Wavelength switchable fiber-optic Sagnac filter

A wavelength switchable fiber-optic comb filter based on an in-line Sagnac interference is proposed and demonstrated. The proposed filter consists of a polarizer, two polarization controllers (PCs) and two sections of polarization maintaining fiber (PMFs). The output comb spectrum characteristics of the configuration are theoretically analyzed by Jones matrix, and then numerically simulated and experimentally demonstrated, of which the results present four comb filter-types (sinusoidal, flat-top and narrow-band superposition, and line-shaped spectra) by adjusting the polarizations of light with PCs.