A temperature sensor based on liquid crystal coated grapefruit microstructer fiber with core-offset splicing structure

A temperature sensor based on liquid crystal coated grapefruit microstructure fiber (GMF) with core-offset splicing structure is proposed and prepared. Both ends of the GMF are core-offset spliced with the single-mode fibers (SMF). The capillary glass tube is sleeved outside the GMF and filled with the liquid crystal. Due to the mismatch between the core mode fields of the input SMF and the GMF, a part of the light out of of the input SMF enters the core of the GMF, and the rest is coupled into the cladding of the GMF forming the cladding mode. The core-offset splicing structure forms the Mach-Zehnder interferometer and two beams interfere in the output SMF. Immersed in the liquid crystal solution, The interferometer generates the phase difference between the core mode and cladding modes of GMF with the change of external temperature. The temperature could be measured by detecting the change of the interference spectrum of the sensor. The experimental results show that the transmission spectrum appears red shift with the increase of temperature in 30 ∼ 90 °C, achieving the maximum temperature sensitivity of 202.26 pm/°C and good linearity. The sensor has the advantages of simple fabrication and high sensitivity, and has good applications in environment monitoring and industrial productions.