Acousto-optic attenuation filters based on tapered optical fibres

This paper studies the acousto-optic interaction induced by an acoustic flexural wave among the optical propagation modes supported by tapered optical fibres. We have investigated the evolution of the acousto-optic resonance condition as the fibre is progressively tapered, showing that the taper radius can be regarded as a new degree of freedom in the design of acousto-optic filters. Finally, we demonstrate a novel acousto-optic filter based on nonuniform tapers for dynamic gain flattening of optical fibre amplifiers