Railway vehicle signal detection device and method based on optical fiber magnetofluid sensitization

Abstract

The invention discloses a railway vehicle signal detection device and method based on optical fiber magnetofluid sensitization, belongs to the technical field of optical fiber sensing, and particularly relates to the railway vehicle signal detection device and method based on optical fiber magnetofluid sensitization. Comprising a laser light source, a first optical fiber, a coupler, a magnetofluid rod, a reference optical fiber, a wavelength division multiplexer, a transmission optical fiber, a demodulator, a non-magnetic shell, a magnetofluid filler, a second optical fiber and a refraction type grating. When an external magnetic field or mechanical stress changes, the transmission characteristic of the optical fiber changes accordingly, so that the abnormity of the in-out signal or the magnetic field of the rail car is detected. According to the invention, the optical fiber sensing technology, the magnetofluid technology and the non-magnetic-conductive material are utilized to realize high-sensitivity detection of rail car in-out signal and rail magnetic field abnormity.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a device and method for detecting rail vehicle signals based on optical fiber magnetic fluid sensitization. Background Art

[0002] In recent years, optical fiber magnetic field sensors have emerged in various sensing applications due to their compact structure, anti-electromagnetic interference, high sensitivity, strong stability, and easy construction of distributed networks. With the development of nanotechnology, new functional media are widely used in photonic devices such as optical gratings, optical switches, modulators, couplers, and magnetic field sensors due to their customizable magneto-optical properties.

[0003] Existing technologies mainly include traditional magnetic sensors, fiber Bragg grating (FBG) sensors, magnetic fluid sensors, and electromagnetic induction sensors. These technologies have their own applications in the fields of magnetic field detection and rail vehicle signal monitoring, but they also have obvious disadvantages. Although traditional magnetic sensors, such as Hall sensors, magnetoresistive sensors, and fluxgate sensors are widely used in magnetic field detection, their sensitivity is limited and it is difficult to detect weak magnetic field changes. They are also susceptible to external electromagnetic interference, such as power lines or radio signals, resulting in reduced detection accuracy. In addition, some magnetic sensors, such as fluxgate sensors, are large in size and difficult to install in a small space, which limits their application scenarios. Fiber Bragg grating (FBG) sensors use the Bragg grating in the optical fiber to reflect light of a specific wavelength and sense external stress or temperature changes by detecting wavelength changes. However, they are insensitive to magnetic field changes and cannot be directly used for magnetic field detection. They also require complex optical demodulation equipment, which increases system complexity and cost. Magnetic fluid sensors use the changes in the optical properties of magnetic fluids under an external magnetic field, such as refractive index and transmittance, to detect magnetic fields. However, their optical properties are easily affected by environmental factors such as temperature and pressure, resulting in unstable detection results. When used alone, they have limited ability to detect weak magnetic field changes. Electromagnetic induction sensors detect magnetic field changes based on the principle of electromagnetic induction and are often used for rail vehicle detection. However, their response speed is slow, making it difficult to detect rapidly changing magnetic fields in real time. They are also easily affected by external electromagnetic noise, which affects detection accuracy. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to provide a device and method for rail vehicle signal detection based on optical fiber magnetic fluid sensitization, aiming to solve the problems of low sensitivity, poor anti-interference ability, insufficient real-time performance, weak environmental adaptability, and complex installation and maintenance existing in traditional rail vehicle signal detection technology. It is able to stably work and detect in harsh environments such as high temperature, high humidity, and strong vibration, reducing the impact of environmental factors on detection accuracy. Through compact structural design, the sensor is easy to install and deploy, reducing the need for frequent calibration and maintenance, thereby reducing operating costs. It provides a signal detection solution for rail transit systems with high sensitivity, high reliability, strong real-time performance and easy maintenance.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a device for rail vehicle signal detection based on optical fiber magnetofluid enhancement, the device comprising a multi-channel wavelength decomposition modulation optical path system based on magnetofluid grating; the multi-channel wavelength decomposition modulation optical path system based on magnetofluid grating comprises a laser light source, a first optical fiber, a coupler, a magnetofluid rod, a reference optical fiber, a wavelength division multiplexer, a transmission optical fiber and a demodulator; the laser light source is at the input port side of the coupler, and the two are connected through the first optical fiber, and the magnetofluid rod, the reference optical fiber and the coupler are connected through the first optical fiber closed loop; the wavelength division multiplexer is connected through the first optical fiber closed loop. The output end side of the wavelength division multiplexer is connected to the output end side of the coupler through the first optical fiber, and at least two transmission optical fibers are connected in parallel on the output end side of the wavelength division multiplexer, and a demodulator is arranged in series on each of the transmission optical fibers, and the number and connection relationship of the transmission optical fibers and the demodulators are one-to-one corresponding; the magnetic fluid rod includes a non-magnetic shell, a magnetic fluid filler, a second optical fiber and a refractive grating; the second optical fiber is coaxially sealed in the non-magnetic shell to form an annular gap, the magnetic fluid filler is filled in the annular gap formed by the second optical fiber and the non-magnetic shell, and the second optical fiber is engraved with a refractive grating.

