Wavelength assignment method for optical fiber sensing spectrum detection module based on scanning light source

Abstract

The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source disclosed in the present invention belongs to the field of optical fiber sensing. The optical fiber sensing spectrum detection module is an optical fiber sensing spectrum detection module based on diffraction grating spectrometry and array detector. The present invention outputs a narrowband wavelength covering the entire C+L working band of the assigned spectrum detection module in a scanning manner, and utilizes the characteristic that the output wavelength interval of the high-precision scanning light source is much higher than the sampling rate of the spectrum detection module to form a series of center wavelength positioning arrays for each pixel, and then uses the zero-crossing point of the linear fitting function to locate the center wavelength, which is used to assign wavelengths to the pixels of the optical fiber sensing spectrum detection module based on diffraction grating spectrometry and array detector. The present invention can solve the problem of a small number of standard light sources in the working band, and can improve the problem of spectral profile broadening caused by pixel width leading to peak position blur, thereby improving the assignment accuracy of the full band range.

Description

Technical Field

[0001] The present invention relates to a high-precision wavelength assignment method based on a scanning light source, which is used for performing high-precision wavelength assignment on pixels and corresponding wavelengths of an optical fiber sensing spectrum detection module based on diffraction grating spectrometry and array detectors operating in the C+L band (about 1510nm-1625nm), and belongs to the field of optical fiber sensing. Background Art

[0002] In recent years, with the widespread application of fiber optic sensing technology in more and more fields, the performance requirements for fiber optic sensor demodulation instruments have become increasingly higher. Among them, fiber optic sensor demodulation instruments based on diffraction grating spectrometers and array detectors have the advantages of high stability and good environmental adaptability because they have no moving parts inside, and have important application prospects in cutting-edge fields such as aerospace.

[0003] The basic principle of the fiber optic sensor demodulation instrument based on diffraction grating spectrometry and array detector is to combine the diffraction grating 3 and the near-infrared array detector (CCD) 5 through an auxiliary optical lens (usually including a collimating lens 2 and an imaging lens 4) to form a spectral detection module with a fixed optical path structure. Figure 1 As shown, the optical signal containing different wavelengths reflected by the optical fiber sensor is incident on the collimating lens through the optical fiber 1. The optical signal after spatial expansion is imaged on the CCD by utilizing the spectral characteristics of the diffraction grating. The pixel of the CCD converts the light intensity of the optical signal into an electrical signal output to form the spectral line data of the optical signal. Figure 2 This is a typical spectrum diagram of the optical signal of the fiber Bragg grating imaged on the CCD. The distribution of the optical signal received by the CCD in the wavelength domain is shown in curve 6. After the photoelectric conversion is completed by the CCD, discrete voltage signals of varying sizes are formed 7. These voltage signals are then converted into intensity signals by the computer to form a series of discrete data points 8. It can be seen that there is a one-to-one correspondence between the CCD pixels on the spectrum detection module and the input light wavelength. Therefore, the accurate assignment of the correspondence between the pixel and the wavelength is a prerequisite for the demodulation instrument based on this principle to accurately demodulate the wavelength. The impact of the assignment accuracy is a key factor in the wavelength demodulation accuracy of the demodulation instrument.

[0004] The general idea of ​​wavelength assignment is to use multiple narrowband light sources with known wavelengths as standard sources, input them into the spectrum acquisition module, obtain a series of pixel positions corresponding to the central wavelength of the spectrum, and then use data processing methods such as polynomial fitting to obtain the functional relationship between the array detector pixel and the wavelength, so as to obtain the wavelength value corresponding to each pixel. Therefore, the main factors affecting the accuracy of assignment include the number of standard light sources used in the assignment and the accuracy of obtaining the pixel position corresponding to the input standard light source.

