Chirp modulation based forward transmission distributed optical fiber sensing detection method, system, terminal and storage medium

Abstract

The present application relates to the field of optical fiber sensing detection, and discloses a forward transmission distributed optical fiber sensing detection method and system based on chirp modulation, a terminal and a storage medium.The method comprises the following steps: obtaining a sensing detection task of a sensing optical fiber, obtaining a single-frequency continuous optical signal and a radio frequency signal according to the sensing detection task, and chirp-modulating the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals; superimposing all the modulated optical signals to obtain a swept optical field, and dividing the swept optical field to obtain a sensing optical field and a reference optical field; performing interference processing on the target sensing optical field output by the sensing optical fiber and the reference optical field to obtain beat frequency interference light intensity, and performing filtering to obtain a target beat frequency interference signal; demodulating the target beat frequency interference signal to obtain optical field phase changes, and performing vibration positioning on the sensing optical fiber to obtain an optical fiber vibration position, so as to obtain a sensing detection result.The present application not only reduces the detection cost, but also can accurately position the vibration on the sensing optical fiber.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber sensing detection, and particularly relates to a forward transmission distributed optical fiber sensing detection method and system based on chirp modulation, a terminal and a computer readable storage medium. BACKGROUND

[0002] At present, optical fiber sensing technology can be used to realize physical, chemical, biological and many other parameter measurements, and provides a novel detection means for the development of natural science. As a new type of vibration sensing and detection technology integrating signal sensing and signal transmission, distributed optical fiber vibration sensing technology can realize continuous distributed measurement of vibration events along the optical fiber through direct sensing and detection of optical wave signals.

[0003] The distributed optical fiber vibration sensing technology can be roughly divided into two structures according to its sensing mechanism. One is a distributed vibration optical fiber sensing system based on backscattering in the optical fiber, such as an optical time domain reflectometry (OTDR) and an optical frequency domain reflectometry (OFDR). The distributed optical fiber sensing system uses a time-of-flight method for positioning, has high spatial resolution and high positioning accuracy. However, the sensing distance is limited (for example, the sensing distance is less than 100Km) due to the weak Rayleigh backscattering in the optical fiber. The other is a distributed vibration optical fiber sensing system based on forward transmission of light (FTDVS). The FTDVS uses forward continuous light in the optical fiber as a probe light, has the advantages of long transmission distance, large dynamic range and wide frequency band response. However, the existing FTDVS still faces many bottlenecks. For example, it needs bidirectional transmission for positioning, so that most systems need to set up a ring-shaped sensing optical fiber, which greatly increases the cost of optical fiber laying. In addition, to avoid the influence of backscattering Rayleigh in long distance, the bidirectional transmission structure needs to use a double-core optical fiber or a double-wavelength light source, which increases the hardware cost.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] The main purpose of the present application is to provide a forward transmission distributed optical fiber sensing detection method and system based on chirp modulation, a terminal and a storage medium, which aims to solve the problem that the detection result obtained by sensing and detecting the whole sensing optical fiber by the optical wave signal in the prior art is not accurate, which leads to the failure to accurately locate the vibration on the whole sensing optical fiber, so that the intrusion event cannot be found in time, and the cost of sensing and detection is too high.

[0006] To achieve the above object, the application provides a forward transmission distributed optical fiber sensing detection method based on chirp modulation, which comprises the following steps:

[0007] Obtaining a sensing detection task of a sensing optical fiber, obtaining a single-frequency continuous optical signal and a radio frequency signal according to the sensing detection task, and chirp modulating the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals;

[0008] Superimposing all the modulated optical signals to obtain a swept optical field, dividing the swept optical field to obtain a sensing optical field and a reference optical field, and inputting sensing light of the sensing optical field into the sensing optical fiber;

[0009] Receiving a target sensing optical field output by the sensing optical fiber, interfering the target sensing optical field with the reference optical field to obtain beat frequency interference light intensity, and filtering the beat frequency interference light intensity to obtain a target beat frequency interference signal;

[0010] Demodulating the target beat frequency interference signal to obtain an optical field phase change, positioning vibration of the sensing optical fiber according to the optical field phase change to obtain an optical fiber vibration position, and obtaining a sensing detection result according to the optical fiber vibration position.

[0011] Optionally, the forward transmission distributed optical fiber sensing detection method based on chirp modulation, wherein the radio frequency signal comprises a first chirp swept frequency signal and a second chirp swept frequency signal, and the modulated optical signal comprises a first I-channel modulated optical signal, a second I-channel modulated optical signal, a first Q-channel modulated optical signal and a second Q-channel modulated optical signal;

[0012] The chirp modulation of the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals specifically comprises:

[0013] Phase-opposite modulating the single-frequency continuous optical signal and the first chirp swept frequency signal through a first I-channel modulation channel to obtain a first I-channel modulated optical signal;

[0014] Phase-opposite modulating the single-frequency continuous optical signal and the first chirp swept frequency signal through a second I-channel modulation channel to obtain a second I-channel modulated optical signal;

[0015] Modulating the single-frequency continuous optical signal and the second chirp swept frequency signal through a first Q-channel modulation channel to obtain a first Q-channel modulated optical signal;

[0016] The single-frequency continuous light signal is modulated with the second chirp sweep signal through a second Q-channel modulation channel to obtain a second Q-channel modulation light signal.

[0017] Optionally, the forward transmission distributed optical fiber sensing detection method based on chirp modulation, wherein the target sensing light field comprises Rayleigh backscattering light field, first light field and second light field.

[0018] The target sensing light field is interfered with the reference light field to obtain beat frequency interference light intensity, and the beat frequency interference light intensity is filtered to obtain a target beat frequency interference signal, specifically comprising:

[0019] The Rayleigh backscattering light intensity is calculated according to the Rayleigh backscattering light field and the reference light field.

[0020] The first light intensity is calculated according to the first light field and the reference light field.

[0021] The second light intensity is calculated according to the second light field and the reference light field.

[0022] The Rayleigh backscattering light intensity, the first light intensity and the second light intensity are superimposed to obtain beat frequency interference light intensity, and a plurality of bandpass filter passbands of different frequencies are set.

