Sensing system and method of high-capacity partitioned random scattering point array

Abstract

The invention relates to the field of optical fiber sensing, and provides a sensing system and method for a high-capacity partition random scattering point array, and the system comprises an optical signal generation and modulation module, a circulator, a signal receiving and processing module, and a random scattering point partition array optical fiber. The circulator is respectively connected with the optical signal generating and modulating module, the signal receiving and processing module and the random scattering point partition array optical fiber, and the optical signal generating and modulating module is used for generating and modulating optical signals; the circulator is used for transmitting and distributing optical signals so as to guide the optical signals to the random scattering point partition array optical fiber; the signal receiving and processing module is used for receiving the optical signal returned by the circulator and converting the optical signal into an electric signal; the random scattering point partition array optical fiber is used for forming a chaotic spectrum through randomly distributed scattering points. According to the invention, high-efficiency transmission and processing of optical signals are realized, and the resolution and multiplexing capacity of a sensing system are improved, so that the high-capacity sensing requirement is met.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing, and in particular to a sensing system and method for a large-capacity partitioned random scattering point array. Background Art

[0002] Fiber optic sensor arrays can be divided into point sensor arrays and distributed sensor arrays according to different measurement methods. The two are suitable for different application scenarios due to their different advantages. The former is more suitable for precise measurement of physical parameters at key points of the measured object due to its higher spatial resolution and smaller physical sensing area, such as health monitoring of stress concentration points of composite material structures. Existing point sensors often use fiber Bragg gratings (FBG) as sensing units. Under the influence of the external environment, the characteristic wavelength of FBG will drift. By demodulating the wavelength change, the changes in the measured parameters in the external environment can be restored.

[0003] The FBG spectrum is directly obtained through the spectrum demodulation module, and then the cross-correlation calculation of the FBG spectrum is performed through the cross-correlation method to obtain the cross-correlation spectrum of the FBG spectrum, in which the left and right movement of the cross-correlation peak corresponds to the left and right drift of the spectrum, that is, the change of physical parameters such as external temperature or strain. The bandwidth of the cross-correlation peak determines the resolution ability of the wavelength demodulation method to demodulate the wavelength change. The narrower the bandwidth, the higher the resolution accuracy of the wavelength change.

[0004] As the requirements for sensing accuracy in sensing applications such as structural health monitoring continue to increase, how to improve spectral correlation and reduce the bandwidth of the cross-correlation peak of the sensing spectrum has become a difficult problem in the industry. Researchers often use weighted algorithms to improve spectral correlation, but the algorithm is highly complex and easily introduces noise, so the improvement effect is limited. Summary of the invention

[0005] In view of this, the present invention proposes a sensing system and method for a large-capacity partitioned random scattering point array, which solves the problem that the prior art improves spectral correlation through weighted algorithms, but has high complexity and is prone to introducing noise.

[0006] The technical solution of the present invention is implemented as follows: On the one hand, the present invention provides a sensing system of a large-capacity partitioned random scattering point array, the system comprising an optical signal generation and modulation module, a circulator, a signal receiving and processing module and a random scattering point partitioned array optical fiber, the circulator is respectively connected to the optical signal generation and modulation module, the signal receiving and processing module and the random scattering point partitioned array optical fiber, wherein:

[0007] The optical signal generation and modulation module is used to generate and modulate optical signals;

[0008] The circulator is used to transmit and distribute optical signals to guide the optical signals to the random scattering point partition array optical fiber;

[0009] The signal receiving and processing module is used to receive the optical signal returned by the circulator and convert the optical signal into an electrical signal;

[0010] The random scattering point partition array optical fiber is used to form a chaotic spectrum through randomly distributed scattering points.

[0011] On the basis of the above technical solution, preferably, the optical signal generation and modulation module includes a laser, a pulse modulation module and an optical amplification module, wherein:

[0012] The laser is connected to the pulse modulation module, and is used to generate a tunable laser signal and output a continuous frequency sweep light to the pulse frequency modulation module;

[0013] The pulse modulation module is connected to the optical amplification module and is used to modulate the continuous frequency sweeping light into a single wavelength pulse tube;

[0014] The optical amplification module is connected to the circulator and is used to amplify the optical signal.

