CN108760080B - A distributed optical fiber Raman temperature measurement device and method based on ASE noise - Google Patents

Abstract

The present invention relates to distributed optical fiber sensing system, specially a kind of distributed fiber Raman temperature measuring equipment and method based on ASE noise.The present invention solves the contradiction between spatial resolution present in the existing distributed fiber Raman temp measuring system based on pulsed light and measurement distance, overcomes the problem of bringing system performance to decline in itself as transducing signal due to chaotic laser light in the distributed fiber Raman temp measuring system based on chaotic laser light.This system includes ASE noise light source, the first adjustable light wave-filter, the one 1 × 2nd fiber coupler, photodetector, optical circulator, the 21 × 2nd fiber coupler, the second adjustable light wave-filter, the first avalanche photodetector, the first low noise amplifier, third adjustable light wave-filter, the second avalanche photodetector, the second low noise amplifier, data collecting card, computer, sensor fibre.

Description

A distributed optical fiber Raman temperature measurement device and method based on ASE noise

technical field

The invention relates to a distributed optical fiber sensing system, in particular to a distributed optical fiber Raman temperature measuring device and method based on ASE noise.

Background technique

There are more and more large buildings such as submarine tunnels, bridge tunnels, skyscrapers, giant factories, etc. Once a fire or other accident occurs in these places, it will not only cause major economic losses to the country, but also cause huge casualties. For example: at about 11 o'clock on March 15, 2004, a huge fire broke out in Zhongbai Commercial Building, Jilin City, Jilin Province. The fire eventually killed 54 people, injured 70 others, and caused a direct economic loss of 4.26 million yuan; A fire broke out in the Jintian Commercial Building in Lishi District, Lvliang City, killing 8 people. At 14:00 on November 15, 2010, a high-rise apartment building on Jiaozhou Road, Yuyao Road, Shanghai caught fire. The fire eventually killed 58 people and injured more than 70 others. It is impossible for any accident to happen suddenly, especially before an accident such as a fire occurs, there will be some omens, such as the temperature will be significantly higher than the temperature during the working hours or the temperature will rise suddenly, and timely detection of these temperature changes will avoid accidents occur. Therefore, it is particularly important to develop a reliable temperature measurement system for the prevention of fire and other accidents.

At present, the distributed optical fiber sensing temperature measurement system based on Raman scattering can realize the temperature information measurement on the long-distance continuous optical path, and the system cost is low and has high cost performance, so it has been widely used. For example, the distributed optical fiber Raman temperature sensing system developed by Jin Zhongxie et al. of Chongqing University has achieved a spatial resolution of 1m and a measurement distance of less than 5 km [Zhu Haipeng, Jin Zhongxie. Distributed Raman temperature measurement system based on multimode optical fiber, Acta Photonica Sinica, 2015, 44(01), 75-79]; Zhang Zaixuan's research team at China Jiliang University developed a 30 km long-distance distributed optical fiber Raman temperature sensor system with a spatial resolution of 4 m [Zhang Zaixuan, Wang Jianfeng, Liu Honglin, Yu Xiangdong , Guo Ning, Insoo S.KIM, 30km long-distance distributed optical fiber Raman temperature sensor system, Optoelectronics·Laser, 2004(10), 1174-1177]. The laser source used in the existing distributed optical fiber Raman sensing technology is mainly pulsed laser. For pulsed lasers, on the one hand, the response accuracy of the receiving end is high, and signal capture is difficult; on the other hand, the monitoring distance of the system is proportional to the pulse width, and the spatial resolution is inversely proportional to the pulse width. If the pulse width is narrowed in order to improve the spatial resolution It will cause the reduction of the monitoring distance, which will lead to the contradiction between the monitoring distance and the spatial resolution. At present, the distributed optical fiber Raman sensing system based on pulsed laser has a spatial resolution of more than 1 meter, which is difficult to meet the needs of practical applications. In order to solve the contradiction between spatial resolution and monitoring distance, a distributed optical fiber Raman temperature measurement system based on chaotic laser was proposed [Chinese patent: ZL 201110227239.9]. However, chaotic laser is usually provided by optical feedback or optical injection, or It is generated by optical feedback combined with optical injection to disturb the semiconductor laser, which will contain periodic signals introduced by optical injection and optical feedback, which will seriously affect the spatial resolution of the Raman temperature measurement system. At the same time, to generate a chaotic laser signal with adjustable spectrum and controllable coherence length, multiple parameters need to be adjusted, and the light source structure and implementation process are complex and time-consuming.