[0006] Furthermore, the non-magnetic shell contains SiO 2 The magnetic fluid filler is Fe 3 O 4 Particles.

[0007] Furthermore, the number of the transmission optical fibers and the number of the demodulators are at least 12.

[0008] Furthermore, the first optical fiber, the second optical fiber, the reference optical fiber and the transmission optical fiber are all single-mode optical fibers.

[0009] A method for detecting rail vehicle signals based on optical fiber magnetic fluid sensitization, the method uses an apparatus for detecting rail vehicle signals based on optical fiber magnetic fluid sensitization to detect rail vehicle signals, comprising the following steps: Step S1: a laser light source emits broadband or tunable laser light, and the optical signal is transmitted to a coupler through a first optical fiber.

[0010] Step S2: The coupler divides the input optical signal into two paths, the main path enters the magnetic fluid rod; the reference path is directly transmitted to the reference optical fiber.

[0011] Step S3: The optical signals emitted from the main path and the reference path are output to the wavelength division multiplexer through the coupler; the refractive grating in the magnetic fluid rod of the main path only reflects the Bragg wavelength The magnetic fluid filling in the magnetic fluid rod moves with the change of the external magnetic field H caused by the vehicle entering and leaving the detection area, resulting in the deformation of the refractive grating and the Bragg wavelength shift wavelength optical signal, its calibration curve is ,in, represents the Bragg wavelength shift caused by the refraction grating, k represents the proportionality constant, and H represents the external magnetic field.

[0012] Step S4: The wavelength division multiplexer distributes the optical signal outputted by the coupler to the transmission optical fiber channels according to different wavelength ranges.

[0013] Step S5: Each transmission optical fiber channel corresponds to an independent demodulator to extract magnetic field information to complete wavelength detection, which specifically includes: using a Fabry-Perot filter or a spectrometer to measure the wavelength of each channel, and according to the Bragg wavelength offset With calibration curve , calculate the local magnetic field strength corresponding to each channel, perform differential operation on the reference signal and the main signal to eliminate common-mode interference, and integrate multiple sets of magnetic field data output by the demodulator into a global magnetic field distribution map through an algorithm.

[0014] Furthermore, in step S1, the laser light source emits broadband or tunable laser light in the 1550 nm band.

[0015] Furthermore, the transmission optical fiber channel range of step S4 covers the C band and the L band, and the band range is greater than or equal to 1530 nm and less than or equal to 1625 nm.

[0016] Furthermore, the multiple groups of magnetic field data output by the demodulator in step S5 are calculated by weighted averaging or spatial interpolation algorithm.

[0017] Furthermore, the demodulator performs digital filtering on 50 Hz power frequency interference and high-frequency noise, and the high-frequency noise is ≥ 1 kHz.

