A method and system for eliminating intensity noise of optical fiber sensing

Abstract

The present invention discloses a method and system for eliminating optical fiber sensing intensity noise, which belongs to the technical field of optical fiber sensing noise suppression. The present invention artificially enhances the light intensity fluctuation output by the light source by actively modulating the current. I t And introduce phase noise, so that the discrete points composed of three-way interference signals p i The spatial elliptical cone surface distribution is significant in space. The linear interference of the intensity noise is converted into spatial geometric parameters by fitting the spatial elliptical cone surface, and the linear component of the intensity noise is stripped off by mapping the cutting plane, so that the discrete points p i Only the phase information is retained to eliminate the interference of intensity noise; finally, the vibration signal is demodulated through the ellipse fitting algorithm and the differential cross-multiplication algorithm, which significantly reduces the demodulation error and improves the demodulation accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber sensing noise suppression, and in particular to an optical fiber sensing intensity noise elimination method and system. Background Art

[0002] In fiber-optic vibration sensors based on a 3x3 coupler solution, random intensity noise is present in the two-way interference signal output due to random fluctuations in the light source's output power or connection loss. This noise directly affects the accuracy of the ellipse fitting, causing the fitting curve to shift and, in turn, affecting the demodulated output signal.

[0003] Conventional methods for eliminating intensity noise rely on more expensive narrow-linewidth light sources, which only partially suppress high-frequency noise. Intensity division noise reduction, which uses the interference signal divided by the light source intensity fluctuation signal to eliminate intensity noise, is affected by factors such as phase delay, resulting in a noise suppression rate of less than 40% in real-world situations, failing to achieve the desired effect. Existing ellipse fitting algorithms suffer from significant phase demodulation errors when subjected to intensity noise interference. How to simultaneously eliminate the effects of intensity noise and phase delay, while achieving high-precision demodulation of micro-vibration signals using low-cost hardware, has become a pressing technical challenge in the field of high-precision fiber optic sensing. Summary of the Invention

[0004] In order to solve the above problems, a method and system for eliminating intensity noise in optical fiber sensing is provided. The present invention actively modulates the driving current of the light source to enhance the light intensity fluctuation and introduce phase noise. Combining spatial elliptical cone fitting and cutting plane mapping, the intensity noise of the light source is converted into separable spatial geometric parameters, and the discrete points are converted into phase noise through cutting plane mapping. p i Mapping to the elliptical ring formed by the cutting plane realizes the stripping of the linear component of the intensity noise, making the discrete points p i The coordinates retain only phase information, resulting in a pure, closed fitting elliptical ring. Combining the ellipse fitting algorithm with the differential cross-multiplication algorithm eliminates the offset interference of intensity noise on the ellipse fitting, solving the technical problem of intensity noise causing reduced demodulation accuracy in fiber optic vibration sensing, achieving high-precision phase demodulation and significantly improving noise suppression.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for eliminating optical fiber sensing intensity noise, comprising the following steps: S1: actively modulating the light source driving current to make the light source output light intensity fluctuate I t Enhance and introduce phase noise , synchronously collect three-way interference signals to form discrete points;

[0006] S2: Perform spatial elliptical conic surface fitting on the discrete points to solve the vertex p 0( x 0, y 0, z 0) and the central axis unit vector d =( A , B , C );

[0007] S3: Select a reference point on the center axis p a ( x a , y a , z a ), with the central axis unit vector d Construct cutting plane for normal vector;

[0008] S4: Each discrete point p i Along the vertex p 0 The direction of the line is projected onto the intersection of the cutting plane and the elliptical conic surface, and the mapping point is calculated. p j coordinate;

[0009] S5: Extracting mapping points p j The spatial coordinates of any two corresponding interference signals are used to calculate the fitting parameters through the ellipse fitting algorithm;

[0010] S6: Construct an orthogonal signal pair based on the fitting parameters and demodulate the phase change through the differential cross-multiplication algorithm i s .

[0011] Preferably, the light source driving current of S1 increases stepwise from a first threshold current to a second threshold current, and the duration of the increase is controlled to be 0.5-2 seconds; the number of discrete points collected synchronously is greater than 3000, and the sampling frequency is set to be ≥3.0Ksps.

