A weak fiber grating array sensing system and its adaptive gain adjustment method and device

Abstract

This invention discloses an adaptive gain adjustment method for a weak fiber Bragg grating array sensing system, comprising: Step 20: setting the gain value of each weak fiber Bragg grating to the same initial value; Step 30: determining the bias current corresponding to each weak fiber Bragg grating based on its corresponding gain value; Step 40: sequentially outputting the bias current corresponding to each weak fiber Bragg grating to a high-speed SOA photoelectric switch, so that the SOA photoelectric switch amplifies the reflected light signal of each weak fiber Bragg grating using the corresponding bias current; Step 50: acquiring the amplified reflected light signal of each weak fiber Bragg grating to determine the amplified reflected signal intensity of each weak fiber Bragg grating; Step 60: adjusting the gain value of each weak fiber Bragg grating to a corresponding correction value based on the amplified reflected signal intensity of each weak fiber Bragg grating; Step 70: repeating steps 30-60 using the adjusted gain value to complete the next scanning cycle. This invention also discloses a gain adjustment method and a weak fiber Bragg grating array sensing system based on the above adaptive gain adjustment method.

Description

Technical Field

[0001] This invention relates to fiber optic grating sensing technology, and more particularly to a weak fiber optic grating array sensing system and its adaptive gain adjustment method and apparatus. Background Technology

[0002] Fiber Bragg grating (FBG) sensors are widely used in aerospace, deep-sea sensing, ecological environment monitoring, and medical diagnostics due to their advantages such as small size, light weight, electromagnetic interference resistance, intrinsic safety, and ease of building sensor networks. A FBG array refers to a technology that connects multiple FBGs in series on a single optical fiber to achieve distributed fiber optic sensing.

[0003] Ordinary fiber gratings have high reflectivity, and optical signals attenuate rapidly after being reflected by multiple ordinary fiber gratings during transmission. Therefore, the number of ordinary fiber gratings connected in series on a single optical fiber is generally limited to a few dozen, which greatly restricts the sensing distance of optical fibers. However, by using weak fiber gratings with low reflectivity (such as 0.1% reflectivity) and based on time-division multiplexing technology, hundreds of weak fiber gratings can be connected in series on a single optical fiber. If extremely weak gratings (such as 0.01% reflectivity) are used, thousands or even tens of thousands of extremely weak fiber gratings can be connected in series on a single optical fiber, which significantly increases the sensing distance of optical fibers.

[0004] For example, Chinese patent application number CN201210391578.5 discloses an extremely weak fiber Bragg grating sensing system and its query method. It uses two SOA high-speed photoelectric switches to realize the modulation module and sampling module of the extremely weak fiber Bragg grating sensing system. The first SOA high-speed photoelectric switch in the modulation module is used to modulate and amplify the light source signal input into the extremely weak fiber Bragg grating array. The second SOA high-speed photoelectric switch in the sampling module is used to separate and amplify the reflected light pulse output by the extremely weak fiber Bragg grating array.

[0005] However, the SOA high-speed photoelectric switch uses a fixed gain value, which cannot be adjusted by feedback. Furthermore, the reflected signal intensity of each extremely weak fiber grating will vary due to temperature fluctuations, fiber aging, and increased insertion loss. Therefore, frequent manual adjustment of the gain value of the second SOA high-speed photoelectric switch is required, making system maintenance cumbersome. In addition, the reflected signal intensity of each extremely weak fiber grating is not uniform; some are strong, some are weak. As the number of gratings increases, the reflected signal intensity of the extremely weak fiber gratings closer to the fiber end is lower, while the reflected signal intensity of the extremely weak fiber gratings closer to the fiber beginning is higher. The fixed gain value of the second SOA high-speed photoelectric switch obviously cannot simultaneously address the issues of weak signal detection sensitivity and strong signal gain amplification saturation, which seriously affects demodulation accuracy and system stability. Summary of the Invention

[0006] To address the shortcomings of the prior art, this invention provides a weak fiber optic grating array sensing system and its adaptive gain adjustment method and apparatus, which can feedback adjust the gain value of the SOA high-speed photoelectric switch.

