Peak wavelength tracking method for enhancing measurement accuracy of optical fiber sensor

Abstract

A peak wavelength tracking method for enhancing the measurement accuracy of an optical fiber sensor, the method comprising the following steps: obtaining all initial peak wavelengths from a reflection spectrum; calibrating the initial peak wavelengths under the constraint of a set error ε; when the absolute value of the average error between all the initial peak wavelengths and calculated peak wavelengths, which respectively correspond to all calibrated peak wavelengths, is less than or equal to the set error ε, stopping the calibration process, and determining that the calculated peak wavelengths obtained in the final calibration process are all accurate peak wavelengths, and that peak orders mcalculated respectively corresponding to all the accurate peak wavelengths are all accurate peak orders; and then, on the basis of the obtained accurate peak wavelengths and accurate peak orders, tracking the corresponding peak wavelengths. Accurate peak wavelengths obtained by the method have high accuracy, and thus the method is highly suitable for peak wavelength tracking.

Description

Peak wavelength tracking method for enhancing measurement accuracy of fiber optic sensor TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber optic sensor, in particular to a peak wavelength tracking method for enhancing measurement accuracy of fiber optic sensor. BACKGROUND

[0002] At present, fiber Fabry-Perot interferometer (FPI) has become the best choice for high-sensitivity sensing, mainly because fiber Fabry-Perot interferometer (FPI) has excellent performance in measurement accuracy, resolution and stability. Because fiber Fabry-Perot interferometer (FPI) can set an open detection cavity, fiber Fabry-Perot interferometer (FPI) technology can be used to measure parameters such as refractive index, density, temperature and concentration of seawater. At present, in the prior art, the optical path difference (OPD) between two adjacent peak wavelengths in the spectrum is calculated, and then the fixed order wavelength is tracked by tracking the adjacent peak wavelengths. However, it is difficult to accurately track the peak wavelength by demodulation method. Therefore, the present application provides a peak wavelength tracking method for enhancing the measurement accuracy of fiber optic sensor. SUMMARY

[0003] In order to make up for the shortcomings of the prior art, the present application provides a peak wavelength tracking method for enhancing the measurement accuracy of fiber optic sensor.

[0004] The present application is realized by the following technical scheme: a peak wavelength tracking method for enhancing the measurement accuracy of fiber optic sensor, comprising the following steps: obtaining all initial peak wavelengths from the reflected spectrum, correcting the initial peak wavelengths under the constraint of a set error ε, until the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all corrected peak wavelengths respectively is less than or equal to the set error ε, stopping the correction process, and determining that the calculated peak wavelengths obtained by the last correction process are all accurate peak wavelengths, and the peak order mcalculated corresponding to all accurate peak wavelengths is an accurate peak order; then, based on the obtained accurate peak wavelengths and accurate peak orders, the corresponding peak wavelengths are tracked.

[0005] Preferably, before correcting the initial peak wavelengths under the constraint of the set error ε, the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths respectively corresponding to all initial peak wavelengths is calculated; and the calculation of the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths respectively corresponding to all initial peak wavelengths comprises the following steps: 1) calculating the effective cavity length value nL by using the peak wavelength corresponding to the first peak in all the obtained peak values of the reflection spectrum and the peak wavelength corresponding to the last peak; 2) calculating the peak order mcalculated corresponding to all initial peak wavelengths by using the effective cavity length value nL obtained in step 1) and all initial peak wavelengths; 3) calculating the calculated peak wavelengths respectively corresponding to all initial peak wavelengths by using the effective cavity length value nL obtained in step 1) and the corresponding integer m of the peak order mcalculated corresponding to all initial peak wavelengths; 4) calculating the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths respectively corresponding to all initial peak wavelengths obtained in step 3).