Therefore, it is necessary to develop a new Raman temperature measurement system, which can not only solve the contradiction between the spatial resolution and the monitoring distance of the traditional Raman temperature measurement system, but also overcome the problem caused by the chaotic laser as the sensing signal. It itself brings the problem of system performance degradation.

Contents of the invention

In order to solve the problems existing in the existing distributed Raman temperature measurement system, the present invention provides a distributed optical fiber Raman temperature measurement device and method based on ASE noise.

The present invention adopts following technical scheme to realize:

A distributed optical fiber Raman temperature measurement device based on ASE noise signal, including ASE noise light source, first tunable optical filter, first 1×2 fiber coupler, photodetector, optical circulator, second 1× 2 fiber optic coupler, second tunable optical filter, first avalanche photodetector, first low noise amplifier, third tunable optical filter, second avalanche photodetector, second low noise amplifier, data acquisition card , computer, sensing optical fiber;

The output end of the ASE noise light source is connected to the input end of the first tunable optical filter through an ordinary single-mode optical fiber jumper, and the output end of the first tunable optical filter is connected to the first 1×2 optical filter through an ordinary single-mode optical fiber jumper. The incident end of the fiber coupler is connected, one of the output ends of the first 1×2 fiber coupler is connected to the input end of the photodetector, and the output end of the photodetector is connected to the first input end of the data acquisition card through a coaxial cable. The other output end of the first 1×2 fiber coupler is connected to the incident end of the optical circulator through a common single-mode fiber jumper, and the reflection end of the optical circulator is connected to the sensing fiber through a common single-mode fiber jumper. The output end of the optical circulator is connected to the incident end of the second 1×2 fiber coupler through an ordinary single-mode fiber jumper, and one of the output ends of the second 1×2 fiber coupler is connected to the second tunable optical filter, The output end of the second tunable optical filter is connected to the input end of the first avalanche photodetector through an ordinary single-mode fiber jumper, and the output end of the first avalanche photodetector is connected to the first low-noise amplifier through a coaxial cable. , the output end of the first low-noise amplifier is connected with the second input end of the data acquisition card through the coaxial cable; the other output end of the second 1×2 fiber coupler is connected with the third tunable optical filter, and the third The output end of the tunable optical filter is connected to the input end of the second avalanche photodetector through an ordinary single-mode fiber jumper, and the output end of the second avalanche photodetector is connected to the second low-noise amplifier through a coaxial cable. The output end of the second low noise amplifier is connected with the third input end of the data acquisition card through the coaxial cable; the output end of the data acquisition card is connected with the computer.

A distributed optical fiber Raman temperature measurement method based on ASE noise signal, the specific working process of the method is as follows:

a. The noise signal generated by the ASE noise light source passes through the first tunable optical filter to generate a noise optical signal with a suitable spectral bandwidth, and then is divided into two paths through a 1×2 fiber coupler, one of which is used as a reference light, and It is converted into an electrical signal by the photodetector, and then input to the data acquisition card; the other optical signal is used as the pump light, and enters the sensing fiber through the optical circulator, and generates Raman backscattered light at each point of the fiber, and then pulls The Raman backscattered light is injected into the optical circulator through the reflection end of the optical circulator, and then output through the output end of the optical circulator; the output Raman backscattered light is divided into two paths through the second 1×2 fiber coupler , one of the optical signals passes through the second tunable optical filter to filter out the backward Stokes light, and the filtered Stokes light is converted into an electrical signal by the first avalanche photodetector, and then passes through the first low The noise amplifier is amplified, and then input to the data acquisition card; the other optical signal output by the second fiber coupler is filtered by the third tunable optical filter to filter out the anti-Stokes light, and then converted by the second avalanche photodetector It is an electrical signal, then amplified by the second low-noise amplifier, and then input into the data acquisition card, and then input into the computer after A/D conversion;

b. With the support of the corresponding software, the computer uses the characteristic that the intensity of the anti-Stokes light obtained by the backscattering of the pump light varies linearly with temperature, and calculates the intensities of the anti-Stokes light and the Stokes light The temperature information of each section of the sensing fiber can be obtained by comparison; the position signal of the temperature of the fiber can be determined by performing cross-correlation processing between the Stokes optical signal and the reference optical signal.

