Chirped fibre gratings for temperature-independent strain sensing

Abstract

Fibre Bragg grating sensors are of considerable interest for a number of sensing applications [1-6]. More recently, chirped Bragg gratings are attracting research interest for strain sensing [2,3]. However, undesirable temperature sensitivity of the fibre grating sensor may complicate its use as a strain gauge. Morey et. al. have suggested that the temperature can be measured and compensated for using a second grating element contained within a different material and placed in series with the first grating [4]. We have also demonstrated that the problem can be resolved by arranging for the simultaneous measurement of strain and temperature [5], or by arranging for the thermal response to be cancelled [6]. Nevertheless, all of the above methods are difficult to implement when a large number of fibre gratings are involved in a multiplexed sensing system. In this paper we describe a novel temperature-independent strain sensor based on the use of a chirped fibre grating in a tapered optical fibre.