CN101813496A - Fiber Bragg grating sensor and Raman sensor-fused sensing system - Google Patents

Abstract

The invention discloses a sensing system that integrates fiber optic Bragg grating sensing and Raman sensors, including a light source 1, a circulator 2, several fiber Bragg gratings 3, a wavelength division multiplexer 4, a coupler 5, and a slope filter 6 , a first photodetector 7 , a second photodetector 8 , a third photodetector 9 , a fourth photodetector 10 , a first divider 11 , a second divider 12 and a sensing signal response processing module 13 . Beneficial effects of the present invention: can realize simultaneous measurement of temperature and other multiple parameters, use Raman effect to measure a group of temperature parameters, and FBG to measure other parameters, so that there are more monitoring points and the measurement system has higher precision.

Description

A sensing system integrating fiber Bragg grating sensor and Raman sensor

technical field

The invention relates to the technical field of optical fiber sensing, in particular to a sensing system in which a fiber Bragg grating (FBG) sensing system and a Raman sensor are fused.

Background technique

Fiber Bragg Grating (FBG) is a fiber optic filter that can reflect specific wavelengths, and its central wavelength will change with the changes of parameters such as temperature, stress, and pressure in the external environment. According to this principle, the change of the physical quantity of the external environment can be measured by measuring the change of FBG wavelength. Because FBG has many advantages such as low cost, simple processing, and small size, it has become the most widely used sensor in fiber optic sensors.

The working line width of a single FBG is very narrow, and only one parameter can be measured at a time. If multi-parameter measurement is required, multiple FBGs are required, which seriously affects the capacity of the FBG. Therefore, how to improve the capacity of FBG so that temperature and other parameters can be measured simultaneously is an urgent and unresolved problem.

The Raman scattering effect of optical fiber is an inherent characteristic of optical fiber itself. The scattering effect of optical fiber has been recognized by people for a long time. With the deepening of its research, its application prospect has attracted more and more attention. The distributed optical fiber sensor developed by using the Raman scattering effect has a long service life, low optical fiber loss, and is easy to process and lay.

Based on the above analysis, if the above two can be combined, it will greatly solve the problem of simultaneous measurement of FBG sensor temperature and other parameters, and can realize multi-point detection in engineering.

Contents of the invention

The problem to be solved by the present invention is: how to provide a sensor system that combines fiber Bragg grating sensor and Raman sensor, and the sensor system can realize simultaneous detection of temperature and other parameters.

The technical problem proposed by the present invention is solved in this way: provide a kind of sensing system of fusion fiber Bragg grating sensing and Raman sensor, it is characterized in that:

① Including light source 1, circulator 2, several fiber Bragg gratings 3, wavelength division multiplexer 4, coupler 5, slope filter 6, first photodetector 7, second photodetector 8, third photodetector 9. The fourth photodetector 10, the first divider 11, the second divider 12 and the sensing signal response processing module 13;

②The signal enters the circulator 2 through the light source 1, and the circulator 2 connects several fiber Bragg gratings 3 and the wavelength division multiplexer 4, and the wavelength division multiplexer 4 divides the signal into three paths: the first path enters the coupler 5 and Be divided into two beams, one beam is connected with the slope filter 6 and the third photodetector 9, and the other beam directly enters the first photodetector 7, and these two beam signals are all divided by the first divider 11, and then combined with The sensing signal response processing module 13 is connected; the second path passes through the second photodetector 8 and the second divider 12 and enters the sensing signal response processing module 13; the third path passes through the fourth photodetector 10 and the second divider After 12, it also enters the sensing signal response processing module 13.

According to the sensing system of fusion fiber Bragg grating sensing and Raman sensor provided by the present invention, it is characterized in that the working wavelengths of the three channels of the wavelength division multiplexer (4) correspond to the fiber Bragg grating (3) used in the system respectively The center wavelength of fiber Bragg grating (3) minus 13THZ, the center wavelength of fiber Bragg grating (3), and the center wavelength of fiber Bragg grating (3) plus 13THZ.

According to the sensor system of the fusion of fiber Bragg grating sensor and Raman sensor provided by the present invention, it is characterized in that the slope wavelength range of the slope filter 6 covers the central wavelength range of the fiber Bragg grating 3 .

The working principle of the present invention is: after the laser light source is modulated, it is sent to the sensing fiber through the circulator 2, and the central wavelength reflected by the FBG changes with the external temperature or stress, etc., and the sensing can be realized. The laser pulse light will continuously generate back Raman scattered light waves (namely Anti_Stokes and Stokes light respectively), and the intensity of Anti_Stokes light changes with the change of parameters such as the temperature of the scattering point of the optical fiber, which can realize sensing.