[0012] Preferably, the first threshold current is 90 mA, the second threshold current is 120 mA; the number of discrete points is 3200, and the sampling frequency is set to 3.2Ksps.

[0013] Preferably, the three-way interference signal of S1 is:

[0014] ;

[0015] in, a1( I t ), a 2( I t ), a 3( I t ) is the DC bias of the three-way interference signal; b 1( I t ), b 2( I t ), b 3( I t ) is the AC bias of the three-way interference signal; I t is the light intensity fluctuation, i s is the phase change; β is a fixed phase difference, is the phase noise introduced.

[0016] Preferably, the point normal equation of the cutting plane in S3 is:

[0017] ;

[0018] in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0.

[0019] Preferably, each discrete point in S4 p i Along the vertex p 0 The parametric equation of the straight line formed by the lines is:

[0020] ;

[0021] Where t is the equation parameter, and the parametric equation and the point normal equation of the cutting plane are combined to obtain:

[0022] ;

[0023] in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y0. z 0 is the vertex p The corresponding coordinate value of 0; x a 、 y a 、 z a Pick a reference point for the central axis p a The corresponding coordinate values ​​of ; x i 、 y i 、 z i For each discrete point p i The corresponding coordinate values ​​of .

[0024] Preferably, the mapping point in S4 p j The mapping relationship satisfies:

[0025] ;

[0026] in, x j 、 y j 、 z j For mapping points p j The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0; x i 、 y i 、 z i For each discrete point p i The corresponding coordinate values ​​of .

[0027] Preferably, the orthogonal signal pair in S6 and The formula is:

[0028] ;

[0029] in, a 1. a 2 is the DC bias of any two interference signals; b 1. b 2 is the AC bias of any two interference signals; i s is the phase change; βis a fixed phase difference; V 1. V 1 is any two-way interference signal.

[0030] Preferably, the formula of the differential cross-multiplication algorithm in S6 is:

[0031] ;

[0032] in, and is an orthogonal signal pair, i s is the phase change.

[0033] A fiber optic sensing intensity noise elimination system includes a light source driving module for outputting an adjustable light source driving current, an optical interference unit for sensing external vibration signals and outputting three-way interference signals, a circulator, a signal acquisition unit for acquiring the three-way interference signals, and a signal processing unit; the optical interference unit includes a 3×3 coupler, a Faraday rotator, a reference arm and a sensing arm respectively wound around a mass block and an elastic body; the signal processing unit sets the light source driving module to output a linearly increasing light source driving current to the light source, the laser output by the light source enters the 3×3 coupler through the circulator and is split into sensing light, reference light, and a third light path, the third light path undergoes anti-reflection processing, the sensing light and reference light are respectively output to the Faraday rotator through the elastic body and the mass block, and after reflection, return along the original path to the 3×3 coupler to generate interference and output three-way interference signals, which are acquired by the signal acquisition unit and output to the signal processing unit, and the signal processing unit uses the intensity noise elimination method to demodulate the phase change i s .

[0034] Due to the adoption of the above technical solution, the present invention has the following beneficial effects.

[0035] (1) The present invention actively modulates the light source driving current to enhance the light intensity fluctuation and introduce phase noise, combines the spatial elliptical cone surface fitting and cutting plane mapping, and converts the intensity noise of the light source into separable spatial geometric parameters. p i Mapping to the elliptical ring formed by the cutting plane realizes the stripping of the linear component of the intensity noise, making the discrete points p i The coordinates retain only phase information, resulting in a pure, closed fitting elliptical ring. Combining the ellipse fitting algorithm with the differential cross-multiplication algorithm eliminates the offset interference of intensity noise on the ellipse fitting, solving the technical problem of intensity noise causing reduced demodulation accuracy in fiber optic vibration sensing, achieving high-precision phase demodulation and significantly improving noise suppression.

