Patent ID: 8003932

Claim:
A position sensor including: an optical waveguide; a transmission stage for launching a sensing signal into the waveguide; a receiving stage arranged to receive a returned sensing signal, which returned sensing signal is a time distributed signal derived from backscattered components of the sensing signal, the waveguide being arranged along a path having a plurality of overlap regions such that a disturbance in an overlap region causes a first disturbance feature and a second disturbance feature in the returned sensing signal; and monitoring means for monitoring the returned signal, such that a respective time of return can be associated with the first disturbance feature and with the second disturbance feature; wherein the sensing signal comprise a series of pairs of pulses, each pair of pulses having been generated by power-splitting a single pulse, wherein each member of a respective pair of pulses is temporally off-set from the other member of said respective pair of pulses.