The sensing signal reflected from the FBG and the backward Raman scattered light wave are divided into three paths by the wavelength division multiplexer for processing respectively, one path enters the 1×2 coupler, and the other two paths are directly connected to the photodetector, and the two paths of signals are divided by After being divided by the sensor, and then processed by the sensor signal response processing module, by analyzing the time domain reflection waveform and using the principle of OTDR (Optical Time Domain Reflectometer), it can be concluded that the change in the intensity of the back Raman scattered light wave occurs position, analyze the result of the divider, and obtain the size after the light intensity changes. The signal entering the 1×2 coupler is divided into two by the coupler, one is connected to the slope filter and the photodetector, and the other is directly connected to the photodetector. The two signals are also divided by the divider. After processing with the sensing signal response processing module, the location where the FBG wavelength change occurs can be obtained, and the result of the divider can be analyzed to obtain the magnitude of the wavelength change. By analyzing the sensing signal processing module, the temperature and other parameters can be calculated respectively. value.

Beneficial effects of the present invention: only a simple system can realize simultaneous measurement of temperature and multiple other parameters, use Raman effect to measure a group of temperature parameters, and FBG to measure other parameters, so that there are more monitoring points and the measurement system has higher precision.

Description of drawings

Fig. 1 is a system block diagram of the present invention.

Among them, 1. light source, 2. circulator, 3. several fiber Bragg gratings, 4. wavelength division multiplexer, 5. coupler, 6. slope filter, 7. the first photodetector, 8. the second photoelectric Detector, 9, third photodetector, 10, fourth photodetector, 11, first divider, 12, second divider, 13, sensing signal response processing module.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1, the pulsed light generated by the laser light source is sent to the sensing fiber through the circulator, and enters the FBG (assuming that the wavelength of the FBG is 1550nm, and the reflectivity is > 90%), the sensing signal reflected from the FBG and the backward The Raman scattered light wave is divided into three paths by the wavelength division multiplexer (the working wavelength of the wavelength division multiplexer is 1450nm/1550nm/1665nm), and the light with a wavelength of 1550nm enters the 1×2 coupler, and the other two paths (the wavelength 1450nm/1665nm) is directly connected to the photodetector, the two signals are divided by a divider, and then processed by the sensing signal response processing module, by analyzing the time domain reflection waveform, using OTDR (Optical Time Domain Reflectometer optical time domain reflectometer ) principle, the location where the intensity change of the back-scattered light wave occurs can be obtained, and the result of the divider can be analyzed to obtain the size of the light intensity change. The signal entering the 1×2 coupler is divided into two by the coupler, one is connected to the slope filter and the photodetector, and the other is directly connected to the photodetector. The two signals are also divided by the divider. After processing with the sensing signal response processing module, the location where the FBG wavelength change occurs can be obtained, and the result of the divider can be analyzed to obtain the magnitude of the wavelength change. By analyzing the sensing signal processing module, the temperature and other parameters can be calculated respectively. value.

Claims (3)

1. A sensing system that fuses fiber Bragg grating sensing and Raman sensors, is characterized in that: ① Including light source (1), circulator (2), several fiber Bragg gratings (3), wavelength division multiplexer (4), coupler (5), slope filter (6), first photodetector (7 ), the second photodetector (8), the third photodetector (9), the fourth photodetector (10), the first divider (11), the second divider (12) and the sensing signal response processing module(13); ②The signal enters the circulator (2) through the light source (1), and the circulator (2) connects several fiber Bragg gratings (3) and wavelength division multiplexers (4), and the wavelength division multiplexers (4) divide the signal It is three ways: the first way enters the coupler (5) and is divided into two beams, one beam is connected with the slope filter (6) and the third photodetector (9), and the other beam directly enters the first photodetector (7), these two bunches of signals are all divided by the first divider (11), and then connected with the sensing signal response processing module (13); the second road passes through the second photodetector (8) and the second divider (12) and then enter the sensing signal response processing module (13); the third path also enters the sensing signal response processing module (13) after passing through the fourth photodetector (10) and the second divider (12). 2. the sensing system of fusion fiber Bragg grating sensing and Raman sensor according to claim 1, is characterized in that, the working wavelength of three channels of wavelength division multiplexer (4) corresponds to the used fiber Bragg grating of system respectively The center wavelength of (3) minus 13THZ, the center wavelength of fiber Bragg grating (3), and the center wavelength of fiber Bragg grating (3) plus 13THZ. 3. the sensing system of fusion fiber Bragg grating sensing and Raman sensor according to claim 1, is characterized in that the slope wavelength range of described slope filter (6) covers the center wavelength variation of fiber Bragg grating (3) scope.

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