阅读说明：本技术 基于随机激光放大的长距离大容量fbg传感系统 (Long-distance large-capacity FBG sensing system based on random laser amplification ) 是由 饶云江 董诗盛 杨泽元 王子南 刘杰 韩冰 吴明埝 栗鸣 于 2021-09-06 设计创作，主要内容包括：本发明公开了基于随机激光放大的长距离大容量FBG传感系统,涉及光纤传感技术领域,解决FBG传感系统中的大容量复用及长距离传感问题,系统包括信号光源模块、环形器、波分复用器、低噪声随机激光泵浦光源、传输光纤、传感FBG以及信号解调模块；本发明在FBG传感系统中采用随机激光放大与遥泵掺铒光纤放大结合的新型分布式放大技术,可显著延长系统传感距离；同时,本发明利用混合时分复用和波分复用方式结合反射率补偿式分布的FBG复用方式,进一步提高了系统复用率和传感距离,可实现适用于电力安全监测等领域的长距离、大容量的FBG传感系统。(The invention discloses a long-distance large-capacity FBG sensing system based on random laser amplification, which relates to the technical field of optical fiber sensing and solves the problems of large-capacity multiplexing and long-distance sensing in the FBG sensing system, wherein the system comprises a signal light source module, a circulator, a wavelength division multiplexer, a low-noise random laser pumping light source, a transmission optical fiber, a sensing FBG and a signal demodulation module; the invention adopts a novel distributed amplification technology combining random laser amplification and remote pump erbium-doped fiber amplification in the FBG sensing system, and can obviously prolong the sensing distance of the system; meanwhile, the invention further improves the system multiplexing rate and the sensing distance by utilizing a hybrid time division multiplexing and wavelength division multiplexing mode and combining a reflectivity compensation type distributed FBG multiplexing mode, and can realize a long-distance and large-capacity FBG sensing system suitable for the fields of electric power safety monitoring and the like.)

1. The long-distance large-capacity FBG sensing system based on random laser amplification comprises a signal light source module (1), a circulator (2), a wavelength division multiplexer (3) and a transmission optical fiber (5) which are sequentially connected, and is characterized in that a third port of the circulator (2) is connected with a signal demodulation module (7), and the output end of a low-noise random laser pumping module (4) is connected with the wavelength division multiplexer (3);

pulsed light emitted by the signal light source module (1) is coupled with pump light output by the low-noise random laser pump light source module (4) through the wavelength division multiplexer (3) and enters the transmission optical fiber (5) to realize distributed random laser amplification, and a section of erbium-doped optical fiber (8) is positioned in the sensing optical fiber (5) to realize remote pump erbium-doped optical fiber amplification and prolong the system distance, wherein the length of the erbium-doped optical fiber is 1-50 m;

the sensing FBGs (6) are distributed in the transmission optical fiber (5) in a compensation mode, the reflectivities of the FBGs (6) arranged at different positions in the transmission optical fiber (5) are different, and the reflectivity range is-60 dB-0 dB;

the signal light reflected by the sensing FBG (6) enters the signal demodulation module (7) through the circulator (2), carries external information, and is analyzed through the signal demodulation module (7) to restore the external information.

2. The long-distance large-capacity FBG sensing system based on the random laser amplification as claimed in claim 1, wherein the signal light source module (1) comprises a broadband light source (1-1) and an acousto-optic modulator (1-2), wherein the output end of the broadband light source (1-1) is connected with the acousto-optic modulator (1-2); the output end of the acousto-optic modulator (1-2) is sequentially connected with the first erbium-doped fiber amplifier (10-1) and the first port of the circulator (2);

light at the first port of the circulator (2) comes out from the second port, sequentially passes through the wavelength division multiplexer (3) and the strong feedback module (12), and then enters the transmission optical fiber (5); the reflected light of the sensing FBG (6) in the transmission optical fiber (5) enters from the second port of the circulator (2) and exits from the third port of the circulator, the third port of the circulator (2) is connected with a second erbium-doped optical fiber amplifier (10-2), and the output of the second erbium-doped optical fiber amplifier (10-2) is connected with a signal demodulation module (7).

3. The long-distance large-capacity FBG sensing system based on random laser amplification as claimed in claim 2, wherein the acousto-optic modulator (1-2) is connected with a signal demodulation module (7) through a signal generator (9), and the signal demodulation module (7) is connected with an upper computer (11).

