Novel spectrum properties of the periodic π-phase-shifted fiber Bragg grating

A special periodic π-phase-shifted (π-PS) fiber Bragg grating (FBG) is proposed to achieve multichannel reflections. The Fourier analysis and the simulations based on the transfer matrix method show that this simple structure can generate multichannel response with high reflectivity. The reflectivity is much greater than that of the traditional sampled FBG for the same value of κL. Therefore the length of the fiber or the amplitude of refractive index modulation can be greatly reduced if such a periodic π-PS FBG is used instead of the traditional sampled FBG in the applications of comb filtering and optical wavelength division multiplexing. Besides, when the duty cycle is 0.5, this periodic π-PS FBG can create dual wavelength spectrum with high reflectivity.