A fiber Bragg grating sensing demodulation system to solve the wavelength double peak problem

Abstract

The present invention provides a fiber Bragg grating sensing demodulation system for solving the wavelength double peak problem, comprising: a demodulation center and a fiber Bragg grating group of matching combination mode connected to the demodulation center through an optical cable; the demodulation center comprises: a server and a demodulation unit, when the total number of light wave signals obtained after demodulation of the reflected light of the detection light emitted by the demodulation unit is greater than the number of the grating fiber sensors actually installed, it is determined that the fiber Bragg grating center wavelength is split into two peak wavelengths, the position of the double peak wavelength is obtained through the server, and the two peak wavelengths are averaged to obtain the original fiber Bragg grating center wavelength. The fiber Bragg grating sensor limits the optical power of the reflected light to the input optical power range of the demodulation center, which can greatly reduce the number of wavelength double peaks. The present invention restores the wavelength double peak to a single peak wavelength carrying reliable information, thereby accurately measuring the physical change carried by the fiber Bragg grating.

Description

Technical Field

[0001] The invention relates to the technical field of fiber grating sensing demodulation, and in particular to a fiber grating sensing demodulation system for solving the problem of double wavelength peaks. Background Art

[0002] With the development of Internet technology, in recent years, with the continuous development of infrastructure construction and large-scale production activities in my country, more and more occasions have put forward new requirements for monitoring methods of various parameters. Among them, fiber optic sensing technology has shown more advantages and attention in practical applications by virtue of its passiveness, intrinsic safety, anti-electromagnetic interference, and easy networking in the application process of fiber Bragg grating sensors. The sensitivity of FBG sensors to the physical parameters of the measured object is reflected in the drift of the central wavelength of its reflected light signal. Based on this characteristic, FBG can be packaged in certain ways according to the characteristics of different sensing physical quantities, and sense various measurements such as temperature, pressure, and displacement. The key technology for the practical application of this FBG sensing method is to accurately measure the tiny drift of its central wavelength through FBG demodulation technology. The essence of demodulation technology is to convert the optical signal carrying specific wavelength information into the wavelength value of the optical signal.

[0003] Although the current demodulation technology is relatively mature, in actual applications, for a certain FBG sensor demodulation system that has been adopted, the reflected light signal of the FBG sensor may have a wavelength double peak on the demodulation system due to the high optical power. Usually, the demodulation algorithm in the FBG demodulation system will demodulate the double peak of the FBG into two central wavelengths, which directly leads to the loss of the original central wavelength of the FBG. Therefore, the problem of wavelength double peaks will have a serious impact on the optical fiber sensing system, and it is impossible to accurately measure the physical change information carried by the FBG. Summary of the invention

[0004] The object of the present invention is to provide a fiber Bragg grating sensing demodulation system that solves the wavelength double peak problem and can solve at least one of the above-mentioned technical problems.

[0005] According to a specific embodiment of the present invention, the present invention provides a fiber Bragg grating sensing demodulation system for solving the wavelength double peak problem, comprising:

[0006] A demodulation center and a fiber grating group of matching combination mode connected to the demodulation center via an optical cable;

[0007] The demodulation center includes: a server and a demodulation unit, wherein the demodulation unit is used to demodulate the optical signal measured by the fiber Bragg grating group of the matching combination mode; the server is used to calculate the optical signal demodulated by the demodulation unit to obtain the original fiber Bragg grating center wavelength, specifically, the total number of optical wave signals obtained after demodulation of the reflected light of the detection light emitted by the demodulation unit is compared with the number of fiber Bragg grating sensors actually installed, when the total number of optical wave signals obtained after demodulation of the reflected light of the detection light emitted by the demodulation unit is greater than the number of fiber Bragg grating sensors actually installed, it is determined that the fiber Bragg grating center wavelength is split into two peak wavelengths, the position of the fiber Bragg grating sensor where the double peak wavelength is located is obtained through the server, and the two peak wavelengths are averaged to obtain the original fiber Bragg grating center wavelength;

[0008] The fiber grating group of the matching combination mode includes multiple fiber grating sensors, each measuring point is equipped with at least one fiber grating sensor, and the multiple fiber gratings are distributed in series in order from near to far according to the distance to the demodulation center, so as to limit the optical power of the reflected light to within the input optical power range of the demodulation center.

