A dual-optical path magnetic field sensing system and signal demodulation method thereof

Abstract

The present invention discloses a dual-optical path magnetic field sensing system and a signal demodulation method thereof, and relates to a sensing device of magnetic field intensity and a signal demodulation technical field thereof. The system comprises: a dual-beam polarized optical path generation module: used to generate a first polarized light signal and a second polarized light signal; a sensing optical path transmission module: used to amplify and filter the first polarized light signal to obtain a first gain result; a reference optical path transmission module: used to amplify and filter the second polarized light signal to obtain a second gain result; an optical signal processing and display module: used to process and judge the gain difference between the first gain result and the second gain result, determine the direction of the external magnetic field according to the judgment result, and process the input signal of the stepping motor accordingly and display it. The present invention has low cost, a simple demodulation method, and can accurately demodulate the magnetic field intensity.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field intensity sensing devices and signal demodulation technology thereof, and in particular to a dual-optical path magnetic field sensing system and a signal demodulation method thereof. Background Art

[0002] With the rapid development of science and technology and industrial production, the detection and analysis of magnetic fields play a vital role in national defense security, deep sea and space exploration, geological exploration, aerospace and automatic control. The high-precision measurement of magnetic fields has also put forward higher and higher requirements. Traditional magnetic field sensing technology has gradually shown its inability. Therefore, many fields are in urgent need of developing some new magnetic field sensing technologies to meet various strict application requirements and accurately give the required magnetic field.

[0003] In recent years, there have been the emergence of tapered fiber magnetic field sensors, photonic crystal fiber-filled magnetic field sensors, coreless and single-mode fiber structures, and fiber Bragg grating structures. They usually rely on power value detection and wavelength offset detection methods for signal demodulation. Traditional power value detection is easily affected by factors such as light source power fluctuations, with large errors and low precision. The high precision of wavelength detection often relies on relatively complex optical equipment, and these optical equipment often rely on imports to have better performance. Therefore, as people put forward more and more precise demands for magnetic field detection in different fields, a convenient and fast detection device, a low-cost sensing system and a demodulation method that are easy to improve detection accuracy are urgently needed in the field of magnetic field measurement, so as to better meet the requirements of various fields for magnetic field measurement accuracy and relatively simple sensing systems. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a dual-optical path magnetic field sensing system and a signal demodulation method thereof, which utilizes a Faraday rotator magnetic field sensitive element and uses the information of the reference optical path as reference information for comparison, thereby achieving a relatively simple sensing system and high magnetic field detection accuracy.

[0005] On the one hand, to achieve the above object, the present invention provides a dual-optical path magnetic field sensing system, comprising:

[0006] Dual-beam polarization light path generation module: used to generate a first polarization light signal and a second polarization light signal;

[0007] The sensing optical path transmission module is used to amplify and filter the first polarized light signal to obtain a first gain result;

[0008] Reference optical path transmission module: used for amplifying and filtering the second polarized light signal to obtain a second gain result;

[0009] Optical signal processing and display module: used to process and judge the gain difference between the first gain result and the second gain result, determine the direction of the external magnetic field according to the judgment result, process the input signal of the stepper motor accordingly, and display it.

[0010] Preferably, the dual-beam polarization light path generation module includes a laser and a polarization beam splitter; the laser is used to emit an optical signal, and the polarization beam splitter is used to decompose the optical signal into the first polarization light signal and the second polarization light signal; wherein the first polarization light signal and the second polarization light signal are perpendicular to each other.

[0011] Preferably, the sensing light path transmission module comprises:

[0012] A first beam splitter: used for splitting the first polarized light signal according to a preset ratio to obtain a first high-power light beam and a first low-power light beam;

[0013] Faraday rotator: used to sense the environmental magnetic field and transmit the first high-power light beam;

[0014] Focusing lens: used for focusing the first high-power light beam;

[0015] A first semiconductor optical amplifier: used for amplifying the focused first high-power light beam;

[0016] A first detection amplification and filtering module is used to filter and amplify the amplified first high-power light beam and the first low-power light beam to obtain a first processed signal and a second processed signal;

[0017] The first comparator is used to compare the first processed signal with the second processed signal, determine the gain of the first polarized light signal after being amplified, and output a first gain result.