[0005] Influencing factors 1) The number of standard light sources used in the assignment: Within the working band of the spectrum acquisition module, the more standard light sources involved in the assignment, the more corresponding relationships between wavelengths and pixels are obtained, and the more accurate the functional relationship between pixels and wavelengths after fitting. Common standard light sources include gas light sources, broadband light sources combined with gas absorption cells, etc. However, for the fiber optic sensing spectrum detection module working in the C+L band, the number of available gas light sources is scarce. For example, the mercury lamp (Hg) has a spectrum line with a wavelength of 1529.6nm, and the xenon (Xe) lamp has a spectrum line of 1541.8nm. Obviously, even if used in combination, the scarce number of assignment points cannot meet the assignment requirements well. Gases with obvious absorption peaks in the C+L band include acetylene, hydrogen cyanide, etc. Although the gas absorption cell has a large number of absorption peaks in the C+L band, the energy difference between the absorption peaks is large. In practical applications, only a few relatively obvious absorption peaks can be selected for assignment, which has limited effect on improving the accuracy of assignment. For example, invention patent CN103557879B "Fiber Bragg Grating Sensing Wavelength Calibration Device Based on Cavity Absorption" uses a broadband light source in combination with a gas absorption cell to produce a standard light source, and only uses the two more obvious absorption peaks of the gas absorption cell in the near-infrared region as the assigned spectral lines.

[0006] Influencing factor 2) The accuracy of obtaining the pixel position corresponding to the input standard light source: Since the pixels of the array detector have a certain width, the existence of this width leads to problems such as spectral profile broadening and peak position blurring when the spectral curve is subsequently reproduced, which affects the positioning of the pixel center wavelength. Taking a 1024-pixel array detector as an example, if its operating wavelength range is 40nm, the average wavelength width occupied by each pixel is about 40pm, so theoretically a group of wavelengths within the range of 40pm can be roughly considered to be the center wavelength value corresponding to the same pixel. Figure 3 As shown, for pixel ②, Figure 3 The three input wavelengths can all be considered as the central wavelength of pixel ②, but in fact, only the wavelength value whose wavelength peak point completely coincides with the center of pixel ② is the true central wavelength of pixel ②, such as Figure 3As shown by the curve in the center. Invention patent CN105424185B "A computer-aided wavelength calibration method for a full-band spectrometer" uses a combined light source to assign wavelengths to the spectrometer. After acquiring a certain amount of spectral data within the wavelength range of the spectrometer, it uses a computer-aided method to acquire and process the spectrum. It uses the Ford function to fit the data of each spectral line to reconstruct the spectral line profile and determine the pixel position corresponding to the recurring peak. However, when this processing method is applied to the assignment of the spectrum acquisition module of the C+L band, it cannot improve the problem of the relatively scarce standard spectral lines in this band, and the improvement in the assignment accuracy is limited. Invention patent 200710177242.8 "A wavelength calibration method for a spectral instrument" also noticed the influence of pixel width on the assignment accuracy, and proposed to improve the sampling rate by moving the array detector or rotating the grating to form changes in the optical path, and perform sub-pixel reconstruction. This method has no application value for the spectral detection module that must form a stable optical path structure.

[0007] Therefore, in order to improve the wavelength assignment accuracy of the optical fiber sensing spectrum detection module working in the C+L band, improvements should be made in two aspects: the number of standard light sources and the pixel position positioning, so as to improve the wavelength demodulation accuracy of the demodulation instrument based on this principle. Summary of the invention

[0008] In view of the problems existing in the existing wavelength assignment methods, such as the scarcity of standard light sources and the difficulty in locating the peak pixel position, the main purpose of the present invention is to provide a wavelength assignment method for a fiber optic sensing spectrum detection module based on a scanning light source, which can provide a high-precision wavelength assignment method over the entire band range for the fiber optic sensing spectrum detection module based on diffraction grating spectrometry and array detector working in the C+L band, thereby improving the wavelength demodulation accuracy of the demodulation instrument based on this principle.

