In-Line Mach–Zehnder Interferometric Sensor Based on a Seven-Core Optical Fiber

An in-line Mach–Zehnder interferometer (MZI) is proposed and experimentally demonstrated. The sensor is fabricated by splicing a segment of seven-core fiber (SCF) and two segments of very short multi-mode fibers (MMFs). The mode field of the MMF used in our experiments close to the region of hexagonally distributed fiber cores of the SCF, which help to obtain a higher coupling efficiency. A clear interference spectrum of the proposed MZI is obtained by injecting a broadband light into a lead-in single-mode fiber. Such an MZI could be used to realize the measurement of temperature and curvature. The temperature and curvature sensitivities are 55.81 pm/°C and 31.54 nm/ $\text{m}^{-1}$ , respectively.