[0018] Preferably, if the magnetic field environment to be measured has a magnetic field parallel to the transmission direction of the light beam acting on the Faraday rotator, the first polarized light signal will produce a rotation of no more than 90°, and the rotated first polarized light signal is focused on the first semiconductor optical amplifier for single-pass amplification, and is no longer orthogonal to the polarization direction of the reference light path; wherein the thickness of the Faraday rotator is designed according to the size range of the magnetic field environment to be measured.

[0019] Preferably, the reference optical path transmission module comprises:

[0020] A second beam splitter: used for splitting the second polarized light signal according to a preset ratio to obtain a second high-power light beam and a second low-power light beam;

[0021] Focusing lens: used for focusing the second high-power light beam;

[0022] A second semiconductor optical amplifier: used for amplifying the focused second high-power light beam;

[0023] A second detection amplification and filtering module is used to filter and amplify the amplified second high-power light beam and the second low-power light beam to obtain a third processing signal and a fourth processing signal;

[0024] The second comparator is used to compare the third processed signal with the fourth processed signal, determine the gain of the second polarized light signal after being amplified, and output a second gain result.

[0025] Preferably, a rotatable bracket is provided on the first semiconductor optical amplifier, and a stepper motor is provided on the rotatable bracket. The rotating shaft of the stepper motor drives the rotatable bracket to rotate, so that the semiconductor optical amplifier rotates counterclockwise or clockwise in a direction perpendicular to the light path; wherein the semiconductor optical amplifier is fixed to the rotatable bracket by a plurality of fastening screws.

[0026] Preferably, the active region of the first semiconductor optical amplifier and the active region of the second semiconductor optical amplifier are placed perpendicular to each other; the first detection amplification and filtering module and the second detection amplification and filtering module both include a detector, an amplifier and a filtering circuit, and the detector, the amplifier and the filtering circuit are connected in sequence.

[0027] Preferably, the optical signal processing and display module comprises:

[0028] A third comparator: used for calculating a gain difference between the first gain result and the second gain result, and sending the gain difference to the processing and display device;

[0029] Processing and display device: used for displaying the gain difference output by the third comparator;

[0030] A controller: used for adjusting an input signal of the stepper motor according to the gain difference as an input signal;

[0031] The third comparator is connected to the processing and display device and the controller respectively, and the controller is connected to the processing and display device.

[0032] Preferably, based on the input signal, the controller applies a forward or reverse pulse signal to the stepper motor, causing the semiconductor optical amplifier to rotate clockwise or counterclockwise by an angle less than 10° under the drive of the rotating bracket, and judges the direction of rotation of the Faraday rotation plate caused by the ambient magnetic field according to the gain result obtained by the third comparator during the rotation process, thereby determining the direction of the external magnetic field.

[0033] On the other hand, to achieve the above object, the present invention also provides a signal demodulation method, comprising:

[0034] Applying magnetic fields of different magnitudes and determined directions to the magnetic field sensing system of the dual optical paths to obtain the rotation angle of the first polarized light signal;

[0035] Calibrate the corresponding relationship between the gain difference of one output by the third comparator and the rotation angle of the first polarized light signal caused by the Faraday rotator;

[0036] The artificially applied magnetic field is released, and the gain difference 2 output by the third comparator under the action of the magnetic field to be measured is measured, the rotation angle caused by the magnetic field to be measured is determined through the corresponding relationship between the gain difference 1 output by the third comparator and the rotation angle of the first polarized light signal caused by the Faraday rotator, and the size of the magnetic field to be measured is calculated based on the rotation angle;

[0037] Determine the input signal of the stepper motor, and obtain the relationship between the change of the gain difference and the input signal of the stepper motor according to the change of the gain difference output by the third comparator, and calibrate the relationship between the forward and reverse pulses and the direction of the magnetic field to be measured;

[0038] Based on the relationship between the forward and reverse pulses and the direction of the magnetic field to be measured, the direction of the magnetic field to be measured is determined according to the change of the gain difference output by the third comparator.