[0023] The beat frequency interference light intensity is signal extracted according to all the bandpass filter passbands to obtain Rayleigh backscattering beat frequency interference signal, first beat frequency interference signal and second beat frequency interference signal.

[0024] The Rayleigh backscattering beat frequency interference signal is filtered to obtain a processing result, and the first beat frequency interference signal and the second beat frequency interference signal are combined according to the processing result to obtain a target beat frequency interference signal.

[0025] Optionally, the forward transmission distributed optical fiber sensing detection method based on chirp modulation, wherein the calculating of the Rayleigh backscattering light intensity according to the Rayleigh backscattering light field and the reference light field specifically comprises:

[0026] ;

[0027] The calculating of the first light intensity according to the first light field and the reference light field specifically comprises:

[0028] ;

[0029] The calculating of the second light intensity according to the second light field and the reference light field specifically comprises:

[0030] ;

[0031] wherein, is the Rayleigh backscattered light intensity, is the propagation time of the sensing light for one round trip in the sensing fiber, is the sensing fiber length, is the propagation time, is the light frequency output by the light source, is the start frequency of the sweep, is the beat frequency of the Rayleigh backscattered beat interference signal, is the sweep time, is the sweep speed, is the phase change caused by the external disturbance, is the first light intensity, is the propagation time of the sensing light in the first time delay fiber, is the carrier frequency of the first beat interference signal, is the second light intensity, is the propagation time of the sensing light in the second time delay fiber.

[0032] Optionally, the method for detecting the distributed optical fiber sensing based on the forward transmission of the chirp modulation, wherein the light field phase change comprises a first light field phase change and a second light field phase change.

[0033] The demodulation processing of the target beat interference signal to obtain the light field phase change specifically comprises:

[0034] signal construction of the first beat interference signal of the target beat interference signal to obtain a first analytic signal, and component calculation of the first analytic signal to obtain a first I component and a first Q component;

[0035] signal construction of the second beat interference signal of the target beat interference signal to obtain a second analytic signal, and component calculation of the second analytic signal to obtain a second I component and a second Q component;

[0036] the first light field phase change is obtained according to the first I component and the first Q component, and the second light field phase change is obtained according to the second I component and the second Q component.

[0037] Optionally, the method for detecting the distributed optical fiber sensing based on the forward transmission of the chirp modulation, wherein the signal construction of the first beat interference signal of the target beat interference signal specifically comprises:

[0038] ;

[0039] the signal construction of the second beat interference signal of the target beat interference signal specifically comprises:

[0040] ;

[0041] wherein, is a first analytic signal, is a first beat frequency interference signal, is an imaginary expression, is a Hilbert transform result of the first beat frequency interference signal, is an amplitude of the first analytic signal, is a carrier frequency of the first beat frequency interference signal, is a sweep time, is a first optical field phase change, is a second analytic signal, is a second beat frequency interference signal, is a Hilbert transform result of the second beat frequency interference signal, is an amplitude of the second analytic signal, is a carrier frequency of the second beat frequency interference signal, is a second optical field phase change.

[0042] Optionally, the method for detecting a forward transmission distributed optical fiber sensor based on a chirp modulation, wherein the vibration positioning of the sensing optical fiber according to the optical field phase change to obtain an optical fiber vibration position and the sensing detection result according to the optical fiber vibration position, specifically comprises:

[0043] performing phase reconstruction on the first optical field phase change and the second optical field phase change to obtain a first phase and a second phase, and performing cross-correlation processing on the first phase and the second phase to obtain a second path propagation time;

[0044] performing vibration position detection according to the second path propagation time to obtain an optical fiber vibration position, and obtaining a sensing detection result according to the optical fiber vibration position;

[0045] wherein the vibration position detection according to the second path propagation time specifically comprises:

[0046] ;

[0047] wherein, is an optical fiber vibration position, is a propagation time of a sensing light in a sensing optical fiber for one round trip, is a second path propagation time, is a propagation time of a sensing light in a second delay optical fiber, is a refractive index of a sensing optical fiber, is a light speed in vacuum.

[0048] Optionally, the forward transmission distributed optical fiber sensing detection method based on chirp modulation, wherein the forward transmission distributed optical fiber sensing detection system based on chirp modulation comprises:

[0049] a signal modulation module, configured to acquire a sensing detection task of the sensing optical fiber, acquire a single-frequency continuous optical signal and a radio frequency signal according to the sensing detection task, and perform chirp modulation on the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals;

[0050] an optical field division module, configured to perform superposition processing on all the modulated optical signals to obtain a swept optical field, perform division processing on the swept optical field to obtain a sensing optical field and a reference optical field, and input sensing light of the sensing optical field to the sensing optical fiber;

[0051] an optical field interference module, configured to receive a target sensing optical field output by the sensing optical fiber, perform interference processing on the target sensing optical field and the reference optical field to obtain beat frequency interference light intensity, and perform filtering processing on the beat frequency interference light intensity to obtain a target beat frequency interference signal;

[0052] a sensing detection module, configured to perform demodulation processing on the target beat frequency interference signal to obtain an optical field phase change, perform vibration positioning on the sensing optical fiber according to the optical field phase change to obtain an optical fiber vibration position, and obtain a sensing detection result according to the optical fiber vibration position.

[0053] In addition, to achieve the above object, the present application also provides a terminal, wherein the terminal comprises a memory, a processor, and a forward transmission distributed optical fiber sensing detection program based on chirp modulation stored in the memory and executable on the processor, and the forward transmission distributed optical fiber sensing detection program based on chirp modulation implements the steps of the forward transmission distributed optical fiber sensing detection method based on chirp modulation when executed by the processor.

[0054] In addition, to achieve the above object, the present application also provides a computer readable storage medium, wherein the computer readable storage medium stores a forward transmission distributed optical fiber sensing detection program based on chirp modulation, and the forward transmission distributed optical fiber sensing detection program based on chirp modulation implements the steps of the forward transmission distributed optical fiber sensing detection method based on chirp modulation when executed by a processor.

