Investigations on seven-core fiber based interferometric all-fiber sensor for curvature and temperature measurements

Abstract

An all-fiber Mach-Zehnder interferometer (MZI) sensor structure for measurement of temperature and curvature is proposed and demonstrated experimentally, which consists of two parts of no-core fiber (NCF) and seven-core fiber (SCF) sandwiched between two single-mode fibers (SMF). Since the two no-core fibers are respectively cascaded at both ends of SCF to improve light separation and recombination, the intermodal interference effect can be generated in the fiber inside structure. Based on the theoretical optimization analysis, we confirmed the sensing characteristics of the proposed all-fiber MZI-based sensors. The experiment results demonstrate that the spectral interference dips of proposed sensor have different responses for curvature and temperature. The wavelength shift is sensitive to temperature change and has better linearity, but insensitive to curvature variation. The spectral intensity is not only sensitive to curvature variation but also temperature change with a certain nonlinearity. The maximum temperature and curvature sensitivities of 100.1 pm/℃ in temperature range of 50–100 ℃ and 10.22 dB/m−1 in curvature range of 0.82–1.226 m−1 are obtained respectively. These sensing characteristics and the advantages of simple fabrication, high repeatability and common materials can make the proposed sensor be widely used in building structure detection and engineering.