University of Southampton

Stuart John Russell

John P Dakin

A Sagnac or loop type interferometer is disclosed which uses a single broadband Erbium-doped fibre source ( ) and a single IngaAs detector ( ) together with a 40 km long sensor loop ( ). A wavelength division multiplexer ( ) spectrally slices the broadband light from the source ( ) into two sub-bands, with different optical paths being defined between the source ( ) and detector ( ) for the light in the different spectrally sliced sub-bands. The two optical paths include separate phase modulators ( ) which modulate the two signals at different frequencies, and also separate delay loops ( ) at different places relative to the sensor loop ( ). Effectively, two separate Sagnac loops are provided with a single sensor loop ( ), source ( ) and detector ( ). Standard phase locked loop techniques can be used to extract information from signals that have passed through the two loops and to determine the location of a mechanical or thermal perturbation applied to the sensor loop ( ).

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Downend, United Kingdom

Stuart John Russell