Optical waveguide couplers for a fibre-optic hydrophone

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Optical waveguide couplers for a fibre-optic hydrophone

Bennion, I. / Duthie, P.J. / Stewart, W.J.

This paper reports the use of integrated optical beamsplitters and recombiners for applications in a monomode fibre-optic hydrophone. We have recently described the development of a fibre-optic hydrophone employing pulse-delay techniques to achieve insensitivity in the fibre down-leads. The scheme utilised is referred to as a differential delay heterodyning interferometer (DDHI) and initial testing has produced promising results with regard to sensitivity and noise immunity. To produce a compact, operational optical system we have considered employing integrated optical techniques; in particular, a number of devices appear to offer attractive options for the frequency-shifting functions performed by the Bragg cells in the system. Further, multiple-fibre arrays would benefit from fast optical switching, achievable using electro-optic waveguide devices. Significant advantage would be gained by incorporating these several components into a single device, since relative alignment of the individual parts is then in-built in a small, compact unit.