High precision temperature and strain discrimination using TCF–TPMF fiber structure based Sagnac interferometer

Abstract

We propose a fiber Sagnac interferometer (FSI) for precise temperature and strain discrimination. A thin core fiber (TCF) and a thin polarization maintaining fiber (TPMF) are firstly fusion spliced with two single mode fibers of a 3 dB coupler, respectively, and then fusion spliced with each other by core offset splicing to fabricate the FSI. Cladding modes are introduced to affect the temperature and strain sensitivities. The spectra composed of polarization modes and dominant cladding modes are extracted from the transmission spectra by a fast Fourier transform (FFT) filter. Temperature and strain discrimination is realized by building a simultaneous measurement matrix. Experimental results show that the temperature and strain resolutions of the proposed FSI can reach 0.0076 °C and 0.018 με, and the maximum measurement errors of temperature and strain variations are ±0.062°C and ±4.48με, respectively. The proposed sensor has promising application prospects in safety monitoring of engineering structures due to the advantages of high precision, ease of fabrication, intrinsic safety and low cost.