[0009] Optionally, each measuring point is equipped with at least one fiber grating sensor, including:

[0010] The reflectivity of the fiber Bragg grating sensor equipped at the near end point is low, and the reflectivity of the fiber Bragg grating sensor equipped at the far end point is high. The reflectivity of the fiber Bragg grating sensors equipped at the same measuring point is the same. Among them, the near end point is the place where the loss from the measuring point to the service station is small, and the far end point is the place where the loss from the measuring point to the service station is large.

[0011] Optionally, the loss from the measuring point to the service station includes:

[0012] The optical path loss from the measuring point to the service station is calculated using an optical fiber loss coefficient of 0.2 dBm / km.

[0013] Optionally, the determination of splitting the fiber Bragg grating central wavelength into two peak wavelengths includes:

[0014] The fiber grating central wavelength is split into two peak wavelengths by determining the wavelength power and the wavelength interval.

[0015] Optionally, the determining by wavelength power and wavelength interval includes:

[0016] A set of initial wavelengths w1, w2, ..., wn obtained by the demodulation unit, wherein n represents a natural number;

[0017] a) Starting from w1, calculate the absolute value of the difference between the wavelengths w1 and w2;

[0018] b) Record the power values of wavelength w1 and wavelength w2 respectively;

[0019] c) Determine it as a double peak when |w1 - w2| < W0 and p1, p2 > p0, where W0 is the wavelength interval of the double peak, p1 is the power of wavelength w1, p2 is the power of wavelength w2, and p0 is the threshold;

[0020] d) Loop a), b), and c) until the last wavelength ends.

[0021] Optionally, the central wavelength of the fiber grating splits into two peak wavelengths, and the wavelength value between the two peaks is less than or equal to 0.5 nm.

[0022] Optionally, the threshold includes:

[0023] Based on the power values of all initial wavelengths measured by the demodulation unit for the first time, take a value between the minimum value of the power at the double - peak wavelength and the maximum value of the power at the non - double - peak wavelength.

[0024] Optionally, obtaining the position of the double - peak wavelength through the server and averaging the two peak wavelengths to obtain the original central wavelength of the fiber grating includes:

[0025] When the conditions of |w1 - w2| < W0 and p1, p2 > p0 are met, obtain the double - peak position;

[0026] Average w1 and w2 to obtain the original central wavelength of the fiber grating sensor.

[0027] Optionally, the calculation formula for averaging is as follows:

[0028] W = (w1 + w2) / 2

[0029] Where W is the average value, the original central wavelength of the fiber grating sensor.

[0030] The above - mentioned solution of the embodiment of the present invention has at least the following beneficial effects compared with the prior art:

[0031] The present invention provides a grating sensing demodulation system for solving the wavelength double peak problem with an optical fiber, comprising: a demodulation center and a fiber grating group of matching combination mode connected to the demodulation center through an optical cable; the demodulation center comprises: a server and a demodulation unit, when the total number of light wave signals obtained after demodulation of the reflected light of the detection light emitted by the demodulation unit is greater than the number of the grating fiber sensors actually installed, it is determined that the fiber grating center wavelength is split into two peak wavelengths, the position of the double peak wavelength is obtained through the server, and the two peak wavelengths are averaged to obtain the original fiber grating center wavelength. The fiber grating sensor limits the optical power of the reflected light to the input optical power range of the demodulation center, which can greatly reduce the number of wavelength double peaks. The present invention restores the wavelength double peak to a single peak wavelength carrying reliable information, thereby accurately measuring the physical change carried by the fiber grating. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings herein are incorporated into and constitute a part of the specification, showing embodiments consistent with the present invention, and together with the specification, are used to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0033] Figure 1 A schematic diagram of a fiber Bragg grating sensing demodulation system for solving the wavelength double peak problem according to an embodiment of the present invention is shown;

[0034] Figure 2 A schematic diagram of a matching combination mode of a fiber Bragg grating according to an embodiment of the present invention is shown;

[0035] Figure 3 A flow chart of a design of a double-peak optimization algorithm for a fiber Bragg grating sensing demodulation system that solves the wavelength double-peak problem according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all 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.

