Inclined grating radiation modulation type all-fiber current sensor with dielectric film filtering

Abstract

The invention discloses an inclined grating radiation modulation type all-fiber current sensor with dielectric film filtering. The inclined grating radiation modulation type all-fiber current sensor comprises a broadband light source, a 45-degree inclined fiber grating, a lens system, a movable fiber with a dielectric film coating, a fixed fiber, a photoelectric detector and a signal processing unit. The 45-degree inclined fiber bragg grating outputs the S polarization component at a wavelength-dependent radiation angle, and the S polarization component is focused to the end face of a movable optical fiber plated with a dielectric film coating through a lens; the side wall of the movable optical fiber is plated with a permanent magnet alloy layer, the movable optical fiber generates transverse micro-displacement under the action of an alternating magnetic field of current to be measured, and meanwhile, the radiation light receiving efficiency of the movable optical fiber and the coupling efficiency between the movable optical fiber and the fixed optical fiber are modulated; the photoelectric detector detects the light intensity change, and the signal processing unit accurately inverts the current value according to the light intensity change. Compared with the prior art, the current sensor has the advantages of being all-fiber passive, resistant to electromagnetic interference and ambient light interference, good in temperature stability and high in sensitivity, and is suitable for high-precision current detection in complex illumination and electromagnetic environments.

Description

Technical Field

[0001] This invention relates to the fields of power system current detection technology and fiber optic sensing technology, specifically to a tilted grating radiation modulation all-fiber current sensor with dielectric film filtering. Background Technology

[0002] With the development of smart grids and industry, higher requirements are being placed on the accuracy, reliability, and environmental adaptability of power system current monitoring. Traditional electromagnetic current transformers have inherent drawbacks such as easy saturation, complex insulation, and poor electromagnetic compatibility. Fiber optic current sensors (FOCS) have become a research hotspot due to their advantages such as good insulation, immunity to electromagnetic interference (EMI), and small size.

[0003] Existing fiber optic current sensors face two main challenges:

[0004] 1. Environmental disturbance sensitivity: FOCS based on the interference principle is extremely sensitive to temperature and vibration; while the optical signal of the fiber optic sensor is easily interfered with by the intrusion of stray light in the environment during transmission and detection, resulting in a decrease in signal-to-noise ratio and poor measurement stability, especially in outdoor or bright industrial environments.

[0005] 2. System complexity and cost: To suppress stray light, it is usually necessary to add an independent filter in front of the detector or use a complex shielding structure, which increases the system size, packaging difficulty and cost.

[0006] Tilted fiber gratings (TFGs) can achieve wavelength-angle encoded radiation output, providing possibilities for novel sensing mechanisms. However, existing TFG-based sensing schemes are mostly concentrated in laboratory environments, failing to adequately consider the suppression of light interference in complex field environments, thus limiting their engineering applications.

[0007] Therefore, there is an urgent need for an all-fiber current sensor that integrates efficient filtering functions within the sensing structure, can suppress stray light interference at the source, and maintains high sensitivity and stability. Summary of the Invention

[0008] Purpose of the invention: To address the problems existing in the background technology, the present invention provides a tilted grating radiation modulation all-fiber current sensor with dielectric film filtering. By directly integrating the dielectric film coating at the input end of the sensing optical path, ambient stray light is filtered out from the source. Furthermore, it cleverly combines the wavelength-selective radiation of TFG with the dual modulation mechanism of mechanical coupling between optical fibers, thereby greatly improving the sensor's anti-interference capability and measurement reliability in complex lighting environments while ensuring high sensitivity.

[0009] Technical solution: This invention discloses a tilted grating radiation modulation all-fiber current sensor with dielectric film filtering, comprising:

[0010] Broadband light source;

[0011] A 45° tilted fiber grating is connected to the output fiber of the broadband light source to radiate the S-polarization component at a wavelength-dependent radiation angle.

[0012] A lens system is disposed in the radiation optical path of the 45° tilted fiber grating;

[0013] The movable optical fiber receives radiated light through the lens system at its input end, and the end face of the input end is coated with a dielectric film coating, while the sidewalls of the input end and the output end are coated with a permanent magnet alloy layer.