[0007] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0008] An adaptive gain adjustment method for a weak fiber Bragg grating array sensing system includes the following steps:

[0009] Step 20: Set the gain value of each weak fiber Bragg grating to the same initial value;

[0010] Step 30: Determine the bias current corresponding to each weak fiber grating based on the gain value of each weak fiber grating.

[0011] Step 40: Sequentially output the bias current corresponding to each weak fiber Bragg grating to the SOA high-speed photoelectric switch, so that the SOA high-speed photoelectric switch can amplify the reflected light signal of each weak fiber Bragg grating by using the corresponding bias current.

[0012] Step 50: Obtain the reflected light signal of each weak fiber grating after gain amplification, so as to determine the intensity of the reflected signal of each weak fiber grating after gain amplification;

[0013] Step 60: Based on the reflected signal intensity of each weak fiber Bragg grating after gain amplification, adjust the gain value of each weak fiber Bragg grating to the corresponding correction value.

[0014] Step 70: Repeat steps 30-60 using the adjusted gain value to complete the next scan cycle.

[0015] Furthermore, the adaptive gain adjustment method also includes the following steps:

[0016] Step 10: Set the initial value.

[0017] Furthermore, in step 60, when adjusting the gain value of each weak fiber grating to the corresponding correction value based on the reflected signal intensity of each weak fiber grating after gain amplification, the following steps are included.

[0018] Step 61: Subtract the intensity of the reflected signal after gain amplification of each weak fiber Bragg grating from the set intensity threshold to calculate the intensity error value of each weak fiber Bragg grating.

[0019] Step 62: Compare the intensity error value of each weak fiber Bragg grating with the set error threshold, and adjust the gain value of each weak fiber Bragg grating to the corresponding correction value according to the comparison result to form the adjusted gain value.

[0020] Furthermore, the adaptive gain adjustment method also includes the following steps:

[0021] Step 10: Set the intensity threshold and error threshold.

[0022] Furthermore, in step 62, if the absolute value of the intensity error of a certain weak fiber Bragg grating is less than the set error threshold, the gain value of the weak fiber Bragg grating remains unchanged; if the intensity error of a certain weak fiber Bragg grating is positive and its absolute value is greater than the set error threshold, the gain value of the weak fiber Bragg grating is decreased; if the intensity error of a certain weak fiber Bragg grating is negative and its absolute value is greater than the set error threshold, the gain value of the weak fiber Bragg grating is increased.

[0023] A gain adjustment device for a weak fiber Bragg grating array sensing system is provided for the aforementioned adaptive gain adjustment method. The gain adjustment device includes a power supply module, a data processing module, and a constant current source module. The data processing module and the constant current source module are connected together, and the power supply module is connected to both the data processing module and the constant current source module.

[0024] The data processing module is used to acquire the reflected light signal of each weak fiber grating after gain amplification, to determine the intensity of the reflected signal of each weak fiber grating after gain amplification, and then adjust the gain value of each weak fiber grating to the corresponding correction value according to the intensity of the reflected signal of each weak fiber grating after gain amplification, and in the next scanning cycle, use the adjusted gain value to redetermine the bias current corresponding to each weak fiber grating.

[0025] The constant current source module is used to sequentially output the bias current corresponding to each weak fiber grating to the SOA high-speed photoelectric switch, so that the SOA high-speed photoelectric switch can use the corresponding bias current to amplify the reflected light signal of each weak fiber grating.

[0026] The power supply module is used to provide operating current for the data processing module and the constant current source module.

[0027] Furthermore, a digital-to-analog converter module is connected between the data processing module and the constant current source module. The digital-to-analog converter module is used to convert the digital signal output by the data processing module into the analog voltage of the constant current source module.

[0028] Furthermore, the constant current source module is connected to the data processing module via a level conversion module to perform level conversion on the digital signal output by the data processing module; the power supply module is also connected to the level conversion module to provide a reference voltage to the level conversion module.

[0029] Furthermore, the data processing module is an FPGA module.

