Multi-source cooperative grating array fiber phase demodulation system and method

Abstract

The application discloses a grating array fiber phase demodulation system with multiple light sources, which comprises three pulse modulation modules, a fiber beam combiner, a photoelectric conversion module and a signal processing module. The three pulse modulation modules are controlled by the signal processing module to modulate corresponding continuous light signals into three groups of pulse light signals. The second group of pulse light signals lags behind the first group of pulse light signals by a first preset time, and the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time. Each group of pulse light signals has two pulse light signals with time delay in a period. The fiber beam combiner combines the three groups of pulse light signals into a pulse light signal string. Each pulse in the pulse light signal string is reflected by each grating in the grating array sensing fiber. The reflected pulse light signal string of the grating array sensing fiber is transmitted to the photoelectric conversion module, and the photoelectric conversion module converts the reflected pulse light signal string into corresponding sensing electric signals. The signal processing module performs phase demodulation processing on the sensing electric signals output by the photoelectric conversion module.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber grating sensing, in particular to a grating array fiber phase demodulation system and method based on multi-light source cooperation. BACKGROUND

[0002] Based on phase-sensitive grating array fiber sensing technology, it has the advantages of strong reflection signal, high positioning accuracy, high sensitivity, and has been widely researched and applied at home and abroad. The traditional phase demodulation technology often uses a Michelson interferometer scheme based on a 3*3 coupler to process optical signals. The length difference between the arms of the interferometer causes the reflection signals of two adjacent gratings in the grating array to interfere. The length change of the fiber between the two adjacent gratings caused by the external disturbance signal is converted into a phase change of the interference signal. Finally, by using the characteristics that the three-end output signals of the 3*3 coupler are 120° out of phase with each other, a series of addition, subtraction, multiplication and division operations are performed to realize the detection of external signals. Although the phase demodulation technology has very high sensitivity, the Michelson interferometer itself is easily disturbed by external temperature, vibration and other environments. The temperature insulation and shock resistance design of the interferometer module often makes it have a large volume, and the installation environment of the system should also be ensured to be relatively stable. In the actual changing environment, the popularization of this technology is hindered to a certain extent. SUMMARY

[0003] The purpose of the present application is to provide a grating array fiber phase demodulation system and method based on multi-light source cooperation without the need for an interferometer structure, to solve the dependence of the existing phase demodulation technology on the interferometer, and to improve the integrability and stability of the system.

[0004] To achieve this purpose, the present application designs a grating array fiber phase demodulation system based on multi-light source cooperation, which comprises a signal processing module, a fiber combiner, a fiber circulator, an optoelectronic conversion module, a grating array sensing fiber and three pulse modulation modules. The three pulse modulation modules are used to modulate the corresponding continuous light signals into three groups of pulse light signals under the control of the signal processing module, respectively. The second group of pulse light signals lags behind the first group of pulse light signals by a first preset time, and the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time. Each group of pulse light signals has two pulse light signals with time delay before and after in a period.

[0005] The fiber combiner is used to combine the three groups of pulse light signals into a pulse light signal string.

[0006] The fiber optical circulator is used for inputting a pulse optical signal string into a grating array sensing optical fiber, each pulse in the pulse optical signal string is reflected when encountering each grating in the grating array sensing optical fiber, the reflected pulse optical signal string of the grating array sensing optical fiber passes through the fiber optical circulator, is transported to a photoelectric conversion module, and is photoelectrically converted by the photoelectric conversion module to obtain corresponding each sensing electric signal; wherein the second pulse optical signal in each group of pulse optical signals reflected by a former grating of two adjacent gratings in the grating array sensing optical fiber interferes with the corresponding first pulse optical signal in each group of pulse optical signals reflected by a latter grating of the two adjacent gratings, to generate a corresponding sensing electric signal.

[0007] The signal processing module is used for performing phase demodulation processing on each sensing electric signal output by the photoelectric conversion module.