[0036] (2) The present invention artificially enhances the light intensity fluctuation of the light source output by actively modulating the light source driving current I t and introduces phase noise , so that the discrete points composed of the three-way interference signal p i The spatial elliptical cone surface distribution is significant in space. The linear interference of the intensity noise is converted into spatial geometric parameters by fitting the spatial elliptical cone surface, and the linear component of the intensity noise is stripped off by mapping the cutting plane, so that the discrete points p i Only the phase information is retained to eliminate the offset distortion of traditional ellipse fitting; finally, the interference of intensity noise is eliminated through the ellipse fitting algorithm and the differential cross-multiplication algorithm, which significantly reduces the demodulation error and improves the demodulation accuracy.

[0037] (3) The present invention enhances the light intensity fluctuation and introduces phase noise by modulating the light source driving current, and combines the linear component of the intensity noise with spatial geometry to achieve the suppression of the full-band intensity noise; p i The linear component of the intensity noise is stripped off by mapping it onto the cutting plane. The intensity noise is converted into a separable spatial variable by combining the ellipse fitting algorithm and the differential cross-multiplication algorithm, eliminating the need for a narrow linewidth light source and achieving low cost and high precision in fiber optic sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The following detailed discussion discusses the making and use of preferred embodiments of the present invention. However, it should be understood that the present invention provides numerous applicable inventive concepts that can be embodied in a variety of specific contexts. The specific embodiments discussed are intended only to illustrate specific ways to make and use the present invention and are not intended to limit the scope of the invention. It would be readily apparent to one of ordinary skill in the art that other embodiments could be derived from these drawings without inventive effort.

[0039] Figure 1 This is a distribution diagram of the discrete points of the present invention on the spatial rectangular coordinate system.

[0040] Figure 2 It is a schematic diagram of the mapping of the present invention in a spatial rectangular coordinate system.

[0041] Figure 3 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0042] The following detailed discussion discusses the making and use of preferred embodiments of the present invention. However, it should be understood that the present invention provides many applicable inventive concepts that can be embodied in a variety of specific circumstances. The specific embodiments discussed are intended only to illustrate specific ways to make and use the present invention and are not intended to limit the scope of the present invention.

[0043] The present invention artificially enhances the light intensity fluctuation of the light source output by actively modulating the light source driving current I t and introduces phase noise , so that the discrete points composed of the three-way interference signal p i The spatial elliptical cone surface distribution is significant in space. The linear interference of the intensity noise is converted into spatial geometric parameters by fitting the spatial elliptical cone surface, and the linear component of the intensity noise is stripped off by mapping the cutting plane, so that the discrete points p i Only the phase information is retained to eliminate the offset distortion of traditional ellipse fitting; finally, the interference of intensity noise is eliminated through the ellipse fitting algorithm and the differential cross-multiplication algorithm, which significantly reduces the demodulation error and improves the demodulation accuracy.

[0044] A novel method and system for eliminating intensity noise in fiber optic sensing uses a 3x3 coupler and a Faraday rotator mirror in the interference optical path to form a balanced Michelson interferometer. The interferometer's sensing arm and reference arm are wound around an elastic body and a mass, respectively. When the interferometer senses external vibrations, the optical path difference between the sensing arm and the reference arm changes. After being reflected by the Faraday rotator, the two light beams return along their original paths to the 3x3 coupler, where they merge and interfere. The vibration signal is modulated into the phase of the interference light, and three light beams with a fixed phase difference are output from the 3x3 coupler. β =2 π The interference signals of the three paths are converted into electrical signals by the photodetector and output to the signal processing unit through the signal acquisition unit, and then demodulated by the signal processing unit. The three-path interference signal with a fixed phase difference can be expressed as:

[0045] ;

[0046] in, a 1( I t ), a 2( I t ), a 3( I t ) is the DC bias of the three-way interference signal; b 1( I t ), b 2( I t ), b 3( I t ) is the AC bias of the three-way interference signal; I tis the light intensity fluctuation, i s is the phase change; β is a fixed phase difference. The DC bias and AC amplitude both change linearly with the light intensity.

