High-performance fiber sensor via Mach-Zehnder interferometer based on immersing exposed-core microstructure fiber in oriented liquid crystals.

Rapid technology development and various applications show great demands for high-quality temperature sensors with super-sensitivity, broad working temperature ranges, excellent linearity and high stability. Although tremendous efforts have been dedicated towards developing fiber sensors with high performance, challenges still remain in achieving all of the four parameters. Herein, we fabricate a fiber sensor via a Mach-Zehnder interferometer (MZI) combined with a liquid crystal (LC)-filled microtube, where the LC in the microtube is uniformly orientated. The LCs with uniform orientation treatment play a vital role in the fiber sensor. The feasibility of this sensor was verified by theoretical simulation and demonstrated through experiments. The fabricated LC fiber sensor has super temperature sensitivity of -21.6 nm/°C with a good linearity of 0.976 from 22°C to 31°C, -558.5 nm/°C from 31°C to 32°C, -37.3 nm/°C with a good linearity of 0.999 from 32°C to 34°C and -6.7 nm/°C with a good linearity of 0.999 from 34°C to 110°C, respectively. The sensitivity of the fiber sensor is increased by up to 155 times, compared to the previously reported fiber sensor filled with LC based on the MZI without LC orientation treatment. The fiber sensor with super-sensitivity, broad working temperature range, excellent linearity and high stability provides great potential applications in such as environment monitoring, food detection, medicine, and chemical industry.