CN114526817A - Wavelength assignment method of optical fiber sensing spectrum detection module based on scanning light source - Google Patents
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Abstract
The invention discloses a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source, and belongs to the field of optical fiber sensing. The optical fiber sensing spectrum detection module is based on diffraction grating light splitting and array type detector optical fiber sensing spectrum detection modules. The invention outputs narrow-band wavelength covering the whole C + L working waveband of an assigned spectrum detection module in a scanning mode, forms a series of central wavelength positioning arrays for each pixel by utilizing the characteristic that the output wavelength interval of a high-precision scanning light source is far higher than the sampling rate of the spectrum detection module, and positions the central wavelength by utilizing the zero crossing point of a linear fitting function for carrying out wavelength assignment on the pixels of the optical fiber sensing spectrum detection module based on diffraction grating light splitting and an array detector. The invention can solve the problem of less standard light sources of the working waveband, can improve the problem of fuzzy peak position caused by spectrum profile broadening caused by the width of the pixel, and further improves the assignment precision of the full waveband range.
Description
Technical Field
The invention relates to a high-precision wavelength assignment method based on a scanning light source, which is used for carrying out high-precision wavelength assignment on pixels and corresponding wavelengths of an optical fiber sensing spectrum detection module working in a C + L waveband (about 1510 nm-1625 nm) and based on diffraction grating light splitting and array detectors, and belongs to the field of optical fiber sensing.
Background
In recent years, with the wide application of optical fiber sensing technology in more and more fields, the performance requirements of optical fiber sensing demodulation instruments are higher and higher. The optical fiber sensing demodulation instrument based on the diffraction grating light splitting and array detector has the advantages of high stability, good environmental adaptability and the like because no moving part is arranged in the optical fiber sensing demodulation instrument, and has important application prospects in the leading-edge fields of aerospace and the like.
The basic principle of the optical fiber sensing demodulation instrument based on the diffraction grating light splitting and array detector is that a diffraction grating 3 and a near infrared array detector (CCD)5 form a spectrum detection module with a fixed light path structure through an auxiliary optical lens (usually comprising a collimating lens 2 and an imaging lens 4), the basic principle is as shown in figure 1, optical signals which are reflected by an optical fiber sensor and comprise different wavelengths are incident on a collimating lens through an optical fiber 1, the light splitting characteristic of the diffraction grating is utilized to image the optical signals after space expansion on the CCD, and the pixel of the CCD converts the light intensity of the optical signals into electric signals to be output, so that spectral line data of the optical signals are formed. Fig. 2 is a spectral diagram of an image of a typical fiber grating light signal on a CCD, wherein the distribution of the light signal received by the CCD in the wavelength domain is shown as curve 6, and after photoelectric conversion by the CCD, discrete voltage signals 7 with different sizes are formed, and after the voltage signals are converted into intensity signals by a computer, a series of discrete data points 8 are formed. Therefore, the CCD pixels on the spectrum detection module have one-to-one correspondence with the input light wavelength. Therefore, accurate assignment of the corresponding relation between the pixel and the wavelength is a precondition for accurate demodulation of the wavelength by the demodulation instrument based on the principle, and the influence of assignment accuracy is a key factor of wavelength demodulation accuracy of the demodulation instrument.
The general idea of wavelength assignment is that a plurality of narrow-band light sources with known wavelengths are used as standard sources and input into a spectrum acquisition module to obtain pixel positions corresponding to a series of spectrum center wavelengths, and then a function relation between pixels of an array detector and the wavelengths is obtained by utilizing data processing means such as polynomial fitting and the like, so that a wavelength value corresponding to each pixel is obtained. Therefore, the main factors influencing the assignment accuracy include two aspects of the number of standard light sources used in assignment and the acquisition accuracy of the pixel positions corresponding to the input standard light sources.
