Optical fiber current sensor based on multi-stage cooperative temperature compensation

Abstract

The application discloses a kind of optical fiber current sensors based on multistage cooperative temperature compensation, including optical sensing unit, modulation and switching unit, monitoring unit and signal processing unit, the modulation and switching unit includes optical switch and parallel first phase modulator, second phase modulator;Signal processing unit is configured to perform cooperative control process: select a phase modulator as main modulator work, based on monitoring unit signal real-time calculation its insertion loss, polarization crosstalk and half-wave voltage;And parameter value is processed with three levels of judgment: when primary judgment parameter value is in first range, start algorithm primary compensation;When based on predicted parameters will enter second range, control optical switch switches to standby modulator work;When parameter exceeds fault threshold, determine fault and alarm switching.The two levels of cooperation of algorithm compensation and device predictive switching effectively inhibit the performance degradation caused by temperature, improve the long-term operation reliability and life of sensor.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing technology, and particularly relates to a fiber optic current sensor based on multi-level coordinated temperature compensation. Background Technology

[0002] Fiber optic current sensors are widely used in power system current monitoring, smart grids, rail transit and industrial measurement due to their advantages such as strong anti-electromagnetic interference capability, excellent insulation performance and large measurement dynamic range.

[0003] As a key component in fiber optic current sensors for phase modulation, the phase modulator's operational stability directly impacts the sensor's measurement accuracy and long-term reliability. However, in actual operation, the phase modulator's performance parameters are highly sensitive to changes in ambient temperature. Temperature fluctuations can cause changes in the phase modulator material's electro-optic coefficient, mechanical structure dimensions, and waveguide effective refractive index, leading to problems such as increased insertion loss, polarization crosstalk fluctuations, and modulation half-wave voltage drift. Furthermore, these temperature-induced parameter drifts are persistent and cumulative, further shortening the modulator's lifespan and significantly reducing the sensor's overall demodulation accuracy and measurement stability, potentially causing current measurement interruptions in severe cases. Summary of the Invention

[0004] This invention provides a fiber optic current sensor based on multi-level coordinated temperature compensation, which addresses the technical problem that temperature-induced parameter drift is persistent and cumulative, further shortening the modulator lifespan, significantly reducing the overall demodulation accuracy and measurement stability of the sensor, and in severe cases, causing current measurement interruption.

[0005] This invention provides an optical fiber current sensor based on multi-level coordinated temperature compensation, comprising:

[0006] An optical sensing unit is used to generate and guide probe light through a current-carrying conductor wound around a sensing fiber, and convert the current signal into an optical phase signal based on the Faraday effect.

[0007] The modulation and switching unit includes an optical switch, a first phase modulator and a second phase modulator connected in parallel. The optical switch is used to selectively guide the probe light from the optical sensing unit to the first phase modulator or the second phase modulator for phase modulation, and to guide the light carrying the current signal back to the optical sensing unit.

[0008] The monitoring unit is used to sample the output light of the first phase modulator and the second phase modulator respectively, and extract optical parameters that reflect the performance state of the output light.

[0009] A signal processing unit, electrically connected to the monitoring unit, the optical switch, the first phase modulator, and the second phase modulator, is configured to execute the following coordinated control flow:

[0010] The optical switch is controlled to make either the first phase modulator or the second phase modulator work as the master modulator, and the other as a backup modulator;

[0011] Based on the sampling signal of the main modulator by the monitoring unit, the performance parameters of the main modulator are calculated in real time, and the performance parameters include at least insertion loss, polarization crosstalk and half-wave voltage.

[0012] The actual values ​​of the performance parameters of the main modulator are subject to three levels of judgment and processing, specifically:

[0013] Obtain the real-time values ​​of the performance parameters of the main modulator, and when the real-time values ​​are within a first preset range, initiate the corresponding primary compensation algorithm.

[0014] Based on the real-time value, the predicted value of the performance parameters of the main modulator is predicted using a long short-term memory network model. When the predicted value is within a second preset range, the optical switch is controlled to switch so that the backup modulator can take over as the main modulator.

[0015] When the real-time value exceeds the fault threshold, the main modulator is determined to be faulty and an alarm is triggered, while switching to the backup modulator.

[0016] Preferably, the optical sensing unit includes a light source, a first coupler, a polarizer, a first 45° fusion splice, a fourth coupler, a delay loop, and a second 45° fusion splice, connected in sequence. Waveplate, the sensing fiber, and reflector;

[0017] The first coupler is also connected to a first photodetector for detecting the returned optical signal and a second photodetector for monitoring the initial optical power.