[0018] Through the above-mentioned design scheme, the present invention can bring the following beneficial effects: the present invention combines the advantages of optical fiber sensing technology and magnetic fluid technology by sealing the optical fiber and magnetic fluid together in a non-magnetic material, overcomes the shortcomings of the existing technology, and significantly improves the detection capability of weak magnetic field changes, and can accurately capture the entry and exit signals of rail vehicles and abnormal changes in the track magnetic field.

[0019] Fiber optic sensing technology has the characteristics of high precision and fast response, and can detect slight environmental changes in real time, meeting the needs of high-speed rail transportation systems. Magnetic fluid technology enhances the sensitivity to changes in external magnetic fields. Non-magnetic materials effectively isolate external electromagnetic interference, ensuring the stability and reliability of detection signals.

[0020] In addition, the structure of the present invention is compact and suitable for installation in a small space, and has a wide range of application prospects. Through this innovative design, the present invention can not only detect rail vehicle entry and exit signals and track magnetic field anomalies with high sensitivity, but also has the advantages of strong anti-interference ability, good real-time performance, and multifunctionality, providing reliable technical support for the safe operation and efficient management of rail transportation systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further described below with reference to the accompanying drawings and specific embodiments: Figure 1 The multi-channel wavelength decomposition and modulation optical path system of the present invention is a block diagram; Figure 2 It is a schematic diagram of the structure of the magnetic fluid rod of the present invention; Figure 3 It is a schematic diagram of the cross-sectional structure of the magnetic fluid rod of the present invention; Figure 4 It is a schematic diagram of an application scenario of the present invention; Among them: 1 is a laser light source, 2 is a first optical fiber, 3 is a coupler, 4 is a magnetic fluid rod, 41 is a non-magnetic shell, 42 is a magnetic fluid filler, 43 is a second optical fiber, 44 is a refractive grating, 5 is a reference optical fiber, 6 is a wavelength division multiplexer, 7 is a transmission optical fiber, and 8 is a demodulator. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific embodiments. However, this should not be understood as the scope of the subject matter of the present invention being limited to the following embodiments, and all technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0023] like Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, this embodiment provides a device for rail vehicle signal detection based on optical fiber magnetofluid enhancement, which includes a multi-channel wavelength decomposition modulation optical path system based on magnetofluid grating; the multi-channel wavelength decomposition modulation optical path system based on magnetofluid grating includes a laser light source 1, a first optical fiber 2, a coupler 3, a magnetofluid rod 4, a reference optical fiber 5, a wavelength division multiplexer 6, a transmission optical fiber 7 and a demodulator 8; the laser light source 1 is on the input port side of the coupler 3, and the two are connected through the first optical fiber 2, and the magnetofluid rod 4, the reference optical fiber 5 and the coupler 3 are connected in a closed loop through the first optical fiber 2; the wavelength division multiplexer 6 is connected to the coupler 3 through the first optical fiber 2. 3, the output end side of the wavelength division multiplexer 6 is connected in parallel with at least two transmission optical fibers 7, each of the transmission optical fibers 7 is serially provided with a demodulator 8, and the number and connection relationship of the transmission optical fibers 7 and the demodulators 8 are one-to-one corresponding; the magnetic fluid rod 4 includes a non-magnetic shell 41, a magnetic fluid filler 42, a second optical fiber 43 and a refractive grating 44; the second optical fiber 43 is coaxially sealed in the non-magnetic shell 41 to form an annular gap, the magnetic fluid filler 42 is filled in the annular gap formed by the second optical fiber 43 and the non-magnetic shell 41, and the second optical fiber 43 is engraved with a refractive grating 44.