[0030] A weak fiber Bragg grating array sensing system includes a broadband light source, a first SOA high-speed photoelectric switch, an erbium-doped fiber amplifier, a fiber circulator, a weak fiber Bragg grating array, a second SOA high-speed photoelectric switch, a photodetector, an analog-to-digital converter, a signal generator, the aforementioned gain adjustment device, and a host computer. The weak fiber Bragg grating array includes a sensing fiber and multiple weak fiber Bragg gratings, each of which is connected in series along the axial direction of the sensing fiber. The output of the broadband light source is connected sequentially to the first end of the fiber circulator via the first SOA high-speed photoelectric switch and the erbium-doped fiber amplifier. The first end of the weak fiber Bragg grating array is connected to the second end of the fiber circulator. The input of the photodetector is connected to the third end of the fiber circulator via the second SOA high-speed photoelectric switch. The output of the photodetector is connected sequentially to the input of the host computer via the analog-to-digital converter and the gain adjustment device. The two outputs of the signal generator are respectively connected to the pump current terminals of the first and second SOA high-speed photoelectric switches. The output of the gain adjustment device is connected to the bias current terminal of the second SOA high-speed photoelectric switch.

[0031] The present invention has the following beneficial effects: The weak fiber Bragg grating array sensing system and its adaptive gain adjustment method and device of the present invention, based on the reflected signal intensity of each weak fiber Bragg grating after being amplified by the SOA high-speed photoelectric switch in the previous scanning cycle, adjust the gain value of the SOA high-speed photoelectric switch in the next scanning cycle, thereby realizing the adaptive gain control of the SOA high-speed photoelectric switch. There is no need to manually adjust the gain value to cope with the effects of temperature fluctuations, fiber aging, increased insertion loss, etc. Moreover, each weak fiber Bragg grating uses a corresponding gain value for gain amplification, which can take into account both the sensitivity of weak signal detection and the saturation problem of strong signal gain amplification. Attached Figure Description

[0032] Figure 1 The schematic diagram of the weak fiber optic grating array sensing system provided by the present invention.

[0033] Figure 2 A schematic diagram illustrating the steps of the adaptive gain adjustment method provided by this invention.

[0034] Figure 3 The structural principle diagram of the gain adjustment device provided by the present invention. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, "multiple" means two or more, unless otherwise explicitly specified.

[0038] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] Example 1

[0040] like Figure 1As shown, a weak fiber grating array sensing system includes a broadband light source 1, a first SOA high-speed photoelectric switch 2, an erbium-doped fiber amplifier 3, a fiber optic circulator 4, a weak fiber grating array 5, a second SOA high-speed photoelectric switch 6, a photodetector 7, an analog-to-digital converter 8, a signal generator 9, a gain adjustment device 10, and a host computer 11. The weak fiber grating array 3 includes a sensing fiber and multiple weak fiber gratings 41, with each weak fiber grating 41 connected in series along the axis of the sensing fiber. The output of the broadband light source 1 is connected in series to the first SOA high-speed photoelectric switch 2 and the erbium-doped fiber amplifier 3 via the first SOA high-speed photoelectric switch 2 and the erbium-doped fiber amplifier 3 in the fiber optic circulator 4. At one end, the first end of the weak fiber grating array 3 is connected to the second end of the fiber optic circulator 4; the input end of the photodetector 7 is connected to the third end of the fiber optic circulator 4 via the second SOA high-speed photoelectric switch 6; the output end of the photodetector 7 is connected to the input end of the host computer 11 via the analog-to-digital converter 8 and the gain adjustment device 10 in sequence; the two output ends of the signal generator 9 are respectively connected to the pump current ends of the first SOA high-speed photoelectric switch 2 and the second SOA high-speed photoelectric switch 6; the output end of the gain adjustment device 10 is connected to the bias current end of the second SOA high-speed photoelectric switch 6.

