Birefringence quantization and optimization method for fiber optic sensing optical path in long-pulse high-current measurement

Abstract

This invention belongs to the field of fiber optic sensing and precision measurement technology. It discloses a method for quantifying and optimizing the birefringence of a fiber optic sensing optical path for long-pulse high-current measurement. The method includes: constructing and discretizing a three-dimensional spatial geometric model of the fiber optic sensing optical path; establishing a hybrid birefringence transmission model with bending and torsional coupling; simulating the polarization state evolution of the entire optical path and quantifying dynamic errors; in-situ calibration of system errors based on zero-current reference conditions; and active input optimization based on polarization state feedback. For sensing fibers deployed in high-current measurement devices (such as nuclear fusion devices, particle accelerators, or high-voltage direct current transmission equipment), this method can accurately decouple and quantify the hybrid birefringence errors generated under dynamic loads (including thermomechanical deformation, mechanical vibration, etc.) during irregular installation paths and equipment operation. Through an active feedback control mechanism, it significantly improves the signal-to-noise ratio and accuracy of high-current measurement.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing and precision measurement technology, and more specifically, relates to a method for quantification and optimization of birefringence in fiber optic sensing paths for long-pulse high-current measurement. Background Technology

[0002] All-fiber current sensors (FOCS) have become the preferred solution for tokamak devices and industrial-grade long-pulse high-current measurements due to their intrinsic insulation and strong resistance to electromagnetic interference. However, in practical applications, to accommodate the thermal expansion and mechanical vibration resistance requirements of the measured conductor under long-pulse operation, the sensing fiber is usually arranged in a helix or spring-like structure, rather than an ideal planar ring. This complex spatial geometry, combined with severe vibrations or abnormal displacements (such as vertical displacement events VDE) during device operation, introduces strong, time-varying mixed birefringence (including bending-induced linear birefringence and torsion-induced circular birefringence) into the fiber. Existing technologies typically rely solely on end-reflecting devices such as Faraday mirrors to cancel the reciprocal phase difference between the round-trip optical paths. However, under the aforementioned complex operating conditions, the non-reciprocal circular birefringence component introduced by fiber torsion cannot be completely canceled, and coupled with the angular errors inherent in the reflective devices themselves, the residual birefringence noise severely affects the accuracy of current measurement.

[0003] In addition, existing technologies typically rely on high-cost specialty optical fibers (such as low-linear birefringence rotating optical fibers) or complex mechanical damping structures to passively resist environmental interference, and studies have shown that some specialty optical fibers (such as high-birefringence optical fibers) still have large measurement errors under lateral collisions.

[0004] Currently, there is a lack of an effective means to quantify and actively optimize this mixed birefringence effect in real time. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a method for birefringence quantization and optimization of optical fiber sensing optical path for long pulse high current measurement, the purpose of which is to improve the accuracy of long pulse high current measurement.

[0006] To achieve the above objectives, this invention provides a method for birefringence quantization and optimization of the optical path of a fiber optic sensor for long-pulse high-current measurement, applied to an all-fiber current sensor FOCS system. The method includes: Based on the actual physical layout trajectory of the sensing fiber in the FOCS system, the sensing fiber path is discretized into several units along its axis, and the geometric parameters of each discrete unit in three-dimensional space, including the local radius of curvature and geometric torsion, are calculated. Based on the aforementioned geometric parameters and the optical properties of the sensing fiber material, the linear birefringence component induced by bending and the circular birefringence component induced by fiber spatial torsion are calculated for each discrete unit to generate the polarization transfer matrix of each discrete unit. The polarization transfer matrices of each discrete unit are then integrated and cascaded to obtain the ellipticity of the output light from the FOCS system. e out and the ellipticity e out As an expected value; Under actual operating conditions, the ellipticity of the output light of the FOCS system is monitored in real time. e out , in ellipticity e out The goal is to minimize the error between the input light and the expected value, adjusting the polarization angle of the input light accordingly. α 0, obtaining the optimal input light polarization angle. α opt At the optimal input light polarization angle α opt Below, the azimuth angle of the output light from the FOCS system. α out As Faraday rotation angle i H To obtain optimized long-pulse high-current measurement values ​​for the device under test. I P .

