Development Of Eccentric Fiber Optic Micro-sensor

Optical fiber sensor has the characteristics of light weight,anti-electromagnetic interference and anti-corrosion.It is widely used in aerospace,petroleum exploration,bridge safety detection,biochemical analysis and so on.The core offset fiber optic micro-sensor has been paid more and more attention because of its controllability,high sensitivity and small size,has been widely used in temperature,refractive index,strain,bending,acceleration and magnetic field measurement.In this paper,an optical fiber refractive index sensor without temperature crosstalk is designed based on the principle of modal interference by the method of core offset spliced.The temperature and refractive index cross sensitivity problem is solved by the common difference temperature self-compensation method,and the strain,bending response and working stability are tested and analyzed.By analyzing the effects of the fiber type,length,symmetrical and asymmetrical structure and offset value on the transmission spectrum of fiber micro-sensors.A method of choosing thin core optical fiber and asymmetrical core offset spliced is found.When the offset value is 6.25?m and 18.75?m,a stable transmission spectrum and large spectral extinction ratio can be obtained.By testing and analyzing the temperature response and refractive index sensing characteristics of the optical fiber micro-sensor,it is found that the sensitivity of the different interference dips of the fiber micro-sensor fabricated by this method to the temperature is as high as 99.12%,therefore a common difference temperature self-compensation method is introduced to solve the refractive index and temperature cross sensitivity problem.This method can obtain a more accurate refractive index sensitivity?-74.22 nm/RIU?,eliminating the error caused by temperature crosstalk?1.2%?,and improving the measurement accuracy of the fiber refractive index sensor.And the strain and bending response of the fiber micro-sensor are tested and analyzed.The strain sensitivity is-1.36 pm/??and 0.00581 dB/??,and the curvature sensitivity is-3.415 nm/m^-1.It has little mechanical disturbance.When the optical fiber refractive index sensor is used in an environment with high mechanical disturbance,the accuracy of measurement can still be guaranteed.In addition,the wavelength fluctuation range of the optical fiber refractive index sensor within 2 hours is±0.02 nm and the intensity fluctuation range is±0.03 dB,which has high stability,can meet the needs of practical work.