[0037] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0038] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0039] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0040] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0041] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0042] Example 1

[0043] Figure 1 The present invention provides a fiber Bragg grating sensing demodulation system for solving the wavelength double peak problem, comprising: a demodulation center and a fiber Bragg grating group of matching combination mode connected to the demodulation center via an optical cable;

[0044] The demodulation center includes: a server and a demodulation unit, wherein the demodulation unit is used to demodulate the optical signal measured by the fiber Bragg grating group of the matching combination mode; the server is used to calculate the optical signal demodulated by the demodulation unit to obtain the original fiber Bragg grating center wavelength, that is, the last fiber Bragg grating sensing demodulation system that solves the wavelength double peak problem processes the demodulation result with a double peak optimization algorithm to obtain the center wavelength value of all FBG sensors.

[0045] Among them, FBG is the abbreviation of Fiber Bragg Grating, that is, fiber Bragg grating, simply referred to as fiber grating.

[0046] Specifically, the total number of optical wave signals obtained after demodulating the reflected light of the detection light emitted by the demodulation unit is compared with the number of grating fiber optic sensors actually installed. When the total number of optical wave signals obtained after demodulating the reflected light of the detection light emitted by the demodulation unit is more than the number of grating fiber optic sensors actually installed, it is determined that the central wavelength of the fiber grating has split into two peak wavelengths. The positions of the two peak wavelengths are obtained through the server, and the average value of the two peak wavelengths is calculated to obtain the original central wavelength of the fiber grating.

[0047] Among them, the positions of the two peak wavelengths are obtained through the server. For example, m measurement points are numbered 1, 2, 3... m respectively, and the fiber grating sensors at each measurement point are numbered respectively. There is a corresponding relationship between the number of each measurement point and the number of the fiber grating sensor on it. The two numbers and the corresponding relationship are stored in the server database. When it is determined that the central wavelength of the fiber grating has split into two peak wavelengths, the server can accurately determine the position of the fiber grating sensor where the two peak wavelengths are located.

[0048] Among them, calculating the average value includes:

[0049] When the conditions of |w1 - w2| < W0 and p1, p2 > p0 are met, the positions of the two peaks are obtained;

[0050] The average value of w1 and w2 is calculated to obtain the original central wavelength of the fiber grating sensor.

[0051] The calculation formula for calculating the average value is as follows:

[0052] W = (w1 + w2) / 2

[0053] Among them, W is the average value, the original central wavelength of the fiber grating sensor.

[0054] The fiber grating group with the matching combination mode includes multiple fiber grating sensors. Each measurement point is at least equipped with one fiber grating sensor. The multiple fiber gratings are successively connected in series according to the distance from near to far to the demodulation center, and are used to limit the optical power of the reflected light within the input optical power range of the demodulation center.

[0055] Among them, each same measurement point is at least equipped with one fiber grating sensor. For example, one measurement point is equipped with one or more fiber grating sensors.

[0056] Among them, fiber Bragg grating is the abbreviation of fiber Bragg grating; the optical power of the reflected light is limited within the input optical power range of the demodulation unit because the reflected light signal of the fiber Bragg grating sensor will have a large number of wavelength double peaks on the demodulation system due to the large optical power. Therefore, the present invention uses a matching combination mode of the fiber Bragg grating to limit the maximum optical power of the reflected signal light to within the input optical power range of a fiber Bragg grating sensing demodulation system that solves the wavelength double peak problem, which can greatly reduce the number of wavelength double peaks.

[0057] Figure 2 This is a schematic diagram of a matching combination mode of a fiber Bragg grating. Within the effective monitoring distance of the fiber Bragg grating demodulation unit, starting from the service station of the fiber Bragg grating demodulation system, the same measurement point is matched with a fiber Bragg grating sensor with the same reflectivity. The choice of reflectivity is determined by the length of the optical cable line from the fiber Bragg grating sensor measurement point to the service station and the optical path loss from each measurement point to the service station is calculated using the optical fiber loss coefficient of 0.2dbm / km. The near end point is matched with a low-reflectivity FBG sensor, and the far end point is matched with a high-reflectivity FBG sensor. The distribution of the reflectivity of the FBG sensor at each measurement point generally increases with the distance.