[0007] Furthermore, at the optimal input light polarization angle α opt The azimuth angle of the output light of the FOCS system is obtained below. α out Subsequently, it also includes in-situ error calibration based on zero-current reference conditions to determine the azimuth angle. α out Background compensation includes: Under the conditions that the device under test is powered on but the large current of the long pulse being measured is zero, or the device under test is in a known reference state, the polarization angle of different input light is measured in real time. α Azimuth angle of FOCS system output light at 0° α ' out To establish by α 0 and α ' out A fingerprint database representing the mapping relationship between them; The azimuth angle α out Subtract the azimuth angle corresponding to the input light polarization angle in the fingerprint database. α ' out To the azimuth angle α out Perform background compensation; and use the azimuth angle after background compensation as the Faraday rotation angle. i H To obtain optimized long-pulse high-current measurement values ​​for the device under test. I P .

[0008] Furthermore, the geometric parameters of each discrete element in three-dimensional space, including the local radius of curvature and geometric torsional rate, are calculated, including: The tangential vector, normal vector, and subnormal vector of the center curve of each discrete element are calculated using the spatial curve geometric analysis method. Geometric parameters of each discrete element in three-dimensional space, including local radius of curvature and geometric torsion, are extracted from the tangential vector, normal vector, and subnormal vector.

[0009] Furthermore, each discrete unit is composed of a linear birefringence component induced by bending and a circular birefringence component induced by optical fiber spatial torsion, respectively:

[0010] in, For the first i Linear birefringence components of a discrete unit k mat These are constants related to the photoelastic coefficient, Poisson's ratio, and core radius of the sensing fiber material. R i For the first i The local radius of curvature of a discrete element;

[0011] in, For the first i The circular birefringence components of a discrete unit g is the optical rotation coefficient of the optical fiber. For the first i Geometric torsion rate of a discrete unit The preset threshold is used to approach zero.

[0012] Furthermore, the polarization transfer matrix of each discrete unit is based on the linear birefringence component. and the circular birefringence component A definite differential Jones matrix or Mueller matrix.

[0013] Furthermore, when the polarization transfer matrix is ​​a differential Jones matrix, integration and concatenation operations are performed on the polarization transfer matrices of each discrete unit to obtain the ellipticity of the output light of the FOCS system. e out ,include: The Jones transfer matrix for each discrete unit is calculated using an exponential mapping. ;in, N T,i For the first i The differential Jones matrix of discrete units, For the first i Length of each discrete unit; Calculate the total transmission matrix of the FOCS system. :

[0014] in, This indicates that when light propagates forward in the sensing fiber, the first... i Jones transfer moment of a discrete unit; This indicates that when light travels back in the sensing fiber, the first... i Jones transfer matrix of discrete units; The matrix representing the end reflector of the FOCS system; Calculate the output electric field vector , This represents the electric field vector of the input light; and the output electric field vector... This is converted into polarization state parameters of the output light to extract the ellipticity of the output light. e out .

[0015] Furthermore, long-pulse high-current measurement values I P With Faraday rotation angle i H The relationship between them is: i H = VI P in, V It is the Verdet constant.

[0016] The present invention also provides a fiber optic sensing optical path birefringence quantization and optimization system for long pulse high current measurement, including a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method described in any of the preceding descriptions.

[0017] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method as described in any of the preceding claims.

[0018] The present invention also provides a computer program product, including a computer program that, when run on a computer, causes the computer to perform any of the methods described above.