[0006] Preferably, when the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths respectively corresponding to all peak wavelengths is greater than the set error ε, the initial peak wavelengths are corrected under the constraint of the set error ε, and the correction of the initial peak wavelengths comprises the following steps: S1, correcting the initial peak wavelengths to obtain corrected peak wavelengths; wherein, when the first correction is performed on all initial peak wavelengths respectively, the first correction peak wavelength The first corrected peak wavelength is obtained after replacing the initial peak wavelength; when the n+1th correction is performed on all initial peak wavelengths respectively, n is an integer greater than or equal to 1, and the n+1th correction peak wavelength The n-th correction peak wavelength is replaced by the n+1th correction peak wavelength S2, calculating the effective cavity length value nL using the first peak wavelength and the last peak wavelength corresponding to all the peak wavelengths obtained in step S1; S3, calculating the peak order mcalculated corresponding to the corrected peak wavelength using the effective cavity length value nL obtained in step S2 and the corrected peak wavelength obtained in step S1; S4, calculating the calculated peak wavelength corresponding to the corrected peak wavelength using the effective cavity length value nL obtained in step S2 and the corresponding integer m of the peak order mcalculated corresponding to the corrected peak wavelength; S5, calculating the absolute value of the average error value between all the initial peak wavelengths and the calculated peak wavelength obtained in step S4, and determining whether the absolute value of the average error value is greater than the set error ε; S6, when the absolute value of the average error value calculated in step S5 is less than or equal to the set error ε, stopping the correction process; otherwise, repeating steps S1 to S5 to continue the correction until the absolute value of the average error value calculated in step S5 is less than or equal to the set error ε, stopping the correction process, and determining that all the calculated peak wavelengths obtained in step S4 in the last correction process are accurate peak wavelengths, and the peak order mcalculated corresponding to all the accurate peak wavelengths is the accurate peak order.

[0007] Preferably, the way of obtaining all the initial peak wavelengths from the reflection spectrum is: using a spectrum detection device to obtain the reflection spectrum signal of the fiber sensor in the form of equal wavelength interval sampling, obtaining an FPI spectrum diagram, and reading all the initial peak wavelengths of the reflection spectrum from the FPI spectrum diagram.

[0008] Preferably, in step 1), when there are two peak values in the wavelength range, the effective cavity length value is calculated using the peak wavelengths corresponding to the two peak values; when there are three or more peak values in the wavelength range, the effective cavity length value is calculated using the peak wavelength corresponding to the first peak value and the peak wavelength corresponding to the last peak value. This setting can more accurately obtain the effective cavity length value.

[0009] Preferably, in step S2, when there are two peak values in the wavelength range, the effective cavity length value is calculated using the peak wavelengths corresponding to the two peak values; when there are three or more peak values in the wavelength range, the effective cavity length value is calculated using the peak wavelength corresponding to the first peak value and the peak wavelength corresponding to the last peak value. This setting can more accurately obtain the effective cavity length value.

[0010] Preferably, in step 3), the corresponding integer m of the peak order mcalculated is the corresponding integer m obtained by rounding off the peak order mcalculated.

[0011] Preferably, in step S4, the corresponding integer m of the peak order mcalculated is the corresponding integer m obtained by rounding the peak order mcalculated.

[0012] Preferably, in step 4), the average error value between all the initial peak wavelengths and the corresponding calculated peak wavelengths is the average of the error values between all the initial peak wavelengths and the corresponding calculated peak wavelengths.

[0013] Preferably, in step S1, the first corrected wavelength is obtained by adding a correction factor to the corresponding calculated peak wavelength of the first corrected wavelength, the correction factor being the average error value / 2, the average error value being the average of the error values between all the initial peak wavelengths and the corresponding calculated peak wavelengths. Preferably, in step S1, the first corrected wavelength is obtained by adding a correction factor to the corresponding calculated peak wavelength of the first corrected wavelength, the correction factor being the average error value / 2, the average error value being the average of the error values between all the initial peak wavelengths and the corresponding calculated peak wavelengths. Preferably, in step S1, the first corrected wavelength is obtained by adding a correction factor to the corresponding calculated peak wavelength of the first corrected wavelength, the correction factor being the average error value / 2, the average error value being the average of the error values between all the initial peak wavelengths and the corresponding calculated peak wavelengths. Preferably, in step S1, the first corrected wavelength Preferably, in step S1, the first corrected wavelength