[0024] The optical signal emitted by the laser light source 1 enters the magnetic fluid rod 4 and the reference optical fiber 5 respectively through the coupler 3 and the first optical fiber 2. The optical signal portion entering the magnetic fluid rod 4 is reflected back to the coupler 3, and the remaining transmitted optical signal is transmitted along the first optical fiber 2 and returns to the coupler 3 through the reference optical fiber 5. The optical signal portion entering the reference optical fiber 5 is reflected back to the coupler 3, and the remaining transmitted optical signal is transmitted along the first optical fiber 2 and returns to the coupler 3 through the magnetic fluid rod 4. The first optical fiber 2 is bidirectional transmission. After the optical signal is emitted through the magnetic fluid rod 4 and the reference optical fiber 5 loop, optical signals of different wavelengths are generated. After the optical signal is interfered by the coupler 3, it is transmitted to the wavelength division multiplexer 6 through the first optical fiber 2. The wavelength division multiplexer 6 distributes the optical signals of different wavelengths to the channels of the corresponding wavelength bands.

[0025] Furthermore, the non-magnetic shell 41 contains SiO 2 The magnetic fluid filler 42 is Fe 3 O 4 Particles.

[0026] Furthermore, the number of the transmission optical fibers 7 and the number of the demodulators 8 are at least 12.

[0027] Furthermore, the first optical fiber 2, the second optical fiber 43, the reference optical fiber 5 and the transmission optical fiber 7 are all single-mode optical fibers.

[0028] A method for detecting rail vehicle signals based on optical fiber magnetic fluid sensitization, the method uses an apparatus for detecting rail vehicle signals based on optical fiber magnetic fluid sensitization to detect rail vehicle signals, comprising the following steps: Step S1: the laser light source 1 emits broadband or tunable laser light, and the optical signal is transmitted to the coupler 3 through the first optical fiber 2 .

[0029] Step S2: The coupler 3 divides the input optical signal into two paths, the main path enters the magnetic fluid rod 4; the reference path is directly transmitted to the reference optical fiber 5; the optical power of the main path is greater than 90%, and the optical power of the reference path is less than 10%; the reference path plays the dual role of "static reference benchmark" and "eliminating common mode interference".

[0030] The "static reference benchmark" and "elimination of common-mode interference" mean that at the physical level, the reference optical fiber 5 and the main optical fiber are made of the same material and packaged with equal lengths to ensure that the two produce equal amplitude optical path changes when they are affected by environmental interference such as temperature and vibration, even if the amplitude and phase of the common-mode interference in the two channels are consistent.

[0031] At the signal reference level, the main signal contains the target magnetic field information and environmental noise, while the reference signal only contains environmental noise. By collecting the main signal and the reference signal, the two are subtracted so that the common mode components (such as temperature and vibration noise) cancel each other out due to the same phase, while the effective signal is retained as the differential mode component to complete the noise compensation. The differential relationship is:

[0032] in, To compensate for the Bragg wavelength shift (net wavelength change after common mode suppression), is the Bragg wavelength shift, is the calibration coefficient (0.95-1.05) used to achieve common-mode noise rejection. Indicates the equivalent wavelength offset of the reference path (including only environmental noise).

[0033] Specifically, the reference path and the main path form a differential measurement pair, and the common mode interference is eliminated by combining time domain adaptive filtering with frequency domain coherent processing. In this method, the reference path collects an optical signal with the same phase noise as the main path but without magnetic field modulation, and inputs it into a digital signal processor (DSP) after analog-to-digital conversion. The compensation coefficient is dynamically adjusted using the least mean square algorithm, so that the system can achieve a common mode rejection ratio (CMRR) of >30dB in the temperature range of -40℃ to 85℃.

[0034] Step S3: The optical signals emitted from the main path and the reference path are output to the wavelength division multiplexer 6 through the coupler 3; the refractive grating 44 in the magnetic fluid rod 4 of the main path only reflects the Bragg wavelength The magnetic fluid filler 42 in the magnetic fluid rod 4 moves with the change of the external magnetic field H caused by the vehicle entering and leaving the detection area, resulting in the deformation of the refractive grating 44 and the Bragg wavelength shift wavelength optical signal, its calibration curve is ,in, represents the Bragg wavelength shift caused by the refraction grating 44, k represents a proportionality constant, and H represents an external magnetic field.

