Nonlinear error modeling method, medium and electronic device of optical fiber current sensor

Abstract

The present invention discloses a nonlinear error modeling method, medium and electronic device for a fiber optic current sensor. The sensing fiber ring, phase modulator, 45° fiber melting point and fiber polarizer in the fiber optic current sensor that may affect the propagated optical signal are modeled to obtain calculation models of the components that affect the optical signal during the light beam propagation process. The light beam emitted by the light source passes through the above calculation models in sequence and reaches the photodetector to obtain a calculation model of the AC component of the interference light intensity detected by the photodetector. This scheme determines the optical signal in each component during the light beam propagation process, determines the interference result of the optical signal entering the sensing fiber ring under the influence of the detected current, and calculates the AC component after the photodetector detects the interference light intensity, and the result is slightly different from the AC component of the actual interference light intensity. The error modeling result of the sensing fiber ring obtained by this application is more accurate, which can ensure that the detection result of the fiber optic current sensor is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of error compensation of optical fiber current sensors, and in particular to a nonlinear error modeling method, a medium and an electronic device of an optical fiber current sensor. Background Art

[0002] Fiber Optic Current Sensor (FOCS) has the advantages of high precision, strong anti-interference ability, small size, light weight, large dynamic range, and can realize contactless AC and DC current measurement. However, in practical applications, since the polarized light transmitted in the sensing optical fiber is not an ideal circular polarization state, nonlinear errors will be generated during large current measurements, which greatly limits the application of FOCS in some fields. It is necessary to use error modeling methods to correct the nonlinear errors, that is, to perform error compensation.

[0003] Most of the existing nonlinear error models are based on quadratic functions, and the measured current usually does not exceed 300kA. However, in actual applications, it is often necessary to detect ultra-large currents (500kA and above). When predicting the nonlinear error in such a test scenario, if the existing common method is used to obtain the nonlinear error model, the error obtained is not accurate, and the error compensation based on this will not be accurate either. Therefore, the accuracy of the detection results obtained by the fiber optic current sensor will be greatly affected. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the existing fiber optic current sensor only uses quadratic functions for nonlinear error modeling, resulting in inaccurate detection results. To this end, the present invention proposes a nonlinear error modeling method, medium and electronic equipment for a fiber optic current sensor.

[0005] In view of the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, the technical solution of the present application provides a nonlinear error modeling method for a fiber optic current sensor, comprising:

[0007] Modeling the sensing fiber ring in the fiber optic current sensor to obtain a computational model of the sensing fiber ring;

[0008] Modeling the phase modulator, 45° fiber melting point and fiber polarizer in the fiber current sensor to obtain a calculation model of the phase modulator, a calculation model of the 45° fiber melting point and a calculation model of the fiber polarizer;

[0009] Obtaining a calculation model of the interference light intensity detected by the signal detection circuit in the fiber optic current sensor according to the calculation model of the sensing fiber ring, the calculation model of the phase modulator, the calculation model of the 45° fiber melting point and the calculation model of the fiber polarizer;

[0010] According to the propagation process of the light beam emitted by the light source in the optical fiber current sensor, a calculation model of the AC component of the interference light intensity of the light beam entering the photoelectric detector after being processed by each calculation model in sequence is obtained;

[0011] According to the modulation phase difference in the calculation model of the phase modulator, the calculation model of the AC component of the interference light intensity, and the conditions satisfied by the closed-loop stability, the feedback phase difference introduced by the phase modulator is obtained;

[0012] A calculation model for obtaining the optical phase difference of the sensing fiber ring according to the feedback phase difference;

[0013] According to the calculation model of the optical phase difference and the Faraday magneto-optical phase difference generated in the sensing optical fiber, a calculation model of the demodulation ratio difference of the sensing optical fiber ring is obtained as a first error model of the sensing optical fiber ring.

[0014] In some embodiments of the nonlinear error modeling method of the optical fiber current sensor, the demodulation ratio difference calculation model is:

[0015]

[0016] Wherein, RE represents the demodulation ratio difference of the sensing optical fiber ring, represents the optical phase difference of the sensing optical fiber ring, and 4F is the Faraday magneto-optical phase difference generated by two orthogonal circularly polarized lights in the sensing optical fiber.