[0008] The present application has the following beneficial effects:

[0009] The present application modulates multiple light sources of different wavelengths by a double pulse modulation method, ensures that the reflection signals of adjacent gratings in the grating array fiber interfere, and there are multiple groups of interference signals under different wavelengths, the phase change of light in the multiple groups of interference signals caused by the external vibration signal is converted into the intensity change of light, the intensity change of the multiple groups of interference signals is used to demodulate the change of the external vibration signal by the difference of the wavelengths, and the demodulation of the sensing network is realized.

[0010] Compared with the traditional fiber phase demodulation system using an interferometer, the present application retains the advantages of long detection distance, large multiplexing capacity and high sensitivity of the original technology, avoids the introduction of the interferometer structure, thereby avoiding the complex structure design of the heat insulation and shock resistance of the interferometer and the installation environment requirements of the strict system, improves the integrability and environmental adaptability of the system, and promotes the wide engineering application of the grating array fiber vibration sensing technology. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is the overall structure diagram of the present application;

[0012] Figure 2 It is the principle diagram of the phase demodulation method of the present application;

[0013] Figure 3 It is the phase change caused by the external disturbance under the action of different wavelengths according to the example of the present application;

[0014] Figure 4 It is the intensity change diagram of the three-way interference signal according to the example of the present application;

[0015] Figure 5 It is the phase demodulation result according to the example of the present application. DETAILED DESCRIPTION

[0016] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0017] As Figure 1 shown in the multi-light-source coordinated grating array fiber phase demodulation system, it comprises a signal processing module, a fiber combiner, a fiber circulator, a fiber amplifier, an optoelectronic conversion module, a grating array sensing fiber, three light source modules and three pulse modulation modules, wherein the output ends of the three light source modules (a first light source module, a second light source module and a third light source module) are respectively connected to the signal input ends of the three pulse modulation modules (a first pulse modulation module, a second pulse modulation module and a third pulse modulation module), the output ends of the three pulse modulation modules are respectively connected to the three input ends of the fiber combiner, the output end of the fiber combiner is connected to the input end of the fiber amplifier, the output end of the fiber amplifier is connected to the first communication end of the fiber circulator, the second communication end of the fiber circulator is connected to the grating array sensing fiber, the third communication end of the fiber circulator is connected to the input end of the optoelectronic conversion module, the output end of the optoelectronic conversion module is connected to the signal acquisition end of the signal processing module, and the three-way control output end of the signal processing module is connected to the control input end of the three pulse modulation units respectively.

[0018] The grating array fiber is a wide-spectrum grating array fiber, the grating spectrum width is 4 nm, the center wavelength is 1551 nm, the sensing network length is 1 km, and the grating pitch is 10 m.

[0019] The three pulse modulation modules are used for respectively modulating the continuous light signals output by the corresponding light source modules into three groups of pulse light signals under the control of the signal processing module, the second group of pulse light signals lags behind the first group of pulse light signals by a first preset time (20 ns), the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time (40 ns), and each group of pulse light signals has two pulse light signals with time delay (100 ns) in a period (1 ms).

[0020] Since only light with the same wavelength can interfere, the interference of the reflection signals of the adjacent two gratings should ensure that the pulse light signal reflected by the former grating and the pulse light signal reflected by the latter grating have the same wavelength. Therefore, the time delay of the two pulse light signals in each group and the pitch between the adjacent gratings satisfy tp=2n eff d / c, wherein n eff is the core refractive index of the grating array sensing fiber, about 1.5, c is the propagation speed of light in vacuum, about 3×10^8 m / s, and d is the pitch of the adjacent gratings in the grating array sensing fiber; the pitch of the gratings in the grating array fiber used is 10 m, and therefore tp=100 ns.

