Acousto-optic superlattice modulation in fiber Bragg gratings

The superposition of a long-period grating and a fiber Bragg grating, which we call an optical superlattice, causes high-efficiency narrow-band reflec tions to be induced on either side of the Bragg wavelength. This effect was recently observed experimentally in a fiber-based acousto-optic superlatti ce modulator. We develop in detail the theory of optical superlattices in f iber Bragg gratings,treating both the acousto-optic and the fixed-grating c ases. Applications include reconfigurable wavelength division multiplexers, fiber lasers and sensors, tunable filters, modulators, and frequency shift ers. (C) 2000 Optical Society of America [S0740-3232(00)01606-9].