Analysis of transmission spectral characteristics of the photonic crystal fiber grating

Researched the transmission spectral and delay characteristics of a kind of photonic crystal fiber Bragg grating. Firstly, we got the mode field and the effective indexes of the base mode by multipole method, then calculated the transmission spectrum of the fiber using the former data through couple-mode theory and transfer-matrix method, got the resonance wavelength and the reflectivity intensity. We also researched the apodization characters of this fiber grating, simulated the reflectivity spectrum and delay spectral of several different apodization functions, such as Gauss, super Gauss, cosine and parabola, got the optimal apodization function. We also compared the differences between conventional fiber grating and photonic crystal fiber grating on their reflection spectrum and delay, the structure influence of photonic crystal fiber was also discussed. It was found that the refractive index of core mode declined as wavelength rising, photonic crystal fiber grating had the similar transmission spectrum compared with conventional grating except the resonance wavelength showing a clear blue shift, cladding structure such as hole diameter, hole space changed the characters remarkably.