[0021] In order to avoid the same grating reflected multiple sets of pulse light signal and multiple beam pulse light signal from being mixed, affecting the acquisition of interference signals, the pulse width tw, the first preset time t1, the second preset time t2 of each pulse light signal meet the formula 0<tw<tp / 3; tw<t1<tp-2tw; tw+t1<t2<tp-tw. In the examples, in order to distinguish the front and rear two pulse light signals in the pulse light signal string and balance the time domain distribution of each pulse in the pulse light signal string, tw is 10ns, t1 is 20ns, and t2 is 40ns;

[0022] Since the single detection period T of the grating array fiber is limited by the length L of the grating array fiber: T>2n eff L / c. The length of the grating array fiber used is 1km, so T>10us; in the examples, T=1ms, according to the sampling law, the signal frequency that the sensing network can detect is <500Hz.

[0023] For a single wavelength lambda optical signal, the interference signal intensity I0 of the reflection signals of adjacent two gratings can be:

[0024]

[0025] Wherein, A represents the direct current amount of the interference signal, and B represents the interference current amount of the interference signal d is the length of the optical fiber between adjacent gratings, and V is the change of the length of the optical fiber between adjacent gratings caused by external vibration.

[0026] In order to solve V, the traditional phase demodulation system adopts a Michelson interferometer scheme based on a 3*3 coupler, uses the characteristics that the three-end output signals of the 3*3 coupler are mutually different by 120° phase, acquires three output signals of the interferometer, and constructs an equation group:

[0027]

[0028] Further, I1, I2 and I3 are solved simultaneously.

[0029]

[0030] However, the interferometer itself in the traditional scheme is easily disturbed by external temperature, vibration and other environments, and the temperature insulation and shock resistance design of the interferometer module often makes it have a large volume, and the installation environment of the system should also be ensured to be relatively stable, so that the popularization of this technology is hindered in the actual variable environment.

[0031] Therefore, the present application adopts a method of cooperation of multiple light sources, introduces different wavelength variables by using multiple light source modules to construct an equation group:

[0032]

[0033] When the change amount V of the fiber length between adjacent gratings in the grating array sensing fiber caused by external vibration is less than the threshold (1 um), the change amount is much smaller than the fiber length L (10 m) between adjacent gratings in the grating array sensing fiber; and the light wavelengths (1550 nm band) of the three light source modules used are similar, fai = 2n eff πV / λ1≈2n eff πV / λ2≈2n eff πV / λ3, let θ1 = 2n eff πd / λ1, θ2 = 2n eff πd / λ2, θ3 = 2n eff πd / λ3 are the fixed phase differences introduced by the fiber length between adjacent two gratings in the grating array sensing fiber under different wavelengths respectively. The phase demodulation formula can be obtained by combining I1, I2, and I3:

[0034]

[0035] The fiber combiner is used to combine three groups of pulsed light signals into a pulsed light signal string;

[0036] The fiber circulator is used to input the pulsed light signal string into the grating array sensing fiber. Each pulse in the pulsed light signal string encounters reflection at each grating in the grating array sensing fiber. The reflected pulsed light signal string of the grating array sensing fiber passes through the fiber circulator, is transmitted to the photoelectric conversion module, and is photoelectrically converted by the photoelectric conversion module to obtain corresponding sensing electrical signals. The second pulsed light signal in each group of pulsed light signals reflected by the first grating of the adjacent two gratings in the grating array sensing fiber interferes with the corresponding first pulsed light signal in each group of pulsed light signals reflected by the second grating of the adjacent two gratings, to produce corresponding sensing electrical signals. The sensing electrical signals contain phase changes caused by external disturbances.

[0037] The signal processing module controls the analog-to-digital conversion chip to collect the electrical signals output by the photoelectric conversion module and performs phase demodulation processing to realize demodulation of the sensing network. The signal processing module is used to perform phase demodulation processing on the sensing electrical signals output by the photoelectric conversion module, to realize demodulation of the grating array fiber.

