Mode hopping and fluctuation detection method of tunable laser based on FP etalon

Abstract

The present invention discloses a method for detecting mode hopping and fluctuation of a tunable laser based on an F-P standard, which mainly relates to the field of fiber Bragg grating sensing technology and is used for mode hopping and fluctuation detection and repair. First, a fiber Bragg grating demodulation system is built based on the F-P standard, and the free spectral range FSR and fineness F of a single F-P standard are determined according to the system demodulation accuracy, and the peak width W of the F-P standard and the number M of the F-P standard are calculated. Then, a priori experiments are performed on the optical path channels corresponding to the M F-P standard, and the optical signal reference data and optical signal measurement data of the F-P standard optical path are calculated. Based on the optical signal reference data and optical signal measurement data of the F-P standard optical path, the mode hopping and power fluctuation of the tunable laser are judged and corrected, and the fiber Bragg grating demodulation system demodulates the central wavelength of the Bragg grating based on the corrected data.

Description

Technical Field

[0001] The present invention relates to the field of fiber grating sensing technology, mainly to the field of high-precision fiber grating demodulation, and specifically to a tunable laser mode hopping and fluctuation detection method based on an FP standard. Background Art

[0002] Fiber Bragg Grating (FBG) sensors are widely used in aerospace, precision instruments, wearable devices and other fields due to their advantages such as good stability, high precision, small size, low cost, corrosion resistance and ease of reuse. Fiber Bragg Grating (FBG) sensors are widely used in aerospace, precision instruments, wearable devices and other fields. The fiber Bragg Grating demodulation system based on tunable laser (hereinafter referred to as laser) is a device that uses fiber Bragg Grating technology and the principle of fiber Bragg Grating for measurement and sensing. When it is working, the laser needs to be tuned continuously and at high speed. The working state of the laser is not only affected by the laser driving current control and the internal temperature of the laser, but also related to the environment in which it is located. When the laser driving current fluctuates or the temperature fluctuates or the working environment changes suddenly, the tuning result of the laser will change. When the tuning result changes beyond a certain threshold, the laser will experience mode hopping or power fluctuations. Mode hopping usually refers to the change of the internal mode competition of the laser due to changes in various factors (such as temperature changes, unstable driving current, loss of optical components, etc.), the reversal of the dominant longitudinal mode and the suppressed longitudinal mode, resulting in discontinuous changes in the output wavelength; power fluctuation refers to the change or instability of the output power during the operation of the laser due to various factors (such as temperature changes, unstable driving current, loss of optical components, etc.), causing the output power of the laser to rise or fall instantaneously. The mode hopping and power fluctuation phenomena of the laser seriously affect the measurement accuracy of the fiber Bragg grating demodulation system, and the decrease in the demodulation accuracy of the center wavelength of the fiber Bragg grating demodulation system caused by laser mode hopping is more serious than the power fluctuation. Therefore, the detection and correction of mode hopping or power fluctuation is one of the key technologies to achieve precise measurement of the fiber Bragg grating demodulation system.

[0003] At present, the common laser mode hopping detection methods include power linearity judgment method and preset wavelength mapping method. The power linearity judgment method is to perform differential calculation on the "power-wavelength" curve of the laser, and consider the tuning point with large changes in the differential value as the mode hopping point of the laser. The power linearity judgment method is relatively simple to implement, but the threshold value for judging the change in laser mode hopping is selected from the empirical value, the misjudgment rate is relatively high, and it is unable to identify the mode hopping situation where the output power remains unchanged (or changes slightly) but the output wavelength changes. The preset wavelength mapping method calculates the theoretical wavelength of the tuning point based on the preset mapping relationship of the laser, and measures the actual wavelength of the laser tuning point, determines the corresponding error value through the theoretical wavelength and the actual wavelength, and judges whether the laser has mode hopping according to the error value. The preset wavelength mapping method has improved the mode hopping detection accuracy compared with the power linearity judgment method, but it requires the use of servers, computers, spectrometers, etc., the actual implementation cost is very high, and the implementation process is also relatively complicated. Summary of the invention

[0004] The present invention aims to solve the problems that the demodulation results of existing fiber Bragg grating demodulation systems change due to laser mode hopping and power fluctuation during operation, affecting the demodulation accuracy of the system, and the problems that the preset wavelength mapping method requires a server, a computer, a spectrometer, etc., and the actual implementation cost is high and the implementation process is complicated. A tunable laser mode hopping and fluctuation detection method based on an FP standard is provided.