[0014] A fixed optical fiber is located at the rear end of the movable optical fiber, with one end of the fixed optical fiber and the output end of the movable optical fiber located in the coupling region, and the cores of the two fibers have a preset initial lateral misalignment in the coupling region.

[0015] A photodetector is connected to the output end of the fixed optical fiber;

[0016] The signal processing unit is electrically connected to the photodetector;

[0017] The dielectric film coating is used to filter ambient stray light that is not at the operating wavelength;

[0018] The permanent magnet alloy layer is subjected to force under the action of the alternating magnetic field generated by the current to be measured, which drives the two ends of the movable optical fiber to produce a lateral micro-displacement. This displacement simultaneously modulates the intensity of the radiated light received by the movable optical fiber through the dielectric film coating and the optical coupling efficiency of the coupling region.

[0019] The photodetector detects the change in light intensity after filtering and modulation, and the signal processing unit calculates the measured current value based on the change in light intensity.

[0020] Furthermore, the dielectric film coating is a multilayer dielectric film, deposited on the input end face of the movable optical fiber, and its center wavelength of transmission spectrum matches the working band of the 45° tilted fiber grating. The transmittance in the working band is not less than 95%, and the suppression ratio in the non-working band is not less than 20dB.

[0021] Furthermore, the multilayer dielectric film is formed by alternating deposition of silicon dioxide and titanium dioxide.

[0022] Furthermore, the initial lateral misalignment between the movable optical fiber and the fixed optical fiber in the coupling region is 3-5 μm, and the lateral micro-displacement amplitude of the movable optical fiber is ±2 μm.

[0023] Furthermore, the lens system is a gradient refractive index lens, and its numerical aperture is matched with that of the movable optical fiber.

[0024] Furthermore, it also includes an integrated rigid fixing base, the integrated rigid fixing base having an inwardly recessed center to form the coupling area, and V-shaped grooves provided on both sides of the integrated rigid fixing base along the direction perpendicular to the coupling area. The movable optical fiber and the fixed optical fiber are respectively fixed to the input and output ends of the movable optical fiber corresponding to the V-shaped groove, which protrude from the V-shaped groove and the output end is located within the coupling area.

[0025] Furthermore, the permanent magnet alloy layer is a nickel-iron alloy or an aluminum-nickel-cobalt alloy, which is attached to the sidewall of the movable optical fiber by magnetron sputtering, and has a thickness of 0.5-2 μm.

[0026] Furthermore, it also includes a magnetic collecting ring, which is sleeved around the current-carrying conductor and fixedly connected to the integrated rigid fixed base, for enhancing and concentrating the alternating magnetic field.

[0027] Furthermore, the signal processing unit has a built-in temperature compensation module and a digital phase-locked amplifier module. The temperature compensation module performs real-time compensation based on data from the built-in temperature sensor, and the digital phase-locked amplifier module extracts the light intensity modulation component using the power grid frequency as a reference signal.

[0028] This invention also discloses a method for operating a tilted grating radiation modulation all-fiber current sensor with dielectric film filtering, comprising the following steps:

[0029] Step 1: The light emitted from the broadband light source is radiated with the S-polarization component at a specific radiation angle after passing through a 45° tilted fiber grating;

[0030] Step 2: After being focused by the lens system, the radiated light is incident on the end face of the movable optical fiber coated with a dielectric film, and the ambient stray light is filtered out by the dielectric film coating.

[0031] Step 3: The alternating magnetic field generated by the current under test acts on the permanent magnet alloy layer, driving the movable fiber end face to produce a lateral micro-displacement;

[0032] Step 4: Micro-displacement simultaneously changes the intensity of the radiated light received by the movable optical fiber after filtering, as well as the coupling efficiency between the movable and fixed optical fibers.

[0033] Step 5: The filtered and double-modulated optical intensity signal output from the fixed optical fiber is converted into an electrical signal by a photodetector;

[0034] Step 6: The signal processing unit processes the electrical signal and obtains the measured current value according to the pre-calibrated light intensity-current relationship.

