Simulation and analysis of sensitivity for tapered fiber Bragg grating evanescent wave sensor

We have carried out a detailed simulative study of the tapered fiber Bragg grating (TFBG) evanescent wave sensor sensitivity by using 3-D Coupled-Mode Theory method. The method is based on the spectral interrogation mode of operation. We also make numerical simulations to figure out how the uniform waist diameter and the difference of the relative refractive indexes between fiber core and external medium affect the sensitivity of this proposed sensor. The simulation results show that the sensitivity of the tapered fiber Bragg grating will be improved when the diameter of the uniform waist decrease as well as the difference of the relative refractive indexes between fiber core and external medium. And with the fixed uniform waist diameter and tapered length, when the difference of the relative refractive index of fiber core and external medium varies is 0.015RIU, the values of wavelength shift is 5.08nm, the sensitivity of the tapered fiber Bragg grating is 317.5nm/RIU. The sensitivity is higher than that of the common FBG. The results are consistent with theoretical models. The simulation results can supply the guidance for the further experimental study and refractive index sensor design, optimization and application.