Simultaneous measurement of strain, curvature, and temperature using a hollow square core fiber

Abstract

The hollow core photonic crystal fibers have attracted a significant interest due to their abilities not only in managing the optical properties, but also to guide light with low loss. In this work, a hollow square core fiber (HSCF), whose guidance is based on the antiresonance (AR), is implemented as an optical fiber sensor to simultaneously measure the strain, curvature, and temperature. The sensor was designed in a transmission layout where the HSCF was spliced between two single mode fibers (SMF), enabling the appearance of two interferometers, the Mach-Zehnder interferometer (MZI) and the cladding modal interferometer (CMI). Both interferometers, allied to the AR guidance, show different responses to the physical measurands. The sensor revealed a maximum strain sensitivity of −2.72 pm/με, for the CMI component within a strain range up to 600με. As for the curvature response, two curvature ranges were analyzed. For the first range (from 0 m−1 to 0.7 m−1) a higher sensitivity of −2.21 nm/m−1 was attained for the CMI, while for the second range (between 0.7 m−1 and 1.5 m−1) a maximum sensitivity of −0.63 nm/m−1 was achieved by the resonance. On the other hand, for the temperature measurements a sensitivity of 32.8 pm/°C was attained by the MZI within a maximum temperature variation of 60°C. The proposed sensor reveals promising to be employed in a wide range of applications where the measurement of several physical parameters is required.