocessed by removing mean value and normalization; (b) The weighted difference value of the signals at adjacent time points is calculated, and the weight is dynamically allocated by the local signal-to-noise ratio; (c) The background noise is estimated based on the 3σ criterion, and a dynamic threshold is set to filter out random interference; (d) The accumulated results are filtered by time-space consistency sliding average to eliminate isolated noise points; The step S4 comprises: The vibration position is located according to the differential phase curve, and the time difference Δt of adjacent vibration positions is calculated; Combined with the sampling point vibration spacing Δx of the optical fiber laying, the real-time speed of the train is calculated through the formula v=Δx / Δt.

5. The train positioning and speed measurement method of the meter-scale resolution TGD-OFDR according to claim 4, characterized in that, The step S2 comprises: The high-speed ADC is driven to convert the optical signal into a digital signal; The phase information is extracted from the digital signal, and the real phase data is obtained by time-space double unwrapping of the phase information; The differential phase data is calculated to obtain the phase curve to locate the vibration position, and the vibration waveform is generated.

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