Multiplexable high-temperature stable and low-loss intrinsic Fabry-Perot in-fiber sensors through nanograting engineering
Mohan Wang, Yang Yang, Sheng Huang, Jingyu Wu, Kehao Zhao, Yuqi Li, Zhaoqiang Peng, Ran Zou, Hui Lan, Paul R. Ohodnicki, Ping Lu, Michael Buric, Bo Liu, Qingxu Yu, Kevin P. Chen
Abstract
This paper presents a method of using femtosecond laser inscribed nanograting as low-loss- and high-temperature-stable in-fiber reflectors. By introducing a pair of nanograting inside the core of a single-mode optical fiber, an intrinsic Fabry-Perot interferometer can be created for high-temperature sensing applications. The morphology of the nanograting inscribed in fiber cores was engineered by tuning the fabrication conditions to achieve a high fringe visibility of 0.49 and low insertion loss of 0.002 dB per sensor. Using a white light interferometry demodulation algorithm, we demonstrate the temperature sensitivity, cross-talk, and spatial multiplexability of sensor arrays. Both the sensor performance and stability were studied from room temperature to 1000°C with cyclic heating and cooling. Our results demonstrate a femtosecond direct laser writing technique capable of producing highly multiplexable in-fiber intrinsic Fabry-Perot interferometer sensor devices with high fringe contrast, high sensitivity, and low-loss for application in harsh environmental conditions.