Channel spacing-tunable sampled fiber Bragg grating by linear chirp and its application to multiwavelength fiber laser

We theoretically investigated the two methods for densifying the channel spacing of sampled fiber Bragg gratings (SFBGs), the multiple-phase-shift (MPS) method and the linear chirp method, and found that the two methods have similar principle and ability, although the chirp method has an advantage that the tuning of channel spacing is easier. Then we realized channel spacing-tunable SFBGs by use of deformation of ring and S-bend structures by 2- and 3-folds. Finally, we applied the chirp method to realize a wavelength spacing-tunable multiwavelength fiber laser.