Research on transmission characteristics of phase-shifted CFBG in 2 μm band

Abstract Principles of single- and multi-phase-shifted chirped fiber Bragg grating (CFBG) in 2 μm band are analyzed with transmission matrix method, and transmission characteristics, including transmissivity, wavelength and bandwidth performance, of single- and multi-phase-shifted CFBG in 2 μm band with different grating parameters are discussed by simulation. It is found that phase-shifted position, grating length, chirped coefficient and refractive index modulation amplitude all have impacts on bandwidth of phase-shifted transmission peak. The transmission peak bandwidths of single-, dual- and tri-phase-shifted CFBG can reach to 0.0270, 0.0172 and 0.0112 nm respectively. The experiment of phase-shifted CFBG verifies the correctness of the simulation, and the bandwidths of 0.0901 and 0.0480 nm are acquired for single- and dual-phase-shifted CFBG respectively, which are narrower than previous filters based on fiber Bragg grating in 2 μm band multi-wavelength fiber laser system.