Mode re-coupling in novel Bragg grating pair

A new type of mode recoupling in a Bragg grating pair, in which one of the gratings is written in the fiber cladding, is proposed to overcome limitations of concatenated long-period and fiber Bragg gratings reported earlier [Opt. Lett. 27, 1214 (2002)]. Its reflection spectrum is similar to that of the previously reported concatenated grating structure; however, the reflectivity can be much larger than the previous limitation of 50%. Furthermore, avoidance of the loss induced by a long-period grating makes such a Bragg grating pair more attractive for practical applications.