Simultaneous measurement for temperature and strain by use of Sagnac interferometer with controlled sensitivity

We propose a novel approach for resolving temperature and strain variations by use of Sagnac interferometer incorporating two types of high birefringence fibers (HBFs) and a polarization controller. The two types of HBFs are spliced together to act as the sensing head for temperature and strain discrimination. The detected parameters are two wavelength dips over a broad wavelength range in the transmission spectrum of the Sagnac interferometer, whose sensitivity responses to temperature and strain both depend on those of the two HBFs. As a result, the sensitivity responses can be controlled by adjusting the polarization controller adjacent to the sensing head to shift the wavelength dips and then change their degrees of dependence on the two HBFs.