[0014] Compared with the prior art, the method described in the present application has the beneficial effect that when the method is used to detect a solution with a refractive index of 1.356048 to 1.397432, the precision of all the accurate peak wavelengths obtained is high, and the accurate peak wavelength and the accurate peak order can effectively improve the effect of tracking the corresponding peak wavelength. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is an FPI cavity sensing probe placed in a solution with a refractive index of 1.356048 to obtain the corresponding FPI spectrum in the embodiment; Figure 2 is an FPI spectrum obtained by placing an optical fiber sensor (FPI cavity sensing probe used in the embodiment) in solutions with refractive indices of 1.364253, 1.370854, 1.379416, 1.387443 and 1.397432, respectively; Figure 3 is a fitting result of linear fitting of the peak order and the corresponding accurate peak wavelength under different refractive indices. DETAILED DESCRIPTION

[0016] A peak wavelength tracking method for enhancing the measurement accuracy of an optical fiber sensor, as shown in FIG. 1, includes the following steps: obtaining all initial peak wavelengths from a reflection spectrum, correcting the initial peak wavelengths under the constraint of a set error ε until the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all corrected peak wavelengths respectively is less than or equal to the set error ε, stopping the correction process, and determining that the calculated peak wavelengths obtained by the last correction process are all accurate peak wavelengths, and the peak orders corresponding to all accurate peak wavelengths are all accurate peak orders; then, tracking the corresponding peak wavelengths based on the obtained accurate peak wavelengths and accurate peak orders; and before correcting the initial peak wavelengths under the constraint of the set error ε, the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths respectively is calculated; and the calculation of the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths respectively includes the following steps: 1) calculating the effective cavity length value nL using the peak wavelength corresponding to the first peak and the peak wavelength corresponding to the last peak of all peaks of the obtained reflection spectrum; 2) calculating the peak order mcalculated corresponding to all initial peak wavelengths using the effective cavity length value nL obtained in step 1) and all initial peak wavelengths; 3) calculating the corresponding integer m of the effective cavity length value nL obtained in step 1) and the peak order mcalculated corresponding to all initial peak wavelengths to obtain the calculated peak wavelengths corresponding to all initial peak wavelengths respectively; and 4) calculating the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths respectively obtained in step 3).

[0017] When the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths respectively is greater than the set error ε, the initial peak wavelengths are corrected under the constraint of the set error ε, which includes the following steps: S1, correcting the initial peak wavelengths to obtain corrected peak wavelengths; specifically, when all initial peak wavelengths are respectively corrected for the first time, the first corrected peak wavelength is obtained by replacing the initial peak wavelength When all initial peak wavelengths are respectively corrected for the nth+1 time, n is an integer greater than or equal to 1, the nth+1 corrected peak wavelength S2, calculating the effective cavity length value nL using the first peak wavelength and the last peak wavelength among all the peak wavelengths obtained in step S1; S3, calculating the peak order mcalculated corresponding to the corrected peak wavelength using the effective cavity length value nL obtained in step S2 and the corrected peak wavelength obtained in step S1; S4, calculating the calculated peak wavelength corresponding to the corrected peak wavelength using the effective cavity length value nL obtained in step S2 and the corresponding integer m of the peak order mcalculated corresponding to the corrected peak wavelength; S5, calculating the absolute value of the average error value between all the initial peak wavelengths and the calculated peak wavelengths obtained in step S4, and determining whether the absolute value of the average error value is greater than the set error ε; S6, when the absolute value of the average error value calculated in step S5 is less than or equal to the set error ε, stopping the correction process; otherwise, determining that the peak order mcalculated corresponding to the corrected peak wavelength obtained in step S3 is incorrect, repeating steps S1 to S5 for continuous correction until the absolute value of the average error value calculated in step S5 is less than or equal to the set error ε, stopping the correction process, and determining that all the calculated peak wavelengths obtained in step S4 in the last correction process are accurate peak wavelengths, and the peak order mcalculated corresponding to all the accurate peak wavelengths is the accurate peak order.

[0018] In the embodiment, the specific way of obtaining all the initial peak wavelengths from the reflection spectrum is: using a spectrum detection device to obtain the reflection spectrum signal of the fiber sensor in an equal wavelength interval sampling manner, obtaining an FPI spectrum diagram, and reading all the initial peak wavelengths of the reflection spectrum from the FPI spectrum diagram; wherein, in the embodiment, the FPI spectrum diagram is an FPI spectrum diagram obtained by placing the fiber sensor (FPI cavity sensor probe used in the embodiment) in a solution to be measured with a refractive index of 1.356048, as shown in FIG. 1, the FPI spectrum response data corresponding to the above FPI spectrum diagram is shown in Table 1, in Table 1, λ m represents the initial peak wavelength, and λ′ m represents the calculated peak wavelength corresponding to the initial peak wavelength, respectively; Table 1 is the FPI spectrum response data corresponding to the FPI spectrum diagram obtained from the solution to be measured with a refractive index of 1.356048

[0019] In Table 1, λ m and λ′ m error value is the error value between the initial peak wavelength and the calculated peak wavelength λ′ m corresponding thereto, respectively.