[0015] On the basis of the above technical solution, preferably, the signal receiving and processing module includes a spectrum demodulation module and a host computer, wherein:

[0016] The spectrum demodulation module is connected to the host computer and the circulator respectively, and is used to convert the optical signal returned by the circulator into an electrical signal to reconstruct the spectrum signal of each partition of the random scattering point partition array;

[0017] The host computer is connected to the spectrum demodulation module and is used to receive the spectrum signal reconstructed by the spectrum demodulation module.

[0018] On the basis of the above technical solution, preferably, the random scattering point partition array optical fiber includes a plurality of random scattering point partitions, and the random scattering point partitions include a cladding, a core and a scattering enhancement point, wherein:

[0019] The cladding is located at the outermost layer of the random scattering point partitioned array optical fiber and is used to wrap the fiber core;

[0020] The fiber core is located at the geometric center of the random scattering point partition array optical fiber and is used to guide the propagation of the optical signal in the optical fiber;

[0021] The scattering enhancement points are formed inside the random scattering point partition array optical fiber by femtosecond laser processing, and are used to change the refractive index of the local fiber core, form reflection points of light, and generate chaotic spectrum.

[0022] On the basis of the above technical solution, preferably, the random scattering point partition also includes multiple random scattering points, and the number of the random scattering points is set to between 100 and 200 to control the partition scattering rate of the random scattering points within -40dB to -50dB, and the grating spacing is set to be greater than 1 meter.

[0023] On the basis of the above technical solution, preferably, the spacing between the random scattering points obeys random distribution, the initial phase difference when interference is formed between the random scattering points is completely random, and when multi-beam interference occurs between multiple random scattering points, the formed spectrum retains the ultra-wide spectrum properties of the scattering points, is no longer flat and has chaotic characteristics, so as to form a narrower cross-correlation peak.

[0024] On the basis of the above technical solution, preferably, the reflected light electric field intensity of the multiple scattering points is specifically:

[0025]

[0026] Where E0 is the incident optical field intensity, exp(·) is an exponential function, α is the attenuation loss constant when light propagates along the optical fiber, d is the distance between scattering points, and r is the maximum value of the scattering point. k (λ) is the reflection coefficient of the kth scattering point, is the phase of the reflected light of the kth scattering point, n is the number of scattering points, i and j are the real and imaginary parts in the imaginary unit, respectively;

[0027] When the reflection coefficients of each scattering point are the same, the calculation formula for the reflected light intensity of the scattering point partition is:

[0028]

[0029] Among them, I(λ) is the reflected light intensity of the scattering point partition, λ is the wavelength of the light wave, and r(λ) is the reflection coefficient of each scattering point.

[0030] On the other hand, the present invention also provides a sensing method for a large-capacity partitioned random scattering point array, comprising the following steps:

[0031] Using a spectrum acquisition system based on OTDR technology and wavelength scanning method, the reflection spectrum of each sensing partition in the large-capacity partition random scattering point array is obtained;

[0032] The reflection spectrum of each sensing partition is demodulated to obtain the sensing information of all sensing partitions.

[0033] On the basis of the above technical solution, preferably, the demodulation method of the sensing partition includes:

[0034] After obtaining the reflection spectrum of a certain partition, the reflection spectrum is evenly divided into several spectrum segments according to the wavelength according to the number of external parameters to be monitored. The number of spectrum segments is greater than the number of external parameters. The cross-correlation method is used to calculate the wavelength representative value of each spectrum segment, and the reflection spectrum of the certain partition at different times is obtained. The wavelength representative value of each spectrum segment at each time is calculated to obtain the wavelength change of each spectrum segment.

[0035] On the basis of the above technical solution, preferably, the wavelength variation of the several spectrum segments is solved by the least squares estimation method for the external parameter, and the calculation formula is:

[0036]

[0037] Among them, Δλ z K is the wavelength change calculated within the wavelength range of the zth spectral segment, zc is the influence coefficient of the cth external parameter on the spectrum within the zth spectral wavelength range, c is the number of types of external parameters, z is the number of segments of the reflection spectrum divided by wavelength, Δα c is the actual change of the cth external parameter.