[0039] Compared with the prior art, the present invention has the following advantages and technical effects:

[0040] The present invention uses a polarization beam splitter to construct a dual-beam polarization optical path, one of which is used as a reference optical path and used as a benchmark for measuring the environmental magnetic field, and the other optical path is used as a sensing optical path for sensing the environmental magnetic field, and the magnetic field is measured based on the output value of the reference optical path. The polarized light signals of the reference optical path and the sensing optical path are amplified by two semiconductor optical amplifiers with exactly the same structural parameters and performance. When arranged in the optical path system, the active regions of the two semiconductor optical amplifiers are placed vertically, and the p-light and s-light decomposed by the polarization beam splitter are set to be orthogonal linear polarized lights. Under the same electrical excitation, the semiconductor optical amplifiers placed vertically in the sensing optical path and the reference optical path have exactly the same amplification effect on them. The amplification effect is determined by separating a part of the beam splitter in the sensing optical path and the reference optical path and then comparing it with the optical power after amplification by the semiconductor optical amplifier. Once the vibration direction of the polarized light of the sensing optical path rotates in a plane perpendicular to the optical path, its gain value will decrease, and there will be a difference with the benchmark value output by the reference optical path. This difference reflects the size of the environmental magnetic field. At the same time, the signal of the gain difference is used As the input signal of the controller, the semiconductor optical amplifier is prompted to rotate clockwise or counterclockwise by an angle, and the direction of the environmental magnetic field is determined according to the change of the gain value when the semiconductor optical amplifier rotates. Therefore, by cleverly constructing the polarized light signal of the dual optical path and the amplification characteristics of the semiconductor optical amplifier for polarized light, the reference optical path is used as a benchmark, and the change of polarized light is converted into a change of light intensity gain for rapid detection. At the same time, the semiconductor optical amplifier rotates an angle to quickly determine the direction of the magnetic field, and there is no accuracy requirement for the angle of rotation of the amplifier. The entire sensing device is relatively simple, does not involve devices with complex processes and structures, is not controlled by foreign technology, has low cost, and has a simple demodulation method. The light intensity gain change is realized according to the Faraday effect, and the magnetic field strength can be accurately demodulated with a stepper motor that does not require very high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0042] Figure 1 Schematic diagram of the structure of a dual-optical-path magnetic field sensing system according to an embodiment of the present invention;

[0043] Figure 2 It is a schematic diagram of assembling a rotating bracket, a stepping motor and a semiconductor optical amplifier according to an embodiment of the present invention;

[0044] Figure 3 The figure is a flow chart of a signal demodulation method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0046] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0047] The present invention proposes a dual-optical path magnetic field sensing system, such as Figure 1 ,include:

[0048] Dual-beam polarization light path generation module: used to generate a first polarization light signal and a second polarization light signal;

[0049] Sensing optical path transmission module: used for amplifying and filtering the first polarized light signal to obtain a first gain result;

[0050] Reference optical path transmission module: used for amplifying and filtering the second polarized light signal to obtain a second gain result;

[0051] Optical signal processing and display module: used to process and judge the gain difference between the first gain result and the second gain result, determine the direction of the external magnetic field according to the judgment result, process the input signal of the stepper motor accordingly, and display it.

[0052] The present invention uses a polarization beam splitter to construct a dual-beam polarization optical path, one of which is used as a reference optical path and as a benchmark for measuring the environmental magnetic field, and the other optical path is used as a sensing optical path for sensing the environmental magnetic field, and the magnetic field is measured based on the output value of the reference optical path. By cleverly constructing the polarized light signal of the dual optical paths and the amplification characteristics of the semiconductor optical amplifier for polarized light, the reference optical path is used as a benchmark, and the change of polarized light is converted into a change of light intensity gain for rapid detection. At the same time, the semiconductor optical amplifier rotates an angle to quickly determine the direction of the magnetic field, and there is no precision requirement for the angle of rotation of the amplifier. The entire sensing device is relatively simple, does not involve devices with complex processes and structures, is not controlled by foreign technologies, has low cost, and has a simple demodulation method. The light intensity gain change is realized according to the Faraday effect, and the magnetic field intensity can be accurately demodulated with a stepping motor that does not require very high precision.

[0053] Furthermore, the dual-beam polarization optical path generation module includes a laser and a polarization beam splitter; the laser is used to emit an optical signal, and the polarization beam splitter is used to decompose the optical signal into a first polarization light signal and a second polarization light signal; wherein the first polarization light signal and the second polarization light signal are perpendicular to each other.