[0038] The above technical solution further includes a fiber amplifier, which is used to amplify the pulsed light signal string. The amplified pulsed light signal string is input into the grating array sensing fiber by the fiber circulator.

[0039] In the technical solution, the two pulses of each group of pulse light signals in a cycle have a time delay tp, the pulse width of each pulse is tw, the second group of pulse light signals lags behind the first group of pulse light signals by a time t1, the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time t2, t2>t1, and the wavelengths of the first, second and third groups of pulse light signals are λ1, λ2 and λ3 respectively.

[0040] The time delay tp=2n eff d / c, where n eff is the core refractive index of the grating array sensing fiber, about 1.5, c is the propagation speed of light in vacuum, about 3×10^8 m / s, and d is the distance between adjacent gratings in the grating array sensing fiber; 0<tw<tp / 3; tw<t1<tp-2tw; tw+t1<t2<tp-tw.

[0041] The pulse light signal string is represented as p11, p21, p31, p12, p22, p32, where p11 represents the first pulse in the first group of pulse light signals, p21 represents the first pulse in the second group of pulse light signals, p31 represents the first pulse in the third group of pulse light signals, p12 represents the second pulse in the first group of pulse light signals, p22 represents the second pulse in the second group of pulse light signals, and p32 represents the second pulse in the third group of pulse light signals. After the pulse light signal string is amplified by the fiber amplifier, it is input to the grating array sensing fiber through the optical fiber circulator. Each pulse in the pulse light signal string will be reflected when it encounters each grating in the grating array sensing fiber, i.e. each grating will return six pulse light signals. The time delay of the corresponding pulse signals reflected by adjacent gratings in the grating array sensing fiber is tp, for example, the time delay between the reflected pulse light signal of pulse p12 by the former grating and the reflected pulse light signal of pulse p11 by the latter grating is tp.

[0042] In the technical solution, the second pulse light signal of each group of pulse light signals reflected by the former grating of the two adjacent gratings in the grating array sensing fiber interferes with the corresponding first pulse light signal of each group of pulse light signals reflected by the latter grating of the two adjacent gratings.

[0043] For the first group of pulse light signals, the reflected pulse light signal of pulse p12 by the former grating and the reflected pulse light signal of pulse p11 by the latter grating interfere with each other at the same time when they reach the photoelectric conversion module.

[0044] For the second group of pulse light signals, the reflected pulse light signal of pulse p22 by the former grating and the reflected pulse light signal of pulse p21 by the latter grating interfere with each other at the same time when they reach the photoelectric conversion module.

[0045] For the third group of pulse optical signals, the reflected pulse optical signal of the former grating pair pulse p32 interferes with the reflected pulse optical signal of the latter grating pair pulse p31 simultaneously reaching the photoelectric conversion module.

[0046] In the technical solution, the specific method for performing phase demodulation processing on the sensing electrical signal is:

[0047] The three interfering pulse signals I1, I2 and I3 can be represented as:

[0048]

[0049] Wherein, A represents the direct current amount of the interference signal, B represents the alternating current amount of the interference signal, θ1=2n eff πd / λ1, θ2=2n eff πd / λ2, θ3=2n eff πd / λ3 are fixed phase differences introduced by the fiber length between adjacent gratings in the grating array sensing fiber under the action of different wavelengths, n eff is the core refractive index of the grating array sensing fiber, d is the interval of adjacent gratings in the grating array sensing fiber, λ1, λ2 and λ3 represent the wavelengths of the first group of pulse optical signals, the second group of pulse optical signals and the third group of pulse optical signals respectively, fa1s1=2n eff πV / λ1, fa1s2=2n eff πV / λ2, fa1s3=2n eff πV / λ3 represent the phase change amount caused by the change V of the fiber length between adjacent gratings in the grating array sensing fiber due to external vibration under the action of different wavelengths, and fa1o represents the initial phase difference between the two signals that interfere, i.e. the phase difference corresponding to p12 and p11, p22 and p21, and p32 and p31.