[0055] In the present application, the sensing detection task of the sensing optical fiber is acquired, a single-frequency continuous light signal and a radio frequency signal are acquired according to the sensing detection task, the single-frequency continuous light signal is chirped modulated according to the radio frequency signal, a plurality of modulated light signals are obtained; all the modulated light signals are superimposed to obtain a swept light field, the swept light field is divided to obtain a sensing light field and a reference light field, and the sensing light of the sensing light field is input to the sensing optical fiber; the target sensing light field output by the sensing optical fiber is received, the target sensing light field is interfered with the reference light field to obtain beat frequency interference light intensity, and the beat frequency interference light intensity is filtered to obtain a target beat frequency interference signal; the target beat frequency interference signal is demodulated to obtain a light field phase change, the sensing optical fiber is vibrated and positioned according to the light field phase change, an optical fiber vibration position is obtained, and a sensing detection result is obtained according to the optical fiber vibration position. The present application not only reduces the detection cost, but also accurately positions the vibration on the sensing optical fiber, discovers the intrusion event in time, and thus guarantees the data transmission and data security on the sensing optical fiber. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 is a flow chart of a preferred embodiment of the present application based on a chirp modulated forward transmission distributed optical fiber sensing detection method;

[0057] Figure 2 is a schematic diagram of the overall process of the present application based on a chirp modulated forward transmission distributed optical fiber sensing detection method;

[0058] Figure 3 is a schematic diagram of the structure principle of the I / Q modulator in the preferred embodiment of the present application;

[0059] Figure 4 is a schematic diagram of the vibration positioning process in the preferred embodiment of the present application;

[0060] Figure 5 is a schematic diagram of the power spectral density of the sensing optical fiber signal at different frequencies and different positions in the preferred embodiment of the present application;

[0061] Figure 6 is a structure diagram of a preferred embodiment of the present application based on a chirp modulated forward transmission distributed optical fiber sensing detection system;

[0062] Figure 7 is a structure diagram of a preferred embodiment of the present application terminal. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below with reference to the drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0064] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, motion condition, etc. between components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directional indications will also change accordingly.

[0065] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0066] The forward transmission distributed optical fiber sensing detection method based on chirp modulation described in the preferred embodiment of the present application, as shown in Figure 1 The forward transmission distributed optical fiber sensing detection method based on chirp modulation includes the following steps:

[0067] Step S10 obtains a sensing detection task of a sensing optical fiber, obtains a single-frequency continuous optical signal and a radio frequency signal according to the sensing detection task, and chirp modulates the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals.

[0068] Specifically, in the embodiments of the present application, in order to solve the problem that the detection result obtained by sensing and detecting the entire sensing optical fiber through an optical wave signal in the prior art is not accurate, which leads to the inability to accurately locate the vibration on the entire sensing optical fiber, thereby failing to discover an intrusion event in time, and the cost of sensing and detection is too high, a forward transmission distributed optical fiber sensing detection method based on chirp modulation is proposed, which is implemented through a single-end forward transmission distributed optical fiber sensing system based on chirp modulation. The system includes a transmitting and receiving module at the near end and a time delay module at the far end. The corresponding system principle diagram is as shown in Figure 2 Specifically, a sensing detection task of a sensing optical fiber is obtained, an LD (Laser Diode, narrow line width single-frequency laser) and an AWG (Arbitrary Waveform Generator, arbitrary waveform generator) are started according to the sensing detection task, a single-frequency continuous optical signal is emitted through the narrow line width single-frequency laser, and a radio frequency signal is generated by the arbitrary waveform generator, wherein the radio frequency signal includes two chirp sweep signals, which are and ,in, is the first chirp sweep signal, is the second chirp sweep signal, is the phase change caused by external disturbance, is the starting frequency of the sweep, is the sweep time, The sweep speed is the first chirp sweep signal and the second chirp sweep signal have a sweep range of 250MHz-750MHz, and a sweep time of 10ms. Therefore, the corresponding sweep speeds are 50GHz / s.

[0069] Afterwards, the RF signal is input into an I / Q modulator, which is composed of two MZMs (Mach-Zehnder Modulators) and a 90° phase shifter; Figure 3 As shown, after the RF signal is input into the I / Q modulator, the automatic bias controller uses the PID (Proportional, Integral, Differential) algorithm to adjust the DC bias voltage so that the I / Q modulator operates at the quadrature point. At this time, the two MZMs inside the I / Q modulator are respectively in the push-pull working state, that is, the phase modulation signals of the upper and lower arms differ by 180 degrees, thereby optimizing the linear response and minimizing the distortion, and the single-frequency continuous optical signal I / Q modulator. The single-frequency continuous optical signal is first split into two MZM sub-modules, the I-channel and the Q-channel. In the I-channel, the single-frequency continuous optical signal passes through the two branch modulation channels, I+ and I-, respectively, and is modulated with the positive and negative components of the radio frequency signal in opposite phases. That is, the single-frequency continuous optical signal and the first chirped swept-frequency signal are modulated in opposite phases through the first I-channel modulation channel to obtain a first I-channel modulated optical signal. The single-frequency continuous optical signal and the first chirped swept-frequency signal are modulated in opposite phases through the second I-channel modulation channel to obtain a second I-channel modulated optical signal. Similarly, in the Q-channel, the single-frequency continuous optical signal passes through the two branch modulation channels, Q+ and Q-, respectively, and is modulated with the positive and negative components of the radio frequency signal after 90° phase shift. That is, the single-frequency continuous optical signal and the second chirped swept-frequency signal are modulated through the first Q-channel modulation channel to obtain a first Q-channel modulated optical signal. The single-frequency continuous optical signal and the second chirped swept-frequency signal are modulated through the second Q-channel modulation channel to obtain a second Q-channel modulated optical signal.

[0070] Step S20: superimpose all the modulated optical signals to obtain a swept light field, divide the swept light field to obtain a sensing light field and a reference light field, and input the sensing light of the sensing light field into the sensing optical fiber.