[0041] During sensing, the signal generator 9 generates two electrical pulse signals, which are output to the first SOA high-speed photoelectric switch 2 and the second SOA high-speed photoelectric switch 6, respectively, to control the regular switching of the first SOA high-speed photoelectric switch 2 and the second SOA high-speed photoelectric switch 6. The continuous optical signal emitted by the broadband light source 1 is modulated and amplified by the first SOA high-speed photoelectric switch 2 to form an optical pulse signal. The optical pulse signal is amplified by the erbium-doped fiber amplifier 3 and then input into the weak fiber grating 41 array 3 through the fiber optic circulator 4. Each weak fiber grating 41 reflects the optical pulse. The reflected light signal generated by the signal is output to the second SOA high-speed photoelectric switch 6 via the fiber optic circulator 4. After being separated and amplified by the second SOA high-speed photoelectric switch 6, it is output to the photodetector 7 for acquisition. The reflected light signal acquired by the photodetector 7 is converted from analog to digital by the analog-to-digital converter 8 and then provided to the gain adjustment device 10 for processing. The gain adjustment device 10 adjusts the gain value of the second SOA high-speed photoelectric switch 6 based on the reflected light signals of each weak fiber grating 41, and provides the final reflected light signal to the host computer 11 for sensing, demodulation, and display.

[0042] The signal generator 9 can be connected to the host computer 11 and directly controlled by the host computer 11, or it can be connected to the gain adjustment device 10 and indirectly controlled by the host computer 11 through the gain adjustment device 10.

[0043] In this patent, the weak fiber grating 41 refers to a fiber grating with a reflectivity of 0.1% or less, including extremely weak fiber gratings with a reflectivity of 0.01% or even fiber gratings with even lower reflectivity.

[0044] In practical implementation, if the power of the broadband light source 1 is sufficiently high, the first SOA high-speed photoelectric switch 2 does not need to amplify the gain of the continuous optical signal emitted by the broadband light source 1; it only needs to modulate the continuous optical signal to form the optical pulse signal. If the power of the broadband light source 1 is relatively low, the first SOA high-speed photoelectric switch 2 can amplify the continuous optical signal with a fixed gain value while modulating it, such as directly using the maximum gain value. Of course, the output terminal of the gain adjustment device 10 can also be connected to the bias current terminal of the first SOA high-speed photoelectric switch 2 to provide feedback adjustment of the gain value of the first SOA high-speed photoelectric switch 2.

[0045] In this embodiment, the gain adjustment device 10 is only used to adjust the gain value of the second SOA high-speed photoelectric switch 6, without adjusting the gain value of the first SOA high-speed photoelectric switch 2.

[0046] Example 2

[0047] like Figure 2 As shown, an adaptive gain adjustment method is used in the weak fiber optic grating array sensing system described in Embodiment 1, so that the gain adjustment device can perform feedback adjustment on the gain value of the second SOA high-speed photoelectric switch.

[0048] The adaptive gain adjustment method includes at least two scan cycles, and its steps are as follows:

[0049] Step 10: Set the initial value, intensity threshold, and error threshold.

[0050] In step 10, the technician sets the initial value, intensity threshold, and error threshold for the gain adjustment device via the host computer. Each initial value, intensity threshold, and error threshold is unique, and all weak fiber Bragg gratings use the same initial value, intensity threshold, and error threshold. The gain adjustment device uses the adaptive gain adjustment method of this patent to adjust the gain value of each weak fiber Bragg grating from the same initial value to its corresponding correction value.

[0051] Step 20: Set the gain value of each weak fiber Bragg grating to the same initial value.

[0052] In step 20, after the weak fiber Bragg grating array sensing system is turned on and initialized, the host computer will send the set initial value, intensity threshold and error threshold to the gain adjustment device. After receiving the initial value, intensity threshold and error threshold, the gain adjustment device will first store them locally, and in the first scan cycle, it will first read the locally stored initial value, and then set the gain value of each weak fiber Bragg grating to the initial value.

[0053] Step 30: Determine the bias current corresponding to each weak fiber Bragg grating based on the gain value of each weak fiber Bragg grating.

[0054] In step 30, the gain adjustment device is equipped with a lookup table or calculation formula between the gain value and the bias current, so as to determine the bias current corresponding to each weak fiber grating by looking up the table or by calculation.

[0055] Step 40: Sequentially output the bias current corresponding to each weak fiber Bragg grating to the second SOA high-speed photoelectric switch, so that the second SOA high-speed photoelectric switch can amplify the reflected light signal of each weak fiber Bragg grating using the corresponding bias current.