[0020] In this application, the effective cavity length value nL mentioned in step 1) and the effective cavity length value nL mentioned in step S2 can both be calculated using formula (1): In equation (1), λ1 and λ x The peak wavelengths of the first and last peaks are respectively, and x-1 is the difference between the peak order corresponding to the last peak wavelength and the first peak wavelength.

[0021] In this application, the peak order mcalculated corresponding to all initial peak wavelengths in step 2) and the peak order mcalculated corresponding to the peak wavelengths after correction in step S3 can both be calculated using formula (2); When calculating the peak order mcalculated corresponding to all initial peak wavelengths in step 2), in equation (2), nL represents the effective cavity length, and λ m Represents any initial peak wavelength; When calculating the peak order mcalculated corresponding to the corrected peak wavelength in step S3, in equation (2), nL represents the effective cavity length, λ m This represents any corrected peak wavelength.

[0022] In this application, the calculated peak wavelengths corresponding to all initial peak wavelengths in step 3) and the calculated peak wavelengths corresponding to the corrected peak wavelengths in step S4 can both be calculated using equation (3): In step 3), the calculated peak wavelength λ′ corresponds to each of the initial peak wavelengths. m In formula (3), λ′ m The calculated peak wavelength λ′ represents the peak wavelength corresponding to the initial peak wavelength, nL represents the effective cavity length, and m represents the peak order corresponding to any initial peak wavelength. m The peak wavelength corresponding to the integer m obtained after rounding the peak order mcalculated is the same as the peak wavelength; In calculating the peak wavelength corresponding to the corrected peak wavelength in step S4, in formula (3), λ′ m The calculated peak wavelength λ′ represents the peak wavelength corresponding to the corrected peak wavelength, nL represents the effective cavity length, m represents the peak order corresponding to any corrected peak wavelength, and mcalculated is the integer obtained by rounding. m The peak wavelength corresponding to the integer m obtained by rounding the peak order mcalculated is the same as the peak wavelength.

[0023] In this application, the calculation method of the n+1th corrected peak wavelength is shown in equation (4): In equation (4), represents the n+1th corrected peak wavelength, n = 1, 2, 3, …, is the n th corrected peak wavelength The corresponding calculated peak wavelength, Δ represents the read initial peak wavelength λ m and the n th corrected peak wavelength The average error value between them, which is also the average error value between the read initial peak wavelength λ m and the n th corrected peak wavelength .

[0024] In this embodiment, the error ε is set to 0.0000013. After step 4) is completed in this embodiment, it is found that the absolute value of the average error value between the initial peak wavelength and the corresponding calculated peak wavelength is greater than the set error ε. Therefore, this embodiment first performs steps S1 to S5 once to achieve the first correction. After step S5 is completed, it is found that the absolute value of the average error value between all initial peak wavelengths and the corresponding calculated peak wavelength obtained in step S4 is still greater than the set error ε. Therefore, this embodiment repeats steps S1 to S5 once again to perform the second correction. During the second correction, after step S5 is completed, it is found that the absolute value of the average error value between all initial peak wavelengths and the corresponding calculated peak wavelength obtained in step S4 is less than the set error ε. Therefore, the corresponding calculated peak wavelength of the corrected peak wavelength obtained in the second correction process is the accurate peak wavelength, and the peak order mcalculated corresponding to the accurate peak wavelength is the accurate peak order. After the first correction, the corrected peak wavelength, i.e., the first correction peak wavelength and the corresponding calculated peak wavelength are shown in Table 2; after the second correction, the corrected peak wavelength, i.e., the second correction peak wavelength and the corresponding calculated peak wavelength are shown in Table 3.