[0038] The sensing system and method of a large-capacity partitioned random scattering point array of the present invention have the following beneficial effects compared with the prior art:

[0039] (1) The chaotic spectrum is formed by randomly scattering point partitioned array optical fiber, which realizes efficient transmission and processing of optical signals. The ultra-wideband characteristics of the chaotic spectrum are used to improve the resolution and multiplexing capacity of the sensing system, thereby meeting the needs of large-capacity sensing.

[0040] (2) A highly correlated ultra-wide chaotic spectrum is formed by partitioning a random scattering point array. Compared with the existing FBG, its cross-correlation spectrum has a narrower bandwidth and a higher peak value, which greatly improves the resolution of the perception of external environmental parameters. It has low complexity, high flexibility, and good repeatability. Combined with time division multiplexing technology, large-scale networking can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a schematic diagram of the structure of a sensing system of a large-capacity partitioned random scattering point array according to the present invention;

[0043] Figure 2 This is a schematic diagram of random scattering point partitioning of the present invention;

[0044] Figure 3 A schematic diagram of the reflectance spectrum of the random scattering point partitions of the present invention;

[0045] Figure 4 A schematic diagram of the reflection spectrum drift of the random scattering point partition of the present invention;

[0046] Figure 5 It is a schematic diagram of the partition spectrum of the scattering points with uniform spacing and random spacing of the present invention;

[0047] Figure 6 It is a schematic diagram of the cross-correlation spectrum of the scattering points with uniform spacing and random spacing of the present invention;

[0048] Figure 7 This is a flow chart of a sensing method for a large-capacity partitioned random scattering point array of the present invention;

[0049] Figure 8 This is a comparison diagram of the effects of the sensor demodulation system of the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] See also Figure 1 The present invention provides a sensing system of a large-capacity partitioned random scattering point array, the system comprising an optical signal generation and modulation module 1, a circulator 2, a signal receiving and processing module 3 and a random scattering point partitioned array optical fiber 4, the circulator 2 is respectively connected to the optical signal generation and modulation module 1, the signal receiving and processing module 3 and the random scattering point partitioned array optical fiber 4, wherein,

[0052] The optical signal generation and modulation module 1 is used to generate and modulate optical signals;

[0053] The circulator 2 is used to transmit and distribute optical signals to guide the optical signals to the random scattering point partition array optical fiber 4;

[0054] The signal receiving and processing module 3 is used to receive the optical signal returned by the circulator 2 and convert the optical signal into an electrical signal;

[0055] The random scattering point partition array optical fiber 4 is used to form a chaotic spectrum through randomly distributed scattering points.

[0056] The optical signal generation and modulation module 1 includes a laser 11, a pulse modulation module 12 and an optical amplification module 13, wherein:

[0057] The laser 11 is connected to the pulse modulation module 12, and is used to generate a tunable laser signal and output a continuous frequency-sweeping light to the pulse frequency modulation module 12;

[0058] The pulse modulation module 12 is connected to the optical amplification module 13 and is used to modulate the continuous frequency sweeping light into a single wavelength pulse tube;

[0059] The optical amplification module 13 is connected to the circulator 2 and is used to amplify the optical signal.

[0060] The signal receiving and processing module 3 includes a spectrum demodulation module 31 and a host computer 32, wherein:

[0061] The spectrum demodulation module 31 is connected to the host computer 32 and the circulator 2 respectively, and is used to convert the optical signal returned by the circulator 2 into an electrical signal to reconstruct the spectrum signal of each partition of the random scattering point partition array;

[0062] The host computer 32 is connected to the spectrum demodulation module 31 and is used to receive the spectrum signal reconstructed by the spectrum demodulation module 31 .

[0063] The random scattering point partition array optical fiber 4 includes a plurality of random scattering point partitions, and a schematic diagram of a single random scattering point partition is shown in FIG. Figure 2 As shown, it includes a cladding 41, a core 42 and a scattering enhancement point 43, wherein d i is the distance between the i-th random scattering point and the i+1-th random scattering point in the random scattering point partition.

[0064] The cladding 41 is located at the outermost layer of the random scattering point partition array optical fiber 4 and is used to wrap the fiber core 42;

[0065] The fiber core 42 is located at the geometric center of the random scattering point partition array optical fiber 4 and is used to guide the optical signal to propagate in the optical fiber;

[0066] The scattering enhancement points 43 are formed inside the random scattering point partition array optical fiber 4 by femtosecond laser processing, and are used to change the refractive index of the local fiber core, form reflection points of light, and generate chaotic spectrum.

