Switchable narrow bandwidth comb filter based on an acoustooptic superlattice modulator in Sinc-sampled fiber gratings

Summary form only given. In recently published papers, we have successfully demonstrated that high efficiency narrow-band acoustooptic tunable reflectors (acoustooptic superlattice modulator (AOSLM)) using a uniform fiber Bragg grating can be achieved by improving overlap between the acoustic waves and optic waves by a HF etching technique. AOSLM which bases on induced coupling between the forward and backward propagating Bloch modes in the grating is dramatically different from all previously reported acoustooptic fiber devices, which depend on co-propagating intermodal coupling. In an AOSLM, the coupled wave propagates in the opposite direction to the original optic wave and therefore can be taken out by a circulator and it can also have subnanometer bandwidth. In this paper, we used Sinc-sampled gratings to further verify the AOSLM performances and to add more switchable channels. Four wavelength channels are simultaneously switched in our implementation with an application of an acoustic wave along the fiber axis. This is the consequence of added side-bands in spatial frequency formed in a periodically phase-modulated Bragg grating. The number of switchable channels can be further increased with an increase in the number of channels in the original Sinc-sampled grating.