High-speed fiber Bragg grating sensor wavelength feature identification method and system

Abstract

The invention relates to a high-speed fiber bragg grating sensor wavelength characteristic identification method and system, and belongs to the technical field of fiber bragg grating sensing demodulation. The method comprises the following steps: acquiring reflected light of a fiber bragg grating sensor to obtain a waveform curve of a reflection center wavelength; performing slope derivation on all data points on the waveform curve to obtain a slope curve corresponding to the slope of each data point; collecting reflected light of the fiber Bragg grating sensor for multiple times to obtain a plurality of waveform curves of reflection center wavelengths, and for the waveform curve collected each time, performing slope derivation on all data points on each waveform curve according to the operation to obtain a plurality of slope curves; and finally, detecting the crest position of the slope curve through a centroid detection algorithm to obtain the centroid position of the crest of the slope curve, namely the half-peak position of the reflection center wavelength of the fiber Bragg grating sensor. According to the invention, by improving the centroid detection algorithm, the wavelength identification precision of the FBG can be improved, and the wavelength demodulation speed can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber Bragg grating sensing demodulation, and relates to a method and system for identifying wavelength characteristics of a high-speed fiber Bragg grating sensor. Background Art

[0002] In recent years, the Internet of Things technology has developed extremely rapidly, and the performance of optoelectronic devices has been significantly improved, making great contributions to humanity's entry into a smart society, especially in the sensing field. Fiber Bragg Grating (FBG) sensors constructed with FBG as the core have the advantages of being passive, anti-electromagnetic interference, good explosion-proof performance, small size, light weight, corrosion resistance, high temperature resistance, and long-distance transmission. These advantages enable fiber Bragg gratings to be applied to various extreme and complex environments, including structural health, fire alarm, and perimeter security in power engineering, deep tunnel engineering, traffic tunnels, and energy exploration. Due to the limitations of the demodulation frequency of traditional fiber grating demodulators, the advantages of fiber grating sensors cannot be fully utilized in the field of dynamic measurement, and the application requirements cannot be met. For the increasing demand for high-frequency dynamic signal monitoring, foreign countries have developed efficient and fast fiber grating demodulation equipment, but the equipment cost is relatively high, making it difficult to be applied. The speed and accuracy of the fiber grating demodulation technology developed in China are relatively limited and difficult to meet the requirements of high-speed demodulation and real-time monitoring. Therefore, it is urgent to study fiber grating demodulation technology with high demodulation frequency and low cost.

[0003] When a fiber Bragg grating sensor is exposed to an external environment, it will be affected by stress, temperature, or magnetic field, resulting in a change in the central wavelength of its reflected light. This change can be used to detect the change in the measured parameter. By using a wavelength characteristic recognition algorithm, a small change in the central wavelength position can be found. To meet the application requirements of a large-capacity fiber Bragg grating sensing network in engineering, it is necessary to study a high-speed wavelength characteristic recognition algorithm to improve the progress and stability of the peak search algorithm.

[0004] The conventional centroid detection algorithm uses the amplitude of waveform data points as weights to perform weighted calculation on the data point positions, and then obtains the centroid position of the reflected light wavelength peak of the fiber Bragg grating sensor, which is the position of the maximum light intensity point of the peak, that is, the central wavelength position. Although this method has a low time complexity and a high demodulation speed, it is easily affected by noise and waveform asymmetry, resulting in an inability to obtain an accurate peak position and a reduction in demodulation accuracy. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for identifying the wavelength characteristics of a high-speed fiber Bragg grating sensor, which improves the centroid detection algorithm to identify the reflection center wavelength characteristics of the fiber Bragg grating, so as to solve the problems that the conventional wavelength characteristic identification algorithm is susceptible to noise and asymmetric waveform distribution and has a low demodulation speed.