[0054] The polarization beam splitter decomposes the optical signal into two polarized light signals with mutually perpendicular vibration directions, namely the first polarized light signal and the second polarized light signal, thereby constructing a dual-optical path sensing system for detecting magnetic fields, in which one branch is used as the sensing optical path and the other branch is used as the reference optical path. The signal of the reference optical path is used as a reference to achieve accurate measurement of the ambient magnetic field.

[0055] The sensing optical path and the reference optical path are respectively provided with a first semiconductor optical amplifier and a second semiconductor optical amplifier. The two orthogonal polarized light beams p light (first polarized light signal) and s light (second polarized light signal) are separated by a polarization beam splitter. The p light is used as the optical signal of the sensing optical path, and the s light is used as the optical signal of the reference optical path. The semiconductor optical amplifiers whose active regions are placed perpendicular to each other have the same gain effect when amplifying the two orthogonal polarized light beams respectively. However, once the Faraday rotator of the sensing optical path is affected by the magnetic field of the environment, the vibration direction of the polarized light will rotate, and the gain of the sensing optical path will decrease accordingly. The amount of decrease is based on the gain of the reference optical path, thereby determining the angle of rotation, and then determining the magnetic field strength of the environment according to the angle of rotation.

[0056] Furthermore, the sensing optical path transmission module includes:

[0057] A first beam splitter: used for splitting the first polarized light signal according to a preset ratio to obtain a first high-power light beam and a first low-power light beam;

[0058] Faraday rotator: used to sense the ambient magnetic field and transmit the first high-power light beam;

[0059] A first focusing lens: used for focusing the first high-power light beam;

[0060] A first semiconductor optical amplifier: used for amplifying the focused first high-power light beam;

[0061] A first detection amplification and filtering module is used to filter and amplify the amplified first high-power light beam and the first low-power light beam to obtain a first processed signal and a second processed signal;

[0062] The first comparator is used to compare the first processed signal with the second processed signal, determine the gain of the first polarized light signal after being amplified, and output a first gain result.

[0063] The light beam of the sensing optical path (the first polarized light signal) is firstly split by the first beam splitter in a ratio of 1:9 to 2:8, and the split lower power light beam (the first low power light beam) is directly received by the detector in the first detection amplification and filtering module and amplified and filtered, and then the processed signal is input to the first comparator, and the higher power light beam (the first high power light beam) firstly passes through the Faraday rotator that senses the environmental magnetic field, and then is focused by the first focusing lens to the first semiconductor optical amplifier for amplification, and the amplified light beam is received by the detector in the first detection amplification and filtering module and filtered and amplified, and then is also input to the first comparator, and the first comparator compares the two input signals to determine the gain of the polarized light of the sensing optical path after being amplified, and the gain result is output to the third comparator, and the output result of the third comparator is displayed after being processed accordingly.

[0064] Furthermore, if the magnetic field environment to be measured has a magnetic field parallel to the transmission direction of the light beam acting on the Faraday rotator, the first polarized light signal will produce a rotation of no more than 90°, and the rotated first polarized light signal will be focused on the first semiconductor optical amplifier for single-pass amplification, and will no longer be orthogonal to the polarization direction of the reference light path; wherein the thickness of the Faraday rotator is designed according to the size range of the magnetic field environment to be measured.

[0065] The thickness d of the Faraday rotator is designed according to the possible maximum value of the environmental magnetic field in which the Faraday rotator is located, so that the angle θ=V×H×d at which the polarized light vibration direction rotates does not exceed 90°, wherein V is the Verdet constant and H is the environmental magnetic field to be measured. That is, in this embodiment, the thickness of the Faraday rotator can be designed according to the size range of the environmental magnetic field to be measured, and different thicknesses are suitable for magnetic field detection of different sizes; if the environment has a magnetic field parallel to the light beam transmission direction acting on the Faraday rotator, the first polarized light signal will produce a rotation of no more than 90°, and the rotated polarized light will be focused on the first semiconductor optical amplifier for single-pass amplification. After the rotation, the polarized light direction is no longer orthogonal to the reference light path, and the gain of the first semiconductor optical amplifier for the rotated polarized light will deviate, and the deviation is related to the rotation angle.