[0071] Specifically, after obtaining the plurality of modulated light signals, all the modulated light signals are coherently superimposed in an optical combiner to form a complex light field (i.e. a swept light field) with adjustable amplitude and phase, so as to realize I / Q modulation of the input radio frequency signal, wherein the expression of the swept light field is:

[0072] ;

[0073] wherein, is the swept light field, is a virtual representation, is the light frequency output by the light source, which is an initial light frequency not modulated, is the sweeping time, and are both the Bayes expansion formula; wherein, , is the starting frequency of the sweep, is the sweep speed, the expression of the swept light field is first-order Bayes expanded and regrouped, and the expression of the expanded swept light field is:

[0074] + ;

[0075] wherein, is the positive first-order expansion coefficient of the Bayes, is the negative third-order expansion coefficient of the Bayes; thus, the +1 order sideband and the -3 order sideband are retained, the carrier and other sidebands are suppressed, and when , the -3 order sideband is significantly suppressed. Therefore, the light frequency of the input single-frequency continuous light signal generates a suppressed carrier single-sideband sweep due to the chirp sweep of the modulated chirp sweep signal, and the sweep linearity of the generated chirp sweep light is basically consistent with the sweep linearity of the chirp sweep signal.

[0076] After that, the swept light field is divided by OC (Optical Fiber Coupler, optical fiber coupler) 1 to obtain a sensing light field and a reference light field, and the sensing light of the sensing light field is input to the sensing fiber through Cir (Circulator, circulator) 1, and then enters the time delay module at the far end through Cir2; after the sensing light enters the time delay module at the far end, the sensing light is divided into two paths by OC2, one path of the sensing light passes through TDF (Time Delay Fiber, time delay fiber) 1 of a first preset length (for example, 10km), and the other path passes through TDF2 of a second preset length (for example, 20km), the two paths of the sensing light are recoupled at OC3, and the target sensing light is obtained by returning to the sensing fiber again through Cir2; then the light field (i.e. the target sensing light field) of the target sensing light and the reference light field are beat interfered at OC4 through Cir1, the corresponding beat interference light intensity is obtained, and finally the BPD (Balance Photoelectric Detector, balance photoelectric detector) is used to detect, convert into a corresponding electrical signal, and be collected by the OSC (Oscilloscope, oscilloscope) for subsequent digital signal processing. On the other hand, due to the isolation of Cir2, the Rayleigh backscattering light in TDF1 and TDF2 does not enter the sensing fiber through the port 2 of Cir2. Therefore, the target sensing light field returned to the receiving end through Cir1 contains three parts, which are Rayleigh backscattering light field , first light field experienced Path1 (propagation path 1) and second light field experienced Path2 (propagation path 2) , wherein, The propagation path PathRBS of is: Cir1->Sensing fiber->Cir1->OC4; The propagation path Path1 of is: Cir1->Sensing fiber->Cir2->OC2->TDF1->OC3->Cir2->Sensing fiber->Cir1->OC4; The propagation path Path2 of is: Cir1->Sensing fiber->Cir2->OC2->TDF2->OC3->Cir2->Sensing fiber->Cir1->OC4.

[0077] From the expression of the expanded swept light field, the +1 order single sideband probe light field (i.e. the swept light field) output by Cir1 can be expressed as:

[0078] ;

[0079] wherein, is the initial amplitude of the optical field, which can be ignored in the embodiment of the present application due to the propagation through three propagation paths, the Rayleigh backscattered optical field, the first optical field and the second optical field, which are returned to the receiving end of the transmitting-receiving module again, are represented as:

[0080] ;

[0081] ;

[0082] ;

[0083] wherein, is the Rayleigh backscattered optical field in the sweep time, is the first optical field in the sweep time, is the second optical field in the sweep time, is the propagation time of the sensing light in the sensing fiber for one round trip, , is the length of the sensing fiber, is the refractive index of the sensing fiber, is the speed of light in vacuum, is the propagation time of the sensing light in the first time delay fiber (i.e. TDF1), , is the length of the TDF1, is the propagation time of the sensing light in the second time delay fiber (i.e. TDF2), , is the length of the TDF2.

[0084] Step S30, receiving the target sensing optical field output by the sensing fiber, performing interference processing on the target sensing optical field and the reference optical field to obtain beat frequency interference light intensity, and performing filtering processing on the beat frequency interference light intensity to obtain a target beat frequency interference signal.

[0085] Specifically, in the embodiment of the present application, after receiving the target sensing optical field output by the sensing fiber, interference processing needs to be performed on the target sensing optical field and the reference optical field, and the specific process is as follows: according to the Rayleigh backscattered optical field and the reference optical field, light intensity calculation is performed to obtain Rayleigh backscattered light intensity, and the corresponding expression is:

[0086] ;

[0087] According to the first optical field and the reference optical field, light intensity calculation is performed to obtain a first light intensity, and the corresponding expression is:

[0088] ;

[0089] According to the second light field and the reference light field, a light intensity calculation is performed to obtain a second light intensity, and the corresponding expression is:

[0090]

[0091] wherein, is a Rayleigh backscattering light intensity, is a light frequency output by a light source, is a starting frequency of sweep, is a beat frequency of a Rayleigh backscattering beat interference signal, is a phase change caused by an external disturbance, is a first light intensity, is a carrier frequency of a first beat interference signal, is a second light intensity; wherein, , , .

[0092] The Rayleigh backscattering light intensity, the first light intensity and the second light intensity are superimposed to obtain a beat interference light intensity, and the corresponding expression is:

[0093]

[0094] From the expression of the Rayleigh backscattering light intensity and the expression of the beat interference light intensity, it can be seen that as long as the length of TDF2 is greater than TDF1, , and they will be clearly separated in the frequency domain. Then, a plurality of bandpass filters with different frequencies are set, and the Rayleigh backscattering beat interference signal, the first beat interference signal and the second beat interference signal can be extracted through the bandpass filters with all the passbands, and the Rayleigh backscattering signal is filtered out at the same time. In the far-end part, due to the characteristics of the circulator, the sensing light entering from port 3 can only exit from port 2, and the sensing light entering from port 2 can only exit from port 1, and the backscattering light cannot enter the sensing optical fiber from port 2, so it is also filtered out, that is, the Rayleigh backscattering beat interference signal is filtered out to obtain a processing result, and the first beat interference signal and the second beat interference signal are combined according to the processing result to obtain a target beat interference signal.

[0095] In step S40, the target beat interference signal is demodulated to obtain a light field phase change, the sensing optical fiber is positioned according to the light field phase change to obtain an optical fiber vibration position, and a sensing detection result is obtained according to the optical fiber vibration position.

