High-Sensitive Microdisplacement Sensor Based on Fiber Mach–Zehnder Interferometer

A fiber-optic sensor based on Mach–Zehnder interferometer, which is composed of two cascaded fiber directional couplers, is investigated and applied for high-sensitive microdisplacement detecting. The free spectrum range of the transmission spectrum varies with the gap sizes in the sensing arm, which is used to sense displacement for the first time to the best of our knowledge. The experimental