[0018] Preferably, in the modulation and switching unit:

[0019] The first port of the optical switch is connected to the polarizer;

[0020] The second port of the optical switch is connected to the input port of the first phase modulator, and the output port of the first phase modulator is connected to the first port of the fourth coupler through the main path of the second coupler.

[0021] The fourth port of the optical switch is connected to the input of the second phase modulator, and the output of the second phase modulator is connected to the third port of the fourth coupler through the main path of the third coupler.

[0022] Preferably, the coupling ratio of the second coupler and the third coupler is 99:1; the coupling ratio of the fourth coupler is 50:50.

[0023] Preferably, the monitoring unit includes:

[0024] A first monitoring branch connected to the auxiliary port of the second coupler, the first monitoring branch includes a second polarization beam splitter, a fifth photodetector and a sixth photodetector, and the first monitoring branch is used to monitor the polarization state of the output light of the first phase modulator;

[0025] A second monitoring branch is connected to the auxiliary port of the third coupler. The second monitoring branch includes a first polarization beam splitter, a third photodetector, and a fourth photodetector. The second monitoring branch is used to monitor the polarization state of the output light of the second phase modulator.

[0026] Preferably, the first preset range includes a first preset sub-range, a second preset sub-range, and a third preset sub-range;

[0027] When the real-time value is within a first preset range, the corresponding primary compensation algorithm is activated, specifically as follows:

[0028] When the insertion loss of the master modulator When the real-time value meets the first preset sub-range, the signal processing unit increases the initial optical power by increasing the driving current of the light source. To compensate for signal attenuation caused by increased insertion loss;

[0029] When the polarization crosstalk of the master modulator When the real-time value meets the second preset sub-range, the signal processing unit calculates the compensation coefficient according to the correlation model between polarization crosstalk and sensor ratio, and then calculates the compensation coefficient based on the compensation coefficient. For current measurement value Corrections are made to compensate for polarization crosstalk errors, wherein the compensation coefficient is used. For current measurement value The corrected expression is:

[0030] ,

[0031] ,

[0032] ,

[0033] ,

[0034] ,

[0035] In the formula, The current measurement value after compensation. To and The corresponding transformation ratio of the fiber optic current sensor, To and The corresponding transformation ratio of the fiber optic current sensor, The polarized crosstalk at the current temperature. For Faraday phase, The polarization crosstalk of the first phase modulator at the current moment. Let be the slope of the fitted curve. This is polarized crosstalk at room temperature (25℃). The current temperature;

[0036] When the half-wave voltage of the master modulator When the real-time value meets the third preset sub-range, the signal processing unit at the half-wave voltage Subtract the monitoring error from the middle This is to achieve real-time correction of the half-wave voltage.

[0037] This application discloses a fiber optic current sensor based on multi-level collaborative temperature compensation. By monitoring the operating status of the phase modulator in real time, it performs online compensation for performance parameter degradation caused by temperature at the algorithm level. At the same time, it learns, analyzes, and predicts the operating data of the phase modulator performance parameters. Through the collaborative mode of algorithm compensation and phase modulator alternating operation, it reduces the long-term workload of a single phase modulator, increases the lifespan of the phase modulator, and improves the long-term reliability of the system under complex operating conditions. This invention has the advantages of high measurement stability, high reliability, and long lifespan, and can meet the requirements of long-term continuous operation and environmental adaptability in power grid and industrial application scenarios. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a circuit block diagram of an optical fiber current sensor based on multi-level coordinated temperature compensation, provided as an embodiment of the present invention.

[0040] Among them, 1. Light source, 2. First coupler, 3. Polarizer, 4. First 45° fusion splice, 5. Optical switch, 6. First phase modulator, 7. Second coupler, 8. Second phase modulator, 9. Third coupler, 10. Fourth coupler, 11. Delay ring, 12. Second 45° fusion splice, 13. 14. Waveplate, 15. Sensing fiber, 16. Current-carrying conductor, 17. Mirror, 18. First photodetector, 19. Second photodetector, 20. Signal processing unit, 21. First polarization beam splitter, 22. Second polarization beam splitter, 23. Third photodetector, 24. Fourth photodetector, 25. Fifth photodetector, 26. Sixth photodetector, 27. Optical switch controller. Detailed Implementation

[0041] 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.

