High-sensitive bending sensor based on a seven-core fiber

A novel fiber bending sensor is proposed based on a home-made seven-core fiber (SCF). The sensing head is formed by splicing a piece of a SCF between two sections of single-mode fibers(SMFs). Two super modes with most of mode energy in the central fiber core and in the six outsider fiber cores are exited in the SCF, which ensures the Mach–Zehnder interferometer (MZI) structure of the proposed sensor and form the mode interference spectrum in the lead-out SMF. The relationship between the dip wavelength shift of the interference spectrum and the bending curvature of the SCF is experimentally investigated. The temperature response of the SCF bending sensor is also experimentally investigated Our experimental results show that the MZI sensor exhibits a high bending sensitivity of 2.65 nm/m−1 and a temperature sensitivity of 0.021 nm/°C, respectively. The compact size, low cost and high sensitivity makes the MZI sensor a good candidate for bending sensing application.