Abstract

The use of a Sagnac interferometer as an acoustic sensor has recently been demonstrated [1]. One reason for using a Sagnac interferometer is that the path imbalance is zero, such that no interferometric conversion of the source phase noise to intensity noise occurs. The low frequency response of a Sagnac interferometer increases with increasing loop length, and a very long length of fibre is needed to achieve high responsivity for acoustical frequencies. In this paper we present a scheme where we enhance the low frequency response using a recirculating ring within the Sagnac loop, as shown in fig. 1, thereby increasing the effective length of the Sagnac loop.

© 1992 Optical Society of America