[0042] like Figure 1 As shown, an optical fiber current sensor based on multi-level coordinated temperature compensation includes a light source 1, a first coupler 2, a polarizer 3, a first 45° fusion splice 4, an optical switch 5, a first phase modulator 6, a second coupler 7, a second phase modulator 8, a third coupler 9, a fourth coupler 10, a delay loop 11, and a second 45° fusion splice 12. Waveplate 13, sensing fiber 14, current-carrying conductor 15, reflector 16, first photodetector 17, second photodetector 18, signal processing unit 19, first polarization beamsplitter 20, second polarization beamsplitter 21, third photodetector 22, fourth photodetector 23, fifth photodetector 24, sixth photodetector 25, optical switch controller 26; the light source is connected to the first port of the first coupler, the second port of the first coupler is connected to the first port of the polarizer, the second port of the polarizer is connected to the first port of the optical switch through the first 45° fusion splice, the second port of the optical switch is connected to the first port of the first phase modulator, the second port of the first phase modulator is connected to the first port of the second coupler, the fourth port of the optical switch is connected to the first port of the second phase modulator, the second port of the second phase modulator is connected to the first port of the third coupler, the second port of the second coupler is connected to the first port of the fourth coupler, the second port of the third coupler is connected to the third port of the fourth coupler, the second port of the fourth coupler is connected to the delay loop, and the delay loop is connected to the second 45° fusion splice... Waveplate connection, A waveplate is connected to a sensing fiber, which is wound around a current-carrying conductor. The sensing fiber is also connected to a reflector. The third port of the first coupler is connected to the first port of the first photodetector. The second port of the first photodetector is connected to the first port of the signal processing unit. The fourth port of the first coupler is connected to the first port of the second photodetector. The second port of the second photodetector is connected to the second port of the signal processing unit. The third port of the signal processing unit is connected to an optical switch controller, which controls the optical switch. The fourth port of the signal processing unit is connected to the third port of the second phase modulator. The fifth port of the signal processing unit is connected to the third port of the first phase modulator. The first port of the first polarization beam splitter is connected to the third port of the third coupler. The connections are as follows: the second port of the first polarization beamsplitter is connected to the first port of the third photodetector; the third port of the first polarization beamsplitter is connected to the first port of the fourth photodetector; the first port of the second polarization beamsplitter is connected to the third port of the second coupler; the second port of the second polarization beamsplitter is connected to the first port of the fifth photodetector; the third port of the second polarization beamsplitter is connected to the first port of the sixth photodetector; the second port of the third photodetector is connected to the sixth port of the signal processing unit; the second port of the fourth photodetector is connected to the seventh port of the signal processing unit; the second port of the fifth photodetector is connected to the eighth port of the signal processing unit; and the second port of the sixth photodetector is connected to the ninth port of the signal processing unit.

[0043] Furthermore, the coupling ratio of the second coupler is 99:1, wherein: the optical power output from the first port of the second coupler accounts for 99%, the optical power output from the second port of the second coupler accounts for 99%, and the optical power output from the third port of the second coupler accounts for 1%.

[0044] Furthermore, the coupling ratio of the third coupler is 99:1, wherein: the optical power output from the first port of the third coupler accounts for 99%, the optical power output from the second port of the third coupler accounts for 99%, and the optical power output from the third port of the third coupler accounts for 1%.

[0045] Furthermore, the coupling ratio of the fourth coupler is 50:50, wherein the optical power output from the first port of the fourth coupler accounts for 50%, the optical power output from the second port of the fourth coupler accounts for 50%, and the optical power output from the third port of the fourth coupler accounts for 50%.

[0046] Furthermore, the optical switch controller controls two operating states of the optical switch. In the first operating state, the input light is transmitted from the first port of the optical switch to the second port of the optical switch, and the second port of the optical switch is connected to the first port of the first phase modulator. At this time, the first phase modulator is working. The third port of the optical switch is connected to the fourth port of the optical switch, and the fourth port of the optical switch is connected to the first port of the second phase modulator. At this time, the second phase modulator is not working. In the second operating state, the input light is transmitted from the first port of the optical switch to the fourth port of the optical switch, and the fourth port of the optical switch is connected to the first port of the second phase modulator. At this time, the second phase modulator is working. The third port of the optical switch is connected to the second port of the optical switch, and the second port of the optical switch is connected to the first port of the first phase modulator. At this time, the first phase modulator is not working.