Based on the above process, compared with the existing distributed optical fiber Raman temperature measurement system, a distributed optical fiber Raman temperature measurement device and method based on the ASE noise source of the present invention has the following advantages:

(1) Spatial resolution determines the minimum distance between two regions with different temperatures on the sensing fiber that the distributed sensing system can identify, and is a key technical indicator of the distributed sensing temperature measurement system. For the Raman temperature measurement system based on pulsed light, it is determined by the width of the light pulse injected into the optical fiber; increasing the pulse width will increase the monitoring distance, but it will also lead to a decrease in spatial resolution, so there are monitoring distance and spatial resolution. rate contradiction problem; and the present invention adopts ASE noise signal, and its correlation curve presents the shape of class delta function, and the spatial resolution is determined by the full width at half maximum of the correlation peak on the cross-correlation curve between the Stokes optical signal and the reference optical signal It has nothing to do with the sensing distance, the length of the monitoring distance is determined by the power of the signal source, which fundamentally solves the problem between the monitoring distance and the spatial resolution in the existing distributed optical fiber Raman temperature measurement system based on pulsed light detection. contradiction problem. The measurement distance can reach more than 100 kilometers, and the spatial resolution can reach the order of centimeters.

(2) The invention patent (ZL 201110227239.9) provides a distributed optical fiber Raman temperature measurement system based on chaotic lasers, which can solve the problem between monitoring distance and spatial resolution in the distributed optical fiber Raman temperature measurement system based on pulsed light detection. contradiction. However, chaotic lasers are usually generated by optical feedback or optical injection, or optical feedback combined with optical injection to disturb the semiconductor laser, and will contain periodic signals introduced by optical injection and optical feedback, which will seriously affect the spatial resolution of the Raman temperature measurement system. . At the same time, to generate a chaotic laser signal with adjustable spectrum and controllable coherence length, multiple parameters need to be adjusted, and the light source structure and implementation process are complex and time-consuming. The ASE noise optical signal used in the present invention is generated by an erbium-doped optical fiber amplifier or a semiconductor optical amplifier. The adjustment of its spectral width (or coherence length) can be realized simply by a tunable optical filter. Therefore, the spatial resolution (determined by the coherence length of ASE noise) of the sensing system described in this application is easier to control. It can be seen that the use of ASE noise light source not only effectively solves the problem of limited spatial resolution fundamentally, but also makes the system structure simpler and the system cost lower.

Description of drawings

FIG. 1 is a schematic structural diagram of a distributed optical fiber Raman temperature measurement device based on ASE noise according to the present invention.

In the figure: 1-ASE noise source, 2-the first tunable optical filter, 3-the first 1×2 fiber coupler, 4-photodetector, 5-optical circulator, 6-the second 1×2 fiber Coupler, 7-second tunable optical filter, 8-first avalanche photodetector, 9-first low-noise amplifier, 10-third tunable optical filter, 11-second avalanche photodetector, 12 - second low noise amplifier, 13 - data acquisition card, 14 - computer, 15 - sensing optical fiber.

Detailed ways

A distributed optical fiber Raman temperature measurement device based on ASE noise, including an ASE noise light source, a first tunable optical filter, a first 1×2 fiber coupler, a photodetector, an optical circulator, a second 1×2 Fiber coupler, second tunable optical filter, first avalanche photodetector, first low-noise amplifier, third tunable optical filter, second avalanche photodetector, second low-noise amplifier, data acquisition card, Computer, sensing optical fiber.