[0067] It should be noted that the optical signal output end of the laser 11 is connected to the optical signal input end of the pulse modulation module 12, the optical signal output end of the pulse modulation module 12 is connected to the optical signal input end of the optical amplifier module 13, the optical signal output end of the optical amplifier module 13 is connected to the first port of the circulator 2, the second port of the circulator 2 is connected to the random scattering point partition array optical fiber 4, the third port of the circulator 2 is connected to the optical signal input end of the spectral demodulation module 31, and the electrical signal output end of the spectral demodulation module 31 is connected to the host computer 32.

[0068] The random scattering point partition further includes a plurality of random scattering points, the number of which is set to be between 100 and 200, so as to control the partition scattering rate of the random scattering points within -40 dB to -50 dB, and the grating spacing is set to be greater than 1 meter. The partition length is usually at the centimeter level.

[0069] The spacing between the random scattering points obeys random distribution, and the initial phase difference when interference is formed between the random scattering points is completely random. When multi-beam interference occurs between multiple random scattering points, the formed spectrum retains the ultra-wide spectrum properties of the scattering points, is no longer flat and has chaotic characteristics, so as to form a narrower cross-correlation peak.

[0070] The reflected light electric field intensity of the multiple scattering points is specifically:

[0071]

[0072] Where E0 is the incident optical field intensity, exp(·) is an exponential function, α is the attenuation loss constant when light propagates along the optical fiber, d is the distance between scattering points, and r is the maximum value of the scattering point. k (λ) is the reflection coefficient of the kth scattering point, is the phase of the reflected light of the kth scattering point, n is the number of scattering points, i and j are the real and imaginary parts in the imaginary unit, respectively;

[0073] Assuming that the reflection coefficient of each scattering point is the same, the calculation formula for the reflected light intensity of the scattering point partition is:

[0074]

[0075] Among them, I(λ) is the reflected light intensity of the scattering point partition, λ is the wavelength of the light wave, and r(λ) is the reflection coefficient of each scattering point.

[0076] When the distance d between scattering points is uniform and constant, the phase difference of the reflected light from adjacent scattering points is The overall reflected light intensity I(λ) of the partition has obvious periodicity with respect to λ, which leads to a wide bandwidth of the cross-correlation peak and low sensing accuracy. When the spacing d between scattering points is no longer uniform but obeys random distribution, the phase difference of the reflected light from adjacent scattering points Therefore, the overall reflected light intensity I(λ) of the partition has the random statistical characteristics of a chaotic signal, which makes the spectrum have a narrower cross-correlation peak bandwidth and achieves higher sensing accuracy.

[0077] It should be noted that the scattering point coordinates x within the partition are used as random variables X, and the random distributions that can be obeyed include but are not limited to normal distribution, uniform distribution, binomial distribution, Bernoulli distribution, etc.

[0078] The present invention also provides a method for preparing a large-capacity partitioned random scattering point array, which uses femtosecond laser processing technology to write multiple scattering points in a section of optical fiber partition, and uses the mixed interference spectrum formed by multiple scattering points for sensing. By controlling the random spacing of the scattering points, the reflection path of the light between the scattering points is disrupted to form an ultra-wide chaotic spectrum with non-periodic interference fringes. Based on the statistical characteristics of the chaotic signal, the ultra-wide chaotic spectrum has better cross-correlation, thereby forming a narrower cross-correlation peak and improving the sensing resolution accuracy of the spectrum; by controlling the random number of scattering points in different optical fiber partitions, the mutual difference between optical fiber partitions is improved, thereby reducing the transmission loss of optical signals of different wavelengths in the scattering point array and improving the multiplexing capacity of the sensing array. The following steps are included:

[0079] Step 1: Set the partition length l and partition spacing L equal to the actual required length of the measured object and the distance between the measured objects. Set the number of partitions m equal to the number of measured objects. The number of random scattering points n contained in each partition is a random positive integer within a~b.