Influence factor 1) number of standard light sources used in the assignment: in the working waveband range of the spectrum acquisition module, the more the number of the standard light sources participating in assignment is, the more the corresponding relation between the obtained wavelength and the pixel is, and the more accurate the functional relation between the pixel and the wavelength after fitting is. Common standard light sources include gas light sources, broadband light sources in combination with gas absorption cells, and the like. However, for the optical fiber sensing spectrum detection module working in the C + L waveband, the number of available gas light sources is small, for example, a mercury lamp (Hg) has a spectral line with a wavelength of 1529.6nm, and a xenon (Xe) lamp has a spectral line with a wavelength of 1541.8nm, and it is obvious that even if the optical fiber sensing spectrum detection module is used in combination, the small number of assigned points cannot well meet the assignment requirement. Gases having an obvious absorption peak in the C + L band include acetylene, hydrogen cyanide, and the like. Although the number of absorption peaks of the gas absorption cell in the C + L wave band is not small, the energy difference of each absorption peak is large, only individual and obvious absorption peaks can be selected for assignment in practical application, and the promotion effect on assignment accuracy is limited. For example, in patent CN103557879B, "fiber bragg grating sensing wavelength calibration device based on cavity absorption" uses a broadband light source to generate a standard light source in cooperation with a gas absorption cell, and also only uses two absorption peaks of the gas absorption cell that are more obvious in the near infrared region as assignment spectral lines.
Influence factor 2) the acquisition accuracy of the pixel position corresponding to the standard light source input: the pixel of the array detector has a certain width, and the existence of the width causes the problems of spectrum profile broadening, peak position blurring and the like when a spectrum curve is reproduced subsequently, so that the positioning of the central wavelength of the pixel is influenced. Taking an array detector with 1024 pixels as an example, if the working wavelength range of the array detector is 40nm, the average wavelength width occupied by each pixel is about 40pm, and therefore theoretically, a group of wavelengths within the range of 40pm can be roughly considered as the central wavelength value corresponding to the same pixel. As shown in fig. 3, for the second pixel, all three wavelengths input in fig. 3 can be regarded as the center wavelength of the second pixel, but actually, only the wavelength value of the wavelength peak point completely coinciding with the center of the second pixel is the true center wavelength of the second pixel, as shown by the curve centered in fig. 3. The invention patent CN105424185B, "a computer-assisted wavelength calibration method for a full-waveband spectrometer," adopts a combined light source to assign a wavelength to the spectrometer, acquires a certain amount of spectral data within the wavelength range of the spectrometer, and performs spectral acquisition and data processing in a computer-assisted manner, and adopts a ford function to fit the data of each spectral line to reconstruct a spectral line profile and determine a pixel position corresponding to a recurring peak value, but when the processing method is applied to assignment of a spectrum acquisition module of a C + L waveband, the problem that a standard spectral line of the waveband is rare cannot be improved, and improvement of assignment accuracy is limited. The invention patent 200710177242.8, "a wavelength calibration method for a spectroscopic instrument", also notes the influence of the pixel width on the assignment accuracy, proposes a mode of forming changes on the light path by moving an array detector or rotating a grating and the like to improve the sampling rate and perform sub-pixel reconstruction, and the method has no application value to a spectroscopic detection module which must form a stable light path structure.
Therefore, in order to improve the wavelength assignment accuracy of the optical fiber sensing spectrum detection module working in the C + L waveband, the two aspects of the number of standard light sources and the pixel position positioning are improved, so that the wavelength demodulation accuracy of the demodulation instrument based on the principle is improved.
Disclosure of Invention
Aiming at the problems of rare standard light source quantity, difficult peak pixel position positioning and the like in the existing wavelength assignment method, the invention mainly aims to provide a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source, which can provide a high-precision wavelength assignment method in a full-waveband range for an optical fiber sensing spectrum detection module based on diffraction grating light splitting and array detectors working in a C + L waveband, thereby improving the wavelength demodulation precision of a demodulation instrument based on the principle.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source. The optical fiber sensing spectrum detection module mainly comprises a diffraction grating, an array type detector CCD and an auxiliary optical lens, and optical signals which are reflected by the optical fiber sensor and contain different wavelengths are imaged on the CCD to carry out spectrum detection after being spatially expanded by utilizing the light splitting characteristic of the diffraction grating. The invention discloses a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source, which comprises the following steps:
step 101: and connecting optical equipment required by wavelength assignment and a data processing control module.