[0035] Beneficial effects:

[0036] 1. The current sensor disclosed in this invention possesses excellent resistance to ambient light interference. This resistance stems from the integrated dielectric film filter. The alternating stacking of silicon dioxide and titanium dioxide forms an optical interference film system, whose transmission spectrum center wavelength is strictly matched with the operating band of a 45° tilted fiber optic grating (e.g., 1550nm). This ensures that stray ambient light is physically filtered out in the first step before entering the sensing optical path, significantly improving the signal-to-noise ratio. The dielectric film coating is integrated at the front end of the sensing optical path, efficiently filtering non-signal light from its physical source. This allows the sensor to operate stably in environments with strong stray light, such as outdoor sunlight and industrial lighting, solving a major application pain point of traditional fiber optic sensors. The dielectric film coating is formed by alternating deposition of silicon dioxide and titanium dioxide.

[0037] 2. The current sensor disclosed in this invention features all-fiber passive operation and high electromagnetic compatibility. The sensor head is completely passive and all-dielectric, requiring no power supply. The entire sensing process is completed via optical signals, without any electronic components, thus fundamentally immune to strong electromagnetic interference. This sensor is particularly suitable for high-precision, high-stability current monitoring in environments with complex light interference, such as high-voltage transmission lines, outdoor substations, and industrial plants.

[0038] 3. The current sensor disclosed in this invention possesses high sensitivity and accuracy: it cleverly combines the wavelength-selective radiation of the TFG with a dual modulation mechanism of mechanical coupling between optical fibers, amplifying the useful signal. Combined with a high signal-to-noise ratio input, it can achieve high-precision current measurement (e.g., 0.5 level). The movable optical fiber and the fixed optical fiber are coupled and modulated in the coupling region. The sidewalls of the input and output ends of the movable optical fiber are coated with a permanent magnet alloy layer, enabling it to undergo lateral micro-displacement under the action of the alternating magnetic field of the current to be measured. This micro-displacement simultaneously modulates the efficiency of the movable optical fiber in receiving radiated light and the coupling efficiency with the fixed optical fiber, forming a dual modulation effect.

[0039] 4. The current sensor disclosed in this invention exhibits excellent temperature and mechanical stability. It features an integrated rigid mounting base and an all-fiber optic structure, providing inherent temperature insensitivity and vibration resistance. It also utilizes a material with an extremely low coefficient of thermal expansion (≤5.5×10⁻⁶). -7 The quartz glass base is made of an integrated rigid fixing base with a thermal expansion coefficient close to that of optical fiber, and the integrated design greatly reduces the thermal stress between different materials.

[0040] 5. The current sensor disclosed in this invention has the advantages of compact structure and ease of mass production. Dielectric film deposition on the fiber end face is a mature process, easily integrated and automated with other fiber optic devices, which helps reduce costs and promotes industrialization. The dielectric film deposition adopts standard magnetron sputtering or electron beam evaporation processes; fiber positioning uses precision-machined V-grooves; overall assembly can be completed on a six-dimensional micro-adjustment stage and cured with UV adhesive. These processes are all mature technologies in the fields of optical communication and MEMS, enabling this sensor to maintain high performance while having low manufacturing costs and good process consistency, which is conducive to large-scale industrialization.

[0041] 6. The invention has a high degree of functional integration: the filtering function is deeply integrated into the sensing unit, eliminating the need for external filter components, making the sensor structure more compact and reliable. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the overall structure of the current sensor of the present invention;

[0043] Figure 2 This is a three-dimensional multi-view of the integrated rigid fixing base for the current sensor of the present invention;

[0044] Figure 3 This is a view from direction B of the current sensor of the present invention, which integrates a magnetic ring, a test current, and an integrated rigid fixed base.

[0045] Figure 4 This is a schematic diagram of the radiation characteristics of the 45° tilted fiber grating of the present invention;

[0046] (a) Schematic diagram of polarization separation of light passing through a grating (P polarization component transmission, S polarization component radiation); (b) Radiation mode image when white light is incident;

[0047] Figure 5 The image shows the angular dispersion characteristics of a 45° tilted fiber grating, and the first-order angular dispersion curves of the grating under different periods (the larger the period, the greater the angular dispersion).

[0048] Figure 6 This is a graph showing the relationship between fiber Bragg grating filtering and demodulation.

