In-line Mach-Zehnder interferometer for simultaneous measurement of temperature and directional torsion

Abstract

An in-line Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated for simultaneous measurement of temperature and directional torsion. The MZI structure is fabricated by fusion splicing a section of multi-core fiber (MCF) between two segments of multi-mode fibers (MMFs). The temperature and torsion sensing characteristics are investigated experimentally. Simultaneous measurement of temperature and torsion can be realized by monitoring the wavelength shift and intensity variation of a resonant dip. The obtained temperature wavelength and intensity sensitivities are 70 pm/℃ and -0.296 dB/℃, respectively. The intensity sensitivities for clockwise and counterclockwise torsion are 1.837 dB/(rad/m) and -1.456 dB/(rad/m), respectively. The wavelength sensitivities for clockwise and counterclockwise torsion are 13.8 pm/(rad/m) and −41 pm/(rad/m), respectively. Furthermore, the sensor has the capability of twist direction discrimination. Due to the different responses of the resonant dip to temperature and torsion, the temperature and torsion can be simultaneously measured by monitoring the wavelength and power changes of only one resonant dip. The spectrum range required to measure is greatly reduced, which is more convenient for practical application.