[0009] The objective of the present invention is achieved through the following technical solutions:

[0010] The present invention discloses a wavelength assignment method for a fiber optic sensing spectrum detection module based on a scanning light source. The fiber optic sensing spectrum detection module is a fiber optic sensing spectrum detection module based on diffraction grating spectrometry and array detector, which is used to realize C+L band spectrum detection of a fiber optic sensing demodulator. The fiber optic sensing spectrum detection module is mainly composed of a diffraction grating, an array detector CCD and an auxiliary optical lens. The light signals containing different wavelengths reflected by the fiber optic sensor are expanded in space by using the spectroscopic characteristics of the diffraction grating, and then imaged on the CCD for spectrum detection. The wavelength assignment method for a fiber optic sensing spectrum detection module based on a scanning light source disclosed by the present invention includes the following steps:

[0011] Step 101: Connect the optical equipment and data processing control module required for wavelength assignment.

[0012] The optical devices to be connected in step 101 include a high-precision scanning light source, an optical attenuator, and a spectrum detection module to be assigned. The high-precision scanning light source is connected to the spectrum detection module to be assigned through the optical attenuator, and the data processing control module is connected to the high-precision scanning light source and the spectrum detection module through control lines. The high-precision scanning light source is used to output the spectrum required for the assignment, and its wavelength range should cover the wavelength range of the spectrum detection module to be assigned, and has a spectrum scanning function synchronously controlled by the data processing control module; the data processing control module is used to control the spectrum output of the high-precision scanning light source, and at the same time control the spectrum detection module to be assigned to perform signal acquisition and processing.

[0013] Step 102: Perform value assignment initialization, including output light energy setting, effective pixel range setting, wavelength range setting and spectrum scanning step length setting.

[0014] The output light energy setting described in step 102 refers to adjusting the output light energy of the high-precision scanning light source and the attenuation of the light attenuator to ensure that the output light energy does not exceed the light intensity detection upper limit of the CCD of the spectrum detection module to be assigned;

[0015] The effective pixel range setting and wavelength range setting in step 102 refer to adjusting the output light of the high-precision scanning light source and recording the minimum pixel P that can be effectively detected. min and the maximum pixel P max , and record the wavelength values ​​λ corresponding to the two pixels min and λ max ; then the minimum valid pixel P1 to be assigned is defined as P1 = P min -1, the maximum valid pixel P to be assigned N Set as P N =P max +1; the minimum assigned wavelength is set to λ 1c =λ min -(λ max -λ min ) / N, the maximum assigned wavelength is set to λ Nc =λ max +(λ max -λ min ) / N;

[0016] The spectrum scanning step length setting in step 102 refers to setting the spectrum scanning step length to the minimum adjustable wavelength Δλ of the high-precision scanning light source.

[0017] Step 103: Control the high-precision scanning light source to output different wavelengths covering the wavelength range of the spectrum detection module to be assigned through the data processing control module, and at the same time record the spectrum measured by the spectrum detection module to be assigned through the data processing control module to obtain "pixel position-energy" data.

[0018] In step 103, the output wavelength of the high-precision scanning light source is controlled to be λ by the data processing control module. 1c At the same time, the data processing control module saves the spectrum measured by the spectrum detection module to be assigned at this time, recorded as λ 1c The corresponding "pixel position-energy" data set (n, I n ); With Δλ as the step, the data processing control module controls the output wavelength of the high-precision scanning light source to λ 1c +Δλ, while the computer software saves λ 1c +Δλ corresponding to the "pixel position-energy" data set (n, I n ); and so on, until the output wavelength of the high-precision scanning light source is λ Nc , and record the "pixel position-energy" data group at this time, and thus complete the acquisition of all "pixel position-energy" data;

[0019] Step 104: The “pixel position-energy” data acquired in step 103 is sequentially subjected to data extraction and preprocessing, data grouping, and pixel center wavelength positioning, and finally a “pixel-center wavelength” data group is formed.