The optical devices to be connected in step 101 include a high-precision scanning light source, an optical attenuator, and a spectral detection module to be assigned. The high-precision scanning light source is connected with the spectrum detection module to be assigned through the optical attenuator, and the data processing control module is respectively connected with the high-precision scanning light source and the spectrum detection module through control lines. The high-precision scanning light source is used for outputting a spectrum required by assignment, the wavelength range of the high-precision scanning light source covers the wavelength range of the spectrum detection module to be assigned, and the high-precision scanning light source has a spectrum scanning function synchronously controlled by the data processing control module; the data processing control module is used for controlling the spectrum output of the high-precision scanning light source and controlling the spectrum detection module with the substitute assignment to carry out signal acquisition and processing.
Step 102: and carrying out assignment initialization, including setting of output light energy, setting of effective pixel range, setting of wavelength range and setting of spectrum scanning step length.
The output light energy setting in step 102 is to adjust the output light energy of the high-precision scanning light source and the attenuation of the optical 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;
the effective pixel range setting and the wavelength range setting in step 102 refer to adjusting output light of the high-precision scanning light source and recording a minimum pixel P capable of performing effective detectionminAnd the maximum pixel PmaxTo and fromRecording wavelength values lambda corresponding to two pixelsminAnd λmax(ii) a The minimum active pixel P to be assigned1Is defined as P1＝Pmin-1, the largest significant pel P to be assignedNIs defined as PN＝Pmax+ 1; the minimum assigned wavelength is defined as λ1c＝λmin-(λmax-λmin) N, maximum assigned wavelength is defined as lambdaNc＝λmax+(λmax-λmin)/N；
The setting of the spectrum scanning step length in step 102 refers to setting the spectrum scanning step length to the minimum tunable wavelength Δ λ of the high-precision scanning light source.
Step 103: the high-precision scanning light source is controlled by the data processing control module to output different wavelengths covering the wavelength range of the spectrum detection module to be assigned, and meanwhile, the spectrum detected by the spectrum detection module to be assigned is recorded by the data processing control module, so that pixel position-energy data is obtained.
In step 103, the output wavelength of the high-precision scanning light source is controlled to be lambda by the data processing control module1cMeanwhile, the data processing control module stores the spectrum measured by the spectrum detection module to be assigned at the moment and records the spectrum as lambda1cCorresponding pixel position-energy data set (n, I)n) (ii) a The data processing control module controls the output wavelength of the high-precision scanning light source to be lambda by taking delta lambda as step1c+ Δ λ, while computer software saves λ1cThe "Pixel position-energy" data set (n, I) corresponding to + Δ λn) (ii) a And so on until the output wavelength of the high-precision scanning light source is lambdaNcRecording the pixel position-energy data set at the moment, and completing the acquisition of all pixel position-energy data;
step 104: and 3, sequentially carrying out data extraction and pretreatment, data grouping and pixel center wavelength positioning on the pixel position-energy data acquired in the step 103 to finally form a pixel-center wavelength data group.
The data extraction and preprocessing in step 104 are: for all data sets (n, I) storedn) Extract the array pairThe pixel n corresponding to the corresponding wavelength value and the maximum energy value, and the energy value difference delta I between the two pixels at the two sides of the pixel n is In-1-In+1Arranging a new 'wavelength-pixel position-energy difference' data set (lambda, n, delta I) according to the sequence of the wavelength values from small to large;
the data grouping in step 104 is: dividing data with the same maximum energy value corresponding to the pixel n into a group, arranging the data according to the sequence of the wavelength values from small to large, wherein the group of data (lambda, delta I) is a positioning array of the central wavelength of the positioning pixel n;
the pixel center wavelength positioning in step 104 is: linear fitting is carried out on the positioning array (lambda, delta I) of the pixel n by taking lambda as an abscissa and delta I as an ordinate, and the wavelength value closest to the zero crossing point of the linear fitting function is the central wavelength lambda of the pixel nn(ii) a By analogy, the center wavelengths of all pixels to be assigned can be positioned one by one to form a pixel-center wavelength data group (n, lambda)n) (ii) a The data set is the wavelength assignment result of the spectrum detection module to be assigned.