[0047] A method for eliminating intensity noise in optical fiber sensing includes the following steps: S1: actively modulating the driving current of the light source to make the light intensity output of the light source fluctuate I t Enhance and introduce phase noise , synchronously collect three-way interference signals to form discrete points. The three-way interference signals are:

[0048] ;

[0049] in, a 1( I t ), a 2( I t ), a 3( I t ) is the DC bias of the three-way interference signal; b 1( I t ), b 2( I t ), b 3( I t ) is the AC bias of the three-way interference signal; I t is the light intensity fluctuation, i s is the phase change; β is a fixed phase difference, The phase noise introduced is the phase noise. The series of discrete points collected synchronously by the signal acquisition unit are p i ( x i , y i , z i ) in the rectangular coordinate system of space is as follows Figure 1 shown.

[0050] The light source driving current increases in a stepwise manner from a first threshold current to a second threshold current, with the duration of the increase controlled to be between 0.5 and 2 seconds. The number of discrete points collected simultaneously is greater than 3000, and the sampling frequency is set to ≥3.0 kilosamples per second. In this embodiment, the first threshold current is 90 mA, the second threshold current is 120 mA, the number of discrete points is 3200, and the sampling frequency is set to 3.2 kilosamples per second.

[0051] S2: Using the above discrete points to do elliptical conic surface fitting in the spatial rectangular coordinate system, that is, performing spatial elliptical conic surface fitting on the discrete points, the vertex can be obtained. p 0( x 0, y 0, z 0) and the central axis unit vector d =( A , B , C );

[0052] S3: Select a reference point on the center axis p a ( x a , y a , z a ), with the central axis unit vector d Construct a cutting plane for the normal vector, the point normal equation of the cutting plane is:

[0053] ;

[0054] in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0. The intersection line of the elliptical cone surface and the cutting plane forms an elliptical ring.

[0055] S4: Each discrete point p i Along the vertex p 0 The direction of the line is projected onto the intersection of the cutting plane and the elliptical conic surface, and the mapping point is calculated. p j Coordinates. The discrete points p i Along the vertex p 0 The parametric equation of the straight line formed by the lines is:

[0056] ;

[0057] in, t is the equation parameter, and the parametric equation and the point normal equation of the cutting plane are combined to obtain:

[0058] ;

[0059] in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0; x a 、 y a 、 z a Pick a reference point for the central axis p a The corresponding coordinate values ​​of ; x i 、 y i 、 z i For each discrete point p i The corresponding coordinate values ​​of .

[0060] Using the above formula, we can get t Values ​​can be collected and discrete points p i ( x i , y i , z i ) is mapped onto the elliptical ring, and the mapping point p j The mapping relationship satisfies:

[0061] ;

[0062] in, x j 、 y j 、 z j For mapping points p j The corresponding coordinate values ​​of ; x 0. y 0. z0 is the vertex p The corresponding coordinate value of 0; x i 、 y i 、 z i For each discrete point p i After completing the above mapping, we can get a series of points p i ( x i , y i , z i ) are distributed on the elliptical ring formed by the elliptical cone surface and the cutting plane, such as Figure 2 shown.

[0063] S5: Extracting mapping points p j The spatial coordinates of any two interference signals corresponding to the ellipse fitting algorithm are used to calculate the fitting parameters. The arbitrary two interference signals satisfy the formula:

[0064] ;

[0065] in a 1 and a 2 represents the DC bias of the two signals. b 1 and b 2 is the AC amplitude, i s is the phase change caused by vibration, β is a fixed phase difference.

[0066] Due to the fixed phase difference of the 3x3 coupler output β =2 π / 3, cannot be solved directly. V 1 and V 2 satisfies the general equation of an ellipse:

[0067] .

[0068] According to the mapping conversion V 1 and V 2 Two sets of data, using the ellipse fitting algorithm, we can get the general equation A 、 B 、 C 、 D 、 E After these 5 coefficients, we can get a 1. a 2. b 1. b2. cos β 、sin β These 6 fitting parameters.

[0069] S6: Based on the fitting parameters, a pair of orthogonal signals containing the phase information to be measured can be constructed, and the phase change can be demodulated by the differential cross-multiplication algorithm. i s .