[0017] In some embodiments, the nonlinear error modeling method of the optical fiber current sensor further comprises:

[0018] The nonlinear error of the optical fiber current sensor is theoretically simulated according to the first error model of the sensing optical fiber ring to obtain a simulation result;

[0019] Determine the minimum polynomial fitting order and the minimum number of measuring points of the nonlinear error according to the simulation results and the range of the maximum value of the measured current;

[0020] A second error model of the sensing optical fiber ring is obtained according to the detection result of each measuring point and the fitting order, and the second error model is a function of the measured current.

[0021] The nonlinear error modeling method of the optical fiber current sensor described in some schemes, wherein the minimum polynomial fitting order and the minimum number of measuring points of the nonlinear error are determined according to the simulation results and the maximum value range of the measured current value, comprises:

[0022] Assuming n and m are positive integers, an ampere-turn sequence Ig[n] is determined. When the maximum value of the measured current is between Ig[n] and Ig[n+1], the fitting order is n; the number of measuring points is (n+2);

[0023] The Faraday magneto-optical phase difference corresponding to the maximum value of the measured current is greater than m times the π phase, and at least one measuring point is included before and after the current points where the Faraday magneto-optical phase differences are π, 2π...mπ phases respectively.

[0024] Some embodiments of the present invention provide a method for modeling nonlinear errors of a fiber optic current sensor.

[0025] The ampere-turn sequence Ig[n] is determined as follows:

[0026] Acquire design parameters of the optical fiber current sensor, and substitute them into the first error model to obtain a target first error model corresponding to the optical fiber current sensor;

[0027] The first-order derivative and the second-order derivative of the target first error model are respectively calculated to obtain an error first-order derivative model and an error second-order derivative model;

[0028] The first-order derivative model of error and the second-order derivative model of error are normalized to obtain a normalized first-order derivative model of error and a normalized second-order derivative model of error, respectively; wherein the normalization processing method is: normalized data = original data / (maximum value of original data - minimum value of original data);

[0029] Obtain the phase difference corresponding to the amplitude of the normalized error first-order derivative model and the normalized error second-order derivative model when the amplitude is 0, and all phase differences form a numerical sequence in ascending order of value

[0030] The ampere-turn sequence Where V is the Verdet constant.

[0031] The nonlinear error modeling method of the optical fiber current sensor described in some embodiments further includes the following steps:

[0032] The original measurement output result of the optical fiber current sensor is corrected according to the second error model to obtain the output value of the optical fiber current sensor, including: let the second error model be represented by f(I), where I is the current value of the measured current, when the original measurement output result of the optical fiber current sensor is I origWhen the output value of the optical fiber current sensor corrected by the second error model is I comp =I orig / [f(I orig )+1].

[0033] In a second aspect, the technical solution of the present application provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the nonlinear error modeling method of the optical fiber current sensor described in any one of the first aspects.

[0034] In a third aspect, the technical solution of the present application provides a computer-readable storage medium having program instructions stored therein, and after a computer reads the program instructions, the computer executes the nonlinear error modeling method for an optical fiber current sensor as described in any one of the first aspects.

[0035] In a fourth aspect, the technical solution of the present application provides an electronic device, comprising at least one processor and at least one memory, wherein at least one of the memories stores program instructions, and after reading the program instructions, at least one of the processors executes the nonlinear error modeling method of the optical fiber current sensor described in any one of the first aspects.

[0036] The technical solution of the present invention has the following technical effects compared with the prior art:

[0037] The nonlinear error modeling method, medium and electronic device of the optical fiber current sensor provided by the present invention are used to model the sensing optical fiber ring, phase modulator, 45° optical fiber melting point and optical fiber polarizer in the optical fiber current sensor, which will affect the propagated optical signal, to obtain the calculation model of each component that affects the optical signal during the light beam propagation process. The light beam emitted by the light source passes through the above calculation model in sequence and reaches the photodetector, and the calculation model of the AC component of the interference light intensity detected by the photodetector is obtained. According to the modulation phase difference set in the calculation model of the phase modulator, the calculation model of the AC component of the interference light intensity and the conditions satisfied by the closed-loop stability, the feedback phase difference introduced by the phase modulator can be obtained. Since the feedback phase difference introduced by the phase modulator is related to the Faraday magneto-optical phase difference generated by the sensing optical fiber ring, the calculation model of the optical phase difference of the sensing optical fiber ring can be derived after the feedback phase difference is obtained. The optical phase difference includes the theoretical Faraday magneto-optical phase difference and the nonlinear error introduced by the sensing optical fiber ring. The demodulation ratio difference calculation model of the sensing optical fiber ring is obtained by the optical phase difference and the Faraday magneto-optical phase difference, which can be used as the first error model of the sensing optical fiber ring. The above scheme of the present application models each component in the light propagation process to obtain a calculation model of each component, thereby determining the light signal in each component during the light beam propagation process, and then determining the interference result of the light signal entering the sensing fiber ring under the influence of the detected current. The calculation of the AC component after the photoelectric detector detects the interference light intensity is slightly different from the result of the AC component of the interference light intensity obtained during the actual light propagation process. The first error model of the sensing fiber ring obtained in the present scheme is obtained by simulating each stage in the light propagation process, rather than simply limiting the error of the sensing fiber ring to a certain fixed order function. Therefore, the error modeling result of the sensing fiber ring obtained by the scheme of the present application is more accurate, thereby ensuring that the detection result of the optical fiber current sensor is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which will help to understand the objects and advantages of the present invention, wherein:

