Abstract: A fibre optic sensor 1 comprises a body 2 of a matrix material which includes an embedded length of optical fibre 3. When the body 2 is exposed to an external disturbance, mechanical and strain forces arising internally can be transmitted to the fibre 3 and will modify the passage of light therein. Pulsed light through the fibre 3 can be sensed for example by interferometry to measure the disturbance. This can provide an inexpensive and sensitive sensor construction which is capable of the remote detection of various parameters.

Abstract: An optical phase modulator comprises a body 1 of a matrix material which supports a length of optical fiber 2, the said body including a polymer material having piezoelectric properties and being provided with spaced electrode areas 4 such that the application of an electrical potential between said areas will produce a mechanical strain in the body 1, the said strain affecting the said fiber 2 so as to control phase modulation of light when this is present in the fibre. This can give a device of inexpensive construction which is robust and has high sensitivity.

Abstract: Inertially insensitive optical fibre hydrophones are described, utilizing materials and configurations to obtain acceleration balanced designs suitable for underwater applications where acceleration is a problem. Balancing and/or insensitivity is obtained both in longitudinal and axially perpendicular directions. Acoustic sensitivity of a coil formed by the fibre is maintained by the properties of materials used to provide a rigid former, encapsulant material and secondary material which form the hydrophone.