[0005] The tunable laser mode hopping and fluctuation detection method based on FP etalon includes:

[0006] S1. Building a fiber Bragg grating demodulation system based on the FP standard, including the optical path part of the fiber Bragg grating demodulation system and the circuit part of the fiber Bragg grating demodulation system;

[0007] S2. Determine the free spectral range FSR and finesse F of a single FP etalon according to the system demodulation accuracy required by the fiber Bragg grating demodulation system;

[0008] S3. Perform a priori experiments on the FP etalon with known free spectral range FSR and finesse F, obtain the periodic comb peaks of the FP etalon, calculate the amplitude variation range of any single peak in the periodic comb peaks of the FP etalon, and calculate the peak width W of the FP etalon according to the amplitude variation range;

[0009] S4. Calculate the number of FP etalons required in the fiber Bragg grating demodulation system M according to the free spectral range FSR and peak width W of a single FP etalon;

[0010] S5. Perform a priori experiments on the optical channels corresponding to the M FP standards, obtain the light intensity output characteristic data of the optical channels corresponding to the M FP standards, and calculate the optical signal reference data of the FP standard optical path;

[0011] S6. Performing photoelectric conversion on the optical signal information of the optical path of the fiber Bragg grating demodulation system through the circuit part of the fiber Bragg grating demodulation system, and collecting and processing the converted electrical signal information to obtain the optical signal measurement data of the FP standard optical path and the optical signal measurement data of the FBG measurement optical path;

[0012] S8. Based on the optical signal reference data and optical signal measurement data of the FP standard optical path, the mode hopping and power fluctuation of the tunable laser are judged, and the positions of the mode hopping points and the power fluctuation points are recorded;

[0013] S9. According to the recorded positions of the mode hopping points and the power fluctuation points, find the data points of the optical signal measurement data of the FBG measurement optical path at the corresponding positions, and correct the optical signal measurement data of the FBG measurement optical path at the data points;

[0014] S10. The fiber Bragg grating demodulation system demodulates the central wavelength of the fiber Bragg grating based on the optical signal measurement data of the corrected FBG measurement optical path.

[0015] In S1, the optical path of the fiber Bragg grating demodulation system includes a tunable scanning light source, a splitter, a reference optical path, an FP etalon optical path, and an FBG measurement optical path;

[0016] The output end of the tunable scanning light source is connected to the input end of the splitter to generate a narrow-band laser of a specified wavelength and provide a light source for the fiber Bragg grating demodulation system;

[0017] The output end of the splitter is connected to the input ends of the reference optical path, the FP etalon optical path, and the FBG measurement optical path respectively, and is used to evenly divide the narrow-band laser according to the number of channels in the optical path, so that the narrow-band laser enters each optical path channel evenly;

[0018] The reference optical path is used to obtain the light intensity output characteristics of the laser;

[0019] The FP etalon optical path is used to filter narrow-band lasers;

[0020] A fiber Bragg grating (FBG) sensor is arranged inside the FBG measurement optical path to obtain external physical quantity information;

[0021] The output end of the circuit part of the fiber Bragg grating demodulation system is connected to the input end of the tunable scanning light source, which is used to control the tunable scanning light source to generate laser and maintain a constant temperature state. The input end of the circuit part is connected to the output end of each optical path channel in the reference optical path, the FP standard tool optical path, and the FBG measurement optical path, and performs photoelectric conversion on the optical signal information of each optical path channel and performs signal acquisition and processing on the converted electrical signal.

[0022] The FP etalon optical path is composed of M FP etalons with the same free spectral range FSR, the same finesse F, and different starting wavelengths. Each FP etalon corresponds to an FP etalon optical path channel, forming an FP etalon array, which is used to filter the narrow-band laser input into each FP etalon optical path channel to generate periodic comb peaks with the same free spectral range FSR, the same finesse F, and different starting wavelengths.

[0023] In S3, a priori experiments are performed on the FP etalon with known free spectral range FSR and finesse F to obtain the periodic comb peaks of the FP etalon and record the starting point of the amplitude change of any single peak in the periodic comb peaks. and end point , according to the starting point and end point Calculate the peak width W:

[0024] ;

[0025] Peak width is the range of amplitude variation of each single peak in the periodic comb peak.

[0026] According to the free spectral range FSR and peak width W of a single FP etalon, the number M of FP etalons required for the FP etalon optical path of the fiber Bragg grating demodulation system is calculated:

[0027] ;

[0028] In the formula, is the number of FP etalons in the FP etalon optical path rounded up.

[0029] In S5, the optical signal reference data of the FP etalon optical path includes the reference output characteristics of the FP etalon optical path and the reference change rate of the output characteristics of the FP etalon optical path. A priori experiments are performed on M FP etalons to obtain the light intensity output characteristics of the light path channels of the FP etalon optical path corresponding to the M FP etalons. Based on the light intensity output characteristics of the light path channels of the M FP etalon optical paths, the reference output characteristics of the FP etalon optical path are calculated. :

[0030] ;

[0031] In the formula, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the first FP etalon, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the second FP etalon, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the Mth FP etalon;

[0032] Reference output characteristics for FP etalon optical path Take the derivative and calculate the reference rate of change of the optical path output characteristics of the FP standard :

[0033] ;

[0034] In the formula, is the wavelength of the narrowband laser, Indicates taking the derivative.

