A dual-parameter sensing system for temperature and curvature based on Nano-EYDF and in-line cascaded Mach-Zehnder interferometer

Abstract

Based on the self-developed erbium ytterbium co-doped fiber, a sensing system consisting of an amplified spontaneous emission (ASE) source and an optical fiber sensor is introduced. The spectrum test results and stability of ASE source are given. A dual-parameter sensor for temperature and curvature based on in-line cascaded Mach-Zehnder interferometer (MZI) is demonstrated theoretically and experimentally. The proposed sensor is mainly composed of single-mode fiber (SMF) and Nano-Erbium-Ytterbium co-doped fiber (Nano-EYDF) to form a symmetrical sensing structure. MZI is formed due to the mode field mismatch between EYDF and SMF. The sensor displays different response to temperature and curvature. By demodulating the wavelength shifts of different peaks or dips, the sensitivity coefficient matrix method can be used to measure the temperature and curvature simultaneously. The experimental results show that, in the range of 25 ∼ 100 °C, the maximum temperature sensitivity is 94.70 pm/ °C and in the curvature range of 0 ∼ 1.03 m−1, the maximum curvature sensitivity is −9.48 nm/m−1. And the power output of ASE source is stable, the spectral unevenness is less than 2.5 dB in the range of 1530 ∼ 1580 nm. The sensor has the advantages of good repeatability, high sensitivity and compact structure. It can be used in 3D reconstruction, robot shape detection, human medicine and other fields.