OPTICAL-PATH AUTOMATIC COMPENSATION LOW-COHERENCE INTERFEROMETRIC FIBEROPTIC TEMPERATURE SENSOR

An interferometric fibre-optic temperature sensing system employing a light emitting diode (LED) as the broadband optical source and a singl e mode fibre coil which was fabricated in a definite length as the sen sor head is described. A reference fibre line transmitting back and fo rth along the same path as the sensing transmitting fibre is used, so the change caused by the environmental temperature fluctuation of the fibre path can automatically be compensated. The sensitivity of the se nsing system can be easily improved by using the long length of the se nsing fibre. The experiment results of the sensing gauge length versus the sensitivity are given. Two typical wavelengths (1300 and 1550 nm) . LED sources are used, it is shown that the sensitivity of the system between the two wavelengths is different. The experimental curve of t he resolution characteristic of the system related to the length of se nsing fibre coil is also discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.