High Sensitivity Cryogenic Temperature Sensors Based on Arc-Induced Long-Period Fiber Gratings

In this paper, we investigated the evolution of the dispersion curves of long-period fiber gratings (LPFGs) from room temperature down to 0 K. We considered gratings arc-induced in the SMF28 fiber and in two B/Ge co-doped fibers. Computer simulations were performed based on previously published experimental data. We found that the dispersion curves belonging to the lowest-order cladding modes are the most affected by the temperature changes, but those changes are minute when considering cladding modes with dispersion turning points (DTP) in the telecommunication windows. The temperature sensitivity is higher for gratings inscribed in the B/Ge co-doped fibers near DTP and the optimum grating period can be chosen at room temperature. A temperature sensitivity as high as -850 pm/K can be obtained in the 100-200 K temperature range, while a value of -170 pm/K is reachable at 20 K.

Automated summary

In this paper, the evolution of dispersion curves of long-period fiber gratings (LPFGs) at different temperatures was investigated. It was found that the dispersion curves of the lowest-order cladding modes were most affected by temperature changes, but the effects were negligible when considering cladding modes with dispersion turning points (DTP) in the telecommunication windows. The temperature sensitivity was higher for LPFGs in the B/Ge co-doped fibers near DTP, and the optimum grating period could be chosen at room temperature.