[0035] Through the fiber Bragg grating demodulation system circuit part, the optical signal information at the output end of the reference optical path, FP standard optical path, and FBG measurement optical path is converted into photoelectric information, and the converted electrical signal information is collected and processed to obtain the optical signal measurement data of the FBG measurement optical path. and the optical signal test data of the FP etalon optical path channel corresponding to the M FP etalons, and the optical signal measurement data of the FP etalon optical path is calculated according to the optical signal test data of the FP etalon optical path channel corresponding to the M FP etalons. :

[0036] ;

[0037] In the formula, is the optical signal test data of the FP etalon optical path channel corresponding to the first FP etalon, is the optical signal test data of the FP etalon optical path channel corresponding to the second FP etalon, is the optical signal test data of the FP etalon optical path channel corresponding to the Mth FP etalon;

[0038] Optical signal measurement data for the FP etalon optical path Differentiating it, we get:

[0039] ;

[0040] In the formula, Indicates the amount of change.

[0041] Based on the optical signal reference data of the FP etalon optical path and the optical signal measurement data of the FP etalon optical path, the optical signal data of each optical path channel of the FP etalon optical path is judged for mode hopping and power fluctuation, and the positions of the mode hopping points and the power fluctuation points are recorded. The specific process is as follows:

[0042] S8.1. Conduct a priori experiments on the FP etalon to obtain the periodic comb peaks of each optical path channel in the FP etalon optical path, and record the position of the central wavelength point of each single peak in the periodic comb peak;

[0043] S8.2. Perform differential calculation on the optical signal test data of each optical path channel of the FP standard optical path, and determine the tuning point based on the result of the differential calculation;

[0044] S8.3. Based on the differential data, determine whether the tuning point is the central wavelength point of each single peak in the periodic comb peak, exclude the tuning point corresponding to the central wavelength point, and perform mode hopping and power fluctuation judgment on the remaining tuning points;

[0045] S8.4. Perform mode hopping judgment on the remaining tuning points based on the reference change rate of the output characteristics of each optical path channel in the FP standard optical path and the differential data of the optical signal test data of each optical path channel in the FP standard optical path, record the tuning points that meet the mode hopping judgment conditions as mode hopping points, and record the position information of the mode hopping points;

[0046] S8.5. Perform power fluctuation judgment on the remaining tuning points that do not meet the mode hopping judgment requirements, record the tuning points that meet the power fluctuation conditions as power fluctuation points, and record the position information of the power fluctuation points.

[0047] Perform mode hopping judgment on the tuning point. If the data at the tuning point meets any one of the conditions for mode hopping judgment among conditions 1, 2, and 3, the tuning point is judged to be a mode hopping point, and the position information of the mode hopping point is recorded in array T1[x].

[0048] Condition one: ;

[0049] Condition two: ;

[0050] Condition three: Relative to Different number;

[0051] The condition for judging the power fluctuation at the tuning point is: If the data at the tuning point meets the conditions for judging power fluctuation, the tuning point is judged to be a power fluctuation point, and the position information of the power fluctuation point is recorded in the array T2[x].

[0052] According to the position information of the tuning points recorded in the arrays T1[x] and T2[x], the data points of the optical signal measurement data of the FBG measurement optical path at the corresponding positions are found, and the mean of the optical signal measurement data of the two points on the left and right of the data point is calculated. The optical signal measurement data of the FBG measurement optical path at the data point is replaced by the mean of the data of the two points on the left and right of the data point, and the optical signal measurement data of the FBG measurement optical path is corrected. The fiber Bragg grating demodulation system demodulates the central wavelength of the Bragg grating based on the optical signal measurement data of the corrected FBG measurement optical path.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. The present invention constructs an FP etalon array based on a single-channel FP etalon to form an FP etalon optical path. By adopting a multi-channel FP etalon and designing a corresponding judgment algorithm, the optical signal data collected by the FBG measurement optical path is corrected to make up for the shortcoming that the single-channel FP etalon is insensitive to the output change of the tunable laser outside the peak width range of its comb peak, greatly improving the accuracy of the system for mode hopping detection and power fluctuation detection, ensuring the long-term stability of the system, and solving the problem of large error and high misjudgment rate in the power linearity judgment method of using the "power-wavelength" curve of the laser for differential calculation and judging the mode hopping point by empirical value, so that the system is more sensitive to the output change of the tunable laser within the full band, especially the detection accuracy of the mode hopping situation where the output power remains unchanged (or changes slightly) but the output wavelength changes is improved;