[0096] ​​Specifically, since the target beat frequency interference signal has a carrier frequency and (i.e. the first beat frequency interference signal has a carrier frequency , and the second beat frequency interference signal has a carrier frequency ), therefore, in the embodiment of the present invention, if Figure 4 As shown, the Hilbert transform is used to generate I / Q components to perform I / Q demodulation on the target beat frequency interference signal. The specific demodulation process is as follows: assuming that the signal containing The signal (i.e., the first beat frequency interference signal) and the The corresponding expressions are:

[0097] ;

[0098] ;

[0099] in, is the first beat frequency interference signal, is the amplitude of the first beat frequency interference signal, is the phase change of the first light field, is the second beat frequency interference signal, is the amplitude of the second beat frequency interference signal, is the phase change of the second light field; then, the corresponding analytical signal needs to be constructed. , that is, the first beat frequency interference signal is constructed to obtain the first analytical signal, and the corresponding expression is:

[0100] ;

[0101] use The expression for the first analytic signal multiplied by the conjugate complex term is:

[0102] ;

[0103] in, is the first analytical signal, is an imaginary expression, is the Hilbert transform result of the first beat frequency interference signal, is the amplitude of the first analytical signal, is the first analytical signal after transformation; and according to The first I component and the first Q component can be obtained, and the corresponding expressions are:

[0104] ;

[0105] ;

[0106] wherein, is a first I component, i.e. a first in-phase component, is a real component of is a first Q component, i.e. a first quadrature component, is an imaginary component of a first optical field phase change

[0107] .

[0108] for i.e. signal construction is performed on the second beat interference signal to obtain a second analytic signal, and the corresponding expression is:

[0109] ;

[0110] with the expression of the second analytic signal multiplied by the conjugate complex term is:

[0111] ;

[0112] wherein, is a second analytic signal, is a Hilbert transform result of the second beat interference signal, is an amplitude of the second analytic signal, is a transformed second analytic signal; and according to which a second I component and a second Q component can be obtained, and the corresponding expressions are:

[0113] ;

[0114] ;

[0115] wherein, is a second I component, i.e. a second in-phase component, is a real component of is a second Q component, i.e. a second quadrature component, is an imaginary component of a second optical field phase change

[0116] .

[0117] After that, vibration positioning needs to be performed according to the optical field phase change, that is, vibration positioning is performed on the sensing optical fiber according to the optical field phase change, to obtain the optical fiber vibration position. The specific positioning process is that the phase changes of the two paths are and The phase change caused by external disturbance can be expressed as:

[0118] ;

[0119] ;

[0120] wherein, is the time of the sensing light propagating in the first path, is the time of the sensing light propagating in the second path (i.e., the second path propagation time); the first path is PZT (Piezoelectric Transducer) -> Cir2 -> TDF1 -> Cir2 -> PZT, and the second path is PZT -> Cir2 -> TDF2 -> Cir2 -> PZT; in subsequent digital signal processing, the first optical field phase change and the second optical field phase change are phase reconstructed to obtain the first phase and the second phase, and the corresponding expressions are respectively:

[0121] ;

[0122] ;

[0123] wherein, is the first phase, is the second phase, is the time difference value, .

[0124] As shown in Figure 4 , the first phase is unfolded, and the unfolded first phase is:

[0125] ;

[0126] At the same time, the second phase is time-shifted, and the shifted second phase can be expressed as:

[0127] ;

[0128] Therefore, can be obtained, and the cross-correlation of and can obtain , according to the second path propagation time, the vibration position detection is performed to obtain the optical fiber vibration position, and the expression is:

[0129] ;

[0130] wherein, is the optical fiber vibration position, is the propagation time of the sensing light in the sensing optical fiber for one round trip, is the propagation time of the sensing light in the second time delay optical fiber, is the refractive index of the sensing optical fiber, is the speed of light in vacuum; and a sensing detection result is obtained according to the optical fiber vibration position, wherein the sensing detection result includes a PSD (Power Spectral Density) at different frequencies and a PSD at different positions, wherein the PSD at different frequencies is as part (a) in Figure 5 , and the PSD at different positions is as part (b) in Figure 5 , and it can also be known from part (b) in Figure 5 that there is a flange attenuation at the optical fiber connection.

[0131] The beneficial effects of the present application are: (1) by using a chirp swept light as a probe light, two time delay optical fibers with different lengths are arranged at the far end to perform frequency division, and a circulator is arranged as an input device at the far end, and the unidirectional input and output characteristics of the circulator are used to isolate the backscattered light, thereby effectively avoiding the backscattered light generated at the far end from entering the sensing optical fiber; (2) an I / Q modulator is used for light intensity modulation, a chirp swept light signal with a phase difference of is input as a modulation signal, single sideband modulation with carrier suppression is performed, and an optical filter is not needed to filter the carrier and the excess sideband, in addition, an automatic bias point controller is used to dynamically adjust the bias voltage, so that the bias voltage is located at the quadrature position, and a single sideband light intensity signal is stably output; (3) two bandpass filters are used in the receiving module at the near end to extract the forward light of the two paths and eliminate the Rayleigh backscattering signal, thereby improving the signal-to-noise ratio of the phase signal and improving the sensing distance; (4) by using a single-core bidirectional structure, the cost of optical fiber laying is reduced; (5) a passive device is used at the end of the optical fiber, so that the system can still effectively operate in remote areas and passive environments at the far end.

[0132] Further, as shown in Figure 6 , based on the above-mentioned forward transmission distributed optical fiber sensing detection method based on chirp modulation, the present application also correspondingly provides a forward transmission distributed optical fiber sensing detection system based on chirp modulation, wherein the forward transmission distributed optical fiber sensing detection system based on chirp modulation comprises:

[0133] a signal modulation module 51 for acquiring a sensing detection task of a sensing optical fiber, acquiring a single-frequency continuous optical signal and a radio frequency signal according to the sensing detection task, and chirping-modulating the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals;

[0134] an optical field division module 52 for superimposing all the modulated optical signals to obtain a swept-frequency optical field, dividing the swept-frequency optical field to obtain a sensing optical field and a reference optical field, and inputting the sensing light of the sensing optical field into the sensing optical fiber;

[0135] The light field interference module 53 is used to receive the target sensing light field output by the sensing optical fiber, perform interference processing on the target sensing light field and the reference light field to obtain a beat frequency interference light intensity, and perform filtering processing on the beat frequency interference light intensity to obtain a target beat frequency interference signal;

[0136] The sensing detection module 54 is used to demodulate the target beat frequency interference signal to obtain a light field phase change, perform vibration positioning on the sensing optical fiber according to the light field phase change to obtain an optical fiber vibration position, and obtain a sensing detection result according to the optical fiber vibration position.

