Gec-marconi Limited

Plessey Overseas Limited

Michael L Henning

Alan C Curtis

Robert John Langston

Christopher Lamb

Philip J Nash

An optical fiber coil assembly comprising two optically interconnected optical fiber coils or coil parts (22, 23) rigidly supported in predetermined positional relationship by respective rigid support means so constructed and arranged that static or quasi-static pressure (P) applied to the assembly produces a decrease in the path length of one of the coils or coil parts, and an increase in the path length of the other.

Optical fibre coil assemblies

An optical sensing system (e.g. hydrophone) includes a plurality of laser light sources for producing light signals of different frequencies which are combined by a Bragg cell and launched into a single optical fibre leading to an optical sensor array arrangement. This sensor array arrangement includes a plurality of optical sensors separated by redirecting means for redirecting light signals along an optical fibre in time displaced relationship to an optical detector.

Optical sensing systems with plural wavelengths and wavelength sensitive

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.

Optical phase modulator

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.

Hydrophone

An optical sensing system comprising single light source and a series of phase shifting switching devices positioned linearly aligned with the light source. Each phase shifting device is driven by a driving device with pulses at different frequencies and sequentially from the most proximately located phase switching device to the most distant phase switching device so that light eventually passes through each of the phase switching devices. Fiber sensor arrays are aligned with each of the phase switching devices and light reflected from the fiber sensor arrays is detected by a plurality of photodetector devices each associated with a fiber sensor array.

Optical sensing systems

A multiplex optical sensing system comprises an optical fibre arranged to be subjected at the longest length to fibre deforming forces during operation of the system and means for producing a plurality of pulse trains of coherent light in which the frequency of frequencies of (F1+.DELTA.F1), (F2+.DELTA.F2), (F3+.DELTA.F3) of the pulses in respective pulse trains lie within a different frequency channel for transmission along said optical fibre. The optical fibre is provided along its length with a nunber of equally spaced discontinuities which effectively divide the fibre into a plurality of discrete fibre elements so that a small proportion of each light being pulse being transmitted along the fibre will be reflected back along the fibre from each of the discontinuities whereby, within any one of the pulse trains, each reflected light pulse after the first is superimposed upon either the previously reflected pulse from the preceding discontinuity or a reference light signal of the same frequency or a frequency with a constant difference frequency to the said transmitted light signal to produce an electrical signal in square law photo-detection means, the difference between respective electrical signals corresponding to successive fibre elements being dependent upon the length of the fibre elements so that changes in optical path length of these elements produced by the incidence of deforming forces will result in changes in the electrical signals which will be detected.

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Somerset, United Kingdom

Michael L Henning