[0035] Step S4: The wavelength division multiplexer 6 distributes the optical signal outputted by the coupler 3 to the channels of the transmission optical fiber 7 according to different wavelength ranges.

[0036] Step S5: Each transmission optical fiber 7 channel corresponds to an independent demodulator 8 to extract magnetic field information to complete wavelength detection, specifically including: using a Fabry-Perot filter or a spectrometer to measure the wavelength of each channel, and according to the Bragg wavelength offset With calibration curve , calculate the local magnetic field strength corresponding to each channel, perform differential operation on the reference signal and the main signal, eliminate common mode interference such as temperature and vibration, and integrate the multiple sets of magnetic field data output by the demodulator 8 into a global magnetic field distribution map through an algorithm.

[0037] Further, in step S1, the laser light source 1 emits broadband or tunable laser light in the 1550 nm band.

[0038] Furthermore, the channel range of the transmission optical fiber 7 in step S4 covers the C band and the L band, and the band range is greater than or equal to 1530 nm and less than or equal to 1625 nm.

[0039] In the field of optical fiber communication, ‌C-band and L-band‌ refers to the optical wavelength range that supports the following two spectral regions at the same time. ‌C-band (Conventional Band): The wavelength range is ‌1530nm to 1565nm‌, which is the earliest commercial low-loss window in optical fiber communication; ‌L-band (Long Band): The wavelength range is ‌1565nm to 1625nm‌, which further improves the optical fiber transmission capacity by expanding the spectrum resources with longer wavelengths.

[0040] This method is based on the above theory and covers the optical wavelength range of the ‌C-band‌ and ‌L-band‌ at the same time. The channels are divided in the following way: the C-band, with a wavelength range greater than or equal to 1530nm and less than 1565nm, is divided into 7 channels, with each 5nm wavelength interval as a channel, including the first transmission optical fiber channel: greater than or equal to 1530nm and less than 1535nm, the second transmission optical fiber channel: greater than or equal to 1535nm and less than 1540nm...the seventh transmission optical fiber channel: greater than or equal to 1560nm and less than 1565nm.

[0041] L band, wavelength range is greater than or equal to 1565nm and less than or equal to 1625nm, divided into 5 channels, each 12nm wavelength interval is a channel, including the eighth transmission fiber channel: greater than or equal to 1565nm and less than 1577nm, the ninth transmission fiber channel: greater than or equal to 1577nm and less than 1589nm... The twelfth transmission fiber channel: greater than or equal to 1613nm and less than or equal to 1625nm.

[0042] The algorithm of the demodulator 8 will further eliminate the potential influence of the boundary wavelength to ensure data continuity.

[0043] Furthermore, the multiple groups of magnetic field data output by the demodulator 8 in step S5 are calculated by weighted averaging or spatial interpolation algorithm.

[0044] Furthermore, the demodulator 8 performs digital filtering on 50 Hz power frequency interference and high-frequency noise, and the high-frequency noise is ≥1 kHz.