[0137] Further, if Figure 7 As shown, based on the above-mentioned forward transmission distributed optical fiber sensing detection method based on chirp modulation, the present invention also provides a terminal, which includes a processor 10, a memory 20 and a display 30. Figure 7 Only some of the components of the terminal are shown, but it should be understood that implementation of all of the shown components is not required, and more or fewer components may be implemented instead.

[0138] The memory 20 can be an internal storage unit of the terminal in some embodiments, such as a hard disk or a memory of the terminal. The memory 20 can also be an external storage device of the terminal in other embodiments, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal. Further, the memory 20 can include both the internal storage unit and the external storage device of the terminal. The memory 20 is used to store application software installed on the terminal and various data, such as program codes of the installed terminal, etc. The memory 20 can also be used to temporarily store data that has been output or will be output. In an embodiment, the memory 20 stores a chirp modulation based forward transmission distributed optical fiber sensing detection program 40, which can be executed by the processor 10 to implement the chirp modulation based forward transmission distributed optical fiber sensing detection method in the present application.

[0139] The processor 10 can be a central processing unit (CPU), a microprocessor or other data processing chip in some embodiments, which is used to run program codes stored in the memory 20 or process data, such as executing the chirp modulation based forward transmission distributed optical fiber sensing detection method, etc.

[0140] The display 30 can be an LED display, a liquid crystal display, a touch liquid crystal display, an OLED (Organic Light-Emitting Diode) touch, etc. in some embodiments. The display 30 is used to display information of the terminal and to display a visualized user interface.

[0141] In an embodiment, the following steps are implemented when the processor 10 executes the chirp modulation based forward transmission distributed optical fiber sensing detection program 40 in the memory 20:

[0142] Obtaining a sensing detection task of a sensing optical fiber, obtaining a single-frequency continuous light signal and a radio frequency signal according to the sensing detection task, and chirp modulating the single-frequency continuous light signal according to the radio frequency signal to obtain a plurality of modulated light signals;

[0143] Superimposing all the modulated light signals to obtain a swept light field, dividing the swept light field to obtain a sensing light field and a reference light field, and inputting sensing light of the sensing light field to the sensing optical fiber;

[0144] Receiving a target sensing light field output by the sensing optical fiber, performing interference processing on the target sensing light field and the reference light field to obtain beat interference light intensity, and performing filtering processing on the beat interference light intensity to obtain a target beat interference signal;

[0145] Performing demodulation processing on the target beat interference signal to obtain a light field phase change, performing vibration positioning on the sensing optical fiber according to the light field phase change to obtain an optical fiber vibration position, and obtaining a sensing detection result according to the optical fiber vibration position.

[0146] The radio frequency signal includes a first chirp sweep frequency signal and a second chirp sweep frequency signal, and the modulated light signal includes a first I-channel modulated light signal, a second I-channel modulated light signal, a first Q-channel modulated light signal, and a second Q-channel modulated light signal.

[0147] The chirp modulation of the single-frequency continuous light signal according to the radio frequency signal to obtain a plurality of modulated light signals specifically includes:

[0148] The single-frequency continuous light signal is phase-inversely modulated with the first chirp sweep frequency signal through a first I-channel modulation channel to obtain a first I-channel modulated light signal.

[0149] The single-frequency continuous light signal is phase-inversely modulated with the first chirp sweep frequency signal through a second I-channel modulation channel to obtain a second I-channel modulated light signal.

[0150] The single-frequency continuous light signal is modulated with the second chirp sweep frequency signal through a first Q-channel modulation channel to obtain a first Q-channel modulated light signal.

[0151] The single-frequency continuous light signal is modulated with the second chirp sweep frequency signal through a second Q-channel modulation channel to obtain a second Q-channel modulated light signal.

[0152] The target sensing light field includes a Rayleigh backscattering light field, a first light field, and a second light field.

[0153] The interference processing of the target sensing light field and the reference light field to obtain beat interference light intensity, and the filtering processing of the beat interference light intensity to obtain a target beat interference signal specifically include:

[0154] The Rayleigh backscattering light intensity is obtained by performing light intensity calculation on the Rayleigh backscattering light field and the reference light field.

[0155] The first light intensity is obtained by performing light intensity calculation on the first light field and the reference light field.

[0156] The second light intensity is obtained by performing light intensity calculation on the second light field and the reference light field.

[0157] superimposing the Rayleigh backscattering light intensity, the first light intensity and the second light intensity to obtain beat interference light intensity, and setting a plurality of band pass filter passbands with different frequencies;

[0158] signal extracting the beat interference light intensity according to all the band pass filter passbands to obtain Rayleigh backscattering beat interference signals, first beat interference signals and second beat interference signals;

[0159] filtering the Rayleigh backscattering beat interference signals to obtain a processing result, and combining the first beat interference signals and the second beat interference signals according to the processing result to obtain target beat interference signals.

[0160] The light intensity calculation according to the Rayleigh backscattering light field and the reference light field is specifically:

[0161] ;

[0162] The light intensity calculation according to the first light field and the reference light field is specifically:

[0163] ;

[0164] The light intensity calculation according to the second light field and the reference light field is specifically:

[0165] ;

[0166] wherein, is the Rayleigh backscattering light intensity, is the propagation time of the sensing light in the sensing optical fiber for one round trip, is the length of the sensing optical fiber, is the propagation time, is the light frequency output by the light source, is the starting frequency of the sweep, is the beat frequency of the Rayleigh backscattering beat interference signals, is the sweep time, is the sweep speed, is the phase change caused by external disturbance, is the first light intensity, is the propagation time of the sensing light in the first time delay optical fiber, is the carrier frequency of the first beat interference signals, is the second light intensity, is the propagation time of the sensing light in the second time delay optical fiber.