The invention discloses a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source, which further comprises the following steps of 105: the wavelength assignment result obtained in step 104 can be directly applied to perform high-precision wavelength demodulation of the fiber grating sensor.
In step 105, light emitted by the ASE light source enters the fiber grating sensor to be detected through the circulator, light reflected by the fiber grating sensor to be detected enters the spectrum detection module which is assigned in the previous step, a data processing circuit of the spectrum detection module obtains a peak pixel position n of the sensor, and the peak pixel position n is compared with the pixel-center wavelength data set (n, lambda) in step 104n) Obtaining the wavelength value lambda corresponding to the pixelnAnd then the demodulation can be completed.
In step 105, the pixel-center wavelength data set (n, λ) of step 104 can be further processedn) And (3) performing polynomial fitting, preferably selecting a second-order polynomial to perform fitting to obtain a relation function between the central wavelength and the pixel position:
λ＝a·n2+b·n+c (1)
substituting the peak pixel position n of the fiber grating sensor to be detected, which is obtained by the data processing circuit of the spectrum detection module, into the formula (1), and calculating to obtain the corresponding wavelength value lambdanAnd then the demodulation can be completed.
Has the advantages that:
1. the invention discloses a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source, which takes a high-precision scanning light source as a standard light source, outputs a series of narrow-band wavelengths covering the whole C + L working waveband of the assigned spectrum detection module in a scanning mode, is used for carrying out wavelength assignment on pixels of the optical fiber sensing spectrum detection module based on diffraction grating beam splitting and an array type detector, solves the problem of less number of standard light sources of the working waveband, and can improve the assignment precision of the full waveband range;
2. the invention discloses a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source, which can form a series of central wavelength positioning arrays for each pixel by utilizing the characteristic that the output wavelength interval of a high-precision scanning light source is far higher than the sampling rate of the spectrum detection module, and then position the central wavelength by utilizing the zero crossing point of a simple linear fitting function to realize assignment. The method can solve the problem of fuzzy peak position caused by spectrum profile broadening caused by the width of the pixel, does not need to introduce complex interpolation and reconstruction algorithms to position the peak, and has simple steps and easy realization.
3. The invention discloses a wavelength assignment method of an optical fiber sensing spectrum detection module based on a scanning light source, which assigns values to each pixel of the spectrum detection module by using a high-precision scanning light source, forms a complete one-to-one correspondence relationship between the pixels and the central wavelength, and improves assignment precision. Subsequently, the assignment result can be directly applied to demodulation or applied to demodulation after polynomial fitting, so that the complexity of a subsequent demodulation algorithm can be reduced, and the demodulation precision is improved.
Drawings
FIG. 1 is a basic schematic diagram of a spectral detection module based on a diffraction grating light splitting and array type detector according to the present invention;
FIG. 2 is a schematic diagram of an exemplary spectrum imaged on an array detector;
FIG. 3 is a schematic diagram of the effect of pixel width on peak wavelength positioning;
FIG. 4 is a schematic diagram of a valuation system of the present invention;
FIG. 5 is a spectral plot of a typical three-spectrum electrical signal reconstruction after photoelectric conversion by the near infrared array detector 5 in an embodiment of the present invention;
FIG. 6 is an enlarged detail view of a spectrum curve of an electric signal reconstruction after photoelectric conversion of a near infrared array detector 5 for three spectra according to an exemplary embodiment of the present invention;
FIG. 7 is a distribution diagram of wavelength and energy difference Δ I of 1000 pixels according to an embodiment of the present invention;
FIG. 8 is a graph of a relationship function between a center wavelength and a pixel position obtained by assignment in the embodiment of the present invention;
FIG. 9 is a single peak etalon evaluation optical path for comparison in an embodiment of the present invention;
FIG. 10 is a spectrum of a 5-singlet etalon used for assignment in an embodiment of the present invention;
FIG. 11 is a plot of center wavelength versus pixel position for 5 single-peak etalon assignments for comparison in an embodiment of the present invention;
fig. 12 is a test light path for verifying beneficial effects in an embodiment of the present invention.