[0019] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: (1) This invention breaks through the passive anti-interference mode that relies on special optical fibers and mechanical protection, and establishes an active polarization state optimization mechanism. Existing technologies usually rely on high-cost special optical fibers (such as low-linear birefringence rotating fibers) or complex mechanical damping structures to passively resist environmental interference, and studies have shown that some special optical fibers (such as high birefringence fibers) still have large measurement errors under lateral collisions. This invention abandons the single-dimensional passive hardware defense and innovatively constructs an active polarization control loop based on output ellipticity feedback. Regardless of the type of sensing fiber or the vibration mode it is in, the ellipticity of the output light of the FOCS system is monitored in real time. e out When the error between the observed value and the expected value approaches the preset minimum value, the system can automatically lock and maintain the "quasi-linear polarization" operating point, which is least sensitive to linear birefringence, by dynamically adjusting the polarization orientation of the incident light in real time. This method, in principle, avoids the stringent limitations of fiber selection, significantly improves the system's adaptability under dynamic loads, and enhances the accuracy of current measurement.

[0020] (2) This invention targets the sensing optical fiber deployed in high current measurement devices (such as nuclear fusion devices, particle accelerators or high voltage DC transmission equipment, etc.). By establishing a differential transmission matrix model containing helical geometric parameters, it achieves precise decoupling of geometric torsion (circular birefringence) and physical bending (linear birefringence). By quantifying the mixed birefringence error generated under dynamic loads (including thermomechanical deformation, mechanical vibration and other conditions) during irregular installation paths and equipment operation, and through an active feedback control mechanism, it significantly improves the signal-to-noise ratio and accuracy of high current measurement.

[0021] (3) This invention solves the problem of compensation failure under non-reciprocity error in traditional end-reflection devices such as Faraday rotators. Although existing systems widely use end-reflection devices such as Faraday rotators to cancel reciprocal linear birefringence, in the complex spiral layout of long-pulse high-current devices, geometric torsion introduces non-reciprocal circular birefringence that cannot be canceled by the reflector, and the angular error of the reflector itself (non-ideal 90 degrees) becomes a new source of error. This invention performs in-situ error calibration based on zero-current reference conditions. Under zero-current reference conditions, the measured ellipticity is determined by the static installation deformation (bending, torsion) of the optical fiber and the error of the end-reflector. By combining the algorithm model with zero-current reference calibration, this invention can identify and eliminate the errors of end-reflectors such as rotators and residual stress in the optical path, so that the measurement accuracy is no longer limited by the manufacturing process level of a single optical device, and the system integration cost is greatly reduced.

[0022] (4) System-level in-situ self-calibration throughout the entire lifecycle is achieved, overcoming the drift problem during long-term operation. Existing high-current measurement systems mostly use phase closed loops to solve linearity problems, but cannot solve the static operating point drift caused by optical path aging or thermomechanical deformation. This invention utilizes the zero-current state or known reference state during the operation gap of high-current devices (such as nuclear fusion devices or high-voltage DC transmission towers) to establish an in-situ polarization fingerprint calibration method. This method can update the background birefringence parameters of the system in real time without disassembling the equipment or interrupting the optical path. This not only solves the zero-point drift problem caused by loose connectors or colloid aging during long-term operation, but also ensures that the sensor maintains the "factory-grade" measurement scaling factor stability throughout its entire lifecycle.

[0023] (5) Improved data confidence under extreme dynamic loads, ensuring the operational safety of critical facilities. Traditional measurement methods often fail due to signal distortion in the "worst-case" situations where sensors undergo severe mechanical deformation caused by earthquakes, short-circuit impacts, or plasma rupture. Simulation verification based on spatial curve geometric analysis shows that, after introducing active feedback control, the real-time measured azimuth angle is background-subtracted based on the constructed fingerprint database. Even under severe deformation causing significant fluctuations in optical path birefringence, the measurement error of the output azimuth angle can still be suppressed to an extremely low level (e.g., compressing the error fluctuation range by more than 60%). This highly robust design makes the method applicable to extreme electromagnetic and mechanical environments with extremely high safety monitoring requirements, filling the gap in existing technologies in the field of dynamic seismic measurement.