[0006] To achieve the above object, on the one hand, the present invention provides a method for identifying the wavelength characteristics of a high-speed fiber Bragg grating sensor, which includes:

[0007] S1. Collect the reflected light of the fiber Bragg grating sensor to obtain the waveform curve of the reflection center wavelength;

[0008] S2. Take the derivative of the slopes of all data points on the waveform curve to obtain the slope curve corresponding to the slopes of each data point;

[0009] S3. Collect the reflected light of the fiber Bragg grating sensor multiple times to obtain multiple waveform curves of the reflection center wavelength. For each collected waveform curve, take the derivative of the slopes of all data points on each waveform curve according to the operation of step S2 to obtain multiple slope curves;

[0010] S4. Detect the peak position of the slope curve through the centroid detection algorithm to obtain the centroid position of the peak of the slope curve, that is, the half-peak position of the reflection center wavelength of the fiber Bragg grating sensor.

[0011] Among them, in the slope curve, the abscissa is time and the ordinate is slope.

[0012] Further, in step S4, detecting the peak position of the slope curve through the centroid detection algorithm specifically means that, with the amplitudes of each data point in the slope curve as weights, perform weighted calculation on all data points in each slope curve to obtain the centroid position of the peak of the slope curve.

[0013] Among them, the weighted calculation is performed through the following calculation formula to obtain the centroid position of the peak of the slope curve:

[0014]

[0015] In the formula, y m,n represents the amplitude corresponding to the nth data point in the slope curve m, that is, the slope; x m,n represents the abscissa of the nth data point in the slope curve m.

[0016] On the other hand, the present invention provides a wavelength characteristic recognition system for a high-speed fiber Bragg grating sensor, which system includes a laser light source, an optical amplifier, an optical fiber circulator, a photodetector, and a data processing module. Among them, the laser light source emits an optical signal, which enters the fiber Bragg grating sensor after passing through the optical amplifier and the optical fiber circulator; the reflected light of the fiber Bragg grating sensor is collected by the photodetector after passing through the optical fiber circulator, and finally the reflected optical signal is converted into an electrical signal by the photodetector and then transmitted to the data processing module for processing.

[0017] In the data processing module, the collected data is processed according to the method described in the first aspect, and finally the reflection center wavelength of the fiber Bragg grating sensor is identified.

[0018] Furthermore, the laser light source is a broadband laser.

[0019] The beneficial effects of the present invention are as follows: In the wavelength curve of the reflected light of the fiber Bragg grating sensor, the slope value at the peak is the smallest, while the slope value at the half-peak is the largest. The position of the center wavelength can be obtained by using the slope value at the half-peak position. Therefore, the present invention improves the centroid detection algorithm, converts the wavelength curve of the reflected light of the fiber Bragg grating sensor into a slope curve, and then takes the slope values corresponding to the data points in the slope curve as weights to perform weighted averaging on all data points, and the centroid position can be obtained. This centroid position is reflected as the position of the maximum slope point of the slope curve, which is the half-peak position of the reflection center wavelength of the fiber Bragg grating sensor, thereby realizing the demodulation of the fiber Bragg grating sensor.

[0020] The present invention calculates the reflection center wavelength of the fiber Bragg grating sensor based on the improved centroid detection algorithm, which can significantly improve the accuracy of wavelength recognition of the fiber Bragg grating sensor, especially the recognition of the center wavelength in a complex environment; and compared with other high-precision wavelength characteristic recognition methods, the present invention can greatly improve the speed of wavelength demodulation, can process a large amount of data in real time, and is suitable for high-speed dynamic signal monitoring. In addition, the present invention is applicable to a variety of complex environments, including aerospace, structural health monitoring and other fields, and has broad application prospects.

[0021] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0023] Figure 1 A wavelength feature recognition system for a high-speed fiber Bragg grating sensor provided by an embodiment of the present invention;

[0024] Figure 2 An improved centroid detection algorithm provided by an embodiment of the present invention;

[0025] Figure 3 It is a waveform curve of the reflected central wavelength of the FBG collected by a photodetector after scanning the FBG sensor;

[0026] Figure 4 is Figure 3 The corresponding slope curve obtained by taking the derivative of the slopes of all data points on the waveform curve shown;

[0027] Figure 5 It is multiple slope curves obtained by scanning the FBG sensor multiple times.

