Characteristics Of Optical Fiber Sensing Based On Interference

Due to lots of requirement of automation industry,aerospace and military,environmental monitoring,testing of building and oil exploration,the experts and scholars in many countries have paid much attention to the exploration of sensor.In the late 1970's,an optical fiber sensing technology was established,which was a new and different from the traditional electrical sensor technology.The optical fiber sensor technology has many property advantages,for instance,little volume,light weight,low loss on power,anti-electromagnetic interference and easily control.Thus the optical fiber sensing technology has been extensively used in monitor the temperature,stress,displacement,humidity,vibration,electricity,acoustics,biochemistry and magnetism.The multimode interference(MMI)fiber principle can apply to filter,sensor and signal processing.The MMI structure can easy to make,package and connect to other optical fiber structure,therefore,it has been widely applied to the research of sensor.In this paper,the principles of two fiber model interference with combining the Sagnac sensing structure have analyzed,and a new type of optical fiber sensor has manufactured in our experiment.Two structure sensors measurement of multiple parameters are realized in theory and experiment,respectively.The main contents include:1)The history of the development,classification and applications of the optical fiber sensor in recent years are depicted.The problems of fiber sensors are presented and analyzed in detail.The research progress of model interference fiber sensors is briefly described and the principles and methods to realized model interference are introduced.2)The multi-mode interference principle of SMS structure is introduced,its theoretical model is described.Based on the multimode interference theory and the sensing characteristics,the fiber-optic sensor composed of a SMF-MMF-SMF(SMS)structure is proposed for the measurement of temperature,strain and refractive index.Because of the different response sensitivities of interference spectrum of SMS structure,and temperature,strain and refraction index,the measurement is realized.The sensing characteristics of the optical fiber system based on SMS fiber structure are discussed,and the differences and advantages and disadvantages of different experimental results are analyzed.3)The sensing principle of MMF-SMF-MMF(MSM)structure is presented.And then we manufactured a new style optical fiber sensing system through combining the Sagnac structure.Because of the different response sensitivities of interference spectrum of sensing structure to temperature,strain and refraction index,the different measurement is realized.Through comparing the different response characteristics of the measured parameters with the fiber structure of SMS,we confirmed the benefits of this structure.