[0039] Figure 1 It is a structural schematic diagram of the optical fiber current sensor;

[0040] Figure 2 A flowchart of a nonlinear error modeling method for a fiber optic current sensor according to an embodiment of the present application;

[0041] Figure 3 A schematic diagram of the evolution of the polarization state of a light wave in a sensing optical fiber ring according to an embodiment of the present application;

[0042] Figure 4It is a schematic diagram of simulation results of error simulation using the first error model of the sensing optical fiber ring in an embodiment of the present application;

[0043] Figure 5 A flowchart of a nonlinear error modeling method for a fiber optic current sensor according to another embodiment of the present application;

[0044] Figure 6a and Figure 6b This is a schematic diagram of a first error model processing process in the process of determining an ampere-turn sequence according to an embodiment of the present application;

[0045] Figure 7 The comparison results of the ultra-large current nonlinear error test data and the theoretical error curve of the optical fiber current sensor using the first error model and the second error model in the embodiment of the present application;

[0046] Figure 8 This is a schematic diagram of the fitting curve results of the second error model in one embodiment of the present application;

[0047] Fig. 9 A schematic diagram of error results of a fiber optic current sensor is shown in the embodiment of the present application, showing the detection results after error compensation using the first error model or the second error model. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0050] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0052] like Figure 1 As shown in the figure, FOCS consists of an acquisition module and a sensing fiber ring. The acquisition module contains an optical transceiver module, an optical modulation module, and a signal processing module. The optical transceiver module contains a light source, a coupler, and a photodetector. The optical modulation module contains a fiber polarizer, a phase modulator, and a polarization-maintaining fiber delay ring. The optical fiber between the fiber polarizer and the phase modulator is 45° axially fused. The signal processing submodule contains a light source driving circuit, a preamplifier circuit, and a signal acquisition and modulation circuit. The signal acquisition and modulation circuit includes an A / D conversion unit, an FPGA processing unit, and a D / A conversion unit. The sensing fiber ring contains a λ / 4 wave plate, a sensing fiber, and a fiber reflector.

[0053] The nonlinear error of FOCS is caused by the sensing fiber ring. Therefore, the following scheme in the embodiment of the present invention is mainly to model the error of the sensing fiber ring. The method includes: Figure 2 Steps shown:

[0054] S10: Modeling the sensing optical fiber ring in the optical fiber current sensor to obtain a calculation model of the sensing optical fiber ring.

[0055] S20: Modeling the phase modulator, 45° fiber melting point and fiber polarizer in the fiber current sensor to obtain a calculation model of the phase modulator, a calculation model of the 45° fiber melting point and a calculation model of the fiber polarizer.

[0056] S30: Obtaining a calculation model of the interference light intensity detected by the signal detection circuit in the fiber optic current sensor according to the calculation model of the sensing fiber ring, the calculation model of the phase modulator, the calculation model of the 45° fiber melting point and the calculation model of the fiber polarizer.

[0057] S40: According to the propagation process of the light beam emitted by the light source in the optical fiber current sensor, a calculation model of the AC component of the interference light intensity of the light beam entering the photoelectric detector after being processed by each calculation model in sequence is obtained.

[0058] S50: Obtaining the feedback phase difference introduced by the phase modulator according to the modulation phase difference in the calculation model of the phase modulator, the calculation model of the AC component of the interference light intensity, and the conditions satisfied by the closed-loop stability.

[0059] S60: Obtaining a calculation model of the optical phase difference of the sensing fiber ring according to the feedback phase difference.