[0045] The overall working process of the present invention is: the power supply circuit supplies power to the entire detection circuit. When a vehicle enters the section on the track, a closed loop is formed between the two rails through the vehicle body, the coil of the intermediate relay circuit is energized, its contacts are activated, and the signal indicator light is on. The present invention arranges high-density optical fiber sensing units on both sides of the platform entrance track, and each unit is composed of optical fiber and magnetic fluid. The optical fiber link is connected to the demodulator 8 of the station control center through a wavelength division multiplexer 6 to process multi-node data in real time. When there is no vehicle, the sensor detects that the baseline value of the geomagnetic field around the track is about 50μT. When the vehicle enters the station, the vehicle body, especially the motor and the metal wheel pair, causes magnetic field distortion, that is, the motor current magnetic field is superimposed on the geomagnetic field, and the local field strength rises to 100-500μT. The movement of the vehicle causes the direction of the magnetic field gradient to be opposite to the driving area outside the station. The magnetic field enhancement increases the refractive index of the magnetic fluid, reduces the optical fiber transmission loss through evanescent field coupling, and increases the transmitted light intensity by 5% to 20%. When the change in its magnetic field intensity reaches a preset base value, it will trigger the sensor nodes distributed along the direction of entering the station in sequence, and trigger the delay difference through adjacent nodes. Calculation speed: Used under uniform speed conditions , where v represents the vehicle speed, ‌ indicates fixed node spacing, Indicates the delay difference between adjacent node triggers. Under non-uniform speed conditions, multiple instantaneous speeds are calculated by combining differentiation. If v is lower than a threshold value such as 30 km / h and continues to decelerate, it is determined to be a station entry behavior. The direction of the difference in magnetic field intensity between adjacent nodes matches the station entry trajectory to exclude false triggers such as reverse vehicles or electromagnetic interference. When the transmitted light intensity exceeds 3 times the baseline value, the convolutional neural network CNN is used to analyze the light intensity time domain waveform to distinguish between vehicles entering the station and other interference.

[0046] The working principle of the magnetic fluid is that the magnetic fluid will move in the direction of the strong magnetic field in the magnetic field, and thus change its shape, gather or form a special pattern. The present invention uses this feature to combine the magnetic fluid with the optical fiber. Under the action of the instantaneous magnetic field generated around the track, the magnetic moment inside the magnetic fluid filler 42 tends to align with the external magnetic field, that is, the magnetic particles in the magnetic fluid filler 42 will be attracted to the place with higher magnetic field intensity, thereby causing the optical fiber in the non-magnetic shell 41 to be unevenly stressed and slightly deformed. Through the slight deformation of the optical fiber, the period, refractive index and intensity of the refractive grating 44 will change, changing the sensing results and detecting whether the environmental magnetic field is abnormal. Therefore, the vehicle entry signal can be predicted earlier, so that the direction and magnitude of the force can be inferred by demodulating the propagation beam information, and the health of the track can be monitored in real time through changes in the magnetic field, such as wear and damage of the rails.

[0047] The core of the present invention lies in the device and method for rail vehicle signal detection based on optical fiber magnetofluid sensitization, including the application of optical fiber sensing technology, magnetofluid technology and non-magnetic materials. The outer shell of the magnetofluid rod 4 in the invention is made of sealed non-magnetic material, and the optical fiber is engraved and placed in the outer shell, and the space between the two is filled with magnetofluid material. The optical fiber is enclosed in the non-magnetic material. When the external magnetic field or mechanical stress changes, the transmission characteristics of the optical fiber will change accordingly, thereby detecting rail vehicle entry and exit signals or magnetic field anomalies. The present invention uses optical fiber sensing technology and magnetofluid technology to achieve high-sensitivity detection of rail vehicle entry and exit signals and track magnetic field anomalies, and has high sensitivity, real-time and broad application prospects.

Claims

1. A device for detecting rail vehicle signals based on optical fiber magnetic fluid sensitization, characterized in that: The device comprises a multi-channel wavelength division modulation optical path system based on a magnetic fluid grating; the multi-channel wavelength division modulation optical path system based on a magnetic fluid grating comprises a laser light source (1), a first optical fiber (2), a coupler (3), a magnetic fluid rod (4), a reference optical fiber (5), a wavelength division multiplexer (6), a transmission optical fiber (7) and a demodulator (8); the laser light source (1) is at the input port side of the coupler (3), and the two are connected through the first optical fiber (2); the magnetic fluid rod (4), the reference optical fiber (5) and the coupler (3) are connected in a closed loop through the first optical fiber (2); the wavelength division multiplexer (6) is connected to the output end side of the coupler (3) through the first optical fiber (2); the wavelength division multiplexer (6) ) is connected in parallel to at least two transmission optical fibers (7) on the output end side, each of the transmission optical fibers (7) is provided in series with a demodulator (8), and the number and connection relationship of the transmission optical fibers (7) and the demodulators (8) are in one-to-one correspondence; the magnetic fluid rod (4) comprises a non-magnetic shell (41), a magnetic fluid filler (42), a second optical fiber (43) and a refractive grating (44); the second optical fiber (43) is coaxially sealed in the non-magnetic shell (41) to form an annular gap, the magnetic fluid filler (42) is filled in the annular gap formed by the second optical fiber (43) and the non-magnetic shell (41), and the second optical fiber (43) is engraved with a refractive grating (44).