[0058] Among them, the same measuring point is equipped with a fiber grating sensor with the same reflectivity, and the multiple fiber grating sensors are distributed in series in order from near to far according to the distance to the service station; the near end point is the place where the loss from the measuring point to the service station is small, and the far end point is the place where the loss from the measuring point to the service station is large.

[0059] Figure 3 This is a flow chart of the design of a double-peak optimization algorithm for a fiber Bragg grating sensor demodulation system that solves the wavelength double-peak problem. The fiber Bragg grating sensor demodulation system demodulates the reflected light of the FBG sensor to obtain the wavelength. First, the total number of wavelengths of the FBG is checked through the fiber Bragg grating wavelength configuration information table data in the database. When the total number of wavelengths obtained by demodulation is greater than the number of FBGs actually installed at each measurement point, the total number of wavelengths obtained by demodulating the reflected light of the detection light emitted by the demodulation unit is compared with the number of grating fiber sensors actually installed:

[0060] a. When the former is equal to the latter, the initial wavelength data is output, that is, the wavelength obtained after demodulation of the reflected light of the detection light emitted by the demodulation unit.

[0061] b. When the former is greater than the latter, it is determined to be a double peak. The location of the sensor of the measuring point where the double peak is located is found through the server, and the original fiber Bragg grating center wavelength is obtained by averaging the wavelengths of the peaks. This average is used as the optimized wavelength data output, that is, a double peak optimization algorithm for a fiber Bragg grating sensor demodulation system that solves the wavelength double peak problem is completed.

[0062] For example, when the total number of wavelengths obtained after demodulating the reflected light of the probe light emitted by the demodulation unit is 100 and the number of actually installed fiber Bragg grating sensors is 90, it is determined that the central wavelengths of 10 fiber Bragg gratings are split into two peak wavelengths.

[0063] Judging that the central wavelength of the FBG is split into two peak wavelengths through two parameter dimensions of wavelength power and wavelength interval, obtaining the positions of the two peak wavelengths, and averaging the two peak wavelengths to obtain the original central wavelength of the FBG.

[0064] Among them, judging that the central wavelength of the fiber Bragg grating is split into two peak wavelengths through wavelength power and wavelength interval, and obtaining the positions of the two peak wavelengths, including:

[0065] For a set of initial wavelengths w1, w2,..., wn obtained by the demodulation unit, where n represents a natural number;

[0066] a) Starting from w1, calculate the absolute value of the difference between the wavelength values of wavelength w1 and wavelength w2;

[0067] b) Record the magnitudes of the power values of wavelength w1 and wavelength w2 respectively;

[0068] c) When |w1 - w2| < W0 and p1, p2 > p0, it is determined as a double peak, where W0 is the double-peak wavelength interval, p1 is the power of wavelength w1, p2 is the power of wavelength w2, and p0 is the threshold;

[0069] Among them, a double peak means that the central wavelength of the fiber Bragg grating is split into two peak wavelengths, and the wavelength value between the two peak wavelengths is less than or equal to 0.5 nm.

[0070] Among them, after determining as a double peak, the position of the fiber Bragg grating sensor where the double-peak wavelength is located is calculated by the server, and the two peak wavelengths are averaged to obtain the original central wavelength of the fiber Bragg grating. Among them, the threshold is obtained by taking a value between the minimum value of the power of all initial wavelengths observed in the first measurement by the demodulation unit and the maximum value of the power of the wavelengths without double peaks.

[0071] d) Loop a), b), and c) until the last wavelength ends.