[0060] S70: Obtaining a demodulation ratio difference calculation model of the sensing fiber ring as a first error model of the sensing fiber ring according to the calculation model of the optical phase difference and the Faraday magneto-optical phase difference generated in the sensing fiber.

[0061] In the above scheme, the sensing fiber ring, phase modulator, 45° fiber melting point, and fiber polarizer in the fiber current sensor that will affect the propagated optical signal are modeled to obtain the calculation model of each component that affects the optical signal during the light beam propagation process. The light beam emitted by the light source passes through the above calculation model in sequence and reaches the photodetector, and the calculation model of the AC component of the interference light intensity detected by the photodetector is obtained. According to the modulation phase difference set in the calculation model of the phase modulator, the calculation model of the AC component of the interference light intensity, and the conditions satisfied by the closed-loop stability, the feedback phase difference introduced by the phase modulator can be obtained. Since the feedback phase difference introduced by the phase modulator is related to the Faraday magneto-optical phase difference generated by the sensing fiber ring, after obtaining the feedback phase difference, the calculation model of the optical phase difference of the sensing fiber ring can be derived. The optical phase difference includes the theoretical Faraday magneto-optical phase difference and the phase difference error introduced by the sensing fiber ring. The demodulation ratio difference calculation model of the sensing fiber ring is obtained by the optical phase difference and the Faraday magneto-optical phase difference, which can be used as the first error model of the sensing fiber ring. The above scheme models each component in the light propagation process to obtain a calculation model of each component, thereby determining the light signal in each component during the light beam propagation process, thereby determining the interference result of the light signal entering the sensing fiber ring under the influence of the detected current, and the calculation of the AC component after the photoelectric detector detects the interference light intensity is slightly different from the result of the AC component of the interference light intensity obtained during the actual light propagation process. The first error model of the sensing fiber ring obtained in this scheme is obtained by simulating each stage in the light propagation process, rather than simply limiting the error of the sensing fiber ring to a certain fixed order function. Therefore, the error modeling result of the sensing fiber ring obtained by the scheme of this application is more accurate, thereby ensuring that the detection result of the optical fiber current sensor is more accurate.

[0062] Furthermore, if Figure 1As shown, since the sensing fiber ring is mainly composed of a fiber wave plate (the λ / 4 wave plate shown in the figure), a sensing fiber and a reflector, the calculation model of the fiber wave plate includes a fiber wave plate outbound model (1.1) and a fiber wave plate return model (1.2):

[0063]

[0064]

[0065] in:

[0066] θ—the subtaxial angle of the fiber wave plate;

[0067] δ—phase delay angle of fiber wave plate;

[0068] λ—The wavelength of the light beam emitted by the light source.

[0069] According to the above models (1.1) and (1.2), the comprehensive model of the sensing fiber outbound, reflector and sensing fiber return can be obtained as (1.3):

[0070]

[0071] in:

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] tanχ=2(F+Γ) / σ (1.10)

[0079] tanζ=2(F-Γ) / σ (1.11)

[0080] F=VNI (1.12)

[0081] In the above formulas:

[0082] F—Faraday magneto-optical phase shift angle generated when circularly polarized light is transmitted in a single path in the sensing optical fiber;

[0083] V—Verdet constant;

[0084] N—Number of sensing optical fiber loops;

[0085] I—measured current;

[0086] Γ—circular birefringence deflection angle of circularly polarized light during one-way transmission in the sensing optical fiber;

[0087] σ—Linear birefringence delay angle of circularly polarized light during single-pass transmission in the sensing optical fiber;

[0088] α—total birefringence in the sensing fiber during the optical path;

[0089] β—total birefringence in the sensing fiber during the return path;

[0090] ζ—2 times the inverse tangent value of the ratio of the minor axis to the major axis of the elliptical polarization state formed in the return path of the light;

[0091] χ—The angle equal to twice the inverse tangent of the ratio of the minor axis to the major axis of the elliptical polarization state formed in the forward path of the light.

[0092] The light wave train entering the wave plate is divided into two types: X-polarized light and Y-polarized light. These two light wave trains are converted into elliptically polarized light after passing through the optical fiber wave plate. The elliptically polarized light is decomposed into a combination of two orthogonal circularly polarized light. When returning to the optical fiber wave plate, the circularly polarized light after passing through the non-ideal sensing optical fiber becomes elliptically polarized light again. Therefore, it is necessary to continue to decompose the elliptically polarized light into a combination of two orthogonal circularly polarized light. Finally, at the optical fiber wave plate, the outgoing light wave is converted back into linearly polarized light. Its evolution process is shown in Figure 3.