[0020] The data extraction and preprocessing described in step 104 are as follows: for all stored data groups (n, I n ), extract the wavelength value corresponding to the array, the pixel n corresponding to the maximum energy value, and the difference in energy values ​​between the two pixels on both sides of pixel n ΔI=I n-1 -I n+1 , arranged in ascending order of wavelength value into a new “wavelength-pixel position-energy difference” data set (λ, n, ΔI);

[0021] The data grouping in step 104 is as follows: grouping the data with the same maximum energy value corresponding to the same pixel n into one group, and still arranging them in the order of wavelength value from small to large, and the group of data (λ, ΔI) is the positioning array of the central wavelength of the positioning pixel n;

[0022] The pixel center wavelength positioning described in step 104 is as follows: the positioning array (λ, ΔI) of pixel n is linearly fitted with λ as the horizontal coordinate and ΔI as the vertical coordinate, and the wavelength value closest to the zero crossing point of the linear fitting function is the center wavelength λ of pixel n. n ; By analogy, the central wavelengths of all pixels to be assigned can be located one by one to form a "pixel-central wavelength" data set (n, λ n ); This data group is the wavelength assignment result of the spectrum detection module to be assigned.

[0023] The wavelength assignment method of the optical fiber sensing spectrum detection module based on the scanning light source disclosed in the present invention also includes step 105: directly applying the wavelength assignment result obtained in step 104 to perform high-precision wavelength demodulation of the optical fiber Bragg grating sensor.

[0024] In step 105, the light emitted by the ASE light source enters the fiber Bragg grating sensor to be tested through the circulator, and the light reflected by the fiber Bragg grating sensor to be tested enters the spectrum detection module that has been assigned in the previous step. The data processing circuit of the spectrum detection module obtains the peak pixel position n of the sensor and compares it with the "pixel-central wavelength" data group (n, λ) in step 104. n ), and get the wavelength value λ corresponding to this pixel n , the demodulation is completed.

[0025] In step 105, the “pixel-central wavelength” data set (n, λ n ) is used for polynomial fitting. As a preferred method, a second-order polynomial can be selected for fitting to obtain a relationship function between the central wavelength and the pixel position:

[0026] λ=a·n 2 +b·n+c (1)

[0027] Substitute the peak pixel position n of the fiber Bragg grating sensor to be tested obtained by the data processing circuit of the spectrum detection module into formula (1) to calculate the corresponding wavelength value λ n , the demodulation is completed.

[0028] Beneficial effects:

[0029] 1. The wavelength assignment method of the optical fiber sensing spectrum detection module based on the scanning light source disclosed in the present invention uses a high-precision scanning light source as a standard light source, and outputs a series of narrow-band wavelengths covering the entire C+L working band of the assigned spectrum detection module by scanning, which is used to assign wavelengths to pixels of the optical fiber sensing spectrum detection module based on diffraction grating spectrometry and array detectors, thereby solving the problem of a small number of standard light sources in the working band and improving the assignment accuracy in the full band range;

[0030] 2. The wavelength assignment method of the optical fiber sensing spectrum detection module based on the scanning light source disclosed in the present invention utilizes the characteristic that the output wavelength interval of the high-precision scanning light source is much higher than the sampling rate of the spectrum detection module, and can form a series of center wavelength positioning arrays for each pixel, and then use the zero-crossing point of a simple linear fitting function to locate the center wavelength to achieve the assignment. This method can improve the problem of peak position blurring caused by the broadening of the spectral profile caused by the pixel width, without the need to introduce complex interpolation and reconstruction algorithms to locate the peak, and the steps are simple and easy to implement.

[0031] 3. The wavelength assignment method of the optical fiber sensing spectrum detection module based on the scanning light source disclosed in the present invention uses a high-precision scanning light source to assign a value to each pixel of the spectrum detection module, forming a complete one-to-one correspondence between the pixel and the central wavelength, thereby improving the assignment accuracy. The assignment result can be directly applied to demodulation, or applied to demodulation after polynomial fitting, which can reduce the complexity of the subsequent demodulation algorithm and improve the demodulation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The basic principle diagram of the spectrum detection module based on diffraction grating spectrometry and array detector of the present invention;

[0033] Figure 2 A schematic diagram of a typical spectrum being imaged on an array detector;

[0034] Figure 3 Schematic diagram of the effect of pixel width on peak wavelength positioning;

[0035] Figure 4 It is a schematic diagram of the value assignment system of the present invention;

[0036] Figure 5 The spectral curves are typical of three spectra reconstructed from the electrical signals after photoelectric conversion of the near-infrared array detector 5 in the embodiment of the present invention;