4. The long-distance large-capacity FBG sensing system based on random laser amplification as claimed in claim 2, wherein the signal demodulation module (7) comprises a spectrum demodulation module and a dispersion compensation demodulation module.

5. The long-distance large-capacity FBG sensing system based on stochastic laser amplification as claimed in claim 1, wherein the relative intensity noise of the low-noise stochastic laser pumping light source module (4) is less than-100 dB/Hz.

6. The long-distance large-capacity FBG sensing system based on random laser amplification as claimed in claim 2, wherein the signal light source module (1) can adopt a pulse light source or a continuous light source and output pulse signal light after being modulated by a modulator, and the modulator comprises an acoustic-optical modulator and an electro-optical modulator.

7. The long-distance large-capacity FBG sensing system based on random laser amplification as claimed in claim 1, wherein the FBG sensing system further comprises a strong feedback module (12), the strong feedback module (12) comprises FBG with strong reflectivity and a fiber ring mirror.

8. The long-distance large-capacity FBG sensing system based on random laser amplification as claimed in claim 1, wherein the FBG sensing system adopts TDM and WDM technology combination, the sensing FBG (6) has different central wavelength, and the central wavelength range is 1510-1590 nm.

Technical Field

The invention relates to the field of fiber bragg gratings and fiber sensing, in particular to a long-distance large-capacity FBG sensing system based on random laser amplification.

Background

Since its first report in 1978 by k.o.hill, FBG became a key passive device widely used in optical fiber communication systems. Meanwhile, the FBG can be used as a structure sensitive element and a novel sensor, the structure can change along with the change of physical quantities such as external temperature, strain and the like, and the FBG has the characteristics of electromagnetic interference resistance, small size resistance, good corrosion resistance, convenience in multiplexing, high sensitivity and the like, and is suitable for being used in extremely severe environments. However, due to the problems of non-linear temperature drift, noise interference, shadow effect during multiplexing, multiple reflection crosstalk and the like of the device, the conventional FBG sensing system has many disadvantages and limitations, for example, how to increase multiplexing capacity, how to increase sensing distance, how to improve demodulation accuracy, and how to increase demodulation speed, and solving the above problems becomes a research hotspot at present.

In the existing optical amplification technology, the sensing range of an FBG sensing system can be effectively enlarged by the distributed amplification technology and the remote pump amplification technology, but the relative intensity noise of the currently adopted pump light source is too high, the relative intensity noise of signal light can be further deteriorated while the signal light is amplified, and the signal-to-noise ratio of the system is reduced. In the FBG large-capacity multiplexing technology, the TDM technology and the WDM technology are widely applied to the FBG sensing system, and compared with the TDM technology and the WDM technology, the TDM + WDM hybrid multiplexing technology becomes a new solution for the large-capacity FBG sensing system, and the hybrid multiplexing technology can improve the multiplexing capacity and the system spatial resolution of the FBG sensing system by times.

The FBG sensing technology can be widely applied to the structure monitoring of various infrastructures. Especially, the long-distance large-capacity FBG sensing system can be used for large-range unrepeatered monitoring of the national grid high-voltage transmission line, and is the content of the current popular research. The distribution environment of the high-voltage transmission line is complex, most of the high-voltage transmission line is distributed in severe environments such as the field in the countryside, the monitoring and maintenance cost is high, and the maintenance of the relay station is a burden for the monitoring of the long-distance FBG sensing system, so that the scheme of the long-distance large-capacity unrepeatered FBG sensing system is urgently needed for the power grid monitoring.

Disclosure of Invention

The invention aims to: the problems of high-capacity multiplexing and long-distance sensing in the FBG sensing system are solved, and a solution is provided for large-range unrepeatered sensing monitoring of a high-voltage transmission line and the like.

The invention specifically adopts the following technical scheme for realizing the purpose:

the long-distance large-capacity FBG sensing system based on random laser amplification comprises a signal light source module, a circulator, a wavelength division multiplexer and a transmission optical fiber which are sequentially connected, wherein a third port of the circulator is connected with a signal demodulation module, and an output end of a low-noise random laser pumping module is connected with the wavelength division multiplexer;

pulsed light emitted by the signal light source module is coupled with pump light output by the low-noise random laser pump light source module through a wavelength division multiplexer and enters a transmission optical fiber to realize distributed random laser amplification, and a section of erbium-doped optical fiber is positioned in a sensing optical fiber to realize remote pump erbium-doped optical fiber amplification and prolong the system distance, wherein the length of the erbium-doped optical fiber is 1-50 m;

the sensing FBGs are distributed in the transmission optical fiber in a compensation mode, the reflectivity of the FBGs placed at different positions in the transmission optical fiber is different, and the reflectivity range is-60 dB-0 dB;

the signal light reflected by the sensing FBG enters the signal demodulation module through the circulator, carries external information, and is analyzed by the signal demodulation module to restore the external information.