[0093] The naming convention of polarization state variables in the figure is:

[0094] (1) There are six basic polarization states, among which: X represents linear polarization along the x-axis, Y represents linear polarization along the y-axis, R represents right-handed circularly polarized light, L represents left-handed circularly polarized light, ER represents right-handed elliptically polarized light, and EL represents left-handed elliptically polarized light;

[0095] (2) In the variable symbol of polarization state, the first capital letter indicates the linear polarization state of the light wave train before entering the λ / 4 wave plate, and the capital letters after the first capital letter indicate the current polarization state of the light wave train;

[0096] (3) The process of generating coupling components in orthogonal polarization states due to the non-ideal optical path is called cross-coupling. The light wave train generated by cross-coupling has an additional s subscript on the basis of the previous polarization state;

[0097] (4) The linear polarization states returned from the wave plate are numbered and placed immediately after the variable name to distinguish them.

[0098] like Figure 3As shown in the figure, among the 16 returning optical wave trains, only when the linear polarization states entering the wave plate and returning from the wave plate are different can they be modulated by the phase modulator and become high-frequency carrier signals, and the AC component can be extracted during closed-loop detection, which is a valid optical wave train signal; when the linear polarization states entering the wave plate and returning from the wave plate are the same, such optical wave trains cannot be modulated by the phase modulator, and are eliminated as DC components during closed-loop detection, so they are invalid optical wave train signals. Figure 3 It can be seen that there are only 8 truly effective light wave trains, namely 2, 4, 6, 8, 9, 11, 13 and 15.

[0099] The X and Y linear polarized light entering the wave plate are normalized, and their calculation models are (1.13) and (1.14) respectively:

[0100]

[0101]

[0102] Combination Figure 3 The calculation model of formula (1.1) to formula (1.12) is used to obtain the calculation formula of the 8-way effective optical wave train as shown in Table 1:

[0103] Table 1 Calculation formula for effective light wave train

[0104]

[0105] The returned 8 effective light wave trains are amplitude superimposed to obtain a superimposed X-polarized light and a superimposed Y-polarized light. These two orthogonal linear polarized lights generate projection components on the fast and slow axes of the subsequent polarization-maintaining optical fiber when returning to the melting point of the 45° polarization-maintaining optical fiber, and interfere with each other in the fast and slow axes of this section of polarization-maintaining optical fiber. After the interference light signal passes through the optical fiber polarizer, the interference component in the depolarization direction is filtered out, and only the interference component in the detection direction is retained. After passing through the coupler and the photodetector again, it is received by the photodetector and converted into an electrical signal and enters the signal processing circuit. The signal detection circuit further analyzes the measured current value by detecting the change in the interference light intensity.

[0106] according to Figure 2 As shown in the flowchart, in order to calculate the interference light intensity, the calculation model of the phase modulator, 45° fiber melting point and fiber polarizer is first defined. The calculation model of the phase modulator is (1.15):

[0107]

[0108] In the above formula, φ m The modulation phase difference introduced by the phase modulator.

[0109] The calculation model of 45° optical fiber melting point is (1.16):

[0110]

[0111] The calculation model of the optical fiber polarizer (assuming X-axis polarization) is:

[0112]

[0113] Therefore, the amplitude of the interference light intensity is:

[0114]

[0115] The calculation formula for interference light intensity is:

[0116]

[0117] In the above formula represents the conjugate transposed matrix of E.

[0118] The calculation formula of the AC component of interference light intensity satisfies the following form:

[0119]

[0120] Among them, let x = sinδsin2θ, y = sin2θcosδ, then:

[0121]

[0122] B=xac+(bcy-cdcos2θ)cos2θ-(cdy+bccos2θ)sin2θ (1.22)

[0123] During closed-loop demodulation, a feedback phase difference is introduced through the phase modulator to cancel the Faraday magneto-optical phase difference. The generation mechanism of the feedback phase difference is the same as that of the modulation phase difference, so it can be regarded as the modulation phase difference φ m An additional feedback phase difference φ is added on the basis of f , the general solution of the closed-loop demodulation optical phase difference can be obtained through equations (1.21) to (1.23), and equation (1.21) can be written as follows:

