Dissimilar-fiber long-period fiber gratings: concept and demonstration

A new type of long-period fiber grating structure that contains dissimilar fiber types is proposed. This dissimilar-fiber long-period fiber grating (DF-LPFG) structure is fabricated by splicing together subperiod sections of dissimilar fiber types. Due to the large index differences that can exist between various fiber types, the resulting DF-LPFGs can be exceptionally short, e.g., a few millimeters. As a demonstration, prototype DF-LPFGs were fabricated by periodically splicing together standard single-mode fiber and dispersion-compensating fiber using a commercially available cleaver and splicer. The resulting DF-LPFGs exhibited clear resonances with attenuations of ∼35  dB and insertion losses of ∼8  dB. To the best of the authors' knowledge, this is the first demonstration of the DF-LPFG concept. Other devices based on this concept may also be realizable.