[0055] 2. Compared with the preset wavelength mapping method, which requires the use of servers, computers, spectrometers and other equipment, and has the characteristics of high actual implementation cost and complicated implementation process, the present invention only needs to construct an FP etalon optical path of an FP etalon array based on the FP etalon, and construct a fiber Bragg grating demodulation system with an ARM microprocessor as the core, without changing the internal hardware structure of the laser itself and the circuit part of the fiber Bragg grating demodulation system, so as to achieve high-precision detection of mode hopping and power fluctuation of the tunable laser, and has high economic benefits;

[0056] 3. The present invention can classify mode hopping and power fluctuation based on corresponding judgment algorithms. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic diagram of the structure of a fiber Bragg grating demodulation system when the number of FP etalons M=4 provided in an embodiment of the present invention;

[0058] Figure 2 An overall schematic diagram of the periodic comb peaks of a single FP etalon provided in an embodiment of the present invention;

[0059] Figure 3 The embodiment of the present invention provides Figure 2 A partial enlarged view of the A area;

[0060] Figure 4 A light intensity output characteristic curve diagram when the number of FP etalons provided in an embodiment of the present invention is M=4;

[0061] Figure 5 The embodiment of the present invention provides Figure 4 Differential data graph corresponding to the medium light intensity output characteristic curve. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] The tunable laser mode hopping and fluctuation detection method based on FP etalon includes:

[0064] S1. Building a fiber Bragg grating demodulation system based on the FP standard, including the optical path part of the fiber Bragg grating demodulation system and the circuit part of the fiber Bragg grating demodulation system;

[0065] S2. Determine the free spectral range FSR and finesse F of a single FP etalon according to the system demodulation accuracy required by the fiber Bragg grating demodulation system;

[0066] S3. Perform a priori experiments on the FP etalon with known free spectral range FSR and finesse F, obtain the periodic comb peaks of the FP etalon, calculate the amplitude variation range of any single peak in the periodic comb peaks of the FP etalon, and calculate the peak width W of the FP etalon according to the amplitude variation range;

[0067] S4. Calculate the number of FP etalons required in the fiber Bragg grating demodulation system M according to the free spectral range FSR and peak width W of a single FP etalon;

[0068] S5. Perform a priori experiments on the optical channels corresponding to the M FP standards, obtain the light intensity output characteristic data of the optical channels corresponding to the M FP standards, and calculate the optical signal reference data of the FP standard optical path;

[0069] S6. Performing photoelectric conversion on the optical signal information of the optical path of the fiber Bragg grating demodulation system through the circuit part of the fiber Bragg grating demodulation system, and collecting and processing the converted electrical signal information to obtain the optical signal measurement data of the FP standard optical path and the optical signal measurement data of the FBG measurement optical path;

[0070] S8. Based on the optical signal reference data and optical signal measurement data of the FP standard optical path, the mode hopping and power fluctuation of the tunable laser are judged, and the positions of the mode hopping points and the power fluctuation points are recorded;

[0071] S9. According to the recorded positions of the mode hopping points and the power fluctuation points, find the data points of the optical signal measurement data of the FBG measurement optical path at the corresponding positions, and correct the optical signal measurement data of the FBG measurement optical path at the data points;

[0072] S10. The fiber Bragg grating demodulation system demodulates the central wavelength of the fiber Bragg grating based on the optical signal measurement data of the corrected FBG measurement optical path.

[0073] In S1, the optical path of the fiber Bragg grating demodulation system includes a tunable scanning light source, a splitter, a reference optical path, an FP etalon optical path, and an FBG measurement optical path;

[0074] The output end of the tunable scanning light source is connected to the input end of the splitter to generate a narrow-band laser of a specified wavelength and provide a light source for the fiber Bragg grating demodulation system;

[0075] The output end of the splitter is connected to the input ends of the reference optical path, the FP etalon optical path, and the FBG measurement optical path respectively, and is used to evenly divide the narrow-band laser according to the number of channels in the optical path, so that the narrow-band laser enters each optical path channel evenly;

[0076] The reference optical path is used to obtain the light intensity output characteristics of the laser;

[0077] The FP etalon optical path is used to filter narrow-band lasers;

[0078] A fiber Bragg grating (FBG) sensor is arranged inside the FBG measurement optical path to obtain external physical quantity information;

[0079] The output end of the circuit part of the fiber Bragg grating demodulation system is connected to the input end of the tunable scanning light source, which is used to control the tunable scanning light source to generate laser and maintain a constant temperature state. The input end of the circuit part is connected to the output end of each optical path channel in the reference optical path, the FP standard tool optical path, and the FBG measurement optical path, and performs photoelectric conversion on the optical signal information of each optical path channel and performs signal acquisition and processing on the converted electrical signal.

