Reflectivity measuring device and method for weak reflectivity fiber grating array

Abstract

The invention provides a reflectivity measuring device and method for a weak reflectivity fiber grating array. The device comprises a broadband light source, a circulator, a fiber grating array, a spectrum analyzer, a fiber fusion point, a narrow linewidth laser, an acousto-optic modulator, a signal generator, a photoelectric converter and a signal collector. The broadband light source comprises an optical fiber interface; the circulator comprises a first interface, a second interface and a third interface; the fiber bragg grating array comprises a first fiber bragg grating, a plurality of subsequently engraved fiber bragg gratings and a tail breakpoint; the spectrum analyzer comprises a spectrum interface and a single-mode optical fiber; the narrow linewidth laser comprises a laser interface used for outputting narrow-bandwidth laser. The acousto-optic modulator and the signal generator are used for modulating continuous light output by the narrow linewidth laser into pulsed light with a set period and duty ratio. According to the invention, the reflectivity of the fiber bragg grating in the weak-reflectivity fiber bragg grating array can be accurately measured, and the problem of insufficient measurement precision in the prior art is effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber grating technology, and in particular to a reflectivity measurement device and method for a weak reflectivity optical fiber grating array. Background Art

[0002] As an optical passive device, Bragg grating is equivalent to a narrowband reflector embedded in an optical fiber. It is widely used in the field of optical fiber sensing due to its small size and no need for fusion splicing. As a new generation of technology, Bragg grating array sensing uses the online writing of fiber gratings by a drawing tower and uses a hybrid multiplexing method of wavelength division and time division to demodulate massive sensor signals. It combines the advantages of "discrete fiber grating sensing" and "distributed fiber sensing" and is an ideal choice for building a large-capacity, high-precision, high-density, long-distance, and high-reliability optical fiber sensing network.

[0003] At present, although the online preparation technology of grating array optical fiber has broken the limitations of multiplexing capacity and mechanical strength in traditional processes, in order to pursue a larger measurement range and higher accuracy, it is inevitable to build a longer sensor network with a larger multiplexing capacity. Among the many technologies for building sensor networks, wavelength division multiplexing, time division multiplexing, and frequency division multiplexing are more commonly used. However, for a typical distributed sensor network composed of fiber gratings, the spectral shadows and multiple reflection crosstalk between gratings seriously weaken its multiplexing capability.

[0004] To solve this problem, weak-reflectivity fiber Bragg gratings came into being. By reducing the reflectivity, they reduce the crosstalk of multiple reflections and enhance the multiplexing capability of the fiber optic sensing system. However, in a weak-reflection fiber Bragg grating array, the light reflectivity of a single fiber Bragg grating needs to be controlled at about one thousandth, and the reflected light power is at a lower order of magnitude, which makes it difficult to accurately measure its light reflectivity. Moreover, the difference in reflectivity of each grating in the array will reduce the overall multiplexed array signal pickup and demodulation effect. In the grating engraving process of large-scale fiber Bragg grating multiplexing arrays, it is extremely critical to accurately monitor and ensure the consistency of the reflectivity of each grating.

[0005] Through searching patent documents, it was found that the invention patent with publication number CN104833381B discloses a large-capacity weak-reflection grating sensing device and method based on single-photon technology, wherein the device includes a broadband light source, an optical isolator, an acousto-optic modulator, an optical attenuator, an optical circulator, N sequentially connected weak-reflection fiber grating arrays, an edge filter, a single-photon detector, a data processing module and a control module; the weak-reflection fiber grating array includes a number of gratings with different spacings; wherein N is an integer and N>1. This patent cannot achieve a relatively accurate measurement of the reflectivity of the fiber grating in the weak-reflectivity fiber grating array, nor can it accurately determine the consistency of the reflectivity between the fiber gratings.

[0006] In summary, in view of the above problems of the prior art, researching a reflectivity measurement device and method for a weak reflectivity fiber grating array has become a key task that needs to be solved urgently. Summary of the invention

[0007] In view of the defects in the prior art, the object of the present invention is to provide a reflectivity measurement device and method for a weak reflectivity fiber grating array.