[0037] Figure 6 It is a detailed enlarged diagram of the spectral curves reconstructed from the electrical signals of three typical spectra after photoelectric conversion by the near-infrared array detector 5 in the embodiment of the present invention;

[0038] Figure 7 is a distribution diagram of wavelength and energy difference ΔI of 1000 pixels in an embodiment of the present invention;

[0039] Figure 8 A function curve of the relationship between the central wavelength and the pixel position obtained by assigning values ​​in an embodiment of the present invention;

[0040] Fig. 9 Assigning an optical path to a single peak etalon used for comparison in an embodiment of the present invention;

[0041] Fig.10 Spectra of five single-peak etalons used for value assignment in the embodiments of the present invention;

[0042] Fig.11 A function curve showing the relationship between the central wavelength and the pixel position obtained by assigning values ​​to five single-peak etalons used for comparison in an embodiment of the present invention;

[0043] Fig.12 This is a test optical path used to verify the beneficial effects in the embodiment of the present invention.

[0044] Among them, 1-optical fiber, 2-collimating lens, 3-diffraction grating, 4-imaging lens, 5-near-infrared array detector, 6-distribution curve of optical signal of fiber Bragg grating in wavelength domain, 7-discrete voltage signal of optical signal of fiber Bragg grating, 8-discrete voltage signal of optical signal of fiber Bragg grating, 9-high-precision scanning laser, 10-optical attenuator, 11-spectral detection module to be assigned, 12-data processing and control module, 13-ASE light source, 14-single-peak standard tool, 15-high-precision wavelength meter, 16-circulator, 17-fiber Bragg grating sensor. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0046] The number of pixels of the near-infrared array detector 5 used in the spectrum detection module 11 to be assigned in this embodiment is 2048, the pixel width is 12.5 μm, and its designed working band is 1525nm~1565nm. The wavelength range of the selected high-precision scanning light source 9 can reach 1480nm~1640nm, with a wavelength accuracy of ±2pm, a wavelength resolution of 0.1pm, and a line width of <8pm.

[0047] The wavelength assignment method of the optical fiber sensing spectrum detection module based on the scanning light source disclosed in this embodiment is specifically implemented in the following steps:

[0048] Step 1, follow Figure 4 As shown, the optical equipment and data processing control module required for wavelength assignment are connected.

[0049] Step 2, perform value initialization, including output light energy setting, effective pixel range setting, wavelength range setting and spectrum scanning step setting.

[0050] Output light energy setting: adjust the output light energy of the high-precision scanning light source 9 and the attenuation of the light attenuator 10 to ensure that the output light energy does not exceed the upper limit of the light intensity detection of the near-infrared array detector 5;

[0051] Wavelength range and effective pixel range setting: adjust the output light of the high-precision scanning light source 9 and record the minimum pixel P that can be effectively detected. min =11 and the maximum pixel P max =2047, and record the wavelength values ​​λ corresponding to the two pixels min =1525nm and λ max =1565nm; then the minimum effective pixel P1 to be assigned is set to P1=10, and the maximum effective pixel P N Set as P N =2048,; the minimum assigned wavelength is set to λ 1c=1524.98nm, the maximum assigned wavelength is set to λ Nc =1526.02nm;

[0052] Spectrum scanning step size setting: The spectrum scanning step size is set to the minimum adjustable wavelength Δλ=0.1 pm of the high-precision scanning light source 9.

[0053] Step 3, control the high-precision scanning light source to output different wavelengths covering the wavelength range of the spectrum detection module to be assigned through the data processing control module, and at the same time record the spectrum measured by the spectrum detection module to be assigned through the data processing control module to obtain the "pixel position-energy" data.