[0080] The FP etalon optical path is composed of M FP etalons with the same free spectral range FSR, the same finesse F, and different starting wavelengths. Each FP etalon corresponds to an FP etalon optical path channel, forming an FP etalon array, which is used to filter the narrow-band laser input into each FP etalon optical path channel to generate periodic comb peaks with the same free spectral range FSR, the same finesse F, and different starting wavelengths.

[0081] In S3, a priori experiments are performed on the FP etalon with known free spectral range FSR and finesse F to obtain the periodic comb peaks of the FP etalon and record the starting point of the amplitude change of any single peak in the periodic comb peaks. and end point , according to the starting point and end point Calculate the peak width W:

[0082] ;

[0083] Peak width The range of amplitude variation of each single peak in the periodic comb peak. A priori experiments are conducted on the FP etalon with known free spectral range FSR and finesse F to obtain the periodic comb peak of the FP etalon. Within the wavelength range of the FP etalon, the shapes of all single peaks in the periodic comb peak are approximately the same, and the slight difference can be ignored. Therefore, it is considered that the peak width of all single peaks in the periodic comb peak is It's the same.

[0084] According to the free spectral range FSR and peak width W of a single FP etalon, the number M of FP etalons required for the FP etalon optical path of the fiber Bragg grating demodulation system is calculated:

[0085] ;

[0086] In the formula, is the number of FP etalons in the FP etalon optical path rounded up. If the free spectrum range of the FP etalon selected in the fiber Bragg grating demodulation system is 100 GHz and the finesse is , that is, the free spectral range of the FP etalon , precision , a priori experiments were performed on the FP etalon, and we obtained , According to the formula, we can get , that is, the number of FP etalons required for the FP etalon optical path of the fiber Bragg grating demodulation system is 4. The fiber Bragg grating demodulation system built on this basis is as follows: Figure 1 shown.

[0087] In S5, the optical signal reference data of the FP etalon optical path includes the reference output characteristics of the FP etalon optical path and the reference change rate of the output characteristics of the FP etalon optical path. A priori experiments are performed on M FP etalons to obtain the light intensity output characteristics of the light path channels of the FP etalon optical path corresponding to the M FP etalons. Based on the light intensity output characteristics of the light path channels of the M FP etalon optical paths, the reference output characteristics of the FP etalon optical path are calculated. :

[0088] ;

[0089] In the formula, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the first FP etalon, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the second FP etalon, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the Mth FP etalon;

[0090] Reference output characteristics for FP etalon optical path Take the derivative and calculate the reference rate of change of the optical path output characteristics of the FP standard :

[0091] ;

[0092] In the formula, is the wavelength of the narrowband laser, Indicates taking the derivative.

[0093] Through the fiber Bragg grating demodulation system circuit part, the optical signal information at the output end of the reference optical path, FP standard optical path, and FBG measurement optical path is converted into photoelectric information, and the converted electrical signal information is collected and processed to obtain the optical signal measurement data of the FBG measurement optical path. and the optical signal test data of the FP etalon optical path channel corresponding to the M FP etalons, and the optical signal measurement data of the FP etalon optical path is calculated according to the optical signal test data of the FP etalon optical path channel corresponding to the M FP etalons. :

[0094] ;

[0095] In the formula, is the optical signal test data of the FP etalon optical path channel corresponding to the first FP etalon, is the optical signal test data of the FP etalon optical path channel corresponding to the second FP etalon, is the optical signal test data of the FP etalon optical path channel corresponding to the Mth FP etalon;

[0096] Optical signal measurement data for the FP etalon optical path Differentiating it, we get:

[0097] ;

[0098] In the formula, Indicates the amount of change.

[0099] Based on the optical signal reference data of the FP etalon optical path and the optical signal measurement data of the FP etalon optical path, the optical signal data of each optical path channel of the FP etalon optical path is judged for mode hopping and power fluctuation, and the positions of the mode hopping points and the power fluctuation points are recorded. The specific process is as follows:

[0100] S8.1. Conduct a priori experiments on the FP etalon to obtain the periodic comb peaks of each optical path channel in the FP etalon optical path, and record the position of the central wavelength point of each single peak in the periodic comb peak;

[0101] S8.2. Perform differential calculation on the optical signal test data of each optical path channel of the FP standard optical path, and determine the tuning point based on the result of the differential calculation;

[0102] S8.3. Based on the differential data, determine whether the tuning point is the central wavelength point of each single peak in the periodic comb peak, exclude the tuning point corresponding to the central wavelength point, and perform mode hopping and power fluctuation judgment on the remaining tuning points;

[0103] S8.4. Perform mode hopping judgment on the remaining tuning points based on the reference change rate of the output characteristics of each optical path channel in the FP standard optical path and the differential data of the optical signal test data of each optical path channel in the FP standard optical path, record the tuning points that meet the mode hopping judgment conditions as mode hopping points, and record the position information of the mode hopping points;

[0104] Perform mode hopping judgment on the tuning point. If the data at the tuning point meets any one of the conditions for mode hopping judgment among conditions 1, 2, and 3, the tuning point is judged to be a mode hopping point, and the position information of the mode hopping point is recorded in array T1[x].