The system comprises an optical fiber 1, an optical fiber 2, a collimating lens 3, a diffraction grating 4, an imaging lens 5, a near infrared array detector 6, a distribution curve of optical signals of the optical fiber grating in a wavelength domain 7, discrete voltage signals of the optical fiber grating 8, a high-precision scanning laser 9, an optical attenuator 10, a spectrum detection module to be assigned 11, a data processing control module 12, an ASE light source 13, a unimodal etalon 14, a high-precision wavelength meter 15, a circulator 16 and an optical fiber grating sensor 17.
Detailed Description
The invention is further illustrated by the following figures and examples.
In the embodiment, the number of pixels of the near-infrared array detector 5 used by the spectrum detection module 11 to be assigned is 2048, the width of the pixels is 12.5 μm, and the designed working band is 1525nm to 1565 nm. The wavelength range of the selected high-precision scanning light source 9 can reach 1480-1640 nm, the wavelength precision is +/-2 pm, the wavelength resolution is 0.1pm, and the line width is less than 8 pm.
The wavelength assignment method of the optical fiber sensing spectrum detection module based on the scanning light source disclosed by the embodiment comprises the following specific implementation steps:
And 2, carrying out assignment initialization, including output light energy setting, effective pixel range setting, wavelength range setting and spectrum scanning step length setting.
Output light energy setting: adjusting the output light energy of the high-precision scanning light source 9 and the attenuation of the optical attenuator 10 to ensure that the output light energy does not exceed the upper detection limit of the light intensity of the near-infrared array detector 5;
setting a wavelength range and an effective pixel range: adjusting the output light of the high-precision scanning light source 9, and recording the minimum pixel P capable of effective detectionmin11 and maximum picture element Pmax2047 and recording the wavelength value lambda corresponding to two pixelsmin1525nm and λ max1565 nm; the minimum active pixel P to be assigned1Is defined as P 110, the largest valid pel P to be assignedNIs defined as PN2048,; the minimum assigned wavelength is defined as λ1c1524.98nm, with a maximum assigned wavelength of λNc＝1526.02nm；
Setting the spectrum scanning step length: the spectral scanning step is set to 0.1pm as the minimum tunable wavelength Δ λ of the high-precision scanning light source 9.
And 3, controlling 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 simultaneously recording the spectrum detected by the spectrum detection module to be assigned through the data processing control module to obtain pixel position-energy data.
The output wavelength of the high-precision scanning light source 9 is lambda by using the data processing control module1c1524.98nm, and the software of the data processing control module stores the spectrum measured by the spectrum detection module 11 to be assigned at the moment and records the spectrum as lambda1cCorresponding pixel position-energy data set (n, I)n) (ii) a The step is delta lambda being 0.1pm, the data processing control module controls the output wavelength of the high-precision scanning light source to be lambda1c+ Δ λ, while the data processing control module software saves λ1cThe "Pixel position-energy" data set (n, I) corresponding to + Δ λn) (ii) a And so on until the output wavelength of the high-precision scanning light source 9 is lambdaNcRecording the pixel position-energy data set at the moment, and completing the pixel position-energy data acquisition step; fig. 5 is a spectrum curve reconstructed by the electrical signals 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, and fig. 6 is an enlarged view of the curve near the peak point of fig. 5. As can be seen from FIG. 6, although the maximum peak points of the three wavelengths are all at 1000 pixels, it can be seen from the comparison of the light intensity values of 999 pixels and 1001 pixels that the spectrum of 1548.4308nm is approximately symmetrical around 1000 pixels, and the other two wavelengths are actually deviated;
and 4, sequentially carrying out data extraction and pretreatment, data grouping and pixel center wavelength positioning on the pixel position-energy data acquired in the step 3 to finally form a pixel-center wavelength data group.