[0054] The output wavelength of the light source 9 is scanned with high precision by the data processing control module to be λ 1c =1524.98nm, and at the same time, the software of the data processing control module saves the spectrum measured by the spectrum detection module 11 to be assigned at this time, which is recorded as λ 1c The corresponding "pixel position-energy" data set (n, I n ); with Δλ=0.1pm as the step, the data processing control module controls the output wavelength of the high-precision scanning light source to λ 1c +Δλ, while the data processing control module software saves λ 1c +Δλ corresponding to the "pixel position-energy" data set (n, I n ); and so on, until the output wavelength of the high-precision scanning light source 9 is λ Nc , and record the "pixel position-energy" data group at this time, and thus complete the "pixel position-energy" data acquisition step; Figure 5 is a spectral curve reconstructed from the electrical signal after photoelectric conversion of the near-infrared array detector 5 when the output wavelengths of the high-precision scanning light source 9 are 1548.4385nm, 1548.4308nm and 1548.4332nm respectively, Figure 6 for Figure 5 The enlarged view of the curve near the peak point. Figure 6 It can be seen that although the peak maximum points of these three wavelengths are all at 1000 pixels, from the comparison of the light intensity values ​​of 999 pixels and 1001 pixels, it can be seen that the spectrum of 1548.4308nm is nearly symmetrical with 1000 pixels as the center, while the other two wavelengths actually have deviations;

[0055] Step 4, extracting and preprocessing the "pixel position-energy" data obtained in step 3, data grouping, and pixel center wavelength positioning are performed in sequence to finally form a "pixel-center wavelength" data group.

[0056] Data extraction and preprocessing: For all stored data sets (n, I n), extract the wavelength value corresponding to the array, the pixel n corresponding to the maximum energy value, and the difference in energy values ​​between the two pixels on both sides of pixel n ΔI=I n-1 -I n+1 , arranged in ascending order of wavelength value into a new “wavelength-pixel position-energy difference” data set (λ, n, ΔI);

[0057] Data grouping: group the data with the same maximum energy value corresponding to the pixel n into one group, and still arrange them in the order of wavelength value from small to large. This group of data (λ, ΔI) is the positioning array of the central wavelength of the positioning pixel n; taking pixel 1000 as an example, the data (λ, ΔI) that can be obtained in the assignment system constructed in this embodiment is a group of data ranging from 1548.4215nm to 1548.4410nm;

[0058] Pixel center wavelength positioning: The positioning array (λ, ΔI) of pixel n is linearly fitted with λ as the horizontal coordinate and ΔI as the vertical coordinate. The wavelength value closest to the zero crossing point of the linear fitting function is the center wavelength λ of pixel n. n ; Taking 1000 pixels as an example, the data (λ, ΔI) is plotted with λ as the horizontal coordinate and ΔI as the vertical coordinate. Figure 7 As shown, after linear fitting, it can be determined that the ΔI of 1548.4308nm is closest to zero, that is, the wavelength value corresponding to 1000 pixels is 1548.4308nm;

[0059] By analogy, the central wavelengths of all pixels to be assigned can be located one by one to form a "pixel-central wavelength" data set (n, λ n ), the data group is the wavelength assignment result of the spectrum detection module to be assigned.

[0060] Step 5: Apply the wavelength assignment result obtained in step 4 to perform high-precision wavelength demodulation of the fiber grating sensor.

[0061] For the "pixel-central wavelength" data set (n, λ n ) is fitted with a second-order polynomial to obtain the relationship function λ=f(n) between the central wavelength and the pixel position, as shown in Figure 8 As shown, formula (2) is the functional relationship between the wavelength and the pixel position of the spectrum detection module measured in this embodiment:

[0062] λ=-2.112×10 -6 ·n 2 +0.02378·n+1526 (2)

[0063] In order to compare the beneficial effects of the wavelength assignment method proposed in the present invention, a comparison assignment device was built using 5 single-peak standards, and its optical path is as follows: Fig. 9As shown. The light emitted by the ASE light source 13 enters the single-peak etalon 14, and is first connected to the high-precision wavelength meter 15 to measure the wavelength value of the etalon. Then, the light emitted by the ASE light source 13 enters the single-peak etalon 14 and then is connected to the spectrum detection module to be assigned through the attenuator 10. The spectrum of the etalon is obtained through the data processing control module 12, and its peak pixel position is determined. The comparative test uses 5 single-peak etalons, using Fig. 9 The optical path shown in Table 1 obtains the five wavelength values ​​and their corresponding peak pixel values. The spectrum is shown in Fig.10 shown.