[0105] Condition one: ;

[0106] Condition two: ;

[0107] Condition three: Relative to Different number;

[0108] S8.5. Perform power fluctuation judgment on the remaining tuning points that do not meet the mode hopping judgment requirements, record the tuning points that meet the power fluctuation conditions as power fluctuation points, and record the position information of the power fluctuation points.

[0109] The condition for judging the power fluctuation at the tuning point is: If the data at the tuning point meets the conditions for judging power fluctuation, the tuning point is judged to be a power fluctuation point, and the position information of the power fluctuation point is recorded in the array T2[x].

[0110] One FP etalon corresponds to an optical path channel of the FP etalon optical path. Differential calculation is performed on the optical signal test data of each optical path channel of the FP etalon optical path. The tunable points are obtained according to the result of the differential calculation. The number of tunable points obtained is the data length of the FP etalon optical path channel. , based on the judgment conditions and judgment process of the mode hopping point and power fluctuation point, perform mode hopping and power judgment on each tuning point of each optical path channel, and set the initial judgment value , initial cycle value ,like , Then for the The optical path channel corresponds to The tuning points are used to judge the mode hopping points and power fluctuation points, and the position information of the tuning points that meet the mode hopping judgment conditions are recorded in the array T1[x], and the position information of the tuning points that meet the power fluctuation judgment conditions are recorded in the array T2[x]. The value increases by 1 until , this round of cycle judgment ends, and a new round of mode hopping and power fluctuation judgment begins. The value is increased by 1, The initial value is 1. The optical path channels correspond to 1 to The mode hopping point and power fluctuation point are judged by the tuning points until , the judgment ends.

[0111] According to the position information of the tuning points recorded in the arrays T1[x] and T2[x], the data points of the optical signal measurement data of the FBG measurement optical path at the corresponding positions are found, and the mean of the optical signal measurement data of the two points on the left and right of the data point is calculated. The optical signal measurement data of the FBG measurement optical path at the data point is replaced by the mean of the data of the two points on the left and right of the data point, and the optical signal measurement data of the FBG measurement optical path is corrected. The fiber Bragg grating demodulation system demodulates the central wavelength of the Bragg grating based on the optical signal measurement data of the corrected FBG measurement optical path.

[0112] like Figure 1 The fiber Bragg grating demodulation system when the number of FP standards is 4 includes a fiber Bragg grating demodulation system circuit part and a fiber Bragg grating demodulation system optical path part, and the fiber Bragg grating demodulation system optical path part includes a tunable scanning light source, a splitter, a reference optical path, an FP standard optical path composed of 4 FP standards, and a FBG measurement optical path, wherein the tunable scanning light source is controlled by the fiber Bragg grating demodulation system circuit part, and the output ends of the reference optical path, the FP standard optical path, and the FBG measurement optical path are connected to the fiber Bragg grating demodulation system circuit part.

[0113] like Figure 2 and Figure 3 As shown, the peak width of each single peak in the periodic comb peak of the optical path channel corresponding to a single FP etalon same, is the starting point of any significant change in the amplitude of a single peak, is the end point of any single peak amplitude change, and the starting point and end point The peak width between the FP standard Point B and point C are the positions of the central wavelength points of the corresponding single peak, and the length BC between point B and point C is the free spectral range of the corresponding FP etalon. .

[0114] Figure 4 is the local light intensity output characteristic curve of each FP etalon optical path channel in the FP etalon optical path when the number of FP etalons in the FP etalon optical path is M=4, Figure 5 For Figure 4 The data diagram of the differential calculation of the light intensity output characteristic curve in , that is Figure 5 for Figure 4 The differential data graph corresponding to the medium light intensity output characteristic curve is as follows: Figure 4 and Figure 5 As shown in Figure 1, when the laser mode hops at a certain tuning point, the differential data corresponding to the light intensity output characteristic curve of the FP standard optical path channel will suddenly change, such as Figure 4 The leftward mode hopping phenomenon occurs in the middle D area, that is, the wavelength value of the current tuning point jumps to a wavelength value smaller than that point. Figure 5 The absolute value of the amplitude of the differential data in the D1 region decreases sharply toward 0, such as Figure 4 The mode hopping phenomenon occurs to the right in the middle E region, that is, the wavelength value of the current tuning point jumps to a wavelength value greater than that point. Figure 5 The absolute value of the amplitude of the differential data in the E1 region will increase dramatically. When the laser power fluctuates at a certain tuning point, the differential data corresponding to the light intensity output characteristic curve of the FP standard optical path channel will also change dramatically, but the amplitude of the power fluctuation is smaller than the amplitude of the mode hopping.