[0167] The light field phase change includes a first light field phase change and a second light field phase change.

[0168] demodulating the target beat interference signal to obtain a light field phase change, specifically comprising:

[0169] signal constructing a first beat interference signal of the target beat interference signal to obtain a first analytic signal, and component calculating the first analytic signal to obtain a first I component and a first Q component;

[0170] signal constructing a second beat interference signal of the target beat interference signal to obtain a second analytic signal, and component calculating the second analytic signal to obtain a second I component and a second Q component;

[0171] obtaining a first light field phase change according to the first I component and the first Q component, and obtaining a second light field phase change according to the second I component and the second Q component.

[0172] wherein the signal constructing the first beat interference signal of the target beat interference signal specifically comprises:

[0173]

[0174] the signal constructing the second beat interference signal of the target beat interference signal specifically comprises:

[0175]

[0176] wherein, the first analytic signal, the first beat interference signal, the imaginary number expression, the Hilbert transform result of the first beat interference signal, the amplitude of the first analytic signal, the carrier frequency of the first beat interference signal, the sweep time, the first light field phase change, the second analytic signal, the second beat interference signal, the Hilbert transform result of the second beat interference signal, the amplitude of the second analytic signal, the carrier frequency of the second beat interference signal, the second light field phase change.

[0177] wherein the vibration positioning the sensing optical fiber according to the light field phase change to obtain an optical fiber vibration position, and obtaining a sensing detection result according to the optical fiber vibration position, specifically comprising: ​​

[0178] performing phase reconstruction on the first optical field phase change and the second optical field phase change to obtain a first phase and a second phase, and performing cross-correlation processing on the first phase and the second phase to obtain a second path propagation time;

[0179] performing vibration position detection according to the second path propagation time to obtain a fiber vibration position, and obtaining a sensing detection result according to the fiber vibration position;

[0180] The performing vibration position detection according to the second path propagation time is specifically:

[0181] ;

[0182] wherein, is a fiber vibration position, is a propagation time of sensing light in a sensing fiber for one round trip, is a second path propagation time, is a propagation time of sensing light in a second delay fiber, is a refractive index of a sensing fiber, is a light speed in vacuum.

[0183] The application further provides a computer readable storage medium, wherein the computer readable storage medium stores a forward transmission distributed fiber sensing detection program based on chirp modulation, and the forward transmission distributed fiber sensing detection program based on chirp modulation, when executed by a processor, implements the steps of the forward transmission distributed fiber sensing detection method based on chirp modulation.

[0184] In summary, the present application provides a forward transmission distributed optical fiber sensing detection method, system, terminal and storage medium based on chirp modulation, the method comprising: obtaining a sensing detection task of a sensing optical fiber, obtaining a single-frequency continuous optical signal and a radio frequency signal according to the sensing detection task, and chirp modulating the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals; superimposing all the modulated optical signals to obtain a swept optical field, dividing the swept optical field to obtain a sensing optical field and a reference optical field, and inputting the sensing light of the sensing optical field into the sensing optical fiber; receiving a target sensing optical field output by the sensing optical fiber, interfering the target sensing optical field with the reference optical field to obtain beat frequency interference light intensity, and filtering the beat frequency interference light intensity to obtain a target beat frequency interference signal; demodulating the target beat frequency interference signal to obtain an optical field phase change, positioning vibration of the sensing optical fiber according to the optical field phase change to obtain an optical fiber vibration position, and obtaining a sensing detection result according to the optical fiber vibration position. The present application not only reduces the detection cost, but also accurately locates the vibration on the sensing optical fiber, discovers the intrusion event in time, and thus guarantees the data transmission and data security on the sensing optical fiber.

[0185] It should be noted that in this document, the terms "comprising", "containing", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices that include a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or device that includes the element.

[0186] Of course, those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing relevant hardware (such as a processor, a controller, etc.) through a computer program, and the program can be stored in a computer-readable computer-readable storage medium, and the program can include the processes of the above-mentioned method embodiments when executed. The computer-readable storage medium can be a memory, a disk, an optical disk, etc.

[0187] It should be understood that the application of the present application is not limited to the above examples, and those skilled in the art can improve or modify the above description, all of which should be within the scope of the appended claims of the present application.

Claims

1. A method for distributed optical fiber sensing detection based on chirped modulation forward transmission, characterized in that, The chirp modulation-based forward transmission distributed optical fiber sensing detection method comprises: obtaining a sensing detection task of a sensing optical fiber, obtaining a single-frequency continuous optical signal and a radio frequency signal according to the sensing detection task, and chirp-modulating the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals; the radio frequency signal comprises a first chirp sweep signal and a second chirp sweep signal, and the modulated optical signal comprises a first I-path modulated optical signal, a second I-path modulated optical signal, a first Q-path modulated optical signal and a second Q-path modulated optical signal; the chirp-modulating the single-frequency continuous optical signal according to the radio frequency signal to obtain a plurality of modulated optical signals specifically comprises: phase-opposite modulating the single-frequency continuous optical signal and the first chirp sweep signal through a first I-path modulation channel to obtain a first I-path modulated optical signal; phase-opposite modulating the single-frequency continuous optical signal and the first chirp sweep signal through a second I-path modulation channel to obtain a second I-path modulated optical signal; modulating the single-frequency continuous optical signal and the second chirp sweep signal through a first Q-path modulation channel to obtain a first Q-path modulated optical signal; modulating the single-frequency continuous optical signal and the second chirp sweep signal through a second Q-path modulation channel to obtain a second Q-path modulated optical signal; superimposing all the modulated optical signals to obtain a sweep optical field, dividing the sweep optical field to obtain a sensing optical field and a reference optical field, and inputting sensing light of the sensing optical field into the sensing optical fiber; receiving a target sensing optical field output by the sensing optical fiber, interfering the target sensing optical field with the reference optical field to obtain beat interference light intensity, and filtering the beat interference light intensity to obtain a target beat interference signal; demodulating the target beat interference signal to obtain an optical field phase change, positioning vibration of the sensing optical fiber according to the optical field phase change to obtain an optical fiber vibration position, and obtaining a sensing detection result according to the optical fiber vibration position.