[0066] Furthermore, the reference optical path transmission module includes:

[0067] A second beam splitter: used for splitting the second polarized light signal according to a preset ratio to obtain a second high-power light beam and a second low-power light beam;

[0068] Second focusing lens: used for focusing the second high-power light beam;

[0069] The second semiconductor optical amplifier is used to amplify the focused second high-power light beam;

[0070] The second detection amplification and filtering module is used to filter and amplify the amplified second high-power light beam and the second low-power light beam to obtain a third processing signal and a fourth processing signal;

[0071] The second comparator is used to compare the third processed signal with the fourth processed signal, determine the gain of the second polarized light signal after being amplified, and output a second gain result.

[0072] The light beam of the reference optical path (the second polarized light signal) is firstly split by the second beam splitter in a ratio of 1:9 to 2:8, and the split lower power light beam (the second low power light beam) is directly received by the detector in the second detection amplification and filtering module and amplified and filtered, and then input to the second comparator, and the higher power light beam (the second high power light beam) is focused by the second focusing lens to the second semiconductor optical amplifier for amplification, and the amplified light beam is received by the detector in the second detection amplification and filtering module and filtered and amplified, and then the processed signal is input to the second comparator, and the second comparator compares the two input signals to determine the gain of the polarized light of the sensing optical path after being amplified, and the gain result is output to the third comparator.

[0073] A first semiconductor optical amplifier and a second first semiconductor optical amplifier are respectively arranged on the sensing optical path and the reference optical path. The two orthogonal polarized light beams p light and s light separated by the polarization beam splitter, one beam is used as the optical signal of the sensing optical path, and the other beam is used as the optical signal of the reference optical path. The semiconductor optical amplifiers whose active regions are placed perpendicular to each other have the same gain effect when amplifying the two orthogonal polarized light beams respectively. However, once the Faraday rotator of the sensing optical path is affected by the magnetic field of the environment, the vibration direction of the polarized light will rotate, and the gain of the sensing optical path will decrease accordingly. The magnitude of the decrease is based on the gain of the reference optical path, so as to determine the rotation angle, and then determine the magnetic field strength of the environment according to the rotation angle;

[0074] Furthermore, a rotatable bracket is provided on the first semiconductor optical amplifier, and a stepper motor is provided on the rotatable bracket. The rotating shaft of the stepper motor drives the rotatable bracket to rotate, so that the semiconductor optical amplifier rotates counterclockwise or clockwise in a direction perpendicular to the light path; wherein the semiconductor optical amplifier is fixed to the rotatable bracket by a plurality of fastening screws.

[0075] The rotatable bracket is installed on the first semiconductor optical amplifier (it can also be installed on the second semiconductor optical amplifier, but in this case the Faraday rotator is also on the polarized light branch of the second semiconductor optical amplifier). The rotatable bracket is provided with a stepper motor. The shaft of the stepper motor drives the bracket to rotate, so that the semiconductor optical amplifier can rotate counterclockwise and clockwise in a direction perpendicular to the light path. The maximum angle of rotation clockwise and counterclockwise is 10°. The assembly diagram of the rotatable bracket, the stepper motor and the first semiconductor optical amplifier is shown in FIG. Figure 2 , the semiconductor optical amplifier is fixed to the bracket by 4 fastening screws.

[0076] Furthermore, the active area of ​​the first semiconductor optical amplifier and the active area of ​​the second semiconductor optical amplifier are placed vertically to each other; the first detection amplification and filtering module and the second detection amplification and filtering module both include a detector, an amplifier and a filtering circuit, which are connected in sequence.

[0077] Furthermore, the optical signal processing and display module includes:

[0078] A third comparator: used for calculating a gain difference between the first gain result and the second gain result, and sending the gain difference to the processing and display device;

[0079] Processing and display device: used for displaying the gain difference output by the third comparator;

[0080] Controller: used to adjust the input signal of the stepper motor according to the gain difference as the input signal;

[0081] The third comparator is connected to the processing and display device and the controller respectively, and the controller is connected to the processing and display device.

[0082] Based on the input signal, the controller applies a forward or reverse pulse signal to the stepper motor, causing the semiconductor optical amplifier to rotate clockwise or counterclockwise by an angle less than 10° under the drive of the rotating bracket. The direction of rotation of the Faraday rotation plate caused by the ambient magnetic field is judged according to the gain result obtained by the third comparator during the rotation process, thereby determining the direction of the external magnetic field.