[0024] In summary, this invention provides an error compensation technique for all-fiber current sensors (FOCS) based on the Faraday effect. This invention is particularly suitable for quasi-steady-state current measurement under long-pulse, high-current, and strong electromagnetic environments, primarily addressing the difficulty in quantifying and eliminating the optical path birefringence effect caused by complex fiber optic routing and dynamic thermomechanical loads (such as thermal expansion and mechanical vibration) under these conditions. Attached Figure Description

[0025] Figure 1 This is a general flowchart of an embodiment of the present invention.

[0026] Figure 2 This is a detailed flowchart of an embodiment of the present invention.

[0027] Figure 3 This is a flowchart of the feedback control system in an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Example 1 like Figure 1 and Figure 2 As shown, this invention provides a method for birefringence quantization and optimization of the optical path of a fiber optic sensor for long-pulse high-current measurement, applied to an all-fiber current sensor FOCS system. In the FOCS system, the sensing fiber is spirally arranged within the high-current measurement device. The method includes the following five steps: Step 1: Construct and discretize the three-dimensional spatial geometric model of the fiber optic sensing optical path.

[0030] Based on the actual physical layout trajectory of the FOCS sensing fiber in the high-current measurement device (usually a complex three-dimensional curve adapted to the device structure, such as a helical tube structure), the entire fiber path is discretized along its axis into several tiny spatial units (each discrete unit has a length of...). For each discrete element, the tangential, normal, and binormal vectors of the center curve of each discrete element are calculated using spatial curve geometric analysis methods, thereby accurately solving for the geometric parameters of the optical fiber in three-dimensional space, including: local radius of curvature (…). R ) and geometric torsion ( t This is to achieve digital reconstruction of changes in the spatial morphology of optical fibers.

[0031] Step 2: Establish a hybrid birefringence transmission model with bending and torsion coupling.

[0032] Based on the geometric parameters obtained in step one, and combined with the optical properties of the fiber material, the mixed birefringence effect within each discrete unit is calculated. Based on the photoelastic effect, the linear birefringence component induced by bending (Δ) is calculated using the local radius of curvature. n Based on the geometric torsion rate, the circular birefringence component induced by the spatial torsion of the optical fiber is calculated. r Based on this, a polarization transfer matrix (such as a differential Jones matrix or a Mueller matrix) containing linear birefringence components and circular birefringence components is constructed to describe the coupling evolution of polarization states during the propagation of polarized light along the optical fiber.

[0033] Step 3: Simulation of polarization state evolution and dynamic error quantification across the entire optical path.

[0034] A full-link transmission simulation model of light in a FOCS system is established, encompassing: incident light transmission, forward transmission in the sensing fiber, reflection by end-reflecting devices (such as Faraday rotators), and reverse return transmission in the sensing fiber. The simulation model incorporates non-ideal parameters of the reflecting devices (such as rotation angle deviation) and the Faraday rotation angle generated by the large current being measured. By integrating and cascading the transmission matrices of each discrete unit, the polarization state parameters (such as Stokes parameters) of the final output light are obtained, thereby enabling the measurement of the ellipticity of the output light under dynamic load conditions such as equipment vibration and deformation. e out ) and azimuth ( α out Precise quantization of the output optical ellipticity ( ). e out () as the expected value.

[0035] Step 4: In-situ calibration of system error based on zero-current reference condition.

[0036] When the measuring device is powered on but the current to be measured is zero ( I P = 0) or under a known reference condition, the output polarization state of the system is measured in real time. This state characterizes the background birefringence noise caused by the inherent installation morphology (bending and twisting) of the optical fiber and the superposition of device deviations. The output azimuth and ellipticity measured under this condition are used to establish a system error calibration reference, which is then applied to the FOCS output data (azimuth) during subsequent high-current measurements. α out and ellipticity e outBackground compensation is performed to eliminate systematic errors caused by the static optical path.