[0064] Table 1 Data for pixel assignment using a single-peak etalon

[0065] Serial number Wavelength value measured by wavelength meter (nm) Peak pixel position 1 1532.2674 295 2 1540.1720 659 3 1543.3312 812 4 1548.1070 1053 5 1556.1345 1491

[0066] Using the data in Table 1 to perform a second-order polynomial fit, the relationship function λ between the central wavelength and the pixel position is obtained: 对比 =f(n), its curve is as follows Fig.11 As shown, the functional relationship between wavelength and pixel position is:

[0067] λ 对比 =-2.132×10 -6 ·n 2 +0.02377·n+1525 (3)

[0068] Build as Fig.12 The demodulation optical path shown in the figure is shown in the figure. The light emitted by the ASE light source 13 enters the fiber Bragg grating sensor 17 after passing through the circulator 16. The light reflected by the fiber Bragg grating sensor 17 first enters the high-precision wavelength meter 15 to measure the accurate wavelength value of the sensor. Then the light reflected by the fiber Bragg grating sensor 17 enters the spectrum detection module, and the peak pixel position of the sensor is obtained through the data processing control module 12. Then, the fiber Bragg grating sensor is demodulated using formula (2) and formula (3) respectively, and compared with the wavelength value measured by the high-precision wavelength meter 15. The comparison results are shown in Table 2.

[0069] Table 2 Effect of the assignment method of the present invention on improving demodulation accuracy

[0070]

[0071] From the comparison results in Table 2, it can be seen that after the spectrum detection module is assigned values ​​by the assignment method proposed in the present invention, its demodulation accuracy is higher than the method of assigning values ​​using only 5 single-peak standards.

[0072] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wavelength assignment method for an optical fiber sensing spectrum detection module based on a scanning light source, characterized in that: The optical fiber sensing spectrum detection module is an optical fiber sensing spectrum detection module based on diffraction grating spectrometry and array detector, and is used to realize C+L band spectrum detection of the optical fiber sensing demodulator; the optical fiber sensing spectrum detection module is mainly composed of a diffraction grating, an array detector CCD and an auxiliary optical lens, and utilizes the spectroscopic characteristics of the diffraction grating to expand the light signals containing different wavelengths reflected by the optical fiber sensor in space, and then image them on the CCD for spectrum detection; The wavelength assignment method comprises the following steps: Step 101: Connecting optical equipment and data processing control modules required for wavelength assignment; Step 102: performing value assignment initialization, including output light energy setting, effective pixel range setting, wavelength range setting and spectrum scanning step length setting; The output light energy setting described in step 102 refers to adjusting the output light energy of the high-precision scanning light source and the attenuation of the light attenuator to ensure that the output light energy does not exceed the light intensity detection upper limit of the CCD of the spectrum detection module to be assigned; Step 103: Control the high-precision scanning light source to output different wavelengths covering the wavelength range of the spectrum detection module to be assigned through the data processing control module, and record the spectrum measured by the spectrum detection module to be assigned through the data processing control module to obtain "pixel position-energy" data; Step 104: The "pixel position-energy" data acquired in step 103 is sequentially subjected to data extraction and preprocessing, data grouping, and pixel center wavelength positioning, and finally forms a "pixel-center wavelength" data group.

2. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source according to claim 1, characterized in that: The step 105 is also included: directly applying the wavelength assignment result obtained in the step 104 to perform high-precision wavelength demodulation of the fiber grating sensor; In step 105, the light emitted by the ASE light source enters the fiber Bragg grating sensor to be tested through the circulator, and the light reflected by the fiber Bragg grating sensor to be tested enters the spectrum detection module that has been assigned in the previous step. The data processing circuit of the spectrum detection module obtains the peak pixel position n of the sensor and compares it with the "pixel-central wavelength" data group (n, λ) in step 104. n ), and get the wavelength value λ corresponding to this pixel n , that is, to achieve high-precision wavelength demodulation of the fiber grating sensor.

3. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source as claimed in claim 2, characterized in that: The optical devices to be connected in step 101 include a high-precision scanning light source, an optical attenuator and a spectrum detection module to be assigned; wherein the high-precision scanning light source is connected to the spectrum detection module to be assigned through the optical attenuator, and the data processing control module is respectively connected to the high-precision scanning light source and the spectrum detection module through control lines; the high-precision scanning light source is used to output the spectrum required for assignment, and its wavelength range should cover the wavelength range of the spectrum detection module to be assigned, and has a spectrum scanning function synchronously controlled by the data processing control module; the data processing control module is used to control the spectrum output of the high-precision scanning light source, and at the same time control the spectrum detection module to be assigned to perform signal acquisition and processing.

4. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source according to claim 3, characterized in that: The effective pixel range setting and wavelength range setting in step 102 refer to adjusting the output light of the high-precision scanning light source and recording the minimum pixel P that can be effectively detected. min and the maximum pixel P max , and record the wavelength values ​​λ corresponding to the two pixels min and λ max ; then the minimum valid pixel P1 to be assigned is defined as P1 = P min -1, the maximum valid pixel P to be assigned N Set as P N =P max +1; the minimum assigned wavelength is set to λ 1c =λ min -(λ max -λ min ) / N, the maximum assigned wavelength is set to λ Nc =λ max +(λ max -λ min ) / N; The spectrum scanning step length setting in step 102 refers to setting the spectrum scanning step length to the minimum adjustable wavelength Δλ of the high-precision scanning light source.

5. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source according to claim 4, characterized in that: In step 103, the output wavelength of the high-precision scanning light source is controlled to be λ by the data processing control module. 1c At the same time, the data processing control module saves the spectrum measured by the spectrum detection module to be assigned at this time, recorded as λ 1c The corresponding "pixel position-energy" data set (n, I n ); With Δλ as the step, the data processing control module controls the output wavelength of the high-precision scanning light source to λ 1c +Δλ, while the computer software saves λ 1c +Δλ corresponding to the "pixel position-energy" data set (n, I n ); and so on, until the output wavelength of the high-precision scanning light source is λ Nc , and record the "pixel position-energy" data group at this time, thus completing the acquisition of all "pixel position-energy" data.

6. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source according to claim 5, characterized in that: The data extraction and preprocessing described in step 104 are as follows: for all stored data groups (n, I n ), extract the wavelength value corresponding to the array, the pixel n corresponding to the maximum energy value, and the difference in energy values ​​between the two pixels on both sides of pixel n ΔI=I n-1 -I n+1 , and are arranged in ascending order of wavelength value into a new "wavelength-pixel position-energy difference" data set (λ, n, ΔI).

7. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source according to claim 6, characterized in that: The data grouping described in step 104 is: grouping the data with the same maximum energy value corresponding to the same pixel n into one group, and still arranging them in order from small to large wavelength values. This group of data (λ, ΔI) is the positioning array for positioning the central wavelength of pixel n.

8. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source according to claim 7, characterized in that: The pixel center wavelength positioning described in step 104 is as follows: the positioning array (λ, ΔI) of pixel n is linearly fitted with λ as the horizontal coordinate and ΔI as the vertical coordinate, and the wavelength value closest to the zero crossing point of the linear fitting function is the center wavelength λ of pixel n. n ; By analogy, the central wavelengths of all pixels to be assigned can be located one by one to form a "pixel-central wavelength" data set (n, λ n ); This data group is the wavelength assignment result of the spectrum detection module to be assigned.

9. The wavelength assignment method of the optical fiber sensing spectrum detection module based on scanning light source according to claim 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that: In step 105, the "pixel-central wavelength" data set (n, λ n ) is used for polynomial fitting, and a second-order polynomial is selected for fitting to obtain the relationship function between the central wavelength and the pixel position: λ=a·n 2 +b·n+c (1) Substitute the peak pixel position n of the fiber Bragg grating sensor to be tested obtained by the data processing circuit of the spectrum detection module into formula (1) to calculate the corresponding wavelength value λ n , that is, demodulation is completed.

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