[0083] The gain difference comparison result of the third comparator is output, processed and displayed. At the same time, the output result of the third comparator is used as the input signal of the controller. When necessary, the input signal of the stepper motor is adjusted by the controller, and a forward or reverse pulse signal is applied to it, so that the semiconductor optical amplifier is driven by the rotating bracket to rotate clockwise or counterclockwise by an angle less than 10°. The direction of rotation of the Faraday rotation plate caused by the environmental magnetic field is judged according to whether the gain result obtained by the third comparator during the rotation is increased or decreased, thereby determining the direction of the external magnetic field. The controller processes the input signal of the stepper motor accordingly to determine whether it is a forward or reverse pulse and displays it together with the output result of the third comparator. After determining the direction, the first semiconductor optical amplifier rotates back to the vertical state of the active area.

[0084] This embodiment also provides a signal demodulation method for a dual-optical-path magnetic field sensing system. Figure 3 , specifically:

[0085] Apply magnetic fields of different magnitudes and determined directions to the magnetic field sensing system of the dual optical paths to obtain a rotation angle θ of the first polarized light signal;

[0086] Calibrate the corresponding relationship between the gain difference of one output by the third comparator and the rotation angle θ of the first polarized light signal caused by the Faraday rotator;

[0087] The artificially applied magnetic field is released, and the gain difference 2 output by the third comparator under the action of the magnetic field to be measured is measured, and the rotation angle caused by the magnetic field to be measured is determined by the corresponding relationship between the gain difference 1 output by the third comparator and the rotation angle of the first polarized light signal caused by the Faraday rotator, and the magnitude of the magnetic field to be measured is calculated based on the rotation angle;

[0088] Determine the input signal of the stepper motor, and obtain the relationship between the change of the gain difference and the input signal of the stepper motor according to the change of the gain difference output by the third comparator, and calibrate the relationship between the forward and reverse pulses and the direction of the magnetic field to be measured;

[0089] Based on the relationship between the forward and reverse pulses and the direction of the magnetic field to be measured, the direction of the magnetic field to be measured is determined according to the change of the gain difference output by the third comparator.

[0090] The present invention uses the gain difference signal as the input signal of the controller to prompt the semiconductor optical amplifier to rotate clockwise or counterclockwise by an angle, and determines the direction of the environmental magnetic field according to the change of the gain value when the semiconductor optical amplifier rotates. Therefore, by cleverly constructing the polarized light signal of the dual optical paths and the amplification characteristics of the semiconductor optical amplifier for polarized light, the reference optical path is used as a reference, and the change of polarized light is converted into a change of light intensity gain for rapid detection. At the same time, the semiconductor optical amplifier rotates by an angle to quickly determine the direction of the magnetic field, and there is no accuracy requirement for the angle of rotation of the amplifier. The entire sensing device is relatively simple, does not involve devices with complex processes and structures, is not controlled by foreign technologies, has low cost, and has a simple demodulation method. The light intensity gain change is realized according to the Faraday effect, and the magnetic field strength can be accurately demodulated in conjunction with a stepper motor that does not require very high precision.