[0080] Step 2: Generate the coordinate values ​​of n scattering points in the ith partition. Generate a random number sequence with a length of n-2 and a value between 0 and l through the host computer, and add the sequence elements 0 and l as endpoints at the beginning and end, respectively, to form a coordinate array X with a length of n. i :

[0081] X i =(0 x1 x2 ...x i ...x n-2 l) (1)

[0082] Then X i Each element in is the physical position coordinate of each scattering point.

[0083] Step 3: Set the partition length l, partition spacing L, number of partitions m, and the coordinate array X of the scattering points in each partition i Upload to the femtosecond laser processing platform.

[0084] Step 4: Install the fiber optic reel with sufficient length of optical fiber to be processed on the fiber output shaft of the femtosecond laser processing platform, extract a certain length of optical fiber, wind it onto the fiber optic reel installed on the fiber input shaft of the femtosecond laser processing platform, and use a certain point of this section of optical fiber as the starting position of the array and fix it in the femtosecond laser processing area.

[0085] The single scattering point preparation method is as follows: the femtosecond laser is focused on the core of the optical fiber in the writing area through a programmable shutter. When the program-controlled shutter is opened, the femtosecond laser ionizes the core material at the focus point, thereby changing the refractive index of the core and forming a single scattering point. Then, the electric displacement platform drives the optical fiber to move the next scattering point to the femtosecond laser processing area.

[0086] The preparation method of a single partition is as follows: obtain the length l of the ith optical fiber partition, the number n of scattering points, and the scattering point coordinate array X i . From the coordinate array X i The coordinates of each scattering point are obtained in turn. The preparation of all scattering points in the optical fiber partition is achieved by controlling the electric displacement platform and the femtosecond laser shutter.

[0087] Step 5: Obtain the number of partitions m, the partition spacing L, and the coordinate array X of each partition of the sensor array i . The preparation of the entire sensor array is achieved by using a single partition preparation method.

[0088] In a specific embodiment, according to the preparation method of a large-capacity partitioned random scattering point array and the health monitoring scenario requirements of stress concentration points of composite materials, the partition spacing L is set to 2m, the partition length l is set to 10mm, the number of partitions is set to 100, and the random value range a~b of the number of random scattering points n is set to 100~200.

[0089] Step 1: Generate a random sequence array [154163127…159187193] with 100 elements and a value range of 100 to 200. The value of each element in the array is the number of random scattering points in each partition.

[0090] Step 2: Taking the first partition containing 154 scattering points as an example, calculate the physical location coordinates of each scattering point:

[0091] Since the partition length is 10 mm, the physical position takes values ​​between 0 and 10. Use the rand function of MATLAB to generate a random number sequence with a length of 152 and values ​​between 0 and 10 that conforms to the uniform distribution, and add the sequence elements 0 and 10 mm as endpoints at the beginning and end, respectively, to form a coordinate array X1 (00.09320.5917...9.16389.701610) with a length of 154.

[0092] Similarly, the random coordinate array X2 of the coordinate values ​​of the 163 scattering points in the second partition including the 163 scattering points is (00.01520.2826 . . . 9.25349.865810), and the subsequent partition coordinate arrays are not described one by one in this embodiment.

[0093] Step 3: Set the partition length l = 10 mm, partition spacing L = 2 m, number of partitions m = 100, and the coordinate array X of the scattering points in each partition i Upload to the femtosecond laser processing platform.

[0094] Step 4: Install the fiber optic reel with 1000m of optical fiber onto the fiber output shaft of the femtosecond laser processing platform, extract 10m of optical fiber, wind it onto the fiber optic reel installed on the fiber input shaft of the femtosecond laser processing platform, and use the fiber position at the edge of the femtosecond laser processing area as the starting position of the first partition and fix it in the femtosecond laser processing area.

[0095] Single scattering point preparation method: The femtosecond laser is focused on the core of the optical fiber in the writing area through a programmable shutter. When the program-controlled shutter is opened, the femtosecond laser ionizes the core material at the focus point, thereby changing the refractive index of the core and forming a single scattering point. The electric displacement platform then drives the optical fiber to move the next scattering point to the femtosecond laser processing area.