[0070] Through the above fitting parameters and the two-way interference signal formula, a pair of orthogonal signal pairs containing the phase information to be measured can be constructed. and The formula is:

[0071] ;

[0072] in, a 1. a 2 is the DC bias of any two interference signals; b 1. b 2 is the AC bias of any two interference signals; i s is the phase change; β is a fixed phase difference; V 1. V 1 is any two-way interference signal.

[0073] The formula of the differential cross-multiplication algorithm is:

[0074] ;

[0075] in, and is an orthogonal signal pair, i s is the phase change.

[0076] like Figure 3 The optical fiber sensing intensity noise elimination system shown in the figure includes a light source driver module for outputting an adjustable light source drive current, an optical interference unit for sensing external vibration signals and outputting three-way interference signals, a circulator, a signal acquisition unit for collecting the three-way interference signals, and a signal processing unit; the optical interference unit includes a 3×3 coupler, a Faraday rotator mirror, a reference arm and a sensor arm respectively wound around a mass block and an elastic body; in this embodiment, the signal acquisition unit uses an ADC, and the signal processing unit uses an SOC.

[0077] The SOC sets the light source driving module to output a linearly increasing light source driving current to the light source, the laser output by the light source enters the 3×3 coupler through the circulator and is split into sensing light, reference light and a third light, the third light is subjected to anti-reflection processing, the sensing light and the reference light are respectively output to the Faraday rotator mirror through the elastic body and the mass block, after reflection, return to the 3×3 coupler along the original path to interfere and output three interference signals, the first interference signal enters the photodetector 1 after passing through the circulator, the second interference signal and the third interference signal are respectively output to the photodetector 2 and the photodetector 3, the three interference signals are converted into electrical signals by the photodetector 1, the photodetector 2 and the photodetector 3 and then output to the ADC, which is collected by the ADC and output to the SOC, and the SOC uses the intensity noise elimination method to demodulate the phase change i s .

[0078] The specific implementation process of intensity noise elimination of the present invention is as follows: Step 1: The system is powered on, and the SOC is used to set the light source to drive the output of a stable 120mA current, and wait for the light source to output laser stability, and the waiting time is 3 seconds.

[0079] Step 2: Use the SOC to set the light source driver current output, linearly increasing it from 90mA to 120mA. The duration of the light source driver current change is 0.5-2 seconds, and in this embodiment, the duration is 1 second. Simultaneously, set the ADC sampling rate to ≥3.0Ksps (in this embodiment, the ADC sampling rate is set to 3.2Ksps), and start the ADC to synchronously collect the voltage values ​​output by the three photodetectors. After the current change stops, turn off the ADC acquisition.

[0080] Step 3: Fit the 3200 discrete numerical points collected by the ADC to the elliptical conic surface in the spatial rectangular coordinate system and calculate the vertices of the elliptical conic surface. p 0( x 0, y 0, z 0) and the unit vector in the direction of the central axis d =( A , B , C ).

[0081] Step 4: Select the distance vertex on the center axis p 0 is the reference point of 2 p a ( x a , y a , z a ).

[0082] Step 5: Unit vector of the central axis d Construct a cutting plane for the normal vector, the point normal equation of the cutting plane is:

[0083] ;

[0084] in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0. The intersection line of the elliptical cone surface and the cutting plane forms an elliptical ring.

[0085] Step 6: Disperse the points p i Along the vertex p 0 The direction of the line is projected onto the intersection of the cutting plane and the elliptical conic surface, and the mapping point is calculated. p j Coordinates. The discrete points p i Along the vertex p 0 The parametric equation of the straight line formed by the lines is:

[0086] ;

[0087] in, t is the equation parameter, and the parametric equation and the point normal equation of the cutting plane are combined to obtain:

[0088] ;

[0089] in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0; x a 、 y a 、 z a Pick a reference point for the central axis p a The corresponding coordinate values ​​of ; x i 、 y i、 z i For each discrete point p i The corresponding coordinate values ​​of .

[0090] Using the above formula, we can get t Values ​​can be collected and discrete points p i ( x i , y i , z i ) is mapped onto the elliptical ring, and the mapping point p j The mapping relationship satisfies:

[0091] ;

[0092] in, x j 、 y j 、 z j For mapping points p j The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0; x i 、 y i 、 z i For each discrete point p i After completing the above mapping, we can get a series of points p i ( x i , y i , z i ) are distributed on the elliptical ring formed by the elliptical cone surface and the cutting plane, such as Figure 2 As shown, according to the collected discrete points p i , calculate 3200 mapping points one by one p j ( x j , y j , z j ) coordinates.