2. The device for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to claim 1 is characterized in that: The non-magnetic shell (41) contains SiO2, and the magnetic fluid filler (42) is Fe3O4 particles.

3. The device for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to claim 1 is characterized in that: The number of the transmission optical fibers (7) and the number of the demodulators (8) are both at least 12.

4. The device for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to claim 1 is characterized in that: The first optical fiber (2), the second optical fiber (43), the reference optical fiber (5) and the transmission optical fiber (7) are all single-mode optical fibers.

5. A method for detecting rail vehicle signals based on optical fiber magnetic fluid sensitization, characterized in that: The method uses the device for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to any one of claims 1 to 4 to detect rail vehicle signals, comprising the following steps: Step S1: a laser light source (1) emits broadband or tunable laser light, and the optical signal is transmitted to a coupler (3) via a first optical fiber (2); Step S2: The coupler (3) divides the input optical signal into two paths, the main path enters the magnetic fluid rod (4); and the reference path is directly transmitted to the reference optical fiber (5); Step S3: The optical signals emitted through the main path and the reference path are output to the wavelength division multiplexer (6) through the coupler (3); the refractive grating (44) in the magnetic fluid rod (4) of the main path only reflects the Bragg wavelength The optical signal is transmitted, and the rest is transmitted; the magnetic fluid filler (42) in the magnetic fluid rod (4) moves with the change of the external magnetic field H caused by the vehicle entering and leaving the detection area, causing the refractive grating (44) to deform and cause the Bragg wavelength to shift. wavelength optical signal, its calibration curve is ,in, represents the Bragg wavelength shift caused by the refraction grating (44), k represents a proportionality constant, and H represents an external magnetic field; Step S4: the wavelength division multiplexer (6) distributes the optical signal outputted by the coupler (3) into the channels of the transmission optical fiber (7) according to different wavelength ranges; Step S5: Each transmission optical fiber (7) channel corresponds to an independent demodulator (8) to extract magnetic field information to complete wavelength detection, specifically including: using a Fabry-Perot filter or a spectrometer to measure the wavelength of each channel, and according to the Bragg wavelength offset With calibration curve , calculate the local magnetic field strength corresponding to each channel, perform differential operation on the reference signal and the main signal to eliminate common mode interference, and integrate the multiple sets of magnetic field data output by the demodulator (8) into a global magnetic field distribution map through an algorithm.

6. The method for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to claim 5 is characterized in that: Step S1: The laser light source (1) emits broadband or tunable laser light in the 1550nm band.

7. The method for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to claim 5 is characterized in that: The transmission optical fiber (7) channel range of step S4 covers the C band and the L band, and the band range is greater than or equal to 1530 nm and less than or equal to 1625 nm.

8. The method for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to claim 5, characterized in that: The multiple sets of magnetic field data output by the demodulator (8) in step S5 are calculated by weighted averaging or spatial interpolation algorithm.

9. The method for rail vehicle signal detection based on optical fiber magnetic fluid sensitization according to claim 5, characterized in that: The demodulator (8) performs digital filtering on 50 Hz power frequency interference and high-frequency noise, wherein the high-frequency noise is ≥ 1 kHz.

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