[0096] Preparation method of the first partition: The femtosecond laser processing platform obtains the length of the first optical fiber partition 10mm, the number of scattering points 154 and the scattering point coordinate array X1. The coordinate value of each scattering point is obtained from the coordinate array X1 in turn. By controlling the electric displacement platform and the femtosecond laser shutter, the preparation of all scattering points in the optical fiber partition is realized.

[0097] In this embodiment, the reflectance spectrum of a single random scattering point partition prepared according to the method of the present invention is as follows: Figure 3 As shown, there is no characteristic wavelength similar to that of FBG and an ultra-wide chaotic spectrum with high correlation.

[0098] In this embodiment, the reflection spectrum drift of a single random scattering point partition prepared according to the method of the present invention is as follows: Figure 4 As shown, its overall spectrum is sensitive to external environmental parameters and can produce an overall spectrum drift with a sensitivity coefficient of about 10pm / ℃ or 1pm / με.

[0099] In this embodiment, the partition spectra with uniform and random scattering point spacing prepared by the method of the present invention are respectively as follows: Figure 5 (a) and Figure 5 As shown in (b), the cross-correlation spectra are Figure 6 (a) and Figure 6As shown in (b) in the figure, it can be seen that the random spacing d between scattering points makes the spectrum more chaotic, the cross-correlation peak narrower, and the sensing accuracy higher.

[0100] See also Figure 7 The present invention also provides a sensing method for a large-capacity partitioned random scattering point array, comprising the following steps:

[0101] Using a spectrum acquisition system based on OTDR technology and wavelength scanning method, the reflection spectrum of each sensing partition in the large-capacity partition random scattering point array is obtained;

[0102] The reflection spectrum of each sensing partition is demodulated to obtain the sensing information of all sensing partitions.

[0103] The demodulation method of the sensing partition includes:

[0104] After obtaining the reflection spectrum of a certain partition, the reflection spectrum is evenly divided into several spectrum segments according to the wavelength according to the number of external parameters to be monitored. The number of spectrum segments is greater than the number of external parameters. The cross-correlation method is used to calculate the peak value position of the cross-correlation peak of each spectrum segment, that is, the wavelength representative value of the spectrum segment. The reflection spectrum of the certain partition at different times is obtained, the wavelength representative value of each spectrum segment at each time is calculated, and the wavelength change of each spectrum segment is obtained.

[0105] Since the sensitivity coefficients of light in different wavelength regions to external parameters are different, the wavelength change of the z-segment spectrum can be used to solve the c parameters through the least squares estimation method:

[0106] The wavelength variation of the several spectrum segments is solved by the least squares estimation method to obtain the external parameters, and the calculation formula is:

[0107]

[0108] Among them, Δλ z K is the wavelength change calculated within the wavelength range of the zth spectral segment, zc is the influence coefficient of the cth external parameter on the spectrum within the zth spectral wavelength range, c is the number of types of external parameters, z is the number of segments of the reflection spectrum divided by wavelength, Δα c is the actual change of the cth external parameter.

[0109] In a specific embodiment, the laser 11 is a TSL-770 tunable laser with a wavelength range of 1480nm to 1640nm and a bandwidth of 160nm. The tunable laser outputs continuous frequency sweep light to the pulse modulation module 12 at a sweep speed of 200nm / s.

[0110] The pulse modulation module 12 uses a semiconductor optical amplifier with a minimum modulation pulse width of 10 ns, and continuously modulates the continuous frequency sweeping light into a single wavelength pulse light with a pulse width of 10 ns and inputs it into the optical amplification module 13 .

[0111] The optical amplifier module 13 uses an erbium-doped fiber amplifier with a gain greater than or equal to 35 dB.

[0112] The circulator 2 is a conventional optical circulator for laboratory use, and the optical loss is less than 1 dB. After passing through the random scattering point partition, the light returns to the circulator 2 with the wavelength information and enters the spectrum demodulation module 31 .

[0113] The spectrum demodulation module 31 adopts a PDB450C photoelectric detector, which can detect wavelengths in the range of 1200nm to 1700nm. The photoelectric detector converts light intensity signals into voltage signals and inputs them into a high-speed data acquisition card and a field programmable gate array.

[0114] The field programmable gate array matches the wavelength information and light intensity information carried by each pulse beam one by one, so as to reconstruct the spectrum information of each partition of the random scattering point partition array and input it into the host computer 32 for cross-correlation calculation.