[0049] Among them, 1-broadband light source, 2-fiber grating, 3-lens system, 4-movable optical fiber, 5-fixed optical fiber, 6-photodetector, 7-dielectric film coating, 8-permanent magnet alloy layer, 9-integrated rigid fixed base, 10-magnetic ring, 11-V-groove, 12-coupling area. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1: Current sensor suitable for outdoor power distribution lines

[0052] Component selection

[0053] Broadband light source 1: Superluminescent diode, center wavelength 1550nm, spectral width 60nm.

[0054] 45° Tilted Fiber Grating 2: Fabricated on a single-mode fiber using a phase mask tilt scanning method. The tilt angle is 45° ± 0.5°, and the grating region length is 12 mm. In the 1550 nm band, the S-polarized light radiation efficiency is >35%.

[0055] Lens system 3: 1.8mm diameter, 1 / 4 pitch gradient refractive index lens, NA=0.46.

[0056] Magnetic induction components: The permanent magnet alloy layer 8 is made of nickel-iron alloy (thickness 0.5mm), and the magnetic collecting ring 10 is made of silicon steel (inner diameter 5mm, outer diameter 10mm).

[0057] Optical fiber: SMF-28e single-mode optical fiber is selected.

[0058] Dielectric film coating 7: The coating is made of alternating silicon dioxide and titanium dioxide, and the thickness is optimized according to the transmittance of visible light (transmittance ≥95%).

[0059] Integrated rigid fixing base 9: Made of JGS2 ultraviolet-grade quartz glass, with a coefficient of thermal expansion not exceeding 5.5×10. -7 / ℃, and is precision machined to contain two parallel V-grooves.

[0060] Both the movable optical fiber 4 and the fixed optical fiber 5 are fixed on the V-groove 11 of the integrated rigid fixing base 9, and the optical fibers are bonded in the fixing area using high-strength UV-curable adhesive.

[0061] The V-groove 11 for fixing the movable optical fiber 4 includes a fixing region and a release region. There is no rigid connection between the release region and the movable optical fiber 4, allowing the movable optical fiber 4 to undergo slight lateral displacement within the release region (both the movable optical fiber 4 and the fixing optical fiber 5 are flexible, and the ends of the movable optical fiber 4 can undergo slight displacement). See also Figure 1In this embodiment, the integrated rigid fixing base 9 is recessed in the middle to form a coupling area 12. V-shaped grooves 11 are provided on both sides of the integrated rigid fixing base 11 along the direction perpendicular to the coupling area 12. The movable optical fiber 4 and the fixed optical fiber 5 are respectively fixed in the corresponding V-shaped grooves 11 (bonded with high-strength UV-curable adhesive). The input end and output end of the movable optical fiber 4, which is coated with a permanent magnet alloy layer 8, protrude from the V-shaped grooves 11 and the output end is located in the coupling area 12. In this way, the movable optical fiber 4 can generate lateral micro-displacement in the release area.

[0062] The V-groove spacing design of the V-groove 11 ensures that: the distance between the TFG fiber end face and the lens is 0.5 mm, the distance between the lens and the end face of the movable fiber 4 is equal to its focal length (approximately 1.0 mm), the initial lateral misalignment between the movable fiber 4 and the fixed fiber 5 in the coupling region 12 is 3-5 μm, and the lateral micro-displacement amplitude of the movable fiber 4 is ±2 μm. In this embodiment, the center of the V-groove 11 of the movable fiber 4 and the fixed fiber 5 is laterally offset by 4.0 μm.

[0063] Photodetection and signal processing: An InGaAs photodetector with a transimpedance amplifier is used. The signal processing board is based on an STM32 microcontroller and integrates a 24-bit Σ-Δ ADC and a digital phase-locked loop (for extracting 50Hz power frequency signals).

[0064] Implementation process of the temperature compensation module:

[0065] Hardware Setup: A high-precision digital temperature sensor is integrated on the printed circuit board of the signal processing unit, adjacent to the optical components (or integrated base) of the current sensor head. The temperature sensor is a surface-mount digital temperature sensor or a thermocouple / thermistor (such as MCP9808, resolution ±0.0625℃), integrated on the signal processing unit. The temperature sensor is mounted on the surface of the integrated base to sense the real-time temperature of the current sensor. The temperature sensor is connected to the main control microcontroller (MCU, such as STM32) via an I²C bus, sampling the ambient temperature T in real time at a frequency of at least 1Hz.

