Numerical simulation and analysis of spectral characteristic for weak fiber Bragg grating

Spectral characteristic of the weak optical fiber Bragg grating (WFBG) is simulated by using numerical solution of the mode-coupled equation and Matlab programming. The influences of structural parameters of fiber grating such as length, period, the refractive index modulation on its reflective spectral bandwidth and maximum reflectivity are studied. The results show that if only changing one of the structure parameters, the reflectivity of the WFBG will increase when the fiber grating length and the refractive index modulation increase, and will decrease when the fiber grating period increases. Besides, the reflective spectral bandwidth will decrease when the fiber grating length increases, and will increase when the refractive index modulation and the fiber grating period increase. Through numerical simulation of the Matlab, it is feasible to design low refractive index fiber grating device, therefore avoiding the blindness of design.