Data extraction and preprocessing: for all data sets (n, I) storedn) Extracting the pixel n corresponding to the wavelength value and the maximum energy value corresponding to the array, wherein the difference delta I between the energy values of the two pixels at the two sides of the pixel n is In-1-In+1Arranging a new 'wavelength-pixel position-energy difference' data set (lambda, n, delta I) according to the sequence of the wavelength values from small to large;
data grouping: dividing data with the same maximum energy value corresponding to the pixel n into a group, arranging the data according to the sequence of the wavelength values from small to large, wherein the group of data (lambda, delta I) is a positioning array of the central wavelength of the positioning pixel n; taking the pixel 1000 as an example, the data (λ, Δ I) available in the assignment system constructed in the embodiment is a set of data ranging from 1548.4215nm to 1548.4410 nm;
pixel center wavelength positioning: linear fitting is carried out on the positioning array (lambda, delta I) of the pixel n by taking lambda as an abscissa and delta I as an ordinate, and the wavelength value closest to the zero crossing point of the linear fitting function is the central wavelength lambda of the pixel nn(ii) a Taking 1000 pixels as an example, the data (λ, Δ I) takes λ as abscissa and Δ I as ordinate, the plot is shown in fig. 7, and after linear fitting, it can be judged that Δ I of 1548.4308nm is closest to zero, that is, the wavelength value corresponding to 1000 pixels is 1548.4308 nm;
by analogy, the center wavelengths of all pixels to be assigned can be positioned one by one to form a pixel-center wavelength data group (n, lambda)n) And the data set is the wavelength assignment result of the spectrum detection module to be assigned.
And 5, applying the wavelength assignment result obtained in the step 4 to perform high-precision wavelength demodulation on the fiber grating sensor.
For the "pixel-center wavelength" data set (n, lambda) obtained in step 4n) Performing second-order polynomial fitting to obtain a relation function λ ═ f (n) between the center wavelength and the pixel position, as shown in fig. 8, where equation (2) is a function relation between the wavelength of the spectrum detection module and the pixel position measured in this embodiment:
λ＝-2.112×10-6·n2+0.02378·n+1526 (2)
in order to compare the beneficial effects of the wavelength assignment method provided by the invention, a comparison assignment device is built by using 5 single-peak etalons, and the optical paths of the comparison assignment device are shown in fig. 9. Light emitted by the ASE light source 13 enters the unimodal etalon 14, and is firstly connected to the high-precision wavelength meter 15, and the wavelength value of the etalon is measured. Then, after light emitted by the ASE light source 13 enters the single-peak etalon 14, the light enters 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 the peak pixel position of the etalon is determined. The comparative experiment used 5 unimodal etalons and the 5 wavelength values and their corresponding peak pixel values shown in table 1 were obtained using the optical path shown in fig. 9, the spectrum of which is shown in fig. 10.
