A Sensitivity-Enhanced Sub-Zero Temperature Sensor Based on the Mach-Zehnder Interferometer Coated with Organic...

In this paper, a high-sensitivity sub-zero temperature sensor based on the Mach-Zehnder interferometer coated with organic silicone film is proposed. The sensor is fabricated by polishing four orthogonal sides in the multimode fiber (MMF) of the single-mode-multimode-single-mode (SMS) structure with a CO₂ laser and then coating the structure with a mixed film of hydroxyl-terminated siloxane and methyl MQ silicone resin to form a sub-zero-sensitive layer. The sub-zero temperature sensitivity of the coated sensors is experimentally compared for samples with different numbers of polished facets. The experimental results show that the sub-zero temperature sensitivity of the sensors with one to four polished facets increased from 0.73 nm/K to 2.15 nm/K in the temperature range of 223 K to 273 K. The fiber sub-zero sensor has the advantages of compact structure, high sensitivity and low cost, which lead to the potential for application in fields such as biomedicine, aerospace and energy.