Ultra-Narrow Dual-Channel Filter Based on Symmetrical Sampled Fibre Bragg Grating

Abstract

A kind of ultra-narrow dual-channel filter is proposed in principle and demonstrated experimentally. This filter is designed by means of two sampled fibre Bragg gratings (SFBGs), where one is periodic 0–π sampling and the other is symmetrical spatial sampling. The former can create two stopbands in the transmission spectra and the latter can produce two ultra-narrow passbands. Our filter has the 3-dB bandwidth of about 1 pm, whose value is two orders of magnitude less than the bandwidth of the traditional SFBG filters. The proposed filter has a merit that the channel spacing remains unchanged when tuning the filter.