Comb filters based on superstructure rocking filters in photosensitive optical fibers

We have fabricated superstructure rocking filters which operate on the principle of linear polarization rotation through the twisting of the birefringent axes of photosensitive elliptical-core fibers by UV radiation. The polarization coupling spectrum of these filters consists of a series of narrow resonances which are roughly equally spaced in frequency. This can result in a comb-like response extending over the entire single-mode frequency range of the fiber. Applications of such structures are also discussed.