Switchable Multiwavelength Filter Based on a Hybrid Sagnac Interferometer

Abstract

A switchable multichannel filter based on a hybrid Sagnac interferometer was proposed and experimentally demonstrated. The hybrid Sagnac interferometer was realized by inserting a sampled fiber Bragg grating (SFBG) into a fiber loop mirror by using a polarization-insensitive 3-dB coupler. By using a beam scanning technique, we fabricated a sampled fiber Bragg grating by exposing a photosensitive fiber to a frequency-doubled 244-nm Ar+ laser. The fabricated SFBG had multiple reflection peaks corresponding to the chirp ratio and the spacing of grating. The multiple peaks in the hybrid Sagnac interferometer could be controlled by changing the relative phase difference between two counter-propagating signals. The transmission characteristics of the proposed switchable multichannel filter were analyzed by using a Jones matrix method. Consequently, a switchable multichannel filter based on a sampled fiber Bragg grating incorporating a Sagnac interferometer could be achieved.