[0091] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A dual-optical path magnetic field sensing system, characterized in that: include: Dual-beam polarization light path generation module: used to generate a first polarization light signal and a second polarization light signal; The sensing optical path transmission module is used to amplify and filter the first polarized light signal to obtain a first gain result; The sensing light path transmission module comprises: A first beam splitter: used for splitting the first polarized light signal according to a preset ratio to obtain a first high-power light beam and a first low-power light beam; Faraday rotator: used to sense the environmental magnetic field and transmit the first high-power light beam; Focusing lens: used for focusing the first high-power light beam; A first semiconductor optical amplifier: used for amplifying the focused first high-power light beam; A first detection amplification and filtering module is used to filter and amplify the amplified first high-power light beam and the first low-power light beam to obtain a first processed signal and a second processed signal; A first comparator: used for comparing the first processed signal with the second processed signal, determining the gain of the first polarized light signal after being amplified, and outputting a first gain result; Reference optical path transmission module: used for amplifying and filtering the second polarized light signal to obtain a second gain result; The reference optical path transmission module comprises: A second beam splitter: used for splitting the second polarized light signal according to a preset ratio to obtain a second high-power light beam and a second low-power light beam; Focusing lens: used for focusing the second high-power light beam; A second semiconductor optical amplifier: used for amplifying the focused second high-power light beam; A second detection amplification and filtering module is used to filter and amplify the amplified second high-power light beam and the second low-power light beam to obtain a third processing signal and a fourth processing signal; A second comparator is used to compare the third processed signal with the fourth processed signal, determine the gain of the second polarized light signal after being amplified, and output a second gain result; An optical signal processing and display module is used to process and judge the gain difference between the first gain result and the second gain result, determine the direction of the external magnetic field according to the judgment result, and process the input signal of the stepping motor accordingly and display it; The optical signal processing and display module comprises: A third comparator: used for calculating a gain difference between the first gain result and the second gain result, and sending the gain difference to the processing and display device; Processing and display device: used for displaying the gain difference output by the third comparator; A controller: used for adjusting an input signal of the stepping motor according to the gain difference as an input signal; The third comparator is connected to the processing and display device and the controller respectively, and the controller is connected to the processing and display device; Based on the input signal, the controller applies a forward or reverse pulse signal to the stepper motor, causing the semiconductor optical amplifier to rotate clockwise or counterclockwise by an angle less than 10° under the drive of the rotating bracket, and judges the direction of rotation of the Faraday rotation plate caused by the environmental magnetic field according to the gain result obtained by the third comparator during the rotation process, thereby determining the direction of the external magnetic field.

2. The dual-optical-path magnetic field sensing system according to claim 1, characterized in that: The dual-beam polarization optical path generation module includes a laser and a polarization beam splitter; the laser is used to transmit an optical signal, and the polarization beam splitter is used to decompose the optical signal into the first polarization light signal and the second polarization light signal; wherein the first polarization light signal and the second polarization light signal are perpendicular to each other.

3. The dual-optical-path magnetic field sensing system according to claim 1, characterized in that: If the magnetic field environment to be measured has a magnetic field parallel to the transmission direction of the light beam acting on the Faraday rotator, the first polarized light signal will be rotated by no more than 90°, and the rotated first polarized light signal is focused on the first semiconductor optical amplifier for single-pass amplification, and is no longer orthogonal to the polarization direction of the reference light path; wherein the thickness of the Faraday rotator is designed according to the size range of the magnetic field environment to be measured.

4. The dual-optical-path magnetic field sensing system according to claim 1, characterized in that: A rotatable bracket is provided on the first semiconductor optical amplifier, and a stepper motor is provided on the rotatable bracket. The rotating shaft of the stepper motor drives the rotatable bracket to rotate, so that the semiconductor optical amplifier rotates counterclockwise or clockwise in a direction perpendicular to the light path; wherein the semiconductor optical amplifier is fixed to the rotatable bracket by a plurality of fastening screws.

5. The dual-optical-path magnetic field sensing system according to claim 1, characterized in that: The active region of the first semiconductor optical amplifier and the active region of the second semiconductor optical amplifier are placed vertically to each other; the first detection amplification and filtering module and the second detection amplification and filtering module both include a detector, an amplifier and a filtering circuit, and the detector, the amplifier and the filtering circuit are connected in sequence.

6. A signal demodulation method, applied to the dual-optical-path magnetic field sensing system according to any one of claims 1 to 5, characterized in that: include: Applying magnetic fields of different magnitudes and determined directions to the magnetic field sensing system of the dual optical paths to obtain the rotation angle of the first polarized light signal; Calibrate the corresponding relationship between the gain difference of one output by the third comparator and the rotation angle of the first polarized light signal caused by the Faraday rotator; The artificially applied magnetic field is released, and the gain difference 2 output by the third comparator under the action of the magnetic field to be measured is measured, the rotation angle caused by the magnetic field to be measured is determined through the corresponding relationship between the gain difference 1 output by the third comparator and the rotation angle of the first polarized light signal caused by the Faraday rotator, and the size of the magnetic field to be measured is calculated based on the rotation angle; Determine the input signal of the stepper motor, and obtain the relationship between the change of the gain difference and the input signal of the stepper motor according to the change of the gain difference output by the third comparator, and calibrate the relationship between the forward and reverse pulses and the direction of the magnetic field to be measured; Based on the relationship between the forward and reverse pulses and the direction of the magnetic field to be measured, the direction of the magnetic field to be measured is determined according to the change of the gain difference output by the third comparator.

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