[0047] The working principle of the fiber optic current sensor based on multi-level coordinated temperature compensation is as follows:

[0048] Step A: Light emitted from the light source enters the first coupler through the first port. 50% of the light is transmitted to the polarizer through the second port of the first coupler, and the other 50% of the light enters the second photodetector through the first port of the second photodetector through the fourth port of the first coupler. The light signal is converted into a voltage signal and output from the second port of the second photodetector. The voltage signal output from the second port of the second photodetector enters the signal processing unit through the second port of the signal processing unit for initial optical power monitoring. During the transmission of light from the first port to the second port of the polarizer, it becomes linearly polarized light and is output from the second port of the polarizer. The linearly polarized light is transmitted to the output of the optical switch after passing through the first 45° fusion point.

[0049] Step B: Linearly polarized light enters the optical switch from its first port, and the optical switch is in its first operating state. The linearly polarized light is transmitted from the first port of the optical switch to its second port for output. It then enters the first phase modulator from its first port, receives the modulation voltage applied by the fifth port of the signal processing unit to generate a modulation phase, and the linearly polarized light carrying the modulation phase is output from the second port of the first phase modulator. The linearly polarized light output from the second port of the first phase modulator enters the second coupler from its first port and is split into two polarized beams. One polarized beam is output from the second port of the second coupler, and the other polarized beam is output from the third port of the second coupler. The polarized light output from the second port of the second coupler is input into the fourth coupler from its first port and output from its second port. The linearly polarized light output from the second port of the fourth coupler is transmitted from the delay ring to the second 45° fusion point for output and then enters the second 45° fusion point. Wave plate, linearly polarized light passes through After passing through the waveplate, the light is divided into left-handed and right-handed circularly polarized light. The circularly polarized light enters the sensing fiber and is subjected to the magnetic field generated by the current in the current-carrying conductor, generating a Faraday phase shift F. The circularly polarized light carrying F is transmitted to the reflector and reflected back into the sensing fiber, generating another Faraday phase shift F. The circularly polarized light carrying F is then transmitted to… After passing through the waveplate, the light becomes linearly polarized. After passing through the second 45° fusion point, it exits from the delay ring. The linearly polarized light from the delay ring enters the fourth coupler from its second port and exits from its first port. The linearly polarized light from the first port of the fourth coupler enters the first phase modulator from its second port, where it receives the modulation voltage applied by the fifth port of the signal processing unit to generate a modulation phase. The linearly polarized light carrying the modulation phase exits from the first port of the first phase modulator. The linearly polarized light from the first port of the first phase modulator enters the optical switch from its second port and exits from its first port. After passing through the first 45° fusion point, it is transmitted from the second port of the polarizer to its first port. The light exiting from the first port of the polarizer enters the first coupler from its second port, and 50% of the light exits from the third port of the first coupler. It then enters the first photodetector from its first port, where it is converted from an optical signal to a voltage signal and exits from its second port. The voltage signal output from the second port of the first photodetector enters the signal processing unit from its first port for current calculation.

[0050] Step C: The linearly polarized light output from the third port of the second coupler enters the second polarization beamsplitter from the first port. The second polarization beamsplitter splits the linearly polarized light into fast-axis and slow-axis polarized light, which are output from the second port of the second polarization beamsplitter and the slow-axis polarized light from the third port of the second polarization beamsplitter, respectively. The fast-axis polarized light enters the fifth photodetector from the first port, where it is converted from an optical signal to a voltage signal. It is output from the second port of the fifth photodetector and enters the signal processing unit from the eighth port of the signal processing unit for fast-axis polarized light power analysis. Monitoring: Slow-axis polarized light enters the sixth photodetector from its first port, is converted from an optical signal to a voltage signal, and is output from the second port of the sixth photodetector. It then enters the signal processing unit from its ninth port for power analysis of the slow-axis polarized light. Monitoring; the signal processing unit calculates the insertion loss of the first phase modulator based on the voltage signals transmitted from the second port, fourth port, eighth port, and ninth port of the signal processing unit. Polarized crosstalk Half-wave voltage Monitoring; insertion loss of the first phase modulator Polarized crosstalk Half-wave voltage Perform three-level judgment and implement insertion loss. Polarized crosstalk Half-wave voltage Primary compensation is performed until the primary compensation fails, at which point the optical switch switches to the second working state.

