Bandwidth-tunable filter and spacing-tunable comb filter with chirped-fiber Bragg gratings

We report two chirped-fiber Bragg grating (CFBG) based optical fiber filters: one is the bandwidth-tunable filter with high reflectivity, and the other is a comb filter with a tunable spacing. Both filters are based on a unique chirp-rate tuning technique for CFBGs. In the former case, a record large tuning range of 36 nm (1.8-37.8 nm) in bandwidth has been achieved, with a high reflectivity of ∼0.99 being maintained. In the latter case, a sampled-CFBG is used and the spacing tuning range is up to 2.1 nm (1.2-3.3 nm).