[0028] Reference numerals: 1 - broadband laser light source, 2 - optical amplifier, 3 - fiber optic circulator, 4 - FBG sensor array, 5 - photodetector, 6 - data processing module. Detailed implementation manners

[0029] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0030] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and cannot be understood as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, and do not represent the dimensions of actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0031] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be construed as a limitation of the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0032] Since the conventional centroid detection algorithm uses the amplitude of waveform data points as weights, and then performs weighted calculation on the positions of the data points to obtain the centroid position of the reflection wavelength peak of the fiber Bragg grating sensor, that is, to obtain the central wavelength position. However, the conventional algorithm is easily affected by noise and waveform asymmetry, and cannot obtain the accurate peak position, resulting in a decrease in demodulation accuracy.

[0033] Therefore, the present invention proposes to improve the centroid detection algorithm to identify the reflection central wavelength characteristics of the fiber Bragg grating and improve the identification accuracy of the central wavelength of the fiber Bragg grating in a complex environment. In addition, the present invention also proposes a system for identifying the wavelength characteristics of a high-speed fiber Bragg grating sensor, so as to simply and quickly identify the central wavelength of the fiber Bragg grating sensor.

[0034] Embodiment 1

[0035] This embodiment provides an improved centroid detection algorithm to solve the problems that the conventional wavelength characteristic recognition algorithm is easily affected by noise and asymmetric waveform distribution and has a low demodulation speed.

[0036] As Figure 2 shown, the steps of the algorithm include:

[0037] 1) First, scan the fiber Bragg grating sensor, and collect the central wavelength of the reflected light signal of the fiber Bragg grating through a photodetector. As Figure 3 shown, it is the waveform curve of the central wavelength of the reflected light of the fiber Bragg grating collected by the photodetector.

[0038] 2) Then, take the derivative of the slope of all data points on the collected waveform curve to obtain the corresponding slope curve. As Figure 4 shown. It can be found from the slope curve that the slope values at the peak and valley of the reflection waveform are smaller, and the slope values at the half-peak value are larger.

[0039] 3) Scan the fiber Bragg grating sensor multiple times, collect the central wavelength of the reflected light of the fiber Bragg grating through a photodetector and draw a waveform curve. For each collected waveform curve, according to the operation in step 2), take the derivative of the slope for each data point on each waveform curve, and multiple slope curves can be obtained, as Figure 5 shown;

[0040] 4) Use the centroid detection algorithm to detect the peak position of the slope curve. Take the amplitude of each data point on the slope curve as the weight, perform weighted calculation on all data points, and obtain the centroid position of the peak of the slope curve, which is reflected as the position of the maximum slope point among all slope curves, that is, the half-peak position of the reflected central wavelength of the fiber Bragg grating.

[0041] Among them, the calculation expression of the centroid position is as follows:

[0042]

[0043] Among them, y m,n represents the amplitude corresponding to the nth data point in the slope curve m, that is, the slope; x m,n represents the abscissa of the nth data point in the slope curve m.

[0044] Embodiment 2

[0045] This embodiment provides a wavelength characteristic recognition system for a high-speed fiber Bragg grating sensor, as Figure 1 shown. The system includes: a broadband laser light source 1, an optical amplifier 2, an optical fiber circulator 3, an FBG sensor array 4, a photodetector 5, and a data processing module 6. In the data processing module 6, the improved centroid detection algorithm described in Embodiment 1 is carried.

[0046] The usage method of the system in this embodiment is as follows:

[0047] First, a broadband optical signal is emitted by the broadband laser light source 1, and the optical signal enters the optical fiber circulator 3 after passing through the optical amplifier 2; then the optical fiber circulator 3 outputs the broadband optical signal to the FBG sensor array 4, and the FBG sensor array 4 reflects the broadband optical signal and enters the photodetector 5 through the optical fiber circulator 3; in the photodetector 5, the optical signal is converted into an electrical signal and output to the data processing module 6; finally, in the data processing module 6, it is processed in combination with the improved centroid detection algorithm to obtain the wavelength characteristic recognition result of the fiber Bragg grating sensor.