[0050] In the technical solution, for the solving formula of the three interfering pulse signals I1, I2 and I3, when the change amount of the fiber length between adjacent gratings in the grating array sensing fiber caused by external vibration is less than a threshold value (1um), since the change amount is much smaller than the length of the fiber between adjacent gratings in the grating array sensing fiber;

[0051] In the formula, the wavelengths of the three light source modules used (1550nm band) are close, fa1s1≈fa1s2≈fa1s3, fa1=fa1s1+fa1o, and the phase demodulation formula can be obtained by simultaneously solving I1, I2 and I3:

[0052]

[0053] In the technical solution, the three groups of pulse light signals output by the three pulse modulation modules have wavelengths of 1550.12 nm, 1550.92 nm and 1551.72 nm respectively. In order to ensure that the adjacent gratings can respond to the same light signal, the center wavelengths and spectral widths of the gratings in the grating array fiber are consistent, the wavelengths of the three groups of pulse light signals are within the grating spectrum range, the spectral width of the gratings in the grating array fiber is 4 nm, and the center wavelength is 1551 nm. Therefore, the light source modules with wavelengths of 1550.12 nm, 1550.92 nm and 1551.72 nm in the ITU standard wavelength list are selected.

[0054] In the technical solution, the three light source modules all use narrow linewidth laser modules, and the three pulse modulation modules all use high-speed switch type semiconductor optical amplifier modules. The narrow linewidth is used to improve the sensitivity of the interference signal, and the semiconductor optical amplifier has the functions of pulse modulation and signal amplification.

[0055] A grating array fiber phase demodulation method based on multiple light sources cooperation, which comprises the following steps:

[0056] Step 1: three pulse modulation modules modulate corresponding continuous light signals into three groups of pulse light signals respectively under the control of a signal processing module, the second group of pulse light signals lags behind the first group of pulse light signals by a first preset time, the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time, and each group of pulse light signals has two pulse light signals with time delay in a period;

[0057] Step 2: a fiber combiner combines the three groups of pulse light signals into a pulse light signal string;

[0058] Step 3: a fiber circulator inputs the pulse light signal string into a grating array sensing fiber, each pulse in the pulse light signal string is reflected by each grating in the grating array sensing fiber, the reflected pulse light signal string of the grating array sensing fiber passes through the fiber circulator, is transmitted to a photoelectric conversion module, and is photoelectrically converted by the photoelectric conversion module to obtain corresponding sensing electric signals; wherein the second pulse light signal in each group of pulse light signals reflected by a front grating of adjacent two gratings in the grating array sensing fiber interferes with the corresponding first pulse light signal in each group of pulse light signals reflected by a rear grating of the adjacent two gratings, to generate a corresponding sensing electric signal;

[0059] Step 4: the signal processing module performs phase demodulation processing on the sensing electric signals output by the photoelectric conversion module.

[0060] In order to verify the effectiveness of the present application, it is assumed that the fiber length between the first grating and the second grating is disturbed by a sinusoidal vibration signal with a frequency of 40 Hz and a peak-to-peak value of 100 nm, i.e. V = 50*cos(2*pi*40*t), t is a time variable, and the phase change amount caused by the change of the fiber length between the adjacent two gratings under the action of different wavelengths due to the external vibration is calculated as shown in the following table: Figure 3 It can be seen that the three groups of signals are basically overlapped, and fai1≈fai2≈fai3 is satisfied.

