dismantling the monopoly of public television for the detection of temperature change.

摘要

An optical fibre cable (6) for temperature detection comprises an optical fibre (13) and a temperature-responsive swellable body. The fibre (13) and the swellable body are held together by a helically-wound wire (14). The swellable body includes an elastic tube (11) which contains wax having a given melting point. When the wax melts, it expands in volume and causes the tube (11) to swell and therewith stretch the wire (14), resulting in the bending of the optical fibre (13). The fibre cable (6) is used in an OTDR-system. The propagation of light pulses (P) is measured and a heated section of the fibre cable (6) is detected through the detection of attenuated, reflected light pulses. A desired light attenuation in a range of from 0.01-0.1 Db/m can be obtained by appropriate selection of the parameter values of the fibre cable (6) for example the pitch (S) of the wire helix (14) and the volumetric expansion of the wax. This enables the locations of several heated sections along the fibre cable (6) to be established. IMAGE