Wherein the output end of the ASE noise light source 1 is connected to the input end of the first tunable filter 2 through an ordinary single-mode jumper, and the output end of the first tunable optical filter 2 is connected to the first 1× 2 The incident end of the optical fiber coupler 3 is connected, one of the output ends of the first 1×2 optical fiber coupler 3 is connected with the input end of the photodetector 4, and the output end of the photodetector 4 is connected to the data acquisition card through a coaxial cable One of the input ends of 13 is connected; the other output end of the first 1×2 fiber coupler 3 is connected with the incident end of the optical circulator 5 through an ordinary single-mode fiber jumper, and the reflection end of the optical circulator 5 is connected through an ordinary single-mode optical fiber jumper. The optical fiber jumper is connected with the sensing fiber 15, the output end of the optical circulator 5 is connected with the incident end of the second 1×2 fiber coupler 6 through a common single-mode fiber jumper, and the second 1×2 fiber coupler 6 is One output end of the second tunable optical filter is connected with the second tunable optical filter 7, and the output end of the second tunable optical filter 7 is connected with the input end of the first avalanche photodetector 8 through a common single-mode fiber jumper, and the first avalanche photoelectric detector The output end of detector 8 is connected with the first low-noise amplifier 9 by coaxial cable, and the output end of the first low-noise amplifier 9 is connected with one of the input ends of data acquisition card 13 by coaxial cable; 2 The other output end of the fiber coupler 6 is connected to the third tunable optical filter 10, and the output end of the third tunable optical filter 10 is connected to the input end of the second avalanche photodetector 11 through a common single-mode fiber jumper The output end of the second avalanche photodetector 11 is connected with the second low noise amplifier 12 through the coaxial cable, and the output end of the second low noise amplifier 12 is connected with one of the input ends of the data acquisition card 13 through the coaxial cable Connected; the output terminal of the data acquisition card is connected with the computer 14.

A distributed optical fiber Raman temperature measurement method based on ASE noise, the specific working process of the method is as follows:

a. The noise signal generated by the ASE noise light source 1 passes through the first tunable optical filter 2 to generate a noise optical signal with a suitable spectral bandwidth, and then it is divided into two paths through a 1×2 fiber coupler 3, one of which is an optical signal (below Road) as a reference light, which is converted into an electrical signal by the photodetector 4, and then input to the data acquisition card 13; the other optical signal (upper road) is used as a pump light, enters the sensing fiber 15 through the optical circulator 5, and Raman backscattered light is generated at each point of the optical fiber, and then the Raman backscattered light is injected into the optical circulator 5 through the reflection end of the optical circulator 5 , and then output through the output end of the optical circulator 5 . The output Raman backscattered light is divided into two paths through the second 1×2 fiber coupler 6, and one path of optical signal (left path) passes through the second tunable optical filter 7 to filter out the backward Stokes Light, the filtered Stokes light enters the first avalanche photodetector 8, the optical signal is converted into an electrical signal, then amplified by the first low-noise amplifier 9, and then input to the data acquisition card 13; through the second optical fiber The other optical signal (right) output by the coupler 6 passes through the third tunable optical filter 10 to filter the anti-Stokes light, and then converts it into an electrical signal through the second avalanche photodetector 11, and then passes through the second low Noise amplifier 12 is amplified, then input in the data acquisition card 13, input in the computer 14 after A/D conversion;

b. With the support of Matlab software, the computer uses the characteristic that the intensity of the anti-Stokes light obtained by the backscattering of the pump light varies linearly with temperature, and calculates the difference between the anti-Stokes light and the Stokes light The temperature information of each segment of the optical fiber can be obtained by the intensity ratio; the position signal of the optical fiber temperature can be determined by performing cross-correlation calculation processing between the Stokes optical signal and the reference optical signal.

During specific implementation, the central wavelength of the ASE noise light source 1 is 1550nm, and the spectral bandwidth is 5-30GHz; the first tunable optical filter 2, the second tunable optical filter 7, and the third tunable optical filter 10 use TM- 50-type wavelength and bandwidth tunable optical filter; the coupling ratio of the first 1×2 fiber coupler 3 and the second 1×2 fiber coupler 6 is 50:50; the first avalanche photodetector 8 and the second avalanche photoelectric The detector 11 adopts Fby photoelectric, DTS1550-DA-MM type avalanche photodetector; the sensing optical fiber 15 adopts multimode optical fiber.