[0066] Compensation process: Pre-shipment full-temperature calibration: Place the assembled sensor in a high and low temperature test chamber, and set temperature points at 10°C intervals within the rated operating temperature range (e.g., -40°C to +85°C). After each temperature point stabilizes, record the DC voltage value V output by the photodetector when there is no current input. offset (T), which is the "Temperature-Base Offset" lookup table.

[0067] Establish a compensation model: Store the calibration data in the MCU's FLASH memory. During actual operation, the MCU reads the real-time temperature T and obtains the reference offset V corresponding to the current temperature from a lookup table using linear interpolation. offset (T).

[0068] Real-time compensation calculation: The total voltage V, including signal and noise, acquired in real-time by the ADC. raw (T), first perform temperature offset compensation:

[0069]

[0070] This operation eliminates DC drift caused by temperature and normalizes the operating point of the signal.

[0071] Optional sensitivity temperature coefficient compensation: If further testing reveals that the system sensitivity (i.e., the current-to-signal amplitude conversion coefficient K) also changes slightly with temperature, a second lookup table K(T) can be created to correct for the final current value calculation.

[0072]

[0073] Where A is the signal amplitude extracted by the lock-in amplifier.

[0074] The digital phase-locked amplifier module samples the grid voltage and extracts the 50Hz / 60Hz power frequency signal via a phase-locked loop (PLL). The current signal output from the photodetector is converted into a voltage signal V(t) by a transimpedance amplifier and generates an orthogonal reference signal R with the same frequency as the grid. sin (t), R cos (t) uses a digital low-pass filter to filter out high-frequency noise and extracts the DC component to obtain the amplitude of the modulation signal (light intensity modulation component), which is proportional to the current to be measured.

[0075] Implementation process of digital phase-locked amplifier module:

[0076] Reference signal generation: A power frequency voltage signal is obtained from the grid voltage transformer or a dedicated voltage sampling circuit. After passing through a zero-crossing comparator and a phase-locked loop circuit, a square wave reference clock that is strictly in phase and frequency with the grid current is generated. This clock is input to the MCU's timer capture pin. Internally, using this clock as a reference, a pair of orthogonal digital reference signals are generated through direct digital synthesis technology or a pre-stored sine / cosine table. , Where f0 is the power grid frequency, f s This represents the ADC sampling rate.

[0077] Multiplication operation: Multiplying the temperature-compensated digital signal sequence V... comp (T), respectively with orthogonal reference signal R sin (t) and R cos Performing multiplication on (t) yields two product signals I(t) and Q(t):

[0078] ,

[0079] Low-pass filtering: I(t) and Q(t) are fed into a digital low-pass filter (usually an FIR or IIR filter with a cutoff frequency of a few Hz, such as a Butterworth filter). The filter's function is to remove the high-frequency components generated by multiplication and the harmonic noise of the power grid, and finally output two slowly varying DC components X and Y, which represent the projections of the signal in the in-phase and quadrature directions of the reference signal, respectively.

[0080] X = LPF{I(t)}, Y = LPF{Q(t)}

[0081] Amplitude Calculation: The amplitude A of the effective light intensity modulation signal caused by the measured current is calculated by the following formula:

[0082]

[0083] The amplitude A is proportional to the Lorentz force driving the movable optical fiber, and thus proportional to the effective value of the current to be measured.

[0084] Final current inversion: The calculated signal amplitude A is combined with the pre-calibrated amplitude-current relationship curve (temperature compensation already considered), and the accurate measured current value I is inverted in real time through MCU calculations. measured And output it through the communication interface.

[0085] Installation and calibration:

[0086] Place each component into the corresponding V-groove 11 on the base in sequence. Use a six-dimensional fine-tuning stage and an infrared camera to monitor and precisely adjust the position of the movable optical fiber 4 so that the output optical power of the fixed optical fiber 5 reaches 50% of the maximum coupling power (corresponding to a 4μm misalignment).