[0037] Step 5: Active input optimization based on polarization state feedback.

[0038] Construct a closed-loop feedback control system to monitor the polarization characteristics of the FOCS output light in real time, especially the output ellipticity. e out Based on output ellipticity e out With respect to the polarization state of the input light (such as the polarization angle of the input light) α 0) A functional dependency exists; this step automatically adjusts the polarization state of the incident light through a feedback algorithm. α 0), to make the ellipticity of the real-time output... e out Compared with expected value ( e out Error between ) e out | Approaching the preset minimum value (e.g., | e out | 0). Therefore, the optimal input light polarization angle is obtained. α opt At the optimal input light polarization angle α opt Below, the azimuth angle output by FOCS α out This is the optimized Faraday rotation angle. i H Based on the optimized Faraday rotation angle i H Optimized long-pulse high-current measurement values ​​were obtained. I P This operation aims to lock the fiber optic sensing system at its optimal operating point of "quasi-linear polarization," which is least sensitive to linear birefringence interference. This minimizes the impact of birefringence noise on the accuracy of current inversion when faced with severe device vibration or sudden load changes.

[0039] Preferably, it also includes the azimuth angle output by FOCS. α out Background compensation is performed using the in-situ calibration method for systematic errors in step four to eliminate systematic errors caused by the static optical path.

[0040] The method described above in this invention will be further illustrated below using the example of high-current measurement in a nuclear fusion device. In other embodiments, the high-current measurement device may also be a particle accelerator or high-voltage direct current transmission equipment, etc., and the optimization method remains the same.

[0041] In this embodiment of the invention, the FOCS system includes a laser source, a polarization state controller (SOP Controller), a sensing fiber (deployed within a tokamak vacuum chamber and a spiral tube of a Dewar structure), a Faraday rotator mirror, and a polarization state analyzer. After the laser source generates input light, it undergoes polarization state control by the polarization state controller before entering the sensing fiber for forward transmission. After reflection by the Faraday rotator mirror, it passes through the sensing fiber again for reverse transmission. At the output end, the polarization characteristics of the output light are measured using a polarization state analyzer to obtain the measurement value of the long-pulse high-current.

[0042] The specific steps are as follows: Step 1: Three-dimensional geometric reconstruction and discretization of the sensing optical path.

[0043] Path Discretization: Based on the actual deployment trajectory of the sensing fiber in the high-current measurement device (e.g., a helical tube structure), the entire length of the sensing fiber path is discretized along its axis. N There are 3 tiny spatial units, each discrete unit having a length of 1. (For example, take) = 0.02m).

[0044] Construct a local coordinate system: For the first i Discrete units ( i =1,…, N A local frame is constructed using the differential geometry theory of space curves (Frenet-Serret formula). Let the spatial position vector of the center curve of the sensing fiber be... r ( s The unit tangent vector is calculated using the Frenet-Serret formula. t Principal normal vector n and binormal vector b Based on this, the tangential, normal, and subnormal vectors of the center curve of each discrete unit are obtained.

[0045] Extract the geometric parameters of each discrete element: Based on the vectors mentioned above, calculate the local radius of curvature of each discrete element. R i and geometric torsion t i .

[0046] Step 2: Construct the differential transfer matrix for bending and torsion coupling.

[0047] After obtaining the geometric parameters, the mixed birefringence effect inside each discrete unit is calculated, and the polarization transfer matrix is ​​established.

[0048] Calculating linear birefringence (bending effect): According to the photoelastic effect, bending of an optical fiber leads to anisotropy in the refractive index distribution. i The linear birefringence component Δ of a discrete unit caused by bending n i for: ;in, k mat It is a constant related to the photoelastic coefficient, Poisson's ratio, and core radius of the optical fiber material. R i For the first i The local radius of curvature of a discrete element.