[0072] The present invention provides a fiber Bragg grating sensing demodulation system for solving the wavelength double peak problem, comprising: a demodulation center and a fiber Bragg grating group of matching combination mode connected to the demodulation center through an optical cable; the demodulation center comprises: a server and a demodulation unit, when the total number of light wave signals obtained after demodulation of the reflected light of the detection light emitted by the demodulation unit is greater than the number of the grating fiber sensors actually installed, it is determined that the fiber Bragg grating center wavelength is split into two peak wavelengths, the position of the double peak wavelength is obtained through the server, and the two peak wavelengths are averaged to obtain the original fiber Bragg grating center wavelength. The fiber Bragg grating sensor limits the optical power of the reflected light to the input optical power range of the demodulation center, which can greatly reduce the number of wavelength double peaks; the present invention restores the wavelength double peak to a single peak wavelength carrying reliable information, thereby accurately measuring the physical change amount carried by the fiber Bragg grating.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber Bragg grating sensing demodulation system for solving the wavelength double peak problem, characterized in that: Including: A demodulation center and a fiber grating group with a matching combination mode connected to the demodulation center through an optical cable; The demodulation center includes: a server and a demodulation unit. Among them, the demodulation unit is used to demodulate the optical signal measured by the fiber grating group with the matching combination mode; the server is used to calculate the original fiber grating center wavelength from the optical signal demodulated by the demodulation unit. Specifically, the total number of optical wave signals obtained after demodulating the reflected light of the probe light emitted by the demodulation unit is compared with the number of actually installed fiber grating sensors. When the total number of optical wave signals obtained after demodulating the reflected light of the probe light emitted by the demodulation unit is more than the number of actually installed fiber grating sensors, it is determined that the fiber grating center wavelength splits into two peak wavelengths. The position of the fiber grating sensor where the two peak wavelengths are located is obtained through the server, and the average value of the two peak wavelengths is calculated to obtain the original fiber grating center wavelength; The fiber grating group with the matching combination mode includes multiple fiber grating sensors. Each measurement point is at least equipped with one fiber grating sensor. The multiple fiber grating sensors are respectively connected in series in ascending order of the distance to the demodulation center, and are used to limit the optical power of the reflected light within the input optical power range of the demodulation center.

2. The system according to claim 1, characterized in that Each measurement point is at least equipped with one fiber grating sensor, including: The reflectivity of the fiber grating sensor equipped at the near end point is low, and the reflectivity of the fiber grating sensor equipped at the far end point is high. The reflectivities of the fiber grating sensors equipped at the same measurement point are the same. Among them, the near end point is the location with low loss from the measurement point to the server, and the far end point is the location with high loss from the measurement point to the server.

3. The system according to claim 2, characterized in that The loss from the measurement point to the server includes: Calculating the optical path loss from the measurement point to the server through a fiber loss coefficient of 0.2 dbm / km.

4. The system according to claim 1, characterized in that The determination of the splitting of the fiber grating center wavelength into two peak wavelengths includes: Determining whether the fiber grating center wavelength splits into two peak wavelengths through the wavelength power and wavelength interval.

5. The system according to claim 4, characterized in that The determination through the wavelength power and wavelength interval includes: For a group of initial wavelengths w1, w2,..., wn obtained by the demodulation unit, where n represents a natural number; a) Starting from w1, calculate the absolute value of the difference between the wavelength values of wavelength w1 and wavelength w2; b) Record the magnitudes of the power values of wavelength w1 and wavelength w2 respectively; c) When |w1 - w2| < W0 and p1, p2 > p0, it is determined as a double peak, where W0 is the double peak wavelength interval, p1 is the power of wavelength w1, p2 is the power of wavelength w2, and p0 is the threshold; d) Loop through a), b), and c) until the last wavelength ends.

6. The system according to claim 5, characterized in that When the fiber grating center wavelength splits into two peak wavelengths, the wavelength value between the two peaks is less than or equal to 0.5 nm.

7. The system according to claim 6, characterized in that The threshold includes: Taking a value between the minimum value of the power of the double peak wavelengths and the maximum value of the power of the wavelengths without double peaks according to the power values of all initial wavelengths observed in the first measurement by the demodulation unit.

8. The system according to claim 5, characterized in that Obtaining the position of the dual-peak wavelength through the server and averaging the two peak wavelengths to obtain the original center wavelength of the fiber grating, including: When the conditions of |w1 - w2| < W0 and p1, p2 > p0 are satisfied, obtaining the dual-peak position; Averaging w1 and w2 to obtain the original center wavelength of the fiber grating.

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