[0056] In step 40, the weak fiber Bragg gratings are positioned at different distances within the weak fiber Bragg grating array. Therefore, the reflected light signals generated by each weak fiber Bragg grating have different time delays (i.e., the time interval between the pulsed light signal output by the first SOA high-speed photoelectric switch and the reflected light signal input by the second SOA high-speed photoelectric switch). The gain adjustment device can determine the weak fiber Bragg gratings corresponding to different reflected light signals based on their time delays, and thus sequentially output corresponding bias currents to the second SOA high-speed photoelectric switch, enabling the second SOA high-speed photoelectric switch to amplify the gain of each reflected light signal using the corresponding bias current.

[0057] Step 50: Obtain the reflected light signal of each weak fiber Bragg grating after gain amplification, so as to determine the intensity of the reflected signal of each weak fiber Bragg grating after gain amplification.

[0058] In step 50, the reflected light signals of each weak fiber Bragg grating collected by the photodetector and amplified by the gain are converted from analog to digital by the analog-to-digital converter and then output to the gain adjustment device. The gain adjustment device can determine the intensity of the reflected signal of each weak fiber Bragg grating after gain amplification based on the signal magnitude output by the analog-to-digital converter.

[0059] Step 60: Adjust the gain value of each weak fiber grating to the corresponding correction value according to the reflected signal intensity after gain amplification.

[0060] In step 60, if the reflected light signal of a weak fiber Bragg grating is amplified by the second SOA high-speed photoelectric switch and its reflected signal strength is too high, the gain adjustment device will adjust the gain value corresponding to the weak fiber Bragg grating to decrease. If the reflected light signal of a weak fiber Bragg grating is amplified by the second SOA high-speed photoelectric switch and its reflected signal strength is too low, the gain adjustment device will adjust the gain value corresponding to the weak fiber Bragg grating to increase.

[0061] The gain value corresponding to each weak fiber Bragg grating can be adjusted in a step manner, that is, when increasing or decreasing the gain value corresponding to each weak fiber Bragg grating, the gain variable that increases or decreases each time is fixed.

[0062] After adjusting the gain value of each weak fiber Bragg grating to the corresponding correction value, the gain adjustment device first stores the adjusted gain values ​​locally for reading in the next scan cycle.

[0063] Specifically, in step 60, when adjusting the gain value of each weak fiber Bragg grating to the corresponding correction value based on the reflected signal intensity after gain amplification, the following steps are included:

[0064] Step 61: Subtract the intensity of the reflected signal after gain amplification of each weak fiber Bragg grating from the set intensity threshold to calculate the intensity error value of each weak fiber Bragg grating.

[0065] In step 61, the intensity error value has a numerical attribute and a positive / negative attribute. The numerical attribute represents the degree of deviation between the reflected signal intensity of each weak fiber grating and the target signal intensity, while the positive / negative attribute represents the direction of deviation between the reflected signal intensity of each weak fiber grating and the target signal intensity.

[0066] Step 62: Compare the intensity error value of each weak fiber Bragg grating with the set error threshold, and adjust the gain value of each weak fiber Bragg grating to the corresponding correction value according to the comparison result to form the adjusted gain value.

[0067] In step 62, if the absolute value of the intensity error of a certain weak fiber Bragg grating is less than the set error threshold, the gain value of the weak fiber Bragg grating remains unchanged; if the intensity error of a certain weak fiber Bragg grating is positive and its absolute value is greater than the set error threshold, the gain value of the weak fiber Bragg grating is decreased; if the intensity error of a certain weak fiber Bragg grating is negative and its absolute value is greater than the set error threshold, the gain value of the weak fiber Bragg grating is increased.

[0068] Preferably, the absolute value of the intensity error of each weak fiber Bragg grating is first taken, and then the absolute value of each intensity error is compared with a set error threshold. If the absolute value of a certain intensity error is less than the set error threshold, the gain value of the weak fiber Bragg grating is kept unchanged and stored locally. If the absolute value of a certain intensity error is greater than the set error threshold, the sign of the intensity error is further determined. If the intensity error is positive, the gain value of the weak fiber Bragg grating is decreased and stored locally. If the intensity error is negative, the gain value of the weak fiber Bragg grating is increased and stored locally.

