PARALLEL COHERENGE RECEWER FOR QUASI-DISTRIBUTED OVflCAL SENSOR

We present the implementation of a coherence receiver that is able, in parallel, to demultiplex and measure the phase between up to seven interference signals generated in a "white light " polarimeiric quasi-distributed sensing system. It is based on a Michelson interferometer, one mirror of which has seven reflecting facets with differing thicknesses in its aperture. It was further used to measure the phase variation, between two polarization couplers, versus three point bending loading for optical fibres either surface bonded or embedded in GRP composite.In both cases, the sensitivity to the composite elongation is found in close agreennt with the sensitivity of the fibre itself. 1.INTRODUCIION Intrinsic optical fibre sensors, where the optical fibre is itself the transducer, offer low invasiveness (outer diameter of the order of 100 pm) and the potential capability for distributed measurement along a single fibre. Both properties are of high interest and fmd applications for mapping, for instance, strain and/or temperature fields of various structures. Such sensing system can even be embedded in composite material due to the excellent compatibility between the optical fibre and the reinforcing matrix.Techniques based on OTDR1 have been derived to allo