[0087] The sensor was mounted on a current calibration platform equipped with a standard CT. Under anechoic conditions, a 10-600A (RMS) power frequency current was applied, and the output value of the signal processing unit was recorded. A quadratic polynomial fitting calibration curve was used, with a full-range nonlinearity error of <0.3%.

[0088] Testing process:

[0089] The current in the transmission line generates an alternating magnetic field, and the magnetic ring 10 concentrates the magnetic field on the nickel-iron alloy layer.

[0090] The permanent magnet alloy layer 8 is driven by the Lorentz force to shift the movable optical fiber 4 laterally.

[0091] The light from broadband light source 1 (visible light band) is radiated by the S-polarization component after passing through the grating, and enters the optical fiber after the stray light is filtered by the dielectric film.

[0092] The photodetector 6 receives light intensity that varies with the fiber optic offset. The photodetector 6 converts the optical signal into an electrical signal and transmits it to the signal processing unit.

[0093] The signal processing unit calculates the current value based on the light intensity and calibration curve, and transmits it to the monitoring system.

[0094] Performance verification:

[0095] Basic accuracy test: In a laboratory without ambient light interference, compared with a 0.05 grade standard CT, the sensor measurement error is <±0.5% within the range of 20-600A.

[0096] Immune light interference test (core test):

[0097] a. Test conditions: Use a standard D65 light source to simulate sunlight, vertically illuminating the sensor's optical path area, with an illuminance of 1000 Lux.

[0098] b. Test objects: Two sensors, one is the version of the present invention with a dielectric film coating (A), and the other is the exact same version without a dielectric film coating (B).

[0099] c. Test procedure: Apply a stable 200A power frequency current and monitor continuously for 1 hour.

[0100] d. Test Results: The standard deviation (σ) of the output fluctuation of sensor A was only 0.15%, while the output fluctuation of sensor B was drastic, with σ as high as 2.1%, and there was obvious power frequency flicker interference. This proves that the dielectric film coating effectively suppressed ambient light interference.

[0101] Temperature cycling test: Cycle 3 times in a temperature chamber from -40℃ to 85℃, the sensor's accuracy change across the entire range is <±0.8% (<±0.3% after temperature compensation is enabled).

[0102] Long-term aging test: After 90 days of installation and operation in a simulated outdoor distribution box environment, the daily data drift was <0.2%, indicating stable performance.

[0103] Example 2: Explosion-proof industrial motor current monitoring sensor

[0104] For motor monitoring needs in chemical plants, oil and gas platforms, and other locations with potentially explosive gas environments, explosion-proof reinforced designs are implemented.

[0105] Component adjustment

[0106] The sensing optical components are encapsulated in a stainless steel armored tube filled with inert gas, and the fiber optic inlet and outlet ends are equipped with explosion-proof sealed connectors.

[0107] A diamond-like carbon (DLC) protective film is added to the outermost layer of the dielectric film on the four ends of the movable optical fiber to enhance its wear resistance and anti-fouling ability.

[0108] Application effect

[0109] The sensor was installed and tested on a pump motor in a chemical plant. Despite the presence of oil and gas mist and complex lighting conditions, the sensor was able to stably monitor the motor current, provide early warnings of multiple overload events, meet the industrial 0.5 level accuracy requirements, and pass explosion-proof certification.

[0110] The foregoing description of the embodiments enables those skilled in the art to make or use the present invention. Various modifications to the embodiments will be readily apparent to those skilled in the art. The general principles of the invention may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention should not be limited to the embodiments shown herein, but should cover the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A tilted grating radiation modulation all-fiber current sensor with dielectric film filtering, characterized in that, include: Broadband light source (1); A 45° tilted fiber grating (2) is connected to the output fiber of the broadband light source and is used to radiate the S-polarization component at a wavelength-dependent radiation angle. The lens system (3) is disposed in the radiation optical path of the 45° tilted fiber grating (2); The movable optical fiber (4) receives radiated light through the lens system (3) at its input end, and the end face of the input end is coated with a dielectric film coating (7), and the sidewalls of the input end and the output end are coated with a permanent magnet alloy layer (8). The fixed optical fiber (5) is located at the rear end of the movable optical fiber (4), and one end of it is located in the coupling area (12) with the output end of the movable optical fiber (4), and the cores of the two fibers are pre-set in the coupling area (12). A photodetector (6) is connected to the output end of the fixed optical fiber (5); The signal processing unit is electrically connected to the photodetector (6); The dielectric film coating (7) is used to filter ambient stray light that is not at the working wavelength; The permanent magnet alloy layer (8) is subjected to force under the action of the alternating magnetic field generated by the current to be measured, which drives the two ends of the movable optical fiber (4) to produce a lateral micro-displacement. This displacement simultaneously modulates the radiation intensity received by the movable optical fiber (4) through the dielectric film coating (7) and the optical coupling efficiency of the coupling region (12). The photodetector (6) detects the change in light intensity after filtering and modulation, and the signal processing unit calculates the measured current value based on the change in light intensity.