[0008] A reflectivity measuring device for a weak reflectivity fiber grating array provided by the present invention comprises: a broadband light source, a circulator, a fiber grating array, a spectrum analyzer, a fiber fusion point, a narrow linewidth laser, an acousto-optic modulator, a signal generator, a photoelectric converter and a signal collector;

[0009] The broadband light source includes a fiber interface, which is an FC / APC head for outputting broadband laser light; the circulator includes a first interface, a second interface, and a third interface;

[0010] The fiber grating array includes a first fiber grating that is carved, a plurality of fiber gratings that are subsequently carved, and a terminal breakpoint;

[0011] The optical spectrum analyzer includes an optical spectrum interface and a single-mode optical fiber;

[0012] The narrow linewidth laser includes a laser interface, which is an FC / APC head optical fiber interface for outputting narrow bandwidth laser;

[0013] The acousto-optic modulator and the signal generator are used to modulate the continuous light output by the narrow linewidth laser into pulse light with a set period and duty cycle.

[0014] The present invention also provides a method for measuring the reflectivity of a weak reflectivity fiber grating array, comprising the following steps:

[0015] Step S1, connecting a broadband light source to a circulator so that an optical signal enters the circulator, then fusing the circulator to a fiber grating array and ensuring that the fusing loss between the optical fibers is minimized, so that the optical signal in the circulator enters a first fiber grating, and finally the optical signal reflected by the first fiber grating enters an optical spectrum analyzer;

[0016] Step S2, connecting the broadband light source to the circulator through the optical fiber interface and the first interface, so that the optical signal generated by the broadband light source enters the circulator, and then fusing the circulator to the spectrum analyzer through the optical fiber fusion point, ensuring that the fusion loss between the optical fibers is minimized during the fusion, so that the optical signal enters the spectrum analyzer;

[0017] Step S3, connect the narrow linewidth laser to the acousto-optic modulator to modulate the pulse light signal, then make the pulse light signal enter the fiber grating array and ensure the lowest fusion loss between the optical fibers, then the light pulse signal is reflected and transmitted, and finally the reflected light pulse signal is converted and collected and displayed by the signal collector.

[0018] Preferably, step S1 includes the following sub-steps:

[0019] Step S1.1, connecting the broadband light source to the circulator through the optical fiber interface and the first interface, so that the optical signal generated by the broadband light source enters the circulator;

[0020] Step S1.2, the circulator and the fiber Bragg grating array are fusion-connected through the fiber fusion point, and the fusion loss between the optical fibers is ensured to be minimum during the fusion, so that the optical signal in the circulator enters the first fiber Bragg grating;

[0021] Step S1.3: The optical signal reflected by the first fiber grating enters the spectrum analyzer through the third interface of the circulator and the spectrum interface of the spectrum analyzer.

[0022] Preferably, during splicing, the splicing loss between optical fibers is precisely set to 0.02 dB to achieve the lowest splicing loss.

[0023] Preferably, the reflection center wavelength of the fiber Bragg grating in step S1 is λ0, and the reflection peak power is P0; the power of the incident light signal with wavelength λ0 in step S2 is P1. In the welding process, the difference in welding loss between step S1 and step S2 is within a small range. As a prerequisite for the welding loss to be close, the reflectivity R1 of the first fiber Bragg grating in the fiber Bragg grating array is calculated by the following formula:

[0024]

[0025] Preferably, during the welding process, the welding loss difference range is less than 0.02 dB.

[0026] Preferably, step S3 includes the following sub-steps:

[0027] Step S3.1, connecting the narrow linewidth laser to the acousto-optic modulator through a laser interface, and connecting the acousto-optic modulator to a signal generator to modulate a pulsed optical signal;

[0028] Step S3.2, connecting the circulator and the acousto-optic modulator through the first interface, so that the pulsed light signal enters the fiber grating array through the second interface of the circulator and the fiber fusion point, and ensuring that the fusion loss between the optical fibers is minimized during fusion;

[0029] Step S3.3, the optical pulse signal enters the circulator through the reflection of the first fiber grating and the subsequent fiber gratings, and the remaining transmitted light signal is scattered out of the fiber grating array through the end breakpoint;

[0030] Step S3.4, transmitting the reflected optical pulse signal into the photoelectric converter through the third interface of the circulator, where the optical pulse signal is converted into an electrical pulse signal, which is collected and displayed by the signal collector.

[0031] Preferably, in step S3.1, the modulation method is to set a signal generator so that the acousto-optic modulator outputs a pulse light signal with a specific power, period and duty cycle.

[0032] Preferably, in step S3.4, an oscilloscope is used to collect the electrical pulse signal.

[0033] Preferably, in step S3, the reflectivity and central wavelength of the first fiber grating are measured based on step S1 and step S2, the signal collector collects the pulse electrical signal obtained by converting the optical signal reflected by the first fiber grating through the photoelectric converter, the high level amplitude of the pulse electrical signal is V1, and the high level amplitude of the subsequently engraved nth fiber grating collected at the signal collector is V n , the reflectivity calculation formula of the nth fiber grating subsequently engraved is:

[0034]

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The present invention can measure the reflectivity of the fiber grating in the weak reflectivity fiber grating array more accurately, effectively solving the problem of insufficient measurement accuracy in the prior art.

[0037] 2. The present invention can accurately measure the consistency of reflectivity between fiber gratings, ensuring the optimization and improvement of the signal pickup and demodulation effect of large-scale fiber grating multiplexing arrays.

[0038] 3. The operation steps of the present invention are simple and easy to implement and popularize.

[0039] 4. The optical fiber devices and equipment used in the present invention are of general type that meet industry and market standards and do not require special customization, which greatly reduces the application cost and technical threshold and is conducive to widespread popularization in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0041] Figure 1 is a principle block diagram of step S1 in an embodiment of the present invention;

[0042] Figure 2 is a principle block diagram of step S2 in an embodiment of the present invention;

[0043] Figure 3 The measurement result displayed by the spectrum analyzer in step S1 in the embodiment of the present invention;

[0044] Figure 4 The measurement result displayed by the spectrum analyzer in step S2 in the embodiment of the present invention;

[0045] Figure 5 is a principle block diagram of step S3 in an embodiment of the present invention;

[0046] Figure 6 It is a measurement result displayed by the signal collector in the embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0048] The present invention provides a reflectivity measurement device and method for a weak-reflectivity fiber grating array. When a large-scale weak-reflectivity fiber grating array is engraved, the central wavelength and reflectivity of a single fiber grating in the array can be accurately measured, and the consistency of the reflectivity of each grating in the array can be ensured based on this.

[0049] Embodiment 1:

[0050] The present embodiment provides a reflectivity measurement device for a weak reflectivity fiber grating array, comprising: a broadband light source 1, a circulator 2, a fiber grating array 3, a spectrum analyzer 4, a fiber fusion point 5, a narrow linewidth laser 6, an acousto-optic modulator 7, a signal generator 8, a photoelectric converter 9 and a signal collector 10.

[0051] The broadband light source 1 comprises an optical fiber interface 101 , which is an FC / APC head for outputting broadband laser light.

[0052] The circulator 2 includes a first interface 201 with single-mode optical fiber, a second interface 202 and a third interface 203;

[0053] The fiber grating array 3 includes a first fiber grating 301 etched, a plurality of fiber gratings 302 etched subsequently, and a terminal breakpoint 303 .

[0054] The optical spectrum analyzer 4 includes an optical spectrum interface 401 and a single-mode optical fiber 402 .

[0055] The narrow linewidth laser 6 comprises a laser interface 601 , which is an FC / APC head optical fiber interface for outputting narrow bandwidth laser.

[0056] The acousto-optic modulator 7 and the signal generator 8 are used to modulate the continuous light output by the narrow linewidth laser 6 into pulse light with a set period and duty cycle.

[0057] Embodiment 2:

[0058] This embodiment provides a reflectivity measurement method for a weak reflectivity fiber grating array, based on a reflectivity measurement device for a weak reflectivity fiber grating array in the above embodiment 1, comprising the following steps:

[0059] Step S1, connect the broadband light source 1 to the circulator 2 so that the optical signal enters the circulator 2, then fuse the circulator 2 to the fiber grating array 3 and ensure that the fusion loss between the optical fibers is minimized so that the optical signal in the circulator 2 enters the first fiber grating 301, and finally the optical signal reflected by the first fiber grating 301 enters the spectrum analyzer 4.

[0060] Figure 1 4 is a principle block diagram of step S1 in an embodiment of the present invention.

[0061] like Figure 1 As shown, the reflectivity measuring device used in step S1 includes a broadband light source 1, a circulator 2, a fiber grating array 3, a spectrum analyzer 4 and a fiber fusion point 5. Among them, the broadband light source 1 includes a fiber interface 101, the circulator 2 includes a first interface 201, a second interface 202 and a third interface 203; the fiber grating array 3 includes a first fiber grating 301 and a terminal breakpoint 303; the spectrum analyzer 4 includes a spectrum interface 401. The optical signal entering through the first interface 201 will be output through the second interface 202, and the optical signal passing through the second interface 202 will be output through the third interface 203. The first fiber grating 301 is currently engraved on the weak reflection fiber grating array 3. The tail end of the array is broken to prevent end face reflection, and its port is the terminal breakpoint 303. The optical signal transmitted through the first fiber grating 301 will be scattered out of the array through the terminal breakpoint 303.

[0062] Specifically, step S1 includes the following sub-steps:

[0063] Step S1.1, connecting the broadband light source 1 and the circulator 2 through the optical fiber interface 101 and the first interface 201, so that the optical signal generated by the broadband light source 1 enters the circulator 2;

[0064] Step S1.2, the circulator 2 is fusion-connected with the fiber grating array 3 through the fiber fusion point 5, and the fusion loss between the optical fibers is ensured to be minimum during the fusion, so that the optical signal in the circulator 2 enters the first fiber grating 301;

[0065] Step S1.3, the optical signal reflected by the first fiber grating 301 enters the spectrum analyzer 4 through the third interface 203 of the circulator 2 and the spectrum interface 401 of the spectrum analyzer 4, and the measurement result is as follows: Figure 3 shown.

[0066] In this example, the splicing loss between optical fibers is precisely set to 0.02dB during splicing to achieve the lowest splicing loss.

[0067] Step S2, connect the broadband light source 1 to the circulator 2 through the optical fiber interface 101 and the first interface 201, so that the optical signal generated by the broadband light source 1 enters the circulator 2 through the first interface 201, and then the second interface 202 of the circulator 2 is fusion-connected with the spectrum analyzer 4 through the optical fiber fusion point 5, and the fusion loss between the optical fibers is ensured to be minimum during the fusion, so that the optical signal enters the spectrum analyzer 4, and the measurement result is as follows: Figure 4 shown.

[0068] Figure 2 4 is a principle block diagram of step S2 in an embodiment of the present invention.

[0069] like Figure 2 As shown, the reflectivity measuring device used in step S2 is the same as the reflectivity measuring device used in step S1 , and the difference between the two is mainly reflected in the different connection methods between the device equipment, wherein the spectrum analyzer 4 also includes a single-mode optical fiber 402 .

[0070] Figure 3 is the measurement result displayed by the spectrum analyzer in step S1 in the embodiment of the present invention, Figure 4 It is the measurement result displayed by the spectrum analyzer in step S2 in the embodiment of the present invention.

[0071] like Figure 3 The measurement result displayed by the spectrum analyzer in step S1 shows that its peak value is the fiber grating reflection center wavelength λ0, and the reflection peak power is P0. Figure 4 The spectrum analyzer measurement result of step S2 is presented, which shows that the power of the incident light signal with a wavelength of λ0 is P1. During the welding process, the difference in welding loss between step S1 and step S2 is within a small range. Taking this as a prerequisite for the welding loss to be close, the reflectivity R1 of the first fiber grating 301 in the fiber grating array 3 is calculated by the following formula:

[0072]

[0073] In this embodiment, during the welding process, the welding loss difference range is less than 0.02dB.

[0074] Step S3, connect the narrow linewidth laser 6 with the acousto-optic modulator 7 to modulate a pulse light signal, and then make the pulse light signal enter the fiber grating array 3 and ensure that the fusion loss between the optical fibers is minimized. After that, the light pulse signal is processed by reflection and transmission, and finally the reflected light pulse signal is converted and collected and displayed by the signal collector 10.

[0075] Figure 5 4 is a principle block diagram of step S3 in an embodiment of the present invention.

[0076] like Figure 5 As shown, the reflectivity measuring device used in step S3 includes: a circulator 2, a fiber grating array 3, a fiber fusion point 5, a narrow linewidth laser 6, an acousto-optic modulator 7, a signal generator 8, an optoelectronic converter 9, and a signal collector 10. The circulator 2 includes a first interface 201, a second interface 202, and a third interface 203; the fiber grating array 3 includes a first fiber grating 301 engraved thereon, a plurality of fiber gratings 302 engraved subsequently, and a terminal breakpoint 303; and the narrow linewidth laser 6 includes its interface 601.

[0077] Specifically, step S3 includes the following sub-steps:

[0078] Step S3.1, connecting the narrow linewidth laser 6 and the acousto-optic modulator 7 through the laser interface 601, and connecting the acousto-optic modulator 7 to the signal generator 8 to modulate a pulsed optical signal;

[0079] In this embodiment, the modulation method is to set a signal generator 8 so that the acousto-optic modulator 7 outputs a pulse light signal with a specific power, period and duty cycle.

[0080] Step S3.2, connecting the circulator 2 and the acousto-optic modulator 7 through the first interface 201, so that the pulsed light signal enters the fiber grating array 3 through the second interface 202 of the circulator 2 and the fiber fusion point 5, and ensuring that the fusion loss between the optical fibers is minimized during fusion;

[0081] Step S3.3, the optical pulse signal enters the circulator 2 through the reflection of the engraved first fiber grating 301 and the subsequently engraved multiple fiber gratings 302, and the remaining transmitted light signal is scattered out of the fiber grating array 3 through the end breakpoint 303;

[0082] Step S3.4, transmitting the reflected optical pulse signal into the photoelectric converter 9 through the third interface 203 of the circulator 2, where the optical pulse signal is converted into an electrical pulse signal, which is collected and displayed by the signal collector 10.

[0083] In this embodiment, an oscilloscope is used to collect the electrical pulse signal.

[0084] Figure 6 It is a measurement result displayed by the signal collector in the embodiment of the present invention.

[0085] like Figure 6 According to the measurement results of the signal collector 10 shown in FIG. 1 , based on step S1 and step S2, the reflectivity and central wavelength of the first fiber grating 301 are measured. The signal collector 10 collects the pulse electrical signal obtained by converting the optical signal reflected by the first fiber grating 301 through the photoelectric converter 9. The high level amplitude of the pulse electrical signal is V1. The high level amplitude of the subsequently engraved nth fiber grating 302 collected at the signal collector 10 is V n , the reflectivity calculation formula of the nth fiber grating 302 subsequently engraved is:

[0086]

[0087] Wherein, R1 is the reflectivity of the first fiber grating, n is an integer and n≥2.

[0088] The reflectivity measurement method of a weak reflectivity fiber grating array of this embodiment has the following advantages: the measurement method is relatively simple to operate and the measurement result is relatively accurate. At the same time, during the process of engraving the fiber grating array, the reflectivity of the engraved fiber grating can be monitored and intervened in real time, which not only greatly improves the success rate of preparing the weak reflectivity fiber grating array, but also creates favorable conditions for improving the multiplexing capacity of large-scale fiber grating arrays.

[0089] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0090] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A reflectivity measuring device for a weak reflectivity fiber Bragg grating array, characterized in that: include: Broadband light sources, circulators, fiber grating arrays, spectrum analyzers, fiber splices, narrow linewidth lasers, acousto-optic modulators, signal generators, photoelectric converters, and signal collectors; The broadband light source comprises an optical fiber interface, and the optical fiber interface is an FC / APC head for outputting broadband laser; the circulator comprises a first interface, a second interface and a third interface; The fiber grating array includes a first fiber grating that is carved, a plurality of subsequent fiber gratings that are carved, and a terminal breakpoint; The optical spectrum analyzer comprises an optical spectrum interface and a single-mode optical fiber; The narrow linewidth laser comprises a laser interface, which is an FC / APC head optical fiber interface for outputting narrow bandwidth laser; The acousto-optic modulator and the signal generator are used to modulate the continuous light output by the narrow linewidth laser into pulse light with a set period and duty cycle.

2. A method for measuring the reflectivity of a weak reflectivity fiber Bragg grating array, based on the reflectivity measuring device of a weak reflectivity fiber Bragg grating array according to claim 1, characterized in that: The steps include: Step S1, connecting a broadband light source to a circulator so that an optical signal enters the circulator, then fusing the circulator to a fiber grating array and ensuring that the fusing loss between the optical fibers is minimized, so that the optical signal in the circulator enters a first fiber grating, and finally the optical signal reflected by the first fiber grating enters an optical spectrum analyzer; Step S2, connecting the broadband light source to the circulator through the optical fiber interface and the first interface, so that the optical signal generated by the broadband light source enters the circulator, and then fusing the circulator to the spectrum analyzer through the optical fiber fusion point, ensuring that the fusion loss between the optical fibers is minimized during the fusion, so that the optical signal enters the spectrum analyzer; Step S3, connect the narrow linewidth laser to the acousto-optic modulator to modulate the pulse light signal, then make the pulse light signal enter the fiber grating array and ensure the lowest fusion loss between the optical fibers, then the light pulse signal is reflected and transmitted, and finally the reflected light pulse signal is converted and collected and displayed by the signal collector.

3. The reflectivity measurement method of a weak reflectivity fiber Bragg grating array according to claim 2, characterized in that: The step S1 includes the following sub-steps: Step S1.1, connecting the broadband light source to the circulator through the optical fiber interface and the first interface, so that the optical signal generated by the broadband light source enters the circulator; Step S1.2, fusion-connecting the circulator and the fiber Bragg grating array through the fiber fusion point, ensuring that the fusion loss between the optical fibers is minimized during fusion, so that the optical signal in the circulator enters the first fiber Bragg grating; Step S1.3: The optical signal reflected by the first fiber grating enters the spectrum analyzer through the third interface of the circulator and the spectrum interface of the spectrum analyzer.

4. The reflectivity measurement method of a weak reflectivity fiber grating array according to claim 3, characterized in that: During splicing, the splicing loss between optical fibers is precisely set to 0.02dB to achieve the lowest splicing loss.

5. The reflectivity measurement method of a weak reflectivity fiber grating array according to claim 4, characterized in that: The reflection center wavelength of the fiber Bragg grating in step S1 is λ0, and the reflection peak power is P0; the power of the incident light signal with wavelength λ0 in step S2 is P1. During the welding process, the difference in welding loss between the two welding processes in step S1 and step S2 is within a small range. As a prerequisite for the welding loss to be close, the reflectivity R1 of the first fiber Bragg grating in the fiber Bragg grating array is calculated by the following formula:

6. The reflectivity measurement method of a weak reflectivity fiber grating array according to claim 5, characterized in that: During the welding process, the welding loss difference range is less than 0.02dB.

7. The method for measuring reflectivity of a weak reflectivity fiber Bragg grating array according to claim 2, characterized in that: The step S3 includes the following sub-steps: Step S3.1, connecting the narrow linewidth laser to the acousto-optic modulator through a laser interface, and connecting the acousto-optic modulator to a signal generator to modulate a pulsed optical signal; Step S3.2, connecting the circulator and the acousto-optic modulator through the first interface, so that the pulsed light signal enters the fiber grating array through the second interface of the circulator and the fiber fusion point, and ensuring that the fusion loss between the optical fibers is minimized during fusion; Step S3.3, the optical pulse signal enters the circulator through the reflection of the engraved first fiber grating and the subsequently engraved multiple fiber gratings, and the remaining transmitted light signal is scattered out of the fiber grating array through the end breakpoint; Step S3.4, transmitting the reflected optical pulse signal through the third interface of the circulator into the photoelectric converter, where the optical pulse signal is converted into an electrical pulse signal, which is collected and displayed by a signal collector.

8. The reflectivity measurement method of a weak reflectivity fiber grating array according to claim 7, characterized in that: In the step S3.1, the modulation method is to set the signal generator so that the acousto-optic modulator outputs a pulse light signal with specific power, period and duty cycle.

9. The method for measuring reflectivity of a weak reflectivity fiber Bragg grating array according to claim 7, characterized in that: In step S3.4, an oscilloscope is used to collect the electrical pulse signal.

10. The method for measuring reflectivity of a weak reflectivity fiber grating array according to claim 9, characterized in that: In step S3, based on step S1 and step S2, the reflectivity and central wavelength of the first fiber grating are measured, and the signal collector collects the pulse electrical signal obtained by converting the optical signal reflected by the first fiber grating through the photoelectric converter, and the high level amplitude of the pulse electrical signal is V1. The high level amplitude of the subsequently engraved nth fiber grating collected at the signal collector is V n , the reflectivity calculation formula of the nth fiber grating subsequently engraved is: Wherein, R1 is the reflectivity of the first fiber grating, n is an integer and n≥2.

Images