Acoustic sensitivity of optical-fibre waveguides

The letter describes the interaction between coherent light propagating along an optical fibre and an acoustic wave incident on the fibre. The pressure sensitivity of a single-mode fibre is such that it may be used as a sensitive microphone with a very wide dynamic range. The corresponding effect in multimode fibres is a much more complex process, resulting in a reduction in both sensitivity and linearity. Experimental measurements of the sensitivity are in sensible agreement with the theoretical predictions.