[0051] Step D: The optical switch switches to the second operating state. Linearly polarized light is transmitted from the first port of the optical switch to the fourth port output of the optical switch. It then enters the second phase modulator from the first port, receives the modulation voltage applied by the fourth port of the signal processing unit to generate a modulation phase, and the linearly polarized light carrying the modulation phase is output from the second port of the second phase modulator. The linearly polarized light output from the second port of the second phase modulator enters the third coupler from the first port, splitting into two polarized beams. One polarized beam is output from the second port of the third coupler, and the other polarized beam is output from the third port of the third coupler. The polarized light output from the second port of the third coupler is input into the fourth coupler from the third port and output from the second port of the fourth coupler. The linearly polarized light output from the second port of the fourth coupler is transmitted from the delay ring to the second 45° fusion point output and enters the second 45° fusion point. Wave plate, linearly polarized light passes through After passing through the waveplate, the light is converted into left-handed and right-handed circularly polarized light. The circularly polarized light enters the sensing fiber and is subjected to the magnetic field generated by the current in the current-carrying conductor, resulting in a Faraday phase shift. Carrying Faraday phase shift The circularly polarized light is transmitted to the mirror and reflected back to the sensing fiber, generating a Faraday phase shift again. ; Carrying Faraday phase shift Circularly polarized light is transmitted to After passing through the waveplate, the light becomes linearly polarized. It then passes through the second 45° fusion point and exits from the delay ring. The linearly polarized light from the delay ring enters the fourth coupler from its second port and exits from its third port. The linearly polarized light from the third port of the fourth coupler enters the second phase modulator from its second port, where it again receives the modulation voltage applied by the fourth port of the signal processing unit to generate a modulated phase. The linearly polarized light carrying the modulated phase exits from the first port of the second phase modulator. The linearly polarized light from the first port of the second phase modulator enters the optical switch from its fourth port and exits from its first port. After passing through the first 45° fusion point, it is transmitted from the second port of the polarizer to its first port. The light exiting from the first port of the polarizer enters the first coupler from its second port, with 50% of the light exiting from the third port of the first coupler. It then enters the first photodetector from its first port, where it is converted from an optical signal to a voltage signal and exits from its second port. The voltage signal from the second port of the first photodetector enters the signal processing unit from its first port for current calculation.

[0052] Step E: The linearly polarized light output from the third port of the third coupler enters the first polarization beamsplitter from the first port. The first polarization beamsplitter splits the linearly polarized light into fast-axis and slow-axis polarized light, which are output from the second port of the first polarization beamsplitter and the slow-axis polarized light from the third port of the first polarization beamsplitter, respectively. The fast-axis polarized light enters the third photodetector from the first port, where it is converted from an optical signal to a voltage signal. It is output from the second port of the third photodetector and enters the signal processing unit from the sixth port of the signal processing unit for fast-axis polarized light power analysis. Monitoring: Slow-axis polarized light enters the fourth photodetector from its first port, is converted from an optical signal to a voltage signal, and is output from the second port of the fourth photodetector. It then enters the signal processing unit from its seventh port for power analysis of the slow-axis polarized light. The monitoring and signal processing unit calculates the insertion loss of the second phase modulator based on the voltage signals transmitted from the second, fourth, sixth, and seventh ports of the signal processing unit. Polarized crosstalk Half-wave voltage Monitoring; insertion loss of the first phase modulator Polarized crosstalk Half-wave voltage The three-level judgment is performed, consistent with the three-level judgment method of the first phase modulator, and insertion loss is applied. Polarized crosstalk Half-wave voltage Primary compensation continues until it fails, at which point the optical switch is switched to the first operating state, and step B is repeated.

[0053] Step F: When ≥ and ≥ ,or ≥ and ≥ ,or ≥ and ≥ When this happens, the signal processing unit stops steps B through E and issues a fault alarm for the fiber optic current sensor based on multi-level coordinated temperature compensation.

[0054] Furthermore, the insertion loss of the first phase modulator Polarized crosstalk Half-wave voltage The three-level judgment method is as follows:

[0055] First-level judgment, when > ≥ When the signal processing unit initiates preliminary compensation for the insertion loss of the first phase modulator; when > ≥ When the signal processing unit initiates preliminary polarization crosstalk compensation of the first phase modulator; when > ≥ At that time, the signal processing unit initiates preliminary compensation for the half-wave voltage of the first phase modulator; in the second stage, the long short-term memory network model in the signal processing unit uses the insertion loss of the first phase modulator at the current moment. Polarized crosstalk Half-wave voltage Given the input, predict the insertion loss at the next time step. The polarization crosstalk at the next moment The half-wave voltage at the next moment ,when > ≥ When the signal processing unit outputs a command, it is input to the optical switch controller from the third port of the signal processing unit. After receiving the command, the optical switch controller controls the optical switch to switch to the second working state; when > ≥ When the signal processing unit outputs a command, it is input to the optical switch controller from the third port of the signal processing unit. After receiving the command, the optical switch controller controls the optical switch to switch to the second working state; when > > At this time, the signal processing unit outputs a command, which is input to the optical switch controller from the third port of the signal processing unit. After receiving the command, the optical switch controller controls the optical switch to switch to the second working state; the third level judgment, when ≥ When the signal processing unit outputs a command, it is input to the optical switch controller from the third port of the signal processing unit. After receiving the command, the optical switch controller controls the optical switch to switch to the first working state, and the signal processing unit issues the first phase modulator fault alarm; when ≥ When the signal processing unit outputs a command, it is input to the optical switch controller from the third port of the signal processing unit. After receiving the command, the optical switch controller controls the optical switch to switch to the first working state, and the signal processing unit issues the first phase modulator fault alarm; when > At this time, the signal processing unit outputs a command from its third port to the optical switch controller. After receiving the command, the optical switch controller controls the optical switch to switch to the first working state, and the signal processing unit issues the first phase modulator fault alarm.