[0124]

[0125] The condition is met during closed-loop detection: "The interference light intensity corresponding to the two offset phase points symmetrical about the origin is equal", that is, the waveform obtained by equation 1.23, the horizontal axis is the optical phase difference, the vertical axis is the interference light intensity, the interference light intensity is an even function of the optical phase difference, when the sign of the modulated phase difference is reversed, the interference light intensity remains unchanged, so the following equation is obtained:

[0126]

[0127] Solve to get the feedback phase difference φ f satisfy:

[0128] Asinφ f =Bcosφ f (1.25)

[0129] When cosφ f ≠0, we have:

[0130]

[0131] Therefore, the optical phase difference of closed-loop demodulation is:

[0132]

[0133] The ratio error of closed-loop demodulation is:

[0134]

[0135] The above formula (1.28) can be used as the first error model of the sensing fiber ring. 4F in the above formula is the Faraday magneto-optical phase difference generated by two beams of orthogonal circularly polarized light in the sensing fiber. When the fiber reflector and the fiber wave plate coincide in spatial position, F=VNI.

[0136] According to formula (1.29), the nonlinear error caused by the ratio difference in FOCS changing with the current can be simulated. When the simulation parameters are as shown in Table 2, the ultra-large current nonlinear error model of 21MA·turn (the corresponding Faraday magneto-optical phase difference is about 30π) is obtained as follows Figure 4 shown.

[0137] Table 2. Simulation parameters of ring difference of sensing optical fiber

[0138] Serial number Variable Name symbol unit Numeric 1 Verdet constant V rad / A <![CDATA[1.1×10 -6 ]]> 2 Number of sensor rings N 1 1 3 Sensing fiber length L m 10 4 Sensing fiber pitch <![CDATA[L t ]]> mm 4 5 Central wavelength λ nm 1310 6 Linear birefringence coefficient <![CDATA[Δn L ]]> 1 <![CDATA[8.72×10 -6 ]]> 7 Circular birefringence <![CDATA[Δn C ]]> 1 <![CDATA[2.76×10 -5 ]]>

[0139] Among them, the calculation method of the circular birefringence deflection angle Γ and the linear birefringence retardation angle σ is:

[0140]

[0141]

[0142] Furthermore, if Figure 5 As shown, the method may further include the following steps:

[0143] S80: Perform theoretical simulation on the nonlinear error of the optical fiber current sensor according to the first error model of the sensing optical fiber ring to obtain simulation results. Specifically, the simulation results are as follows: Figure 4 shown.

[0144] S90: Determine the minimum polynomial fitting order and the minimum number of measuring points of the nonlinear error according to the simulation results and the range of the maximum value of the measured current. Specifically, it includes: assuming n and m as positive integers, determining an ampere-turn sequence Ig[n], when the maximum value of the measured current is between Ig[n] and Ig[n+1], the fitting order is n; the number of measuring points is (n+2); the Faraday magneto-optical phase difference corresponding to the maximum value of the measured current is greater than m times the π phase, and at least one measuring point is included before and after the current point where the Faraday magneto-optical phase difference is π, 2π...mπ phases respectively.

[0145] S100: Obtaining a second error model of the sensing optical fiber ring according to the detection result of each measuring point and the fitting order, wherein the second error model is a function of the measured current.

[0146] Preferably, in step S90, the ampere-turn sequence Ig[n] is determined in the following manner:

[0147] S901: Obtain design parameters of the optical fiber current sensor, and substitute them into the first error model to obtain a target first error model corresponding to the optical fiber current sensor, such as Figure 6a shown.

[0148] S902: respectively calculating the first-order derivative and the second-order derivative of the target first error model to obtain an error first-order derivative model and an error second-order derivative model.

[0149] S903: normalize the error first-order derivative model and the error second-order derivative model to obtain a normalized error first-order derivative model and a normalized error second-order derivative model respectively; wherein the normalization method is: normalized data = original data / (maximum value of original data - minimum value of original data). Figure 6b shown.

[0150] S904: Obtain the phase difference corresponding to the normalized error first-order derivative model and the normalized error second-order derivative model when the amplitude is 0, and all phase differences are arranged into a numerical sequence in ascending order.

[0151] S905: the ampere-turn sequence Where V is the Verdet constant.

