Patent ID: 7848645

Claim:
A method of locating or identifying a waveguide, the method comprising: (a) monitoring the waveguide at a first position by transmitting sensing signals onto the waveguide, which sensing signals are in the form of pairs of signal copies introduced onto the waveguide with a time delay relative to one another, to sense a disturbance along the waveguide; (b) causing a disturbance to the waveguide at a second position; (c) transmitting a sensor signal from the first position responsive to said monitoring of the waveguide sensing a disturbance of the waveguide; and (d) inferring, from the sensor signal, the presence or identity of the waveguide at the second position, the inference being made at the second position, wherein at least some of the sensing signals that have traveled at least to the second position are caused to return to the first position; and wherein returned signal copies of respective pairs are temporally re-aligned.