Simultaneous force and temperature measurement using optical microfiber asymmetrical interferometer

Abstract

A novel optical microfiber asymmetric Fabry-Perot interferometric (MAFPI) sensor is developed for simultaneous measurement of force and temperature. The MAFPI structure is formed by a weak fiber Bragg grating (FBG), a section of the microfiber, and a cleaved fiber end surface. The narrowband beam reflected from the low-reflectivity FBG and the broadband beam from the Fresnel reflection interfere lead to its unique sensing performance. The force sensing is performed by detecting the bending-loss induced fringe contrast changes, while the Bragg wavelength shift is employed for temperature measurement. Sensitivities of 9.8 pm/℃ and 0.025 dB/μN were obtained experimentally for temperature and force measurements, respectively.

Dispersion effects of high-order-mode fiber on temperature and axial strain discrimination

“…In this paper, a HOMF-based fiber modal interferometer supporting three dominant modes is achieved with distinct chromatic dispersion of each guided mode and intermodal dispersion. Compared to conventional multimode interference structures (SMF-multimode-SMF structures, taper or lateral-offset in fiber Mach-Zehnder interferometers [23][24][25][26][27][28][29][30][31][32][33][34][35]) with a great amount of high-order optical modes, the proposed HOMF modal interferometer supports only a few steady core-guided modes which only need to be calibrated once for sensing response which is essential for practical applications. Thus the HOMF-based sensor here could be deployed for highly accurate discrimination based on the precise dispersion measurement and analysis on intermodal coupling with a novel phase demodulation scheme.…”