[0048] Embodiment 3

[0049] This embodiment provides a wavelength characteristic recognition method for a high-speed fiber Bragg grating sensor, and the method is as follows:

[0050] 1) First, build a fiber Bragg grating reflection wavelength feature recognition system, including a broadband laser light source, an optical amplifier, an optical fiber circulator, an FBG sensor array, a photodetector, and a data processing module.

[0051] 2) The optical signal is emitted by the broadband light source, transmitted through the circulator to the FBG sensor array for reflection. The reflected optical signal is collected by the photodetector, converted into an electrical signal, and then transmitted to the data processing module. The photodetector collects the optical signal reflected by the FBG sensor array multiple times to obtain multiple spectral signals.

[0052] 3) In the data processing module, the spectral signals collected multiple times are processed by the improved centroid detection algorithm described in Embodiment 1. The reflection waveform curve is differentiated to obtain the slope curve corresponding to the FBG reflection waveform curve. Then, the centroid detection algorithm is used to detect the peak and valley positions of the slope curve, and the maximum slope point of the reflection waveform curve is obtained, which is the half-peak position of the reflection center wavelength.

[0053] In summary, the present invention proposes a method for recognizing the wavelength feature of a high-speed fiber Bragg grating sensor. Through the improved centroid detection algorithm, the accuracy of FBG wavelength recognition can be significantly improved, especially for the recognition of the center wavelength in complex environments. Compared with other high-precision wavelength feature recognition methods, the present invention can greatly improve the wavelength demodulation speed, can process a large amount of data in real time, is applicable to high-speed dynamic signal monitoring, and therefore is applicable to a variety of complex environments, including aerospace, structural health monitoring and other fields, and has broad application prospects.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for identifying the wavelength characteristics of a high-speed fiber Bragg grating sensor, characterized in that, The method includes: S1. Collect the reflected light of the fiber Bragg grating sensor to obtain the waveform curve of the reflection center wavelength; S2. Take the derivative of the slope for all data points on the waveform curve to obtain the slope curve corresponding to the slope of each data point; S3. Collect the reflected light of the fiber Bragg grating sensor multiple times to obtain multiple waveform curves of the reflection center wavelength. For each collected waveform curve, take the derivative of the slope for all data points on each waveform curve according to the operation in step S2 to obtain multiple slope curves; S4. Detect the peak position of the slope curve through the centroid detection algorithm to obtain the centroid position of the peak of the slope curve, that is, the half-peak position of the reflection center wavelength of the fiber Bragg grating sensor.

2. The method according to claim 1, wherein In step S4, the detection of the peak position of the slope curve through the centroid detection algorithm includes weighting and calculating all data points in each slope curve with the amplitude of each data point in the slope curve as the weight to obtain the centroid position of the peak of the slope curve.

3. The method according to claim 2, wherein The following calculation formula is used for weighting calculation to obtain the centroid position of the peak of the slope curve: where y m,n represents the amplitude corresponding to the nth data point in the slope curve m, that is, the slope; x m,n represents the abscissa of the nth data point in the slope curve m.

4. The method according to any one of claims 1 to 3, characterized in that In the slope curve, the abscissa is time and the ordinate is the slope.

5. The method according to claim 1, wherein In step S1, the collection of the reflected light of the fiber Bragg grating sensor includes: first, a laser light source emits an optical signal, and the optical signal enters the fiber Bragg grating sensor through an optical fiber circulator; the reflected light of the fiber Bragg grating sensor is collected by the photodetector after passing through the optical fiber circulator, and finally the reflected optical signal is converted into an electrical signal by the photodetector and then transmitted to the data processing module for processing.

6. The method according to claim 5, characterized in that, The optical signal emitted by the laser light source first passes through an optical amplifier and then enters the optical fiber circulator.

7. The method according to claim 5, wherein The laser light source is a broadband laser.

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