2. The method according to claim 1, wherein, The target sensing optical field comprises a Rayleigh backscattering optical field, a first optical field and a second optical field; the interfering the target sensing optical field with the reference optical field to obtain beat interference light intensity, and filtering the beat interference light intensity to obtain a target beat interference signal specifically comprises: calculating light intensity according to the Rayleigh backscattering optical field and the reference optical field to obtain Rayleigh backscattering light intensity; calculating light intensity according to the first optical field and the reference optical field to obtain first light intensity; calculating light intensity according to the second optical field and the reference optical field to obtain second light intensity; superimposing the Rayleigh backscattering light intensity, the first light intensity and the second light intensity to obtain beat interference light intensity, and setting a plurality of bandpass filters with different frequency passbands; extracting signals according to all the bandpass filter passbands to obtain Rayleigh backscattering beat interference signals, first beat interference signals and second beat interference signals; The Rayleigh backscattering beat frequency interference signal is filtered to obtain a processing result, and the first beat frequency interference signal and the second beat frequency interference signal are combined according to the processing result to obtain a target beat frequency interference signal.

3. The method according to claim 2, wherein, The light intensity calculation is performed according to the Rayleigh backscattering light field and the reference light field, and specifically includes: ； The light intensity calculation is performed according to the first light field and the reference light field, and specifically includes: ； The light intensity calculation is performed according to the second light field and the reference light field, and specifically includes: ； wherein, is the Rayleigh backscattered light intensity, is the propagation time of the sensing light for one round trip in the sensing fiber, is the sensing fiber length, is the propagation time, is the light frequency output by the light source, is the start frequency of the sweep, is the beat frequency of the Rayleigh backscattered beat interference signal, is the sweep time, is the sweep speed, is the phase change due to the external disturbance, is the first light intensity, is the propagation time of the sensing light in the first time delay fiber, is the carrier frequency of the first beat interference signal, is the second light intensity, is the propagation time of the sensing light in the second time delay fiber.

4. The method of claim 1, wherein the method is a chirped modulation based forward transmission distributed fiber sensing method. The light field phase change includes a first light field phase change and a second light field phase change; The demodulation processing of the target beat frequency interference signal includes: The first beat frequency interference signal of the target beat frequency interference signal is signal-constructed to obtain a first analytic signal, and component calculation is performed on the first analytic signal to obtain a first I component and a first Q component; The second beat frequency interference signal of the target beat frequency interference signal is signal-constructed to obtain a second analytic signal, and component calculation is performed on the second analytic signal to obtain a second I component and a second Q component; The first light field phase change is obtained according to the first I component and the first Q component, and the second light field phase change is obtained according to the second I component and the second Q component.

5. The method of claim 4, wherein the chirp-modulated forward transmission distributed fiber sensing method is characterized by, The signal construction of the first beat frequency interference signal of the target beat frequency interference signal specifically includes: ； The signal construction of the second beat frequency interference signal of the target beat frequency interference signal specifically includes: ； wherein is a first analytic signal, is a first beat signal, is an imaginary expression, is a Hilbert transform result of the first beat signal, is an amplitude of the first analytic signal, is a carrier frequency of the first beat signal, is a sweep time, is a first optical field phase change, is a second analytic signal, is a second beat signal, is a Hilbert transform result of the second beat signal, is an amplitude of the second analytic signal, is a carrier frequency of the second beat signal, is a second optical field phase change.

6. The method of claim 4, wherein the chirp-modulated forward transmission distributed fiber sensing method is characterized by, The vibration positioning of the sensing optical fiber according to the light field phase change includes: The phase reconstruction is performed on the first light field phase change and the second light field phase change to obtain a first phase and a second phase, and cross-correlation processing is performed on the first phase and the second phase to obtain a second path propagation time; The vibration position detection is performed according to the second path propagation time to obtain an optical fiber vibration position, and a sensing detection result is obtained according to the optical fiber vibration position; The vibration position detection according to the second path propagation time specifically includes: ； wherein, is the fiber vibration position, is the propagation time of the sensing light for one round trip in the sensing fiber, is the second path propagation time, is the propagation time of the sensing light in the second delay fiber, is the refractive index of the sensing fiber, is the speed of light in vacuum.

7. A chirp modulation based forward transmission distributed optical fiber sensing detection system, characterized in that, The forward transmission distributed optical fiber sensing detection system based on the chirp modulation is applied to the forward transmission distributed optical fiber sensing detection method based on the chirp modulation in any one of claims 1-6, and the forward transmission distributed optical fiber sensing detection system based on the chirp modulation includes: A signal modulation module is configured to obtain a sensing detection task of a sensing optical fiber, obtain a single-frequency continuous light signal and a radio frequency signal according to the sensing detection task, and perform chirp modulation on the single-frequency continuous light signal according to the radio frequency signal to obtain a plurality of modulated light signals. A light field division module is configured to superimpose all the modulated light signals to obtain a swept frequency light field, divide the swept frequency light field to obtain a sensing light field and a reference light field, and input sensing light of the sensing light field to the sensing optical fiber. The light field interference module is configured to receive a target sensing light field output by the sensing optical fiber, perform interference processing on the target sensing light field and the reference light field, obtain beat frequency interference light intensity, and perform filtering processing on the beat frequency interference light intensity to obtain a target beat frequency interference signal. The sensing and detection module is configured to perform demodulation processing on the target beat frequency interference signal to obtain a light field phase change, perform vibration positioning on the sensing optical fiber according to the light field phase change to obtain an optical fiber vibration position, and obtain a sensing and detection result according to the optical fiber vibration position.

8. A terminal, characterized in that: The terminal comprises a memory, a processor, and a program stored in the memory and executable on the processor, and the program, when executed by the processor, implements the steps of the forward transmission distributed optical fiber sensing and detection method based on the chirp modulation according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium has a computer program stored thereon, and the computer readable storage medium stores a forward transmission distributed optical fiber sensing and detection program based on the chirp modulation, and the forward transmission distributed optical fiber sensing and detection program based on the chirp modulation, when executed by the processor, implements the steps of the forward transmission distributed optical fiber sensing and detection method based on the chirp modulation according to any one of claims 1-6.

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