TABLE 1 data for Pixel assignment using unimodal etalons
| Serial number | Wavelength value (nm) measured by a wavelength meter | |
| 1 | 1532.2674 | 295 |
| 2 | 1540.1720 | 659 |
| 3 | 1543.3312 | 812 |
| 4 | 1548.1070 | 1053 |
| 5 | 1556.1345 | 1491 |
Performing second-order polynomial fitting by using the data in Table 1 to obtain a relation function lambda between the central wavelength and the pixel positionComparison ofF (n), the curve is shown in fig. 11, and the functional relationship between the wavelength and the pixel position is:
λcomparison of＝-2.132×10-6·n2+0.02377·n+1525 (3)
A demodulation optical path shown in fig. 12 is built, light emitted by the ASE light source 13 enters the fiber grating sensor 17 after passing through the circulator 16, and light reflected by the fiber grating sensor 17 enters the high-precision wavelength meter 15 to measure an accurate wavelength value of the sensor. Then, the light reflected by the fiber grating sensor 17 enters the spectrum detection module, the peak pixel position of the sensor is obtained through the data processing control module 12, then the fiber grating sensor is demodulated through the formula (2) and the formula (3) respectively, the demodulated fiber grating sensor is compared with the wavelength value measured by the high-precision wavemeter 15, and the comparison result is shown in table 2.
TABLE 2 the effect of the assignment method of the present invention on the demodulation accuracy
As can be seen from the comparison results in table 2, the demodulation accuracy of the spectrum detection module assigned by the assignment method of the present invention is higher than that of the spectrum detection module assigned by only 5 single-peak etalons.
The above detailed description is intended to illustrate the objects, aspects and advantages of the present invention, and it should be understood that the above detailed description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. The wavelength assignment method of the optical fiber sensing spectrum detection module based on the scanning light source is characterized in that: the optical fiber sensing spectrum detection module is based on diffraction grating light splitting and array type detector optical fiber sensing spectrum detection modules and is used for realizing C + L waveband spectrum detection of an optical fiber sensing demodulator; the optical fiber sensing spectral detection module mainly comprises a diffraction grating, an array detector CCD and an auxiliary optical lens, and optical signals which are reflected by the optical fiber sensor and contain different wavelengths are imaged on the CCD to perform spectral detection after being spatially expanded by utilizing the light splitting characteristic of the diffraction grating;
the wavelength assignment method comprises the following steps,
step 101: connecting optical equipment and a data processing control module required by wavelength assignment;
step 102: carrying out assignment initialization, including setting of output light energy, setting of effective pixel range, setting of wavelength range and setting of spectrum scanning step length;
the output light energy setting in step 102 is to adjust the output light energy of the high-precision scanning light source and the attenuation of the optical 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: controlling 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 simultaneously recording the spectrum detected by the spectrum detection module to be assigned through the data processing control module to obtain pixel position-energy data;
step 104: and 3, sequentially carrying out data extraction and pretreatment, data grouping and pixel center wavelength positioning on the pixel position-energy data acquired in the step 103 to finally form a pixel-center wavelength data group.
2. The method for assigning the wavelength of the optical fiber sensing spectral detection module based on the scanning light source according to claim 1, wherein: further comprising the step 105: 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, light emitted by the ASE light source enters the fiber grating sensor to be detected through the circulator, light reflected by the fiber grating sensor to be detected enters the spectrum detection module after being assigned in the previous step, and the data processing circuit of the spectrum detection module obtains the lightThe peak pixel position n of the sensor is compared to the "pixel-center wavelength" data set (n, λ) in step 104n) Obtaining the wavelength value lambda corresponding to the pixelnThe high-precision wavelength demodulation of the fiber grating sensor is realized.
3. The method for assigning the wavelength of the optical fiber sensing spectral detection module based on the scanning light source according to claim 2, wherein: in step 101, the optical equipment to be connected comprises 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 with the spectrum detection module to be assigned through the optical attenuator, and the data processing control module is respectively connected with the high-precision scanning light source and the spectrum detection module through control lines; the high-precision scanning light source is used for outputting a spectrum required by assignment, the wavelength range of the high-precision scanning light source covers the wavelength range of the spectrum detection module to be assigned, and the high-precision scanning light source has a spectrum scanning function synchronously controlled by the data processing control module; the data processing control module is used for controlling the spectrum output of the high-precision scanning light source and controlling the spectrum detection module with the substitute assignment to carry out signal acquisition and processing.
