Investigation of a novel temperature-sensing mechanism based on strain-induced optical path-length difference in a multicore optical fiber

Abstract

A four-core optical fiber is employed to investigate a novel temperature-sensing mechanism, which is based on the strain-induced optical path-length difference between the fiber core pairs. A short segment of a four-core fiber is wound around a solid stainless steel cylinder to form a tight circular loop, which is exposed to temperatures of up to 100 $^{\circ}$C. Temperature-induced radial expansion of the stainless steel cylinder causes a shear strain in the fiber and introduces an optical path-length difference between the fiber core pairs. This results in a total phase shift of about 20.40 $\pm $ 0.29 rad in the interference pattern of the four-core fiber, which is monitored by a CMOS camera. The temperature-induced phase and strain sensitivities are measured to be 3.74 rad/m$^{\circ}$C and 0.18 $\mu \varepsilon$/$^{\circ}$C, respectively.