Research On Optical Fiber Distributed Simultaneous Vibration And Temperature Sensing Technology

Distributed optical fiber sensors have attracted a lot of research interests in recent years.They are now widely used in the area of oil,natural gas,electricity for vibration,temperature and strain detection due to its advantages such as high sensitivity,high electromagnetic interference resistance,large dynamic range,long sensing range,simple terminal structures and so on.Numerous significant researches have been successfully conducted on the optical fiber sensors base on Rayleigh and Raman Scattering.In this paper,we proposed an optical fiber distributed simultaneous vibration and temperature sensing base on Optical Time Domain Reflectometer,in which the wavelength-division multiplexing technology is used to separate the Raman and Rayleigh backscattering.We mainly studies the key technology of optical fiber sensor and analyzes several typical optical fiber vibration sensors and optical fiber temperature sensors.This part provides solid theoretical foundation to the below contents of the paper.On the basis above,a new system of Optical Fiber Distributed Simultaneous Vibration and Temperature Sensing Base on Optical Time Domain Reflectometer is designed,which includes laser,acousto-optic modulator,erbium-doped fiber amplifier,circulator,wavelength division multiplexer,sensing fiber,photodetector and data processing module.The parameters of each module are analyzed and optimized.The signal processing flow and the appropriate processing algorithms are designed,which can realize the positioning and extraction of vibration data and the demodulation and calibration of temperature data,respectively.An experimental system of Optical Fiber Distributed Simultaneous Vibration and Temperature Sensing Base on Optical Time Domain Reflectometer is built.This system has 3200 meter multi-mode sensing fiber which include a 40 meter fiber loop as vibration sensing unit and three 40 meter fiber loops as temperature sensing units.In the vibration experiment,a clean speech is played by a moible phone as the vibration source,then the raw vibration data is processed by algorithm written before.The experimental results show that the positioning accuracy can reach up to about 25 m.In the temperature experiment,the temperature sensing units are heated by a constanttemperature water tank.Three types of temperature measurement experiments are carried out separately.The final experimental results show that the system can measure the temperature with the accuracy of ?1?.