[0115] In order to monitor the external temperature and strain at the same time, the spectrum is divided into two parts according to the wavelength: 1480nm~1560nm and 1560nm~1640nm during the cross-correlation calculation. The cross-correlation peak drift of the two spectrum segments is calculated respectively. Finally, the external temperature and strain information can be restored by combining the temperature and strain influence coefficients of the random scattering point partitions.

[0116] In this embodiment, after cross-correlation calculations were performed on the FBG and random scattering point partition spectra at 6 different temperatures, the following results were obtained: Figure 8 The sensor demodulation system effect comparison chart shown in the figure, Figure 8 (a) and Figure 8 (b) in the figure shows the cross-correlation spectra of FBG and the cross-correlation spectra of random scattering point partitions at 6 different temperatures. The FBG has a similar overall spectral drift, but the half-maximum full width Δv of the cross-correlation spectra of random scattering point partitions is only about one tenth of that of the FBG.

[0117] In this embodiment, the sensing system implements time division multiplexing of scattering point partitions through the pulse modulation module 12 to realize a point sensing system with large-scale networking.

[0118] In this embodiment, the output optical pulse width τ of the pulse modulation module 12 is less than 2n eff In the case of L / c, the spatial resolution of the sensing system is determined by the partition spacing L of the scattering point partition array optical fiber 4. effis the effective refractive index of the fiber core, and c is the speed of light in a vacuum. In this embodiment, the focus of the present invention is the introduction of a random scattering point partition array, which achieves a qualitative change in the sensing system. The partition length and partition spacing of the random scattering point partition array can also be randomly distributed to obtain higher sensing performance and adapt to different application scenarios, which will not be repeated here.

[0119] like Figure 1 The sensor demodulation system shown is only a common implementation form of the sensor demodulation system based on random scattering point partitioning of the present invention. The sensor demodulation system can also be replaced by other achievable structural forms.

[0120] Compared with the existing FBG, the partitioned random scattering point array proposed in the present invention does not have a specific wavelength, has a highly correlated ultra-wide chaotic spectrum, and its cross-correlation spectrum has a narrower bandwidth and a higher peak value, which can greatly improve the perception resolution of external environmental parameters. At the same time, the random scattering point partitioning preparation method proposed in the present invention has low complexity, high flexibility, and good repeatability, and can realize large-scale networking based on time division multiplexing technology.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A sensing system of a large-capacity partitioned random scattering point array, characterized in that: The system comprises an optical signal generation and modulation module (1), a circulator (2), a signal receiving and processing module (3) and a random scattering point partition array optical fiber (4), wherein the circulator (2) is respectively connected to the optical signal generation and modulation module (1), the signal receiving and processing module (3) and the random scattering point partition array optical fiber (4), wherein: The optical signal generation and modulation module (1) is used to generate and modulate an optical signal; The circulator (2) is used to transmit and distribute optical signals so as to guide the optical signals to the random scattering point partition array optical fiber (4); The signal receiving and processing module (3) is used to receive the optical signal returned by the circulator (2) and convert the optical signal into an electrical signal; The random scattering point partition array optical fiber (4) is used to form a chaotic spectrum through randomly distributed scattering points.

2. A sensing system of a large-capacity partitioned random scattering point array as claimed in claim 1, characterized in that: The optical signal generation and modulation module (1) comprises a laser (11), a pulse modulation module (12) and an optical amplification module (13), wherein: The laser (11) is connected to the pulse modulation module (12) and is used to generate a tunable laser signal and output a continuous frequency-sweeping light to the pulse frequency modulation module (12); The pulse modulation module (12) is connected to the optical amplification module (13) and is used to modulate the continuous frequency sweeping light into a single wavelength pulse tube; The optical amplification module (13) is connected to the circulator (2) and is used to amplify the optical signal.

3. A sensing system of a large-capacity partitioned random scattering point array as claimed in claim 2, characterized in that: The signal receiving and processing module (3) comprises a spectrum demodulation module (31) and a host computer (32), wherein: The spectrum demodulation module (31) is connected to the host computer (32) and the circulator (2) respectively, and is used to convert the optical signal returned by the circulator (2) into an electrical signal, so as to reconstruct the spectrum signal of each partition of the random scattering point partition array; The host computer (32) is connected to the spectrum demodulation module (31) and is used to receive the spectrum signal reconstructed by the spectrum demodulation module (31).