[0056] in, The insertion loss value for the fiber optic current sensor is 0.2% when the measurement error is 0.2%, obtained experimentally. , ;

[0057] The value of polarization crosstalk is obtained experimentally when the measurement error of the fiber optic current sensor is 0.2%. , ;

[0058] The value of the half-wave voltage is obtained experimentally when the measurement error of the fiber optic current sensor is 0.2%. , ;

[0059] The Long Short-Term Memory network model uses the insertion loss of the first phase modulator at the current time. The polarization crosstalk of the first phase modulator at the current moment The half-wave voltage of the first phase modulator at the current moment The input is used for training, and the final output is the insertion loss of the first phase modulator at the next time step. The polarization crosstalk of the first phase modulator at the next moment The half-wave voltage of the first phase modulator at the next moment ;

[0060] First, initialize and define the output prediction values ​​for time t-1. (Initialized prediction outputs are all 0) and current information (Currently monitored) , , Enter the forget gate to perform the t-th forget gate value. calculate:

[0061] ,

[0062] In the formula, , These are the weights and biases used in the forget gate calculation; It is the sigmoid function.

[0063] Next, through t Output predicted value at time -1 With the t Real-time monitoring Conduct the first t Input gate value at time 1 Calculation and candidate values calculate:

[0064] ,

[0065] ,

[0066] In the formula, , , , These are the input weights, candidate weights, input bias, and candidate bias. It is the hyperbolic tangent function.

[0067] Then, through the first t Forgetting threshold of time , t Cell state update value at time -1 , No. t Input gate value at time and candidate values The cell state update value at time t was calculated. :

[0068] ,

[0069] Next, through t Output predicted value at time -1 With the t Real-time monitoring Calculate the first t Output gate value at time , No. tOutput gate value at time With the t Cell state update value at time t Calculate the output prediction value at time t together (i.e., the predicted value of insertion loss output) Polarization crosstalk output prediction value Half-wave voltage output prediction value ):

[0070] ,

[0071] ,

[0072] In the formula, , These are the output weights and the output bias, respectively.

[0073] Finally, determine the insertion loss fitness function. Polarization crosstalk fitness function and half-wave voltage fitness function :

[0074] ,

[0075] ,

[0076] ,

[0077] In the formula, To provide the number of input samples for training, The true value corresponding to the predicted insertion loss value. This represents the true value corresponding to the predicted polarization crosstalk value. This is the true value corresponding to the predicted half-wave voltage.

[0078] If the fitness function is less than 0.001%, then the model training is complete, and the currently monitored data will be transferred to the appropriate level. , , As input, predict , , If the fitness function is not minimized, repeat the above process until the fitness function is minimized and the model training is completed.

[0079] Furthermore, the insertion loss of the first phase modulator at the current moment... Polarized crosstalk Half-wave voltage The monitoring methods are as follows:

[0080] After light is transmitted from the second port of the first coupler to the polarizer, the output light is approximately equal to the input light of the first phase modulator. Therefore, the input light power of the first phase modulator... for:

[0081] ,

[0082] Calculate the output optical power of the first phase modulator based on the fast and slow axis optical powers monitored by the fifth and sixth photodetectors. for:

[0083] ,

[0084] Calculate the insertion loss of the first phase modulator :

[0085] ,

[0086] Calculate polarization crosstones :

[0087] ,

[0088] The signal processing unit applies a stepped wave modulation to the phase modulator. When the stepped wave amplitude exceeds At that time, the height of the stepped wave will be reduced by This process is called a step wave. Reset. During the last step-wave modulation cycle before the 2π step-wave reset, the signal processing unit acquires the voltage signal output by the first photodetector. I out1 During the first phase modulation cycle after the 2π reset of the stepped wave, the signal processing unit acquires the voltage signal output by the first photodetector. I out2 Calculate the applied half-wave voltage according to the formula. The actual half-wave voltage of the modulator itself Error between :

[0089] ,

[0090] In the formula: The error between the applied half-wave voltage and the actual half-wave voltage of the modulator itself; for The light intensity received by the first photodetector in the last cycle before reset; for The light intensity received by the first photodetector in the first cycle after reset; denoted as the photoelectric conversion coefficient of the first photodetector; The initial light intensity;

[0091] Calculate half-wave voltage :

[0092] ,

[0093] In the formula: The applied half-wave voltage.