[0093] Step 7: Extract Mapping Points p j The spatial coordinates of any two interference signals corresponding to the ellipse fitting algorithm are used to calculate the fitting parameters. The arbitrary two interference signals satisfy the formula:

[0094] ;

[0095] in a 1 and a 2 represents the DC bias of the two signals. b 1 and b 2 is the AC amplitude, i s is the phase change caused by vibration, β is a fixed phase difference.

[0096] Due to the fixed phase difference of the 3x3 coupler output β =2 π / 3, cannot be solved directly. V 1 and V 2 satisfies the general equation of an ellipse:

[0097] .

[0098] According to the mapping conversion V 1 and V 2 Two sets of data, using the ellipse fitting algorithm, we can get the general equation A 、 B 、 C 、 D 、 E After these 5 coefficients, we can get a 1. a 2. b 1. b 2. cos β 、sin β These 6 fitting parameters.

[0099] Step 8: Save the vertices of the elliptical conic surface mentioned above p 0 , central axis unit vector d , the reference point selected on the central axis p a , and the six fitting parameters obtained by ellipse fitting, the ADC sampling rate is set to 32Ksps, and the ADC is started to collect the three-way interference signals in real time.

[0100] Step 9: The ADC collects 320 data points every 10ms as a frame of data. The SOC calculates a frame of mapping points according to the relevant formula of the above-mentioned fiber optic sensing intensity noise elimination method. pj ( x j , y j , z j ).

[0101] Step 10: Take any two data points of this frame and combine them with the 6 fitting parameters obtained by ellipse fitting to construct an orthogonal signal pair, and then use the differential cross-multiplication algorithm to demodulate the phase change. i s That is, through the above fitting parameters and the two-way interference signal formula, a pair of orthogonal signal pairs containing the phase information to be measured can be constructed. and The formula is:

[0102] ;

[0103] in, a 1. a 2 is the DC bias of any two interference signals; b 1. b 2 is the AC bias of any two interference signals; i s is the phase change; β is a fixed phase difference; V 1. V 1 is any two-way interference signal.

[0104] The formula of the differential cross-multiplication algorithm is:

[0105] ;

[0106] in, and is an orthogonal signal pair, i s is the phase change.

[0107] The present invention enhances the light intensity fluctuation and introduces phase noise by modulating the light source driving current, and combines the linear component of the intensity noise with spatial geometry to achieve the suppression of the full-band intensity noise; p i The linear component of the intensity noise is stripped off by mapping it onto the cutting plane. The intensity noise is converted into a separable spatial variable by combining the ellipse fitting algorithm and the differential cross-multiplication algorithm, eliminating the need for a narrow linewidth light source and achieving low cost and high precision in fiber optic sensing.

[0108] Although the specification has been described in detail, it should be understood that various changes, substitutions, and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. In addition, the specific embodiments described are not intended to limit the scope of the invention, and a person of ordinary skill in the art can readily understand based on the present invention that currently existing or later developed processes, machines, manufactures, material compositions, means, methods, or steps may perform substantially the same functions or obtain substantially the same results as the embodiments of the present invention. Therefore, the appended claims are intended to include such processes, machines, manufactures, material compositions, means, methods, or steps within their scope.

Claims

1. A method for eliminating intensity noise in optical fiber sensing, characterized in that: Including the following step: S1: Actively modulate the light source driving current to make the light source output intensity fluctuate I t Enhance and introduce phase noise , synchronously collect three-way interference signals to form discrete points; S2: Perform spatial elliptical conic surface fitting on the discrete points to solve the vertex p 0( x 0, y 0, z 0) and the central axis unit vector d =( A , B , C ); S3: Select a reference point on the center axis p a ( x a , y a , z a ), with the central axis unit vector d Construct cutting plane for normal vector; S4: Each discrete point p i Along the vertex p 0 The direction of the line is projected onto the intersection of the cutting plane and the elliptical conic surface, and the mapping point is calculated. p j coordinate; S5: Extracting mapping points p j The spatial coordinates of any two corresponding interference signals are used to calculate the fitting parameters through the ellipse fitting algorithm; S6: Construct an orthogonal signal pair based on the fitting parameters and demodulate the phase change through the differential cross-multiplication algorithm θ s .