[0061] According to the formula cos(x) = cos(x+2pi), it can be calculated that theta1, theta2 and theta3 are 3.58, 1.96 and 0.81 respectively, it is assumed that the initial phase difference fai0 is 0, and the interference visibility is 1, i.e. A = B = 1, then the I1, I2 and I3 signals are as shown in the following table: Figure 4 The values of I1, I2, I3, theta1, theta2 and theta3 obtained are brought into the phase demodulation formula to obtain the value of fai, i.e. the phase demodulation of the grating array fiber is completed, as shown in the following table: Figure 5

[0062] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.​

Claims

1. A multi-source cooperative grating array fiber phase demodulation system, characterized in that: It includes a signal processing module, a fiber combiner, a fiber circulator, an optoelectronic conversion module, a grating array sensing fiber and three pulse modulation modules, wherein the three pulse modulation modules are used for respectively modulating corresponding continuous light signals into corresponding three groups of pulse light signals under the control of the signal processing module, the second group of pulse light signals lags behind the first group of pulse light signals by a first preset time, the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time, and each group of pulse light signals has time-delayed front and rear pulse light signals in a period; The fiber combiner is used for combining the three groups of pulse light signals into a pulse light signal string; The fiber circulator is used for inputting the pulse light signal string into the grating array sensing fiber, each pulse in the pulse light signal string is reflected by each grating in the grating array sensing fiber, the reflected pulse light signal string of the grating array sensing fiber passes through the fiber circulator, is input into the optoelectronic conversion module, and is optoelectronically converted by the optoelectronic conversion module to obtain corresponding sensing electric signals; wherein the second pulse light signal in each group of pulse light signals reflected by a front grating between two adjacent gratings in the grating array sensing fiber interferes with the corresponding first pulse light signal in each group of pulse light signals reflected by a rear grating between the two adjacent gratings, to generate a corresponding sensing electric signal; The signal processing module is used for performing phase demodulation processing on each sensing electric signal output by the optoelectronic conversion module; The front and rear pulse light signals of each group of pulse light signals have a time delay tp in a period, the pulse width of each pulse light signal is tw, the second group of pulse light signals lags behind the first group of pulse light signals by a time t1, the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time t2, t2>t1, and the wavelengths of the first group of pulse light signals, the second group of pulse light signals and the third group of pulse light signals are λ1, λ2 and λ3 respectively; The time delay tp=2n eff d / c, where n eff is the core refractive index of the grating array sensing fiber, c is the speed of light in vacuum, d is the pitch of adjacent gratings in the grating array sensing fiber; 0 < tw < tp / 3; tw < t1 < tp-2tw; tw+t1 < t2 < tp-tw; The wavelengths of the three light source modules are close to each other.

2. The multi-source coordinated grating array fiber phase demodulation system according to claim 1, characterized in that: It also includes a fiber amplifier, which is used for amplifying the pulse light signal string, and the amplified pulse light signal string is input into the grating array sensing fiber by the fiber circulator.

3. The multi-source coordinated grating array fiber phase demodulation system according to claim 1, wherein: The pulse light signal string is represented as p11, p21, p31, p12, p22, p32, wherein p11 represents the first pulse in the first group of pulse light signals, p21 represents the first pulse in the second group of pulse light signals, p31 represents the first pulse in the third group of pulse light signals, p12 represents the second pulse in the first group of pulse light signals, p22 represents the second pulse in the second group of pulse light signals, and p32 represents the second pulse in the third group of pulse light signals; the pulse light signal string is amplified by the fiber amplifier and then input into the grating array sensing fiber by the fiber circulator; each pulse in the pulse light signal string is reflected by each grating in the grating array sensing fiber; and the time delay of the pulse signals with corresponding serial numbers reflected by adjacent gratings in the grating array sensing fiber is tp.