[0094] Insertion loss of the second phase modulator The polarization crosstalk of the second phase modulator Half-wave voltage of the second phase modulator The monitoring method is the same as that for the first phase modulator.

[0095] Furthermore, the primary compensation methods for the insertion loss, polarization crosstalk, and half-wave voltage of the first phase modulator are as follows:

[0096] The primary method for insertion loss compensation is as follows:

[0097] when > > At this time, the signal processing unit initiates preliminary compensation for the insertion loss of the first phase modulator, and the information processing unit adjusts the light source drive current to increase the initial optical power. for + Compensation for the increased insertion loss leading to a decrease in the output optical power of the first phase modulator Reduced to , making ,at this time:

[0098] ,

[0099] In the formula, The change in optical power due to the increase in the light source's optical power. The change in optical power is the amount by which the output optical power of the first phase modulator decreases due to the increase in insertion loss.

[0100] The primary method for polarization crosstalk compensation is as follows:

[0101] when At that time, the signal processing unit initiates preliminary polarization crosstalk compensation of the first phase modulator. Based on the closed-loop detection principle of the fiber optic current sensor with multi-level coordinated temperature compensation, the closed-loop feedback phase shift is... The expression is:

[0102] ,

[0103] Assuming the polarization crosstalk of the phase modulator is entirely due to the fiber optic axis error. Introducing polarization crosstalk in the first phase modulator for:

[0104] ,

[0105] Establish the relationship between polarization crosstalk and transformation ratio:

[0106] ,

[0107] ,

[0108] Constructing compensation coefficients :

[0109] ,

[0110] Current measurement value Multiply by a compensation factor to achieve polarization crosstalk error compensation:

[0111] ,

[0112] In the formula, The current measurement value after compensation. To and The corresponding transformation ratio of the fiber optic current sensor, To and The corresponding transformation ratio of the fiber optic current sensor, The polarized crosstalk at the current temperature. For Faraday phase, The polarization crosstalk of the first phase modulator at the current moment. Let be the slope of the fitted curve. This is polarized crosstalk at room temperature (25℃). The current temperature;

[0113] when > > At this time, the signal processing unit initiates preliminary compensation for the insertion loss of the first phase modulator, and the information processing unit adjusts the light source drive current to increase the initial optical power. for + Compensate the output optical power of the first phase modulator This results in higher output optical power. Increase to + , making + = P 输入1 ,

[0114] The primary compensation methods for insertion loss, polarization crosstalk, and half-wave voltage of the second phase modulator are the same as those for the first phase modulator.