[0115] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon, characterized in that: include: S1. Building a fiber Bragg grating demodulation system based on the FP standard, including the optical path part of the fiber Bragg grating demodulation system and the circuit part of the fiber Bragg grating demodulation system; S2. Determine the free spectral range FSR and finesse F of a single FP etalon according to the system demodulation accuracy required by the fiber Bragg grating demodulation system; S3. Perform a priori experiments on the FP etalon with known free spectral range FSR and finesse F, obtain the periodic comb peaks of the FP etalon, calculate the amplitude variation range of any single peak in the periodic comb peaks of the FP etalon, and calculate the peak width W of the FP etalon according to the amplitude variation range; S4. Calculate the number of FP etalon M required in the fiber Bragg grating demodulation system according to the free spectral range FSR and peak width W of a single FP etalon; S5. Perform a priori experiments on the optical path channels corresponding to the M FP standards, obtain the light intensity output characteristic data of the optical path channels corresponding to the M FP standards, and calculate the optical signal reference data of the FP standard optical path; S6. Performing photoelectric conversion on the optical signal information of the optical path of the fiber Bragg grating demodulation system through the circuit part of the fiber Bragg grating demodulation system, and collecting and processing the converted electrical signal information to obtain the optical signal measurement data of the FP standard optical path and the optical signal measurement data of the FBG measurement optical path; S7. Based on the optical signal reference data and optical signal measurement data of the FP standard optical path, the mode hopping and power fluctuation of the tunable laser are judged, and the positions of the mode hopping points and the power fluctuation points are recorded; S8. According to the recorded positions of the mode hopping points and the power fluctuation points, find the data points of the optical signal measurement data of the FBG measurement optical path at the corresponding positions, and correct the optical signal measurement data of the FBG measurement optical path at the data points; S9. The fiber Bragg grating demodulation system demodulates the central wavelength of the Bragg grating based on the optical signal measurement data of the corrected FBG measurement optical path; In S1, the optical path of the fiber Bragg grating demodulation system includes a tunable scanning light source, a splitter, a reference optical path, an FP etalon optical path, and an FBG measurement optical path; The output end of the tunable scanning light source is connected to the input end of the splitter, and is used to generate a narrow-band laser of a specified wavelength to provide a light source for the fiber Bragg grating demodulation system; The output end of the splitter is respectively connected to the input ends of the reference optical path, the FP etalon optical path, and the FBG measurement optical path, and is used to evenly divide the narrow-band laser according to the number of channels in the optical path, so that the narrow-band laser enters each optical path channel evenly; The reference optical path is used to obtain the light intensity output characteristics of the laser; The FP standard optical path is used to filter the narrow-band laser; A fiber Bragg grating (FBG) sensor is provided inside the FBG measurement optical path for acquiring external physical quantity information; The output end of the circuit part of the fiber Bragg grating demodulation system is connected to the input end of the tunable scanning light source, which is used to control the tunable scanning light source to generate laser and maintain the constant temperature state of the tunable scanning light source. The input end of the circuit part is connected to the output end of each optical path channel in the reference optical path, the FP standard tool optical path, and the FBG measurement optical path, and performs photoelectric conversion on the optical signal information of each optical path channel and performs signal acquisition and processing on the converted electrical signal; The FP etalon optical path is composed of M FP etalons with the same free spectral range FSR, the same finesse F, and different starting wavelengths. Each FP etalon corresponds to an FP etalon optical path channel, forming an FP etalon array, which is used to filter the narrow-band laser input into each FP etalon optical path channel to generate periodic comb peaks with the same free spectral range FSR, the same finesse F, and different starting wavelengths.

2. The method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon according to claim 1, characterized in that: In S3, a priori experiments are performed on the FP etalon with known free spectral range FSR and finesse F to obtain the periodic comb peaks of the FP etalon and record the starting point of the amplitude change of any single peak in the periodic comb peaks. and end point , according to the starting point and end point Calculate the peak width W: ； Peak width is the range of amplitude variation of each single peak in the periodic comb peak.

3. The method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon according to claim 2, characterized in that: According to the free spectral range FSR and peak width W of a single FP etalon, the number M of FP etalons required for the FP etalon optical path of the fiber Bragg grating demodulation system is calculated: ； In the formula, is the number of FP etalons in the FP etalon optical path rounded up.