Claims (2)

1. a kind of distributed fiber Raman temperature measuring equipment based on ASE noise signal, including it is ASE noise light source (1), first adjustable Humorous optical filter (2), the one 1 × 2nd fiber coupler (3), photodetector (4), optical circulator (5), the 21 × 2nd optical fiber coupling Clutch (6), the second adjustable light wave-filter (7), the first avalanche photodetector (8), the first low noise amplifier (9), third can Tuned light wave filter (10), the second avalanche photodetector (11), the second low noise amplifier (12), data collecting card (13), meter Calculation machine (14), sensor fibre (15)；

The output end of first adjustable light wave-filter (2) passes through general single mode fiber wire jumper and the one 1 × 2nd fiber coupler (3) Incidence end be connected, the input terminal phase of the one of output end and photodetector (4) of the one 1 × 2nd fiber coupler (3) Even, the another output of the one 1 × 2nd fiber coupler (3) passes through the incidence of general single mode fiber wire jumper and optical circulator (5) End is connected, and the reflection end of optical circulator (5) is connected by general single mode fiber wire jumper with sensor fibre (15), optical circulator (5) Output end be connected with the incidence end of the 21 × 2nd fiber coupler (6) by general single mode fiber wire jumper, the 21 × 2nd optical fiber One of output end of coupler (6) is connected with the second adjustable light wave-filter (7), the second adjustable light wave-filter (7) Output end is connected by general single mode fiber wire jumper with the input terminal of the first avalanche photodetector (8), and the first avalanche optoelectronic is visited The output end for surveying device (8) is connected by coaxial wire with the first low noise amplifier (9), the output of the first low noise amplifier (9) End is connected by coaxial wire with the second input terminal of data collecting card (13)；21 × 2nd fiber coupler (6) it is another A output end is connected with third adjustable light wave-filter (10), and the output end of third adjustable light wave-filter (10) passes through common single Mode fiber wire jumper is connected with the input terminal of the second avalanche photodetector (11), the output end of the second avalanche photodetector (11) It is connected by coaxial wire with the second low noise amplifier (12), the output end of the second low noise amplifier (12) passes through coaxial cable Line is connected with the third input terminal of data collecting card (13)；The output end of data collecting card (13) is connected with computer (14)； It is characterized in that, wherein the output end of ASE noise light source (1) passes through general single mode fiber wire jumper and the first adjustable light wave-filter (2) input terminal is connected, the first input that the output end of photodetector (4) passes through coaxial wire and data collecting card (13) End is connected.

2. a kind of distributed fiber Raman temp measuring method based on ASE noise signal, using device described in claim 1 come real It is existing, it is characterised in that: this method specific work process is as follows:

A. the noise signal that ASE noise light source (1) generates generates spectral bandwidth and closes by the first adjustable light wave-filter (2) Then suitable noise optical signal is divided into two-way by 1 × 2 fiber coupler (3), wherein all the way optical signal as reference light, and Electric signal is converted to through photodetector (4), then is input to data collecting card (13)；Another way optical signal leads to as pump light Optical circulator (5) are crossed into sensor fibre (15), and generate Raman rear orientation light at optical fiber each point, then to scattered after Raman It penetrates light to be injected into optical circulator (5) by the reflection end of optical circulator (5), then the output of the output end through optical circulator (5)；It is defeated Raman rear orientation light out is divided into two-way by the 21 × 2nd fiber coupler (6), wherein optical signal can by second all the way Tuned light wave filter (7), filters out backward stokes light, and the stokes light filtered out is by the first avalanche photodetector (8) Electric signal is converted to, is then amplified by the first low noise amplifier (9), then be input to data collecting card (13)；By The another way optical signal of two fiber couplers (6) output filters out anti-Stokes light by third adjustable light wave-filter (10), Then electric signal is converted to by the second avalanche photodetector (11), is amplified using the second low noise amplifier (12), It is input in data collecting card (13), is input in computer (14) after A/D conversion again；

B. computer (14) is under the support of corresponding software, the anti-Stokes light obtained using pump light back scattering it is strong The characteristic changed with temperature linearity is spent, the intensity ratio by calculating anti-Stokes light and stokes light obtains sensor fibre (15) each section of temperature information；By to making computing cross-correlation processing between Stokes optical signal and reference optical signal, so that it may To determine the position signal of fiber optic temperature.