4. The grating array fiber phase demodulation system of multiple light sources cooperation according to claim 3, characterized in that: The second pulse light signal in each group of pulse light signals reflected by the former grating of the two adjacent gratings in the grating array sensing fiber interferes with the corresponding first pulse light signal in each group of pulse light signals reflected by the latter grating of the two adjacent gratings, and the interference is represented as: For the first group of pulse light signals, the reflected pulse light signal of the pulse p12 of the former grating interferes with the reflected pulse light signal of the pulse p11 of the latter grating when the two signals arrive at the photoelectric conversion module at the same time; For the second group of pulse light signals, the reflected pulse light signal of the pulse p22 of the former grating interferes with the reflected pulse light signal of the pulse p21 of the latter grating when the two signals arrive at the photoelectric conversion module at the same time; For the third group of pulse light signals, the reflected pulse light signal of the pulse p32 of the former grating interferes with the reflected pulse light signal of the pulse p31 of the latter grating when the two signals arrive at the photoelectric conversion module at the same time.

5. The multi-source coordinated grating array fiber phase demodulation system according to claim 4, characterized in that: The specific method for phase demodulation processing of the sensing electric signals is: The three interfering pulse signals I1, I2 and I3 are represented as: Wherein, A represents the direct current of the interference signal, B represents the cross current of the interference signal, θ1=2n eff πd / λ1, θ2=2n eff πd / λ2, θ3=2n eff πd / λ3 respectively are the fixed phase difference introduced by the fiber length between the adjacent two gratings in the grating array sensing fiber under the action of different wavelengths, n eff is the core refractive index of the grating array sensing fiber, d is the interval of the adjacent gratings in the grating array sensing fiber, λ1, λ2 and λ3 respectively represent the wavelengths of the first group of pulse light signals, the second group of pulse light signals and the third group of pulse light signals, fa1s1=2n eff πV / λ1, fa1s2=2n eff πV / λ2, fa1s3=2n eff πV / λ3 respectively represent the phase change amount caused by the change V of the fiber length between the adjacent two gratings in the grating array sensing fiber under the action of different wavelengths, and fa1o represents the initial phase difference between the two signals producing interference.

6. The multi-source coordinated grating array fiber phase demodulation system according to claim 5, wherein: For the solving formula of the three interfering pulse signals I1, I2 and I3, when the change amount of the fiber length between the adjacent gratings in the grating array sensing fiber caused by the external vibration is less than a threshold value, the change amount is much smaller than the length of the fiber between the adjacent gratings in the grating array sensing fiber; In the formula, fai s1≈fai s2≈fai s3, let fai=fai s1+fai0, and the phase demodulation formula can be obtained by combining I1, I2 and I3:

7. The multi-source coordinated grating array fiber phase demodulation system according to claim 6, characterized in that: The wavelengths of the three groups of pulse light signals output by the three pulse modulation modules are 1550.12 nm, 1550.92 nm and 1551.72 nm respectively.

8. A method for phase demodulation of a grating array fiber based on multi- light-source cooperative of the system of claim 1, characterized in that, It comprises the following steps: Step 1: The three pulse modulation modules modulate the corresponding continuous light signals into corresponding three groups of pulse light signals under the control of the signal processing module, the second group of pulse light signals lags behind the first group of pulse light signals by a first preset time, and the third group of pulse light signals lags behind the first group of pulse light signals by a second preset time, each group of pulse light signals has time-delayed front and rear pulse light signals in a period; Step 2: The fiber combiner combines the three groups of pulse light signals into a pulse light signal string; Step 3: The fiber circulator inputs the pulse light signal string into the grating array sensing fiber, each pulse in the pulse light signal string is reflected when encountering each grating in the grating array sensing fiber, the reflected pulse light signal string of the grating array sensing fiber passes through the fiber circulator, is transported to the photoelectric conversion module, and is photoelectrically converted by the photoelectric conversion module to obtain corresponding sensing electric signals; wherein the second pulse light signal in each group of pulse light signals reflected by the former grating of the two adjacent gratings in the grating array sensing fiber interferes with the corresponding first pulse light signal in each group of pulse light signals reflected by the latter grating of the two adjacent gratings, to generate corresponding sensing electric signals; Step 4: The signal processing module performs phase demodulation processing on each sensing electric signal output by the photoelectric conversion module.

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