Sensitivity enhanced temperature and strain sensor based on parallel hybrid interferometers and the Vernier effect

A fiber sensor with significantly enhanced temperature and strain sensitivities is proposed. This sensor, which comprises a fiber Sagnac interferometer (FSI) in parallel with an improved fiber modal interferometer (FMI), has been validated in experiments. The FSI consists of a section of polarization-maintaining fiber (PMF) and a 2x2 3 dB optical coupler (OC), serving as the sensing interferometer. The improved FMI with a higher extinction ratio (ER) consists of a core-offset structure, no core fiber (NCF), single-mode fiber (SMF), and few mode fiber (FMF), serving as the reference interferometer. Different Vernier effect envelopes have distinct responses to temperature and strain, thereby making the sensor a good choice for concurrent monitoring of temperature and strain variations. The experimental outcomes demonstrate an enhancement in both temperature and strain sensitivity, advancing from -1.33 nm/degrees C of a conventional single FSI to 22.26 nm/degrees C and from 2.83 to -50.99 pm/mu epsilon, respectively. The proposed sensor, with its advantages of exceptional sensitivity, uncomplicated design, and economical cost, provides what we believe is a novel and effective solution for the practical measurement of temperature and strain. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.