[0152] Combination Figure 6a and Figure 6bAs shown in the figure, the amplitude of the normalized error first-order derivative model at the measuring points of 0kA·turn, 1012kA·turn, etc. is 0, and the amplitude of the normalized error second-order derivative model at the measuring points of 471kA·turn, 1355kA·turn, etc. is 0, so the ampere-turn value sequence Ig[n] is obtained, where Ig[1] = 0kA·turn, Ig[2] = 471kA·turn, Ig[3] = 1012kA·turn, Ig[4] = 1355kA·turn, etc., when the maximum measured current is When the value is in the range of 0 to 471 kA·turn, the second error model can be fitted using a second-order polynomial, and the number of points required for fitting must not be less than 3. When the maximum value of the measured current is in the range of 471 to 1012 kA·turn, the second error model can be fitted using a third-order polynomial, and the number of points required for fitting must not be less than 4. If the measured current is >714 kA·turn (the corresponding phase difference is π), at least one current measurement point should be included before and after 714 kA·turn.

[0153] Through the scheme of the above embodiment of the present application, a calculation model of nonlinear error in FOCS is obtained, and a general error compensation method of nonlinear error is proposed. The compensation method is applicable to ultra-large currents above 500kA·turn, which fills the gap in the current research on ultra-large current nonlinear error model. Through the scheme in the above embodiment of the present application, an ultra-large current error test is performed on a certain FOCS, and its nonlinear error result is shown in Figure 6. From the comparison of the first test result and the second test result described in the figure with the theoretical model curve, it can be determined that the nonlinear error result obtained by the second error model in this scheme is consistent with the theoretical error obtained by the first error model. Therefore, in the actual application process, if there is no multi-measurement point detection condition, the nonlinear error of the sensing optical fiber ring can be directly determined by the first error model. For multi-measurement point detection conditions, the simulation results of the first error model can be used to determine the measurement point, and the second error model is obtained according to the detection result of the measurement point and the fitting order, and the nonlinear error of the sensing optical fiber ring is obtained by the second error model. In specific applications, the original measurement output result of the optical fiber current sensor can be corrected according to the nonlinear error obtained by the second error model, including: let the second error model be expressed as f(I), where I is the current value of the measured current, when the original measurement output result of the optical fiber current sensor is I orig When the output value of the optical fiber current sensor corrected by the second error model is I comp =I orig / [f(I orig )+1]. In this way, after the second error model and the original measurement output result are determined, the corrected measurement result of the optical fiber current sensor can be automatically obtained.

[0154] Further, select Figure 7There are 9 key measurement points. Since the maximum value of the detected current is between Ig[7] and Ig[8], n=7, and the minimum fitting order is 7. Therefore, a 7th-order polynomial fitting is performed on the ultra-large current nonlinear error of the FOCS. The data of 9 key measurement points are selected for modeling, and the compensation curve of the nonlinear error is obtained as shown in the figure. Figure 8 As shown in , the compensation curve corresponds to the second error model. Fig. 9 As shown, based on Figure 8 The second error model corresponding to the compensation curve shown is used as a modeling model of ultra-large current nonlinear error to compensate for the nonlinear error of FOCS. After compensation, the ultra-large current nonlinear error of FOCS is reduced from ±1.5% to within ±0.1%. Obviously, through the above solution provided by the present invention, the error of the detection result of FOCS is significantly reduced.

[0155] An embodiment of the present application further provides a computer program product, comprising a computer program / instruction, which, when executed by a processor, implements the steps of the nonlinear error modeling method for an optical fiber current sensor as described in any one of the first aspects.

[0156] The embodiment of the present application also provides a computer-readable storage medium having program instructions stored therein. After a computer reads the program instructions, the nonlinear error modeling method for an optical fiber current sensor described in any one of the above method embodiments is executed.

[0157] An embodiment of the present application also provides an electronic device, which includes at least one processor and at least one memory, at least one of the memories storing program instructions, and at least one of the processors reads the program instructions and executes the nonlinear error modeling method of the optical fiber current sensor described in any one of the above method embodiments.