As an optional technical solution, the signal light source module includes a broadband light source and an acousto-optic modulator, wherein an output end of the broadband light source is connected with the acousto-optic modulator; the output end of the acousto-optic modulator is sequentially connected with the first erbium-doped fiber amplifier and the first port of the circulator;

light at the first port of the circulator comes out from the second port, sequentially passes through the wavelength division multiplexer and the strong feedback module, and then enters the transmission optical fiber; the reflected light of the sensing FBG in the transmission optical fiber enters from the second port of the circulator and exits from the third port of the circulator, the third port of the circulator is connected with the second erbium-doped optical fiber amplifier, and the output of the second erbium-doped optical fiber amplifier is connected with the signal demodulation module.

As an optional technical scheme, the acousto-optic modulator is connected with the signal demodulation module through the signal generator, and the signal demodulation module is connected with the upper computer.

As an optional technical solution, the signal demodulation module includes a spectrum demodulation module and a dispersion compensation demodulation module.

As an optional technical solution, the dispersion compensation demodulation module includes two interfaces, one is an external optical interface, the interface is composed of a port of the optical fiber coupler, the other is an upper computer data interface, and the interface is composed of two output ports of the data acquisition module;

one output port of the optical fiber coupler is connected with a common single-mode optical fiber for calibration, the common single-mode optical fiber for calibration is connected with a photoelectric detector, and the photoelectric detector is connected with a first output port of the data acquisition module;

the other output port of the optical fiber coupler is connected with a dispersion compensation module, the dispersion compensation module is connected with a photoelectric detector, and the photoelectric detector is connected with the second output port of the data acquisition module

As an optional technical scheme, the relative intensity noise of the low-noise random laser pumping light source module is less than-100 dB/Hz.

As an optional technical solution, the signal light source module may adopt a pulse light source or a continuous light source, and output pulse signal light after being modulated by a modulator, where the modulator includes an acoustic-optical modulator and an electro-optical modulator.

As an optional technical solution, the FBG sensing system further includes a strong feedback module, and the strong feedback module includes a FBG with strong reflectivity and an optical fiber ring mirror.

As an optional technical scheme, the FBG sensing system adopts the combination of TDM and WDM technologies, the sensing FBG has different central wavelengths, and the central wavelength range is 1510-1590 nm.

The invention has the following beneficial effects:

1. the invention adopts the low-noise optical fiber random laser amplification technology, further combines the random laser amplification technology with the ROPA to form a hybrid amplification technology, and can effectively prolong the unrepeatered sensing distance of the system.

2. In a conventional long-distance FBG sensing system, the intensity of signal light at different positions of a sensing link is different. According to the invention, a sensing FBG reflectivity compensation type distribution technical scheme is adopted, the sensing FBGs at different positions are set to have different reflectivity, and the sensing FBG reflectivity at the position with weak signal light intensity is high, so that the airspace balance performance of the sensing signal can be obviously improved.

3. The long-distance large-capacity FBG sensing system adopts a TDM and WDM combined hybrid multiplexing mode, sensing FBGs are grouped according to central wavelength, a plurality of sensing FBGs with different central wavelengths are grouped into one group, the sensing FBGs with the same central wavelength among the groups are distributed at different positions, demodulation is carried out by adopting a TDM scheme, the sensing FBGs with different central wavelengths in each group occupy different wave bands of a signal light source, and demodulation is carried out by adopting a WDM scheme. A WDM mode is superposed on the premise of TDM, so that each wave band of a signal light source can be efficiently utilized, and the multiplexing number of the sensing FBGs of the system is increased.