[0049] Calculate circular birefringence (torsional effect): The first i The circular birefringence component of a discrete unit caused by geometric twisting r i With torsion rate t i Proportional: ;in, g is the optical rotation coefficient of the optical fiber. For the first i Geometric torsion rate of a discrete unit It means approximately equal to.

[0050] Generating the polarization transfer matrix (differential Jones matrix): Constructing a matrix containing linear birefringence components ( β 0, β 45 ) and circular birefringence component ( β c The differential matrix of ) N T,i (Polarization transfer matrix): ; in, β 0、 β 45 Based on linear birefringence component Δ n i Sure, β c Based on circular birefringence It is determined that the method of determination is existing technology; It represents the imaginary unit.

[0051] This polarization transfer matrix precisely describes the polarization transfer matrix in the first... iWithin a discrete unit, as the intrinsic linear polarization axis of the optical fiber rotates with spatial torsion, the polarization state undergoes a physical process of coupling evolution. In other embodiments, the Mueller matrix can also be used as the polarization transfer matrix.

[0052] Step 3: Simulation of polarization evolution and calculation of error field in the entire optical path.

[0053] Based on the above differential model (differential matrix of each discrete unit), the transmission process of polarized light in the entire all-fiber current sensor system is simulated, and the polarization state of the light output in the FOCS system is quantified.

[0054] Unit integration: For each discrete unit, calculate its Jones transfer matrix via an exponential mapping. .

[0055] End-to-end cascading: The complete transmission path of light in the FOCS system consists of "forward transmission from the sensing fiber — Faraday rotator — reverse transmission from the sensing fiber". The total transmission matrix of the FOCS system. It can be represented as: ;in, This indicates that when light propagates forward in the sensing fiber, the first... i Jones transfer moment of a discrete unit; This indicates that when light travels back in the sensing fiber, the first... i Jones transfer matrix of discrete units; The matrix representing the end reflector is, in this embodiment of the invention, a Faraday rotator matrix.

[0056] Two key variables are introduced in this process: The effect of the current under test: in the total transfer matrix M sys The superimposed current of the measured large current I P The resulting Faraday rotation angle i H = VI P ( V (This is the Verdet constant).

[0057] Device error: in the Faraday rotating mirror matrix M FM Non-ideal rotation angle deviation is introduced.

[0058] Output polarization state calculation: The input light is assumed to be linearly polarized (based on the polarization angle of the input light). α 0 definition), using Calculate the output electric field vector , This represents the electric field vector of the input light, and... Further transformed into Stokes parameters (S 0, S 1, S 2, S 3) thereby extracting the ellipticity of the output light. e out and azimuth α out The polarization angle α Ellipticity corresponding to 0 e out As the expected value, and based on subsequent actual measurements, the polarization angle is determined. α Zero feedback control enables active input optimization based on ellipticity feedback.

[0059] Step 4: In-situ Calibration based on zero-current operating conditions.

[0060] When the device is powered on but there is no load current (I) P During the gap of 0), perform system error calibration: Background data acquisition: Real-time reading of the polarization analyzer's output data (actual measured values). At this point, the polarization analyzer actually measures the rotation angle (azimuth angle) of the output light. α ' out and ellipticity e ' out It is determined solely by the static installation deformation (bending, twisting) of the optical fiber and the error of the Faraday mirror.

[0061] Establish a fingerprint database: Change the polarization angle of the input light α 0, record the corresponding output response curve, i.e. α 0、 α ' out and e ' out The mapping relationship between them. This curve constitutes the "birefringence fingerprint" under the current optical path state.