[0025] Table 2 shows the first correction peak wavelength and the corresponding FPI spectral response data results

[0026] In Table 2, and​​ Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 2, represents the corrected peak wavelength after the first correction, i.e. the first corrected peak wavelength Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 2, represents the corrected peak wavelength after the first correction, i.e. the first corrected peak wavelength Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 2,

[0027] Table 3 is the second corrected peak wavelength corresponding FPI spectrum response data result

[0028] Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 3, Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 3, Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 3, represents the corrected peak wavelength after the second correction, i.e. the second corrected peak wavelength Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 3, Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 3, Error value between the initial peak wavelength and the calculated peak wavelength corresponding to the initial peak wavelength respectively; in Table 3,

[0029] From Table 1, Table 2 and Table 3, it can be seen that the peak value order mcalculated corresponding to the peak wavelength calculated by the method (i.e. the peak value order mcalculated shown in Table 3) is closer to the corresponding integer m rounded off from the peak value order mcalculated corresponding to the peak wavelength (i.e. the peak value order mcalculated shown in Table 1) read from the FPI spectrum than the peak value order mcalculated. This also shows that, under the method and the constraint of setting error ε described in the present application, a more accurate peak value order mcalculated corresponding to the peak wavelength can be obtained.

[0030] ​​In addition, in order to verify that the peak wavelength tracking method described in the present application can also obtain accurate peak wavelengths corresponding to the FPI spectrum of different refractive index to-be-measured solutions, the present application specially places the fiber sensor (FPI cavity sensor probe used in the present embodiment) in to-be-measured solutions with refractive indexes of 1.364253, 1.370854, 1.379416, 1.387443 and 1.397432 to obtain corresponding FPI spectrum, as shown in FIG. 2, wherein RI represents the refractive index of the to-be-measured solution; then, the accurate peak wavelengths corresponding to a peak order mcalculated in the FPI spectrum are tracked and tested, and the test results are shown in Table 4. Then, the present application linearly fits the peak order and the corresponding accurate peak wavelength under different refractive indexes shown in Table 4, and the fitting results are shown in FIG. 3.

[0031] Table 4 is the FPI spectrum response data corresponding to the FPI spectrum obtained from the to-be-measured solutions with refractive indexes of 1.364253, 1.370854, 1.379416, 1.387443 and 1.397432, respectively

[0032] As can be seen from Table 4 and FIG. 3, when the refractive index of the to-be-measured solution is 1.356048 to 1.397432, the refractive index of the to-be-measured solution has a better linear relationship with the accurate peak wavelength, and the fitting parameter R2 is as high as 0.9999 and as low as 0.9990, which shows that when the present application detects the to-be-measured solution with a refractive index of 1.356048 to 1.397432, the accuracy of all the accurate peak wavelengths obtained is high, and the accurate peak wavelength and the accurate peak order can effectively improve the effect of tracking the corresponding peak wavelength.

Claims

1. A peak wavelength tracking method for enhancing the measurement accuracy of a fiber optic sensor, the method comprising: The method comprises the following steps: The absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths is calculated before the initial peak wavelengths are corrected under the constraint of the set error ε; and the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths comprises the following steps: ​ 2. The peak wavelength tracking method for enhancing the measurement accuracy of fiber optic sensors according to claim 1, wherein: 1) the effective cavity length value nL is calculated by using the peak wavelength corresponding to the first peak and the peak wavelength corresponding to the last peak in all peaks of the obtained reflectance spectrum; 2) the peak order mcalculated corresponding to all initial peak wavelengths is calculated by using the effective cavity length value nL obtained in step 1) and all initial peak wavelengths; 3) the calculated peak wavelength corresponding to all initial peak wavelengths is calculated by using the effective cavity length value nL obtained in step 1) and the corresponding integer m of the peak order mcalculated corresponding to all initial peak wavelengths; 4) the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths obtained in step 3) is calculated. When the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelengths corresponding to all initial peak wavelengths is greater than the set error ε, the initial peak wavelengths are corrected under the constraint of the set error ε, and the method comprises the following steps:

3. The method of claim 2, wherein: Then, the peak wavelength after the n+1 correction is obtained; S1, correcting the initial peak wavelength to obtain a corrected peak wavelength; wherein when the first correction peak wavelength is used to correct all initial peak wavelengths respectively After the initial peak wavelength is replaced, a first corrected peak wavelength is obtained; when the n+1th correction is performed on all the initial peak wavelengths respectively, n is an integer greater than or equal to 1, and the n+1th corrected peak wavelength is used as the peak wavelength of the corresponding initial peak wavelength replacement of the nth corrected peak wavelength S2, the effective cavity length value nL is calculated by using the peak wavelength corresponding to the first peak and the peak wavelength corresponding to the last peak in all peak wavelengths obtained in step S1; S3, the peak order mcalculated corresponding to the corrected peak wavelength is calculated by using the effective cavity length value nL obtained in step S2 and the corrected peak wavelength obtained in step S1; S4, the calculated peak wavelength corresponding to the corrected peak wavelength is calculated by using the effective cavity length value nL obtained in step S2 and the corresponding integer m of the peak order mcalculated corresponding to the corrected peak wavelength; S5, the absolute value of the average error value between all initial peak wavelengths and the calculated peak wavelength obtained in step S4 is calculated, and it is judged whether the absolute value of the above average error value is greater than the set error ε; ​ S6, when the absolute value of the average error value calculated in step S5 is less than or equal to the set error ε, the correction process is stopped; otherwise, steps S1 to S5 are repeated to continue correction until the absolute value of the average error value calculated in S5 is less than or equal to the set error ε, the correction process is stopped, and all the calculated peak wavelengths obtained in step S4 in the last correction process are determined to be accurate peak wavelengths, and the peak order mcalculated corresponding to all the accurate peak wavelengths is the accurate peak order.

4. The method of claim 1, wherein: The way to obtain all the initial peak wavelengths from the reflection spectrum is: using a spectral detection device to obtain the reflection spectrum signal of the optical fiber sensor in the form of equal wavelength interval sampling, obtaining the FPI spectrum diagram, and reading all the initial peak wavelengths of the reflection spectrum from the FPI spectrum diagram.

5. The method of claim 2, wherein: In step 1), when there are 2 peaks in the wavelength range, the effective cavity length value is calculated using the peak wavelengths corresponding to the two peaks; when there are 3 or more peaks in the wavelength range, the effective cavity length value is calculated using the peak wavelength corresponding to the first peak and the peak wavelength corresponding to the last peak.

6. The method of claim 3, wherein: In step S2, when there are 2 peaks in the wavelength range, the effective cavity length value is calculated using the peak wavelengths corresponding to the two peaks; when there are 3 or more peaks in the wavelength range, the effective cavity length value is calculated using the peak wavelength corresponding to the first peak and the peak wavelength corresponding to the last peak.

7. The method of claim 2, wherein: In step 3), the corresponding integer m of the peak order mcalculated is the corresponding integer m obtained by rounding the peak order mcalculated.

8. The method of claim 3, wherein: In step S4, the corresponding integer m of the peak order mcalculated is the corresponding integer m obtained by rounding the peak order mcalculated.

9. The method of claim 2, wherein: In step 4), the average error value between all the initial peak wavelengths and the calculated peak wavelengths corresponding to all the initial peak wavelengths respectively is the average value of the error values between all the initial peak wavelengths and the calculated peak wavelengths corresponding to all the initial peak wavelengths respectively.

10. The method of claim 3, wherein: The first corrected wavelength in step S1 The method for obtaining the first corrected wavelength is: adding a correction factor to the calculated peak wavelength corresponding to each initial peak wavelength, the correction factor being the average error value / 2, the average error value being the average of the error values between all initial peak wavelengths and the corresponding calculated peak wavelengths; the nth+1 corrected wavelength The method for obtaining the nth+1 corrected wavelength is: adding a correction factor to the calculated peak wavelength corresponding to the nth corrected wavelength The method for obtaining the calculated peak wavelength corresponding to the nth corrected wavelength is: adding a correction factor to the calculated peak wavelength corresponding to the nth corrected wavelength The method for obtaining the calculated peak wavelength corresponding to the nth corrected wavelength is: adding a correction factor to the calculated peak wavelength corresponding to the nth corrected wavelength The method for obtaining the calculated peak wavelength corresponding to the nth corrected wavelength is: adding a correction factor to the calculated peak wavelength corresponding to the nth corrected wavelength The method for obtaining the calculated peak wavelength corresponding to the nth corrected wavelength is: adding a correction factor to the calculated peak wavelength corresponding to the nth corrected wavelength

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