Drawings

FIG. 1 is a block diagram of a long-distance large-capacity FBG sensing system based on random laser amplification according to the present invention;

FIG. 2 is a block diagram of a long-distance large-capacity FBG sensing system based on random laser amplification according to the first embodiment;

fig. 3 is a block diagram of a long-distance large-capacity FBG sensing system based on a spectrum demodulation module and a hybrid amplification technology according to the second embodiment;

fig. 4 is a block diagram of a long-distance large-capacity FBG sensing system based on a dispersion compensation module and a hybrid amplification technology according to a third embodiment;

fig. 5 is a block diagram of a structure of a signal demodulation module according to a third embodiment;

FIG. 6 is a simulation diagram of the power distribution of the system according to the first and second embodiments;

the labels in the figure are: 1. a signal light source module; 1-1, a broadband light source; 1-2, an acousto-optic modulator; 2. a circulator; 3. a wavelength division multiplexer; 4. a low-noise random laser pumping light source module; 5. a transmission optical fiber; 6. sensing the FBG; 6-x, FBG group; 7. a signal demodulation module; 7-1, an optical fiber coupler; 7-2, a single-mode fiber calibration module; 7-3, a dispersion compensation module; 7-4, a photoelectric detector; 7-5, a data acquisition module; 8. EDF; 9. a signal generator; 10-1, a first erbium-doped fiber amplifier; 10-2, a second erbium-doped fiber amplifier; 11. an upper computer; 12. a strong feedback module.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments of the present invention include, but are not limited to, the following examples, in particular, the random laser amplification technology and the sensing FBG multiplexing technology, although the present invention is used in combination, in fact, the low-noise random laser amplification technology can be used alone for various optical fiber sensing systems to achieve the effect of high-efficiency amplification, and the sensing FBG multiplexing technology can be used alone for various FBG sensing systems to achieve the effect of increasing the multiplexing rate of the sensing FBG.

The following embodiments are illustrated by way of example in the accompanying fig. 1:

the random laser amplification technology is characterized in that pump light is transmitted in a transmission optical fiber and generates random laser, the structure can be composed of a wavelength division multiplexer 3, a low-noise random laser pump light source module 4 and a transmission optical fiber 5, the pump light generated by the low-noise random laser pump light source module 4 enters the transmission optical fiber 5 through the wavelength division multiplexer 3, backward Rayleigh scattering in the transmission optical fiber 5 performs weak feedback on the pump light, stimulated Raman scattering provides gain, and signal light in a sensing system is subjected to distributed amplification. In the structure of the high-order random laser amplification system, the starting end of the transmission optical fiber 5 is also connected with a strong feedback module 12 to generate strong feedback on the high-order random laser to form a semi-cavity-opening random laser structure, and the generated high-order random laser is used as pump light in the transmission optical fiber to perform distributed amplification on signal light.

The ROPA technology in the long-distance large-capacity FBG sensing system is a point amplification mode of separating a pumping light source and an EDF (erbium-doped fiber) serving as a gain medium, the structure can be composed of a wavelength division multiplexer 3, a low-noise random laser pumping light source module 4, a transmission optical fiber 5 and an EDF8, pumping light generated by the low-noise random laser pumping light source module 4 enters a section of transmission optical fiber 5 to reach an EDF8 through the wavelength division multiplexer 3 and signal light coupling, and the EDF can absorb the pumping light and amplify the signal light of a C waveband due to the distribution characteristic of an erbium ion energy band.

The first erbium-doped fiber amplifier is called EDFA10-1 for short; the second erbium-doped fiber amplifier is called EDFA10-2 for short; the erbium-doped fiber is abbreviated as EDF 8.

Example 1

As shown in fig. 2, the long-distance large-capacity FBG sensing system provided by the present embodiment based on random laser amplification is a long-distance large-capacity FBG sensing system based on a higher-order random laser amplification technology. Signal light source module 1, circulator 2, wavelength division multiplexer 3, strong feedback module 12, transmission fiber 5 connects gradually, the logic of circulator 2 is that first port advances the second port and goes out, the second port advances the third port and goes out, the third port advances the first port and goes out, signal demodulation module 7 is connected to the third port of circulator 2, wavelength division multiplexer 3 is connected to low noise random laser pumping light source module 4, sensing FBG6 distributes in transmission fiber 5, multiplexing 200 central wavelength is 1550nm, the reflectivity scope is-50 dB to-10 dB according to the sensing FBG6 that the offset distributes.