2. A method for eliminating optical fiber sensing intensity noise according to claim 1, characterized in that: The light source driving current of S1 is increased stepwise from a first threshold current to a second threshold current, and the duration of the increase is controlled to be 0.5-2 seconds; the number of discrete points collected synchronously is greater than 3000, and the sampling frequency is set to be ≥3.0Ksps.

3. A method for eliminating optical fiber sensing intensity noise according to claim 2, characterized in that: The first threshold current is 90 mA, the second threshold current is 120 mA; the number of discrete points is 3200, and the sampling frequency is set to 3.2Ksps.

4. The method for eliminating optical fiber sensing intensity noise according to claim 1, wherein: The three-way interference signal of S1 is: in, a 1( I t ), a 2( I t ), a 3( I t ) is the DC bias of the three-way interference signal; b 1( I t ), b 2( I t ), b 3( I t ) is the AC bias of the three-way interference signal; I t is the light intensity fluctuation, θ s is the phase change; β is a fixed phase difference, is the phase noise introduced.

5. The method for eliminating optical fiber sensing intensity noise according to claim 1, wherein: The point normal equation of the cutting plane in S3 is: in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0.

6. The method for eliminating optical fiber sensing intensity noise according to claim 1, wherein: Each discrete point in S4 p i Along the vertex p 0 The parametric equation of the straight line formed by the lines is: in, t is the equation parameter, and the parametric equation and the point normal equation of the cutting plane are combined to obtain: in, A 、 B 、 C is the central axis unit vector d The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0; x a 、 y a 、 z a Pick a reference point for the central axis p a The corresponding coordinate values ​​of ; x i 、 y i 、 z i For each discrete point p i The corresponding coordinate values ​​of .

7. The method for eliminating intensity noise in optical fiber sensing according to claim 1, wherein: The S4 mapping point p j The mapping relationship satisfies: in, x j 、 y j 、 z j For mapping points p j The corresponding coordinate values ​​of ; x 0. y 0. z 0 is the vertex p The corresponding coordinate value of 0; x i 、 y i 、 z i For each discrete point p i The corresponding coordinate values ​​of .

8. The method for eliminating optical fiber sensing intensity noise according to claim 1, wherein: The orthogonal signal pair in S6 and The formula is: in, a 1. a 2 is the DC bias of any two interference signals; b 1. b 2 is the AC bias of any two interference signals; θ s is the phase change; β is a fixed phase difference; V 1. V 1 is any two-way interference signal.

9. The method for eliminating intensity noise in optical fiber sensing according to claim 1, wherein: The formula of the differential cross-multiplication algorithm in S6 is: in, and is an orthogonal signal pair, θ s is the phase change.

10. A fiber optic sensing intensity noise elimination system, characterized by: The invention comprises a light source driving module for outputting an adjustable light source driving current, an optical interference unit for sensing external vibration signals and outputting three-way interference signals, a circulator, a signal acquisition unit for acquiring the three-way interference signals, and a signal processing unit; the optical interference unit comprises a 3×3 coupler, a Faraday rotating mirror, a reference arm and a sensor arm respectively wound on a mass block and an elastic body; the signal processing unit sets the light source driving module to output a linearly increasing light source driving current to the light source, the laser output by the light source enters the 3×3 coupler through the circulator and is split into sensing light, reference light and a third light, the third light is subjected to anti-reflection processing, the sensing light and the reference light are respectively output to the Faraday rotating mirror through the elastic body and the mass block, and after reflection, return to the 3×3 coupler along the original path to generate interference and output three-way interference signals, which are acquired by the signal acquisition unit and output to the signal processing unit, and the signal processing unit adopts the intensity noise elimination method described in any one of claims 1 to 9 to demodulate the phase change θ s .

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