[0158] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. However, the obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A nonlinear error modeling method for a fiber optic current sensor, characterized in that: include: Modeling the sensing fiber ring in the fiber optic current sensor to obtain a computational model of the sensing fiber ring; Modeling the phase modulator, 45° fiber melting point and fiber polarizer in the fiber current sensor to obtain a calculation model of the phase modulator, a calculation model of the 45° fiber melting point and a calculation model of the fiber polarizer; Obtaining a calculation model of the interference light intensity detected by the signal detection circuit in the fiber optic current sensor according to the calculation model of the sensing fiber ring, the calculation model of the phase modulator, the calculation model of the 45° fiber melting point and the calculation model of the fiber polarizer; According to the propagation process of the light beam emitted by the light source in the optical fiber current sensor, a calculation model of the AC component of the interference light intensity detected by the photoelectric detector after the light beam is processed by each calculation model in sequence is obtained; Obtaining the feedback phase difference introduced by the phase modulator according to the modulation phase difference in the calculation model of the phase modulator, the calculation model of the AC component of the interference light intensity, and the conditions satisfied by the closed-loop stability; A calculation model for obtaining the optical phase difference of the sensing fiber ring according to the feedback phase difference; Obtaining a demodulation ratio difference calculation model of the sensing optical fiber ring as a first error model of the sensing optical fiber ring according to the calculation model of the optical phase difference and the Faraday magneto-optical phase difference generated in the sensing optical fiber; The demodulation ratio difference calculation model is: Wherein, RE represents the demodulation ratio difference of the sensing optical fiber ring, represents the optical phase difference of the sensing optical fiber ring, and 4F is the Faraday magneto-optical phase difference generated by two orthogonal circularly polarized lights in the sensing optical fiber.

2. The nonlinear error modeling method of the optical fiber current sensor according to claim 1, characterized in that: The method further comprises: The nonlinear error of the optical fiber current sensor is theoretically simulated according to the first error model of the sensing optical fiber ring to obtain a simulation result; Determine the minimum polynomial fitting order and the minimum number of measuring points of the nonlinear error according to the simulation results and the range of the maximum value of the measured current; A second error model of the sensing optical fiber ring is obtained according to the detection result of each measuring point and the fitting order, and the second error model is a function of the measured current.

3. The nonlinear error modeling method of the optical fiber current sensor according to claim 2, characterized in that: The step of determining the minimum polynomial fitting order and the minimum number of measuring points of the nonlinear error according to the simulation results and the maximum value range of the measured current value comprises: Assuming n and m are positive integers, an ampere-turn sequence Ig[n] is determined. When the maximum value of the measured current is between Ig[n] and Ig[n+1], the fitting order is n; the number of measuring points is (n+2); The Faraday magneto-optical phase difference corresponding to the maximum value of the measured current is greater than m times the π phase, and at least one measuring point is included before and after the current points where the Faraday magneto-optical phase differences are π, 2π...mπ phases respectively.

4. The nonlinear error modeling method of the optical fiber current sensor according to claim 3, characterized in that: The ampere-turn sequence Ig[n] is determined as follows: Acquire design parameters of the optical fiber current sensor, and substitute them into the first error model to obtain a target first error model corresponding to the optical fiber current sensor; The first-order derivative and the second-order derivative of the target first error model are respectively calculated to obtain an error first-order derivative model and an error second-order derivative model; The first-order derivative model of error and the second-order derivative model of error are normalized to obtain a normalized first-order derivative model of error and a normalized second-order derivative model of error, respectively; wherein the normalization processing method is: normalized data = original data / (maximum value of original data - minimum value of original data); Obtain the phase difference corresponding to the amplitude of the normalized error first-order derivative model and the normalized error second-order derivative model when the amplitude is 0, and all phase differences form a numerical sequence in ascending order of value The ampere-turn sequence Where V is the Verdet constant.

5. The nonlinear error modeling method of the optical fiber current sensor according to claim 3, characterized in that: The following steps are also included: Correcting the original measurement output result of the optical fiber current sensor according to the second error model to obtain the output value of the optical fiber current sensor includes: Let the second error model be expressed as f(I), where I is the current value of the measured current. When the original measurement output result of the optical fiber current sensor is I orig When the output value of the optical fiber current sensor corrected by the second error model is I comp =I orig / [f(I orig )+1].

6. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the steps of the nonlinear error modeling method for a fiber optic current sensor according to any one of claims 1 to 5 are implemented.

7. A computer-readable storage medium, characterized in that: Program instructions are stored therein, and after the computer reads the program instructions, the nonlinear error modeling method for the optical fiber current sensor according to any one of claims 1 to 5 is executed.

8. An electronic device, characterized in that: The electronic device includes at least one processor and at least one memory, at least one of the memories stores program instructions, and at least one of the processors reads the program instructions and executes the nonlinear error modeling method for the optical fiber current sensor according to any one of claims 1-5.

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