4. The method for assigning the wavelength of the optical fiber sensing spectral detection module based on the scanning light source according to claim 3, wherein: the effective pixel range setting and the wavelength range setting in step 102 refer to adjusting output light of the high-precision scanning light source and recording a minimum pixel P capable of performing effective detectionminAnd the maximum pixel PmaxAnd recording the wavelength values lambda corresponding to the two pixelsminAnd λmax(ii) a The minimum active pixel P to be assigned1Is defined as P1＝Pmin-1, the largest significant pel P to be assignedNIs defined as PN＝Pmax+ 1; the minimum assigned wavelength is defined as λ1c＝λmin-(λmax-λmin) N, maximum assigned wavelength is defined as lambdaNc＝λmax+(λmax-λmin)/N；
The setting of the spectrum scanning step length in step 102 refers to setting the spectrum scanning step length to the minimum tunable wavelength Δ λ of the high-precision scanning light source.
5. The method for assigning the wavelength of the optical fiber sensing spectral detection module based on the scanning light source according to claim 4, wherein: in step 103, the output wavelength of the high-precision scanning light source is controlled to be lambda by the data processing control module1cMeanwhile, the data processing control module stores the spectrum measured by the spectrum detection module to be assigned at the moment and records the spectrum as lambda1cCorresponding pixel position-energy data set (n, I)n) (ii) a The data processing control module controls the output wavelength of the high-precision scanning light source to be lambda by taking delta lambda as step1c+ Δ λ, while computer software saves λ1cThe "Pixel position-energy" data set (n, I) corresponding to + Δ λn) (ii) a And so on until the output wavelength of the high-precision scanning light source is lambdaNcAnd recording the pixel position-energy data set at the moment, so as to complete the acquisition of all pixel position-energy data.
6. The method for assigning wavelengths to the optical fiber sensing spectral detection module according to claim 5, wherein: the data extraction and preprocessing in step 104 are: for all data sets (n, I) storedn) Extracting the pixel n corresponding to the wavelength value and the maximum energy value corresponding to the array, wherein the difference delta I between the energy values of the two pixels at the two sides of the pixel n is In-1-In+1And arranging a new 'wavelength-pixel position-energy difference' data set (lambda, n, delta I) according to the sequence of the wavelength values from small to large.
7. The method for assigning the wavelength of the optical fiber sensing spectral detection module based on the scanning light source according to claim 6, wherein: the data grouping in step 104 is: dividing the data with the same maximum energy value corresponding to the pixel n into a group, and arranging the data according to the order of the wavelength values from small to large, wherein the group of data (lambda, delta I) is a positioning array of the central wavelength of the positioning pixel n.
8. The method for assigning the wavelength of the optical fiber sensing spectral detection module based on the scanning light source according to claim 7, wherein: the pixel center wavelength positioning in step 104 is: linear fitting is carried out on the positioning array (lambda, delta I) of the pixel n by taking lambda as an abscissa and delta I as an ordinate, and the wavelength value closest to the zero crossing point of the linear fitting function is the central wavelength lambda of the pixel nn(ii) a By analogy, the center wavelengths of all pixels to be assigned can be positioned one by one to form a pixel-center wavelength data group (n, lambda)n) (ii) a The data set is the wavelength assignment result of the spectrum detection module to be assigned.
9. The method for assigning the wavelength of the optical fiber sensing spectrum detection module based on the scanning light source according to the claims 1, 2, 3, 4, 5, 6, 7 or 8, wherein the method comprises the following steps: in step 105, the pixel-center wavelength data set (n, λ) of step 104 can also be processedn) And (3) carrying out polynomial fitting, selecting a second-order polynomial to carry out fitting to obtain a relation function between the central wavelength and the pixel position:
λ＝a·n2+b·n+c (1)
substituting the peak pixel position n of the fiber grating sensor to be detected, which is obtained by the data processing circuit of the spectrum detection module, into the formula (1), and calculating to obtain the corresponding wavelength value lambdanAnd then demodulation is completed.
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