[0069] Step 70: Repeat steps 30-60 using the adjusted gain value to complete the next scan cycle.

[0070] In step 70, the gain adjustment device redetermines the bias current corresponding to each weak fiber grating based on the adjusted gain value in the next scanning cycle, and then sequentially outputs the redetermined bias current corresponding to each weak fiber grating to the second SOA high-speed photoelectric switch. By continuously repeating steps 30-60, the reflected signal intensity of each weak fiber grating after gain amplification is within a suitable range.

[0071] Example 3

[0072] like Figure 3 As shown, a gain adjustment device is used in the weak fiber grating array sensing system described in Embodiment 1 to implement the adaptive gain adjustment method described in Embodiment 2.

[0073] The gain adjustment device includes a power supply module, a data processing module, and a constant current source module. The data processing module and the constant current source module are connected together, and the power supply module is connected to both the data processing module and the constant current source module.

[0074] The data processing module is used to acquire the reflected light signal of each weak fiber grating after gain amplification, to determine the intensity of the reflected signal of each weak fiber grating after gain amplification, and then adjust the gain value of each weak fiber grating to the corresponding correction value according to the intensity of the reflected signal of each weak fiber grating after gain amplification, and in the next scanning cycle, use the adjusted gain value to redetermine the bias current corresponding to each weak fiber grating.

[0075] The constant current source module is used to sequentially output the bias current corresponding to each weak fiber grating to the second SOA high-speed photoelectric switch, so that the second SOA high-speed photoelectric switch can use the corresponding bias current to amplify the reflected light signal of each weak fiber grating.

[0076] The power supply module is used to provide operating current for the data processing module and the constant current source module.

[0077] Preferably, a digital-to-analog converter is connected between the data processing module and the constant current source module. The digital-to-analog converter is used to convert the digital signal output by the data processing module into the analog voltage of the constant current source module.

[0078] Preferably, the constant current source module is connected to the data processing module via a level conversion module to perform level conversion on the digital signal output by the data processing module; the power supply module is also connected to the level conversion module to provide a reference voltage to the level conversion module.

[0079] In this embodiment, the data processing module is an FPGA module.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and not to limit them. Although the embodiments of the present invention have been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the embodiments of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adaptive gain adjustment method for a weak fiber Bragg grating array sensing system, used in a gain adjustment device, characterized in that, The gain adjustment device includes a power supply module, a data processing module, and a constant current source module. The data processing module and the constant current source module are connected together, and the power supply module is connected to both the data processing module and the constant current source module. The data processing module is used to acquire the reflected light signal of each weak fiber grating after gain amplification, to determine the intensity of the reflected signal of each weak fiber grating after gain amplification, and then adjust the gain value of each weak fiber grating to the corresponding correction value according to the intensity of the reflected signal of each weak fiber grating after gain amplification, and in the next scanning cycle, use the adjusted gain value to redetermine the bias current corresponding to each weak fiber grating. The constant current source module is used to sequentially output the bias current corresponding to each weak fiber grating to the SOA high-speed photoelectric switch, so that the SOA high-speed photoelectric switch can use the corresponding bias current to amplify the reflected light signal of each weak fiber grating. The power supply module is used to provide operating current for the data processing module and the constant current source module; The adaptive gain adjustment method includes the following steps: Step 20: Set the gain value of each weak fiber Bragg grating to the same initial value; Step 30: Determine the bias current corresponding to each weak fiber grating based on the gain value of each weak fiber grating. Step 40: Sequentially output the bias current corresponding to each weak fiber Bragg grating to the SOA high-speed photoelectric switch, so that the SOA high-speed photoelectric switch can amplify the reflected light signal of each weak fiber Bragg grating by using the corresponding bias current. Step 50: Obtain the reflected light signal of each weak fiber grating after gain amplification, so as to determine the intensity of the reflected signal of each weak fiber grating after gain amplification; Step 60: Based on the reflected signal intensity of each weak fiber Bragg grating after gain amplification, adjust the gain value of each weak fiber Bragg grating to the corresponding correction value. Step 70: Repeat steps 30-60 using the adjusted gain value to complete the next scan cycle.