[0062] Error compensation: In subsequent current measurements, this fingerprint data is used to perform background subtraction on the real-time measurement value (rotation angle) (based on the polarization angle of the current input light). α At 0, the azimuth angle will be measured in real time. α out Subtract the corresponding azimuth angle from the fingerprint database α ' out This step eliminates the systematic offset caused by static linear birefringence and device errors. Experiments show that this step can reduce the azimuth error in the current optical path state from approximately 10°. to -4 ~2 .

[0063] Step 5: Active input optimization based on ellipticity feedback.

[0064] like Figure 3 As shown, in order to maintain high accuracy under dynamic loads (such as mechanical vibration and thermal expansion), closed-loop feedback control is implemented: Monitoring feedback: Under actual working conditions, during the measurement process, the ellipticity error signal of the output light is monitored in real time. e out |(| e out | Represents the ellipticity error signal, the ellipticity measured in real time. e out Compared with expected value e out (The error between them). Theoretically, when the system is minimally affected by linear birefringence, the output light should maintain a linearly polarized state, i.e., | e out | Approaching 0.

[0065] Execute feedback regulation: Utilize gradient descent or PID algorithms, based on | e out The size of the value dynamically adjusts the polarization azimuth angle of the input light. α 0, so that | e out | Approaching 0. Specifically, when | is detected e out |Increase (indicating stress interference in the optical fiber and deviation of the operating point), control system changes. α 0, causing the operating point to shift along the direction of the minimum value of the ellipticity curve (output response curve), such that | e out | Approaching 0.

[0066] Locking in the optimal operating point: The system eventually locks in at the optimal operating point. e out Optimal polarization angle of 0 α opt At this point, the fiber optic system is in "quasi-linear polarization transmission" mode, exhibiting the strongest suppression capability against birefringence noise caused by external vibrations and torsion, thus ensuring the highest signal-to-noise ratio for the extraction of the Faraday rotation angle (i.e., the current signal). Based on the optimal polarization angle... α opt The polarization measuring instrument outputs the optimal azimuth angle. α out That is, the optimized Laday rotation angle. i H ,based on i H = VIP Optimized long-pulse high-current measurement values ​​were obtained. I P .

[0067] Example 2 This invention provides a fiber optic sensing optical path birefringence quantization and optimization system for long-pulse high-current measurement, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the fiber optic sensing optical path birefringence quantization and optimization method for long-pulse high-current measurement in Embodiment 1 above.

[0068] The relevant technical solutions are the same as above, and will not be repeated here.

[0069] Example 3 This invention provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the steps of the long-pulse high-current measurement fiber optic sensing optical path birefringence quantization and optimization method in Embodiment 1 above.

[0070] Specifically, the memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0071] The relevant technical solutions are the same as above, and will not be repeated here.

[0072] Example 4 This invention provides a computer program product, including a computer program that, when run on a computer, causes the computer to execute the steps of the long-pulse high-current measurement fiber optic sensing optical path birefringence quantization and optimization method in Embodiment 1 above.

[0073] The relevant technical solutions are the same as above, and will not be repeated here.

[0074] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for quantizing and optimizing the birefringence of an optical fiber sensing path for long-pulse high-current measurement, characterized in that, The method, applied to an all-fiber optic current sensor FOCS system, includes: Based on the actual physical layout trajectory of the sensing fiber in the FOCS system, the sensing fiber path is discretized into several units along its axis, and the geometric parameters of each discrete unit in three-dimensional space, including the local radius of curvature and geometric torsion, are calculated. Based on the aforementioned geometric parameters and the optical properties of the sensing fiber material, the linear birefringence component induced by bending and the circular birefringence component induced by fiber spatial torsion are calculated for each discrete unit to generate the polarization transfer matrix of each discrete unit. The polarization transfer matrices of each discrete unit are then integrated and cascaded to obtain the ellipticity of the output light from the FOCS system. e out and the ellipticity e out As an expected value; Under actual operating conditions, the ellipticity of the output light of the FOCS system is monitored in real time. e out , in ellipticity e out The goal is to minimize the error between the input light and the expected value, adjusting the polarization angle of the input light accordingly. α 0, obtaining the optimal input light polarization angle. α opt At the optimal input light polarization angle α opt Below, the azimuth angle of the output light from the FOCS system. α out As Faraday rotation angle θ H To obtain optimized long-pulse high-current measurement values ​​for the device under test. I P .

