Research Of The Optical Fiber Sensor Based On FPI

This paper summarizes the theory and development of F-P sensor at first,and introduces the methods of various optical fiber F-P sensors' fabrication.Analyses how to modulate and demodulate the signal of F-P sensor.Then,reveals the process of manufacture for the in-fiber mirrors and the character in sensor.Finally,it proposes three kinds of sensors based on the in-fiber mirrors.(1)It is not sensitive enough for a single FPI which consisted by in-fiber mirrors to test temperature or strain.But it can be improved by cascaded two FPI according to the theory of Vernier Effect.The Femtosecond laser micromachining platform is used and the cavities length of FP accurately controlled by this system relatively.Therefore,the sensor cascaded two FPI realize sensitivity amplification perfectly for avoiding the collapse or deformation of the F-P cavity caused by the refusion after cutting the optical fiber.The sensitivity of the device to strain was 28.11 pm/?? and the sensitivity to temperature was 278.48 pm/?.(2)In order to conduct addressing in the process of demodulation easy,the optimal setting of four in-fiber mirrors cascade structures is achieved by simulation before the experiment being carried out.The output fringe pattern of the device exhibits dominant/highly distinguishable dip wave-length,which helps in unambiguous measurement beyond the free spectral range.The device has excellent thermal stability in high temperature up to 1100?,and the temperature sensitivity obtained is 9.91 pm/? within the temperature range of 100? to 400?,and 15.88pm/? within the temperature range of 400? to 1100?,respectively.(3)The device is composed of a large number of in-fiber reflection mirrors with constant separation,which forms many identical FP cavities cascaded along the single mode fiber(SMF).As a result of superposition of many FPI fringe patters,the output of the device consists of a number of well separated and dominant fringe peaks.The spacing between the fringe peaks depends on the reflection mirror separation.The device has an excellent high-temperature sustainability up to 1100?,with temperature sensitivities of 10.15 pm/? and 16.92 pm/? respectively,within the range from 100 to 400? and from 400 to 1100?,respectively.All in all,this paper provides a new technique for the fabrication Intrinsic Fabry-Perot Interferometer sensor by using Femtosecond laser scribe reflection mirrors in the fiber.It predigests the program for fabrication optical fiber sensor contained Fabry-Perot structure.Some work become simpler and more reliable as the cavities length of F-P resonator controlling more precision by the new system.