4. The method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon according to claim 3, characterized in that: In S5, the optical signal reference data of the FP etalon optical path includes the reference output characteristics of the FP etalon optical path and the reference change rate of the output characteristics of the FP etalon optical path. A priori experiments are performed on M FP etalons to obtain the light intensity output characteristics of the light path channels of the FP etalon optical path corresponding to the M FP etalons. Based on the light intensity output characteristics of the light path channels of the M FP etalon optical paths, the reference output characteristics of the FP etalon optical path are calculated. : ； In the formula, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the first FP etalon, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the second FP etalon, is the light intensity output characteristic of the FP etalon optical path channel corresponding to the Mth FP etalon; Reference output characteristics for FP etalon optical path Take the derivative and calculate the reference rate of change of the optical path output characteristics of the FP standard : ； In the formula, is the wavelength of the narrowband laser, Indicates taking the derivative.

5. The method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon according to claim 4, characterized in that: Through the fiber Bragg grating demodulation system circuit part, the optical signal information at the output end of the reference optical path, FP standard optical path, and FBG measurement optical path is converted into photoelectric information, and the converted electrical signal information is collected and processed to obtain the optical signal measurement data of the FBG measurement optical path. and the optical signal test data of the FP etalon optical path channel corresponding to the M FP etalons, and the optical signal measurement data of the FP etalon optical path is calculated according to the optical signal test data of the FP etalon optical path channel corresponding to the M FP etalons. : ； In the formula, is the optical signal test data of the FP etalon optical path channel corresponding to the first FP etalon, is the optical signal test data of the FP etalon optical path channel corresponding to the second FP etalon, is the optical signal test data of the FP etalon optical path channel corresponding to the Mth FP etalon; Optical signal measurement data for the FP etalon optical path Differentiating it, we get: ； In the formula, Indicates the amount of change.

6. The method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon according to claim 5, characterized in that: Based on the optical signal reference data of the FP etalon optical path and the optical signal measurement data of the FP etalon optical path, the optical signal data of each optical path channel of the FP etalon optical path is judged for mode hopping and power fluctuation, and the positions of the mode hopping points and the power fluctuation points are recorded. The specific process is as follows: S7.

1. Conduct a priori experiments on the FP etalon to obtain the periodic comb peaks of each optical path channel in the FP etalon optical path, and record the position of the central wavelength point of each single peak in the periodic comb peak; S7.

2. Perform differential calculation on the optical signal test data of each optical path channel of the FP standard optical path, and determine the tuning point based on the result of the differential calculation; S7.

3. Based on the differential data, determine whether the tuning point is the central wavelength point of each single peak in the periodic comb peak, exclude the tuning point corresponding to the central wavelength point, and perform mode hopping and power fluctuation judgment on the remaining tuning points; S7.

4. Perform mode hopping judgment on the remaining tuning points based on the reference change rate of the output characteristics of each optical path channel in the FP standard optical path and the differential data of the optical signal test data of each optical path channel in the FP standard optical path, record the tuning points that meet the mode hopping judgment conditions as mode hopping points, and record the position information of the mode hopping points; S7.

5. Perform power fluctuation judgment on the remaining tuning points that do not meet the mode hopping judgment requirements, record the tuning points that meet the power fluctuation conditions as power fluctuation points, and record the position information of the power fluctuation points.

7. The method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon according to claim 6, characterized in that: Perform mode hopping judgment on the tuning point. If the data at the tuning point meets any one of the conditions for mode hopping judgment among conditions 1, 2, and 3, the tuning point is judged to be a mode hopping point, and the position information of the mode hopping point is recorded in array T1[x]. Condition 1: ; Condition 2: ; Condition three: Relative to Different number; The condition for judging the power fluctuation at the tuning point is: If the data at the tuning point meets the conditions for judging power fluctuation, the tuning point is judged to be a power fluctuation point, and the position information of the power fluctuation point is recorded in the array T2[x].

8. The method for detecting mode hopping and fluctuation of a tunable laser based on an FP etalon according to claim 7, characterized in that: According to the position information of the tuning points recorded in the arrays T1[x] and T2[x], the data points of the optical signal measurement data of the FBG measurement optical path at the corresponding positions are found, and the mean of the optical signal measurement data of the two points on the left and right of the data point is calculated. The optical signal measurement data of the FBG measurement optical path at the data point is replaced by the mean of the data of the two points on the left and right of the data point, and the optical signal measurement data of the FBG measurement optical path is corrected. The fiber Bragg grating demodulation system demodulates the central wavelength of the Bragg grating based on the optical signal measurement data of the corrected FBG measurement optical path.

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