The working principle of the invention is as follows: the signal light source module 1 emits a signal light with a wavelength of 1550nm through a first port of a circulator 2 to enter a 1550nm port of a wavelength division multiplexer 3, a low-noise random laser pumping light source 4 is connected with a short-wavelength interface of the wavelength division multiplexer 3, the signal light and the pumping light are both emitted from a common end of the wavelength division multiplexer 3 to enter a transmission optical fiber 5, rayleigh scattering and raman gain generated by the pumping light in the transmission optical fiber 5 form random laser, a strong feedback module 12 provides strong reflection for the random laser to reduce a threshold of the pumping light generating the random laser to form semi-open cavity random laser, the random laser is distributed along the transmission optical fiber 5 to perform low-noise distributed amplification on the signal light, a sensing FBG6 is used as a sensing element of the system, the central wavelength of a reflection spectrum of the sensing FBG is changed along with the change of an external environment physical quantity due to the structural sensitivity characteristic, and the sensing FBG6 reflects the signal light, and make backward signal light carry external information, backward signal light carries out random laser amplification along transmission fiber 5 again, because the reflection spectrum of strong feedback module 12 does not contain the wavelength of signal light, backward signal light passes through circulator 2 second port and gets into signal demodulation module 7, restores external physical quantity through demodulation backward signal light spectral information. The system simulation result is shown in fig. 6(a) (b), wherein the input power of the signal light is 0.02W, the input power of the low-noise random laser pumping light source 4 with the wavelength of 1365nm is 1.5W, the reflection wavelength of the strong feedback module 12 is 1455nm, the reflectivity is 90%, and 1455nm random laser light is generated in the transmission fiber 5 to perform distributed random laser amplification on the signal light.

Example 2

As shown in fig. 3, the present embodiment provides a long-distance large-capacity FBG sensing system based on random laser amplification, which is a long-distance large-capacity FBG sensing system based on a hybrid amplification technology of a spectrum demodulation module. The signal demodulation module 7 adopts a spectrum demodulation module; the output end of a broadband light source 1-1 is connected with an acousto-optic modulator 1-2, a signal generator 9 is connected with the acousto-optic modulator 1-2 and a spectrum adjusting module, the output of the acousto-optic modulator 1-2 is connected with an EDFA10-1 and then enters a first port of a circulator 2, light at the first port of the circulator 2 comes out from a second port and enters a transmission fiber 5 through a strong feedback module 12, reflected light of a sensing FBG6 in the transmission fiber 5 enters from the second port of the circulator 2 and comes out from a third port of the circulator, the third port of the circulator 2 is connected with an EDFA10-2, and the output of the EDFA10-2 is connected with the spectrum adjusting module. The system has 200 multiplexed sensing FBGs 6, the reflectivity ranges from-50 dB to-10 dB, wherein every four sensing FBGs 6 are an FBG group 6-x, and the patterns with different shapes represent sensing FBGs 6 with different central wavelengths, and the total number of the sensing FBGs is 50 (n is 50). The transmission fiber 5 is a common single mode fiber, the length is 150km, the sensing FBGs 6 are distributed at equal intervals, and the interval between each group of groups is 3 km.

Description of the working principle of the invention: continuous light with the wavelength of 1550nm emitted by the broadband light source 1-1 is modulated into periodic pulse light through the acousto-optic modulator 1-2, and the pulse width and the period of the pulse light are determined by the signal generator 9. The periodic pulse light is amplified by EDFA10-1, enters a 1550nm port of a wavelength division multiplexer 3 through a circulator 2, the output of a low-noise random laser pumping light source 4 enters a short wavelength port of the wavelength division multiplexer 3, and the mixed light enters a section of common single-mode optical fiber which is 150km and is engraved with a sensing FBG6 after coming out from a common port of the wavelength division multiplexer 3. The reflection spectrum of the sensing FBG6 does not contain the wavelength of the random laser pump light and is within the wavelength range of the pulsed light. Pulse light and pump light are transmitted together in the transmission optical fiber 5, when the power of the pump light is larger than the threshold value of the optical fiber, the generated stimulated Raman scattering effect can amplify the pulse light by distributed random laser, because the random laser amplification cannot efficiently compensate the loss of the optical fiber and the sensing FBG6 to the signal pulse light at a far end, an EDF8 with the length of 20 meters is placed at a 40km position, the pump light can efficiently amplify the pulse light at the position of the EDF8, and the sensing distance can be successfully prolonged to 150km by the mixed amplification mode. Because the low-noise random laser pumping light source 4 is used, the relative intensity noise of the pumping light is lower than-100 dB/Hz, and the amplified signal light also has relatively low relative intensity noise due to the characteristic of relative intensity noise transfer. The sensing FBGs 6 are classified into four types according to the central wavelength of the reflection spectrum, each FBG sensing unit group 6-n comprises four sensing FBGs 6, WDM is adopted in the group, TDM is adopted between the groups, the reflected light of the FBGs is used as detection signal light, the detection signal light is amplified by the EDFA10-2 through the circulator 2 and enters the spectrum adjusting module to obtain the spectrum information of the reflected light, and therefore the external environment sensing information is deduced, and finally the external environment sensing information is displayed on the upper computer 11 in a visual mode. The sampling frequency and the single sampling time of the spectrum demodulation module 7 are controlled by the signal generator 9. The system simulation results are shown in fig. 6(c) (d), and the simulation parameters are the same as those of example 1.