2. The method according to claim 1, characterized in that, At the optimal input light polarization angle α opt The azimuth angle of the output light of the FOCS system is obtained below. α out Subsequently, it also includes in-situ error calibration based on zero-current reference conditions to determine the azimuth angle. α out Background compensation includes: Under the conditions that the device under test is powered on but the large current of the long pulse being measured is zero, or the device under test is in a known reference state, the polarization angle of different input light is measured in real time. α Azimuth angle of FOCS system output light at 0° α ' out To establish by α 0 and α ' out A fingerprint database representing the mapping relationship between them; The azimuth angle α out Subtract the azimuth angle corresponding to the input light polarization angle in the fingerprint database. α ' out To the azimuth angle α out Perform background compensation; and use the azimuth angle after background compensation as the Faraday rotation angle. θ H To obtain optimized long-pulse high-current measurement values ​​for the device under test. I P .

3. The method according to claim 1 or 2, characterized in that, Calculate the geometric parameters of each discrete element in three-dimensional space, including local radius of curvature and geometric torsion rate, including: The tangential vector, normal vector, and subnormal vector of the center curve of each discrete element are calculated using the spatial curve geometric analysis method. Geometric parameters of each discrete element in three-dimensional space, including local radius of curvature and geometric torsion, are extracted from the tangential vector, normal vector, and subnormal vector.

4. The method according to claim 3, characterized in that, Each discrete element consists of a linear birefringence component induced by bending and a circular birefringence component induced by the spatial torsion of the fiber, respectively: in, For the first i Linear birefringence components of a discrete unit k mat These are constants related to the photoelastic coefficient, Poisson's ratio, and core radius of the sensing fiber material. R i For the first i The local radius of curvature of a discrete element; in, For the first i The circular birefringence components of a discrete unit g is the optical rotation coefficient of the optical fiber. For the first i Geometric torsion rate of a discrete unit The preset threshold is used to approach zero.

5. The method according to claim 4, characterized in that, The polarization transfer matrix of each discrete unit is based on the linear birefringence component. and the circular birefringence component A definite differential Jones matrix or Mueller matrix.

6. The method according to claim 5, characterized in that, When the polarization transfer matrix is ​​a differential Jones matrix, integration and concatenation operations are performed on the polarization transfer matrices of each discrete unit to obtain the ellipticity of the output light of the FOCS system. e out ,include: The Jones transfer matrix for each discrete unit is calculated using an exponential mapping. ;in, N T,i For the first i The differential Jones matrix of discrete units, For the first i Length of each discrete unit; Calculate the total transmission matrix of the FOCS system. : in, This indicates that when light propagates forward in the sensing fiber, the first... i Jones transfer moment of a discrete unit; This indicates that when light travels back in the sensing fiber, the first... i Jones transfer matrix of discrete units; The matrix representing the end reflector of the FOCS system; Calculate the output electric field vector , This represents the electric field vector of the input light; and the output electric field vector... This is converted into polarization state parameters of the output light to extract the ellipticity of the output light. e out .

7. The method according to claim 1 or 2, characterized in that, Long pulse high current measurement value I P With Faraday rotation angle θ H The relationship between them is: θ H = VI P in, V It is the Verdet constant.

8. A fiber optic sensing optical path birefringence quantization and optimization system for long-pulse high-current measurement, characterized in that, Includes computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method according to any one of claims 1-7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1-7.

10. A computer program product, characterized in that, Includes a computer program that, when run on a computer, causes the computer to perform the method described in any one of claims 1-7.

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