4. A sensing system of a large-capacity partitioned random scattering point array as claimed in claim 1, characterized in that: The random scattering point partition array optical fiber (4) comprises a plurality of random scattering point partitions, wherein the random scattering point partitions comprise a cladding (41), a core (42) and a scattering enhancement point (43), wherein: The cladding (41) is located at the outermost layer of the random scattering point partitioned array optical fiber (4) and is used to wrap the fiber core (42); The fiber core (42) is located at the geometric center of the random scattering point partition array optical fiber (4) and is used to guide the propagation of the optical signal in the optical fiber; The scattering enhancement points (43) are formed inside the random scattering point partition array optical fiber (4) by femtosecond laser processing, and are used to change the refractive index of the local fiber core, form light reflection points, and generate chaotic spectrum.

5. A sensing system of a large-capacity partitioned random scattering point array as claimed in claim 4, characterized in that: The random scattering point partition also includes multiple random scattering points, and the number of the random scattering points is set to be within 100 to 200 to control the partition scattering rate of the random scattering points within -40dB to -50dB, and the grating spacing is set to be greater than 1 meter.

6. A sensing system of a large-capacity partitioned random scattering point array as claimed in claim 5, characterized in that: The spacing between the random scattering points obeys random distribution, and the initial phase difference when interference is formed between the random scattering points is completely random. When multi-beam interference occurs between multiple random scattering points, the formed spectrum retains the ultra-wide spectrum properties of the scattering points, is no longer flat and has chaotic characteristics, so as to form a narrower cross-correlation peak.

7. A sensing system of a large-capacity partitioned random scattering point array as claimed in claim 6, characterized in that: The reflected light electric field intensity of the multiple scattering points is specifically: Where E0 is the incident optical field intensity, exp(·) is an exponential function, α is the attenuation loss constant when light propagates along the optical fiber, d is the distance between scattering points, and r is the maximum value of the scattering point. k (λ) is the reflection coefficient of the kth scattering point, is the phase of the reflected light of the kth scattering point, n is the number of scattering points, i and j are the real and imaginary parts in the imaginary unit, respectively; When the reflection coefficients of each scattering point are the same, the calculation formula for the reflected light intensity of the scattering point partition is: Among them, I(λ) is the reflected light intensity of the scattering point partition, λ is the wavelength of the light wave, and r(λ) is the reflection coefficient of each scattering point.

8. A sensing method for a large-capacity partitioned random scattered point array, applied to a sensing system for a large-capacity partitioned random scattered point array as claimed in claims 1-7, characterized in that: The following steps are involved: Using a spectrum acquisition system based on OTDR technology and wavelength scanning method, the reflection spectrum of each sensing partition in the large-capacity partition random scattering point array is obtained; The reflection spectrum of each sensing partition is demodulated to obtain the sensing information of all sensing partitions.

9. A sensing method for a large-capacity partitioned random scattering point array as claimed in claim 8, characterized in that: The demodulation method of the sensing partition includes: After obtaining the reflection spectrum of a certain partition, the reflection spectrum is evenly divided into several spectrum segments according to the wavelength according to the number of external parameters to be monitored. The number of spectrum segments is greater than the number of external parameters. The cross-correlation method is used to calculate the wavelength representative value of each spectrum segment, and the reflection spectrum of the certain partition at different times is obtained. The wavelength representative value of each spectrum segment at each time is calculated to obtain the wavelength change of each spectrum segment.

10. A sensing method for a large-capacity partitioned random scattering point array as claimed in claim 9, characterized in that: The wavelength variation of the several spectrum segments is solved by the least squares estimation method to obtain the external parameters, and the calculation formula is: Among them, Δλ z K is the wavelength change calculated within the wavelength range of the zth spectral segment, zc is the influence coefficient of the cth external parameter on the spectrum within the zth spectral wavelength range, c is the number of types of external parameters, z is the number of segments of the reflection spectrum divided by wavelength, Δα c is the actual change of the cth external parameter.

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