2. The tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 1, characterized in that, The dielectric film coating (7) is a multilayer dielectric film, which is deposited on the input end face of the movable optical fiber (4). The center wavelength of its transmission spectrum matches the working band of the 45° tilted fiber grating (2). The transmittance in the working band is not less than 95%, and the suppression ratio in the non-working band is not less than 20dB.

3. The tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 2, characterized in that, The multilayer dielectric film is formed by alternating deposition of silicon dioxide and titanium dioxide.

4. The tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 1, characterized in that, The initial lateral misalignment of the movable optical fiber (4) and the fixed optical fiber (5) in the coupling region (12) is 3-5 μm, and the lateral micro-displacement amplitude of the movable optical fiber (4) is ±2 μm.

5. A tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 1, characterized in that, The lens system (3) is a gradient refractive index lens, and its numerical aperture is matched with that of the movable optical fiber (4).

6. The tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 1, characterized in that, It also includes an integrated rigid fixing base (9), the integrated rigid fixing base (9) is recessed in the middle to form the coupling area (12), and V-shaped grooves (11) are provided on both sides of the integrated rigid fixing base (9) along the direction perpendicular to the coupling area (12). The movable optical fiber (4) and the fixed optical fiber (5) are respectively fixed in the corresponding V-shaped grooves (11). The input end and output end of the movable optical fiber (4) coated with permanent magnet alloy layer (8) protrude from the V-shaped grooves (11) and the output end is located in the coupling area (12).

7. The tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 1, characterized in that, The permanent magnet alloy layer (8) is a nickel-iron alloy or an aluminum-nickel-cobalt alloy, which is attached to the sidewall of the movable optical fiber by magnetron sputtering process, and has a thickness of 0.5-2μm.

8. A tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 6, characterized in that, It also includes a magnetic ring (10), which is sleeved around the current-carrying conductor and is fixedly connected to the integrated rigid fixed base (9) to enhance and concentrate the alternating magnetic field.

9. A tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to claim 1, characterized in that, The signal processing unit has a built-in temperature compensation module and a digital phase-locked amplifier module. The temperature compensation module performs real-time compensation based on data from the built-in temperature sensor, and the digital phase-locked amplifier module extracts the intensity modulation component using the power grid frequency as a reference signal.

10. A method for operating a tilted grating radiation modulation all-fiber current sensor with dielectric film filtering according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: The light emitted from the broadband light source (1) passes through a 45° tilted fiber grating (2), and the S-polarization component is radiated at a specific radiation angle; Step 2: After being focused by the lens system (3), the radiated light is incident on the end face of the movable optical fiber (4) coated with a dielectric film coating (7), and the ambient stray light is filtered out by the dielectric film coating (7). Step 3: The alternating magnetic field generated by the current to be measured acts on the permanent magnet alloy layer (8), driving the end face of the movable optical fiber (4) to produce a lateral micro-displacement; Step 4: The micro-displacement simultaneously changes the intensity of the radiation received by the movable fiber (4) after filtering, as well as the coupling efficiency between the movable fiber (4) and the fixed fiber (5). Step 5: The light intensity signal output from the fixed optical fiber (5), after filtering and dual modulation, is converted into an electrical signal by the photodetector (6); Step 6: The signal processing unit processes the electrical signal and obtains the measured current value according to the pre-calibrated light intensity-current relationship.

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