2. The adaptive gain adjustment method according to claim 1, characterized in that, The adaptive gain adjustment method further includes the following steps: Step 10: Set the initial value.

3. The adaptive gain adjustment method according to claim 1, characterized in that, In step 60, when adjusting the gain value of each weak fiber grating to the corresponding correction value based on the reflected signal intensity of each weak fiber grating after gain amplification, the following steps are included. Step 61: Subtract the intensity of the reflected signal after gain amplification of each weak fiber Bragg grating from the set intensity threshold to calculate the intensity error value of each weak fiber Bragg grating. Step 62: Compare the intensity error value of each weak fiber Bragg grating with the set error threshold, and adjust the gain value of each weak fiber Bragg grating to the corresponding correction value according to the comparison result to form the adjusted gain value.

4. The adaptive gain adjustment method according to claim 3, characterized in that, The adaptive gain adjustment method further includes the following steps: Step 10: Set the intensity threshold and error threshold.

5. The adaptive gain adjustment method according to claim 3, characterized in that, In step 62, if the absolute value of the intensity error of a certain weak fiber Bragg grating is less than the set error threshold, the gain value of the weak fiber Bragg grating remains unchanged; if the intensity error of a certain weak fiber Bragg grating is positive and its absolute value is greater than the set error threshold, the gain value of the weak fiber Bragg grating is decreased; if the intensity error of a certain weak fiber Bragg grating is negative and its absolute value is greater than the set error threshold, the gain value of the weak fiber Bragg grating is increased.

6. The adaptive gain adjustment method according to claim 1, characterized in that, A digital-to-analog converter is connected between the data processing module and the constant current source module. The digital-to-analog converter is used to convert the digital signal output by the data processing module into the analog voltage of the constant current source module.

7. The adaptive gain adjustment method according to claim 1, characterized in that, The constant current source module is connected to the data processing module via a level conversion module to perform level conversion on the digital signal output by the data processing module; the power supply module is also connected to the level conversion module to provide a reference voltage to the level conversion module.

8. The adaptive gain adjustment method according to claim 1, characterized in that, The data processing module is an FPGA module.

9. A weak fiber Bragg grating array sensing system, characterized in that, The system includes a broadband light source, a first SOA high-speed photoelectric switch, an erbium-doped fiber amplifier, a fiber optic circulator, a weak fiber grating array, a second SOA high-speed photoelectric switch, a photodetector, an analog-to-digital converter, a signal generator, a gain adjustment device, and a host computer. The weak fiber grating array comprises a sensing fiber and multiple weak fiber gratings, with each weak fiber grating connected in series along the axis of the sensing fiber. The output of the broadband light source is connected sequentially to the first end of the fiber optic circulator via the first SOA high-speed photoelectric switch and the erbium-doped fiber amplifier. The first end of the weak fiber grating array is connected to the second end of the fiber optic circulator. The input of the photodetector is connected to the third end of the fiber optic circulator via the second SOA high-speed photoelectric switch. The output of the photodetector is connected sequentially to the input of the host computer via the analog-to-digital converter and the gain adjustment device. The two outputs of the signal generator are respectively connected to the pump current terminals of the first and second SOA high-speed photoelectric switches. The output of the gain adjustment device is connected to the bias current terminal of the second SOA high-speed photoelectric switch. The gain adjustment device includes a power supply module, a data processing module, and a constant current source module. The data processing module and the constant current source module are connected together, and the power supply module is connected to both the data processing module and the constant current source module. The data processing module is used to acquire the reflected light signal of each weak fiber grating after gain amplification, to determine the intensity of the reflected signal of each weak fiber grating after gain amplification, and then adjust the gain value of each weak fiber grating to the corresponding correction value according to the intensity of the reflected signal of each weak fiber grating after gain amplification, and in the next scanning cycle, use the adjusted gain value to redetermine the bias current corresponding to each weak fiber grating. The constant current source module is used to sequentially output the bias current corresponding to each weak fiber grating to the second SOA high-speed photoelectric switch, so that the second SOA high-speed photoelectric switch can use the corresponding bias current to amplify the reflected light signal of each weak fiber grating. The power supply module is used to provide operating current for the data processing module and the constant current source module.

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