[0115] In summary, this device monitors the operating status of the phase modulator in real time, performs online compensation for performance parameter degradation caused by temperature at the algorithm level, and introduces a long short-term memory network model to learn, analyze, and predict the operating data of the phase modulator performance parameters. Through the coordinated approach of algorithm compensation and alternating operation of the phase modulator, the long-term workload of a single phase modulator is reduced, the lifespan of the phase modulator is increased, and the long-term reliability of the system under complex operating conditions is improved. This invention has the advantages of high measurement stability, high reliability, and long lifespan, and can meet the requirements of long-term continuous operation and environmental adaptability in power grid and industrial application scenarios.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber optic current sensor based on multi-level coordinated temperature compensation, characterized in that, include: An optical sensing unit is used to generate and guide probe light through a current-carrying conductor (15) wound around a sensing fiber (14), and convert the current signal into an optical phase signal based on the Faraday effect. The modulation and switching unit includes an optical switch (5), a first phase modulator (6) and a second phase modulator (8) connected in parallel. The optical switch (5) is used to selectively guide the probe light from the optical sensing unit to the first phase modulator (6) or the second phase modulator (8) for phase modulation, and guide the light carrying the current signal back to the optical sensing unit. The monitoring unit is used to sample the output light of the first phase modulator (6) and the second phase modulator (8) respectively, and extract optical parameters that reflect the performance status of the output light. The signal processing unit (19) is electrically connected to the monitoring unit, the optical switch (5), the first phase modulator (6), and the second phase modulator (8), and is configured to execute the following coordinated control process: Control the optical switch (5) to make the first phase modulator (6) or the second phase modulator (8) work as the main modulator, and the other as the backup modulator; Based on the sampling signal of the main modulator by the monitoring unit, the performance parameters of the main modulator are calculated in real time, and the performance parameters include at least insertion loss, polarization crosstalk and half-wave voltage. The actual values ​​of the performance parameters of the main modulator are subject to three levels of judgment and processing, specifically: The real-time values ​​of the performance parameters of the main modulator are obtained. When the real-time values ​​are within a first preset range, the corresponding primary compensation algorithm is started. The first preset range includes a first preset sub-range, a second preset sub-range, and a third preset sub-range. When the real-time value is within a first preset range, the corresponding primary compensation algorithm is activated, specifically as follows: When the insertion loss of the master modulator When the real-time value meets the first preset sub-range, the signal processing unit (19) increases the initial optical power by increasing the driving current of the light source (1). To compensate for signal attenuation caused by increased insertion loss; When the polarization crosstalk of the master modulator When the real-time value meets the second preset sub-range, the signal processing unit (19) calculates the compensation coefficient according to the correlation model between polarization crosstalk and sensor ratio, and calculates the compensation coefficient according to the compensation coefficient. Current measurement value Corrections are made to compensate for polarization crosstalk errors, wherein the compensation coefficient is used. Current measurement value The corrected expression is: ， ， ， ， ， In the formula, The current measurement value after compensation. To and The corresponding transformation ratio of the fiber optic current sensor, To and The corresponding transformation ratio of the fiber optic current sensor, The polarization crosstalk at the current temperature, For Faraday phase, The polarization crosstalk of the first phase modulator at the current moment. Let be the slope of the fitted curve. This is polarized crosstalk at room temperature (25℃). The current temperature; When the half-wave voltage of the master modulator When the real-time value meets the third preset sub-range, the signal processing unit (19) at the half-wave voltage Subtract the monitoring error from the middle This is to achieve real-time correction of the half-wave voltage; Based on the real-time value, the predicted value of the performance parameters of the main modulator is predicted using a long short-term memory network model. When the predicted value is within a second preset range, the optical switch (5) is controlled to switch so that the backup modulator can take over as the main modulator. When the real-time value exceeds the fault threshold, the main modulator is determined to be faulty and an alarm is triggered, while switching to the backup modulator.

2. The fiber optic current sensor based on multi-level coordinated temperature compensation according to claim 1, characterized in that, The optical sensing unit includes a light source (1), a first coupler (2), a polarizer (3), a first 45° fusion splice (4), a fourth coupler (10), a delay ring (11), a second 45° fusion splice (12), a λ / 4 waveplate (13), the sensing fiber (14), and a reflector (16) connected in sequence. The first coupler (2) is also connected to a first photodetector (17) for detecting the returned light signal and a second photodetector (18) for monitoring the initial light power.

3. The fiber optic current sensor based on multi-level coordinated temperature compensation according to claim 2, characterized in that, In the modulation and switching unit: The first port of the optical switch (5) is connected to the polarizer (3); The second port of the optical switch (5) is connected to the input of the first phase modulator (6), and the output of the first phase modulator (6) is connected to the first port of the fourth coupler (10) through the main path of the second coupler (7). The fourth port of the optical switch (5) is connected to the input of the second phase modulator (8), and the output of the second phase modulator (8) is connected to the third port of the fourth coupler (10) through the main path of the third coupler (9).

4. The fiber optic current sensor based on multi-level coordinated temperature compensation according to claim 3, characterized in that, The coupling ratio of the second coupler (7) and the third coupler (9) is 99:1; the coupling ratio of the fourth coupler (10) is 50:

50.

5. A fiber optic current sensor based on multi-level coordinated temperature compensation according to claim 3, characterized in that, The monitoring unit includes: The first monitoring branch is connected to the auxiliary port of the second coupler (7). The first monitoring branch includes a second polarization beam splitter (21), a fifth photodetector (24) and a sixth photodetector (25). The first monitoring branch is used to monitor the polarization state of the output light of the first phase modulator (6). The second monitoring branch is connected to the auxiliary port of the third coupler (9). The second monitoring branch includes a first polarization beam splitter (20), a third photodetector (22) and a fourth photodetector (23). The second monitoring branch is used to monitor the polarization state of the output light of the second phase modulator (8).

Images