A novel temperature sensor based on a long period fiber grating with a unique double-cladding layer structure

A novel temperature sensor based on long period fiber gratings (LPGs) with a unique double-cladding layer structure, which increases the temperature sensitivity, is presented in this paper. Cladding layer of the LPG is etched properly, and then packaged in stainless tube filled with index-matching fluid of relatively low thermal coefficient. It is observed in experiments that sensitivity of 1.1nm/°C for a temperature range of 15°C achieved for such a LPG sensor, which is about 100 times larger than that of sensors made of traditional fiber Bragg grating. It also has a linearity of 99.89% and small size of Φ:1mm*L:50mm, which shows a good promise for future application.