| 摘要 |
An optical fibre cable 6 for temperature detection has an optical fibre 13 and a temperature-dependent expansion body. The fibre 13 and the expansion body are held together by a helically wound wire 14. The expansion body comprises an elastic tube 11 which contains wax with the desired melting point. When the wax melts, it expands and the tube 11 swells so that the wire 14 is stretched and the optical fibre 13 is bent. The fibre cable 6 is used in an OTDR system. The run time of light pulses P is measured and a heated section of the fibre cable 6 is detected by damped, reflected light pulses being detected. By selecting parameter values for the fibre cable 6, for example the pitch S of the helical wire 14 and the volume expansion of the wax, the desired light attenuation in the range 0.01-0.1 dB/m can be obtained. In this way, the positions of a number of heated parts along the fibre cable 6 can be determined. <IMAGE> |