Example 3

As shown in fig. 4, the present embodiment provides a long-distance large-capacity FBG sensing system based on random laser amplification, which is a hybrid amplification technology based on a dispersion compensation module. The output end of a broadband light source 1-1 is connected with an acousto-optic modulator 1-2, a signal generator 9 is connected with the acousto-optic modulator 1-2 and a signal demodulation module 7, the output of the acousto-optic modulator 1-2 is connected with an EDFA10-1 and then enters a first port of a circulator 2, light at the first port of the circulator 2 comes out from a second port and enters a transmission fiber 5 through a strong feedback module 12, reflected light of an FBG in the transmission fiber 5 enters from the second port of the circulator 2 and comes out from a third port of the circulator, the third port of the circulator 2 is connected with an EDFA10-2, the output of the EDFA10-2 is connected with the signal demodulation module 7, the signal demodulation module 7 adopts a dispersion compensation demodulation module, and the mode of system FBG multiplexing is the same as that of the embodiment 2.

As shown in fig. 5: the dispersion compensation demodulation module comprises two interfaces, one is an external optical interface and consists of one port of the optical fiber coupler 7-1, the other is an upper computer data interface and consists of output ports of two data acquisition modules 7-5;

one output port of the optical fiber coupler 7-1 is connected with a common single-mode optical fiber calibration module 7-2, the common single-mode optical fiber calibration module 7-2 is further connected with a photoelectric detector 7-4, and the photoelectric detector 7-4 is further connected with a data acquisition module 7-5;

the other output port of the optical fiber coupler 7-1 is connected with a dispersion compensation module 7-3, the dispersion compensation module 7-3 is connected with a photoelectric detector 7-4, and the photoelectric detector 7-4 is connected with a data acquisition module 7-5.

Description of the working principle of the invention: similar to embodiment 2, light amplified by the EDFA10-2 by the circulator 2 enters the signal demodulation module 7 to obtain spectral information of reflected light, so as to infer external environment sensing information, and finally, the external environment sensing information is displayed visually on the upper computer 11, but the signal demodulation module 7 in embodiment 3 is different from that in embodiment 2.

Description of the principle: the signal demodulation module 7 has two external interfaces, one is an external optical interface, and the other is an upper computer data interface. FBG reflected pulse light enters an optical fiber coupler 7-1 through an external optical interface of a dispersion compensation demodulation module 7, the optical fiber coupler 7-1 disperses incident light into two beams which respectively enter a lower path single-mode optical fiber calibration module 7-2 and an upper path dispersion compensation module 7-3, the upper path dispersion compensation module 7-3 has the function of providing optical fiber dispersion difference, and the lower path single-mode optical fiber calibration module 7-3 has the function of compensating an optical path, so that the passing time of the light on the upper path and the passing time of the light on the lower path are basically the same. Due to chromatic dispersion difference between the upper path and the lower path, when the wavelength of incident light changes, the time difference of the light passing through the two paths changes, and the time change of the arrival of the two paths of signals is analyzed through a software algorithm of the photoelectric detector 7-4, the data acquisition module 7-5 and the upper computer 11 behind the two paths of signals to demodulate wavelength change information, so that the external environment sensing information is deduced.

The three embodiments show that the sensing distance of the FBG sensing system can be effectively prolonged and the multiplexing capacity of the sensing FBG of the system can be effectively increased by using the low-noise random laser amplification technology and the TDM and WDM hybrid multiplexing technology, and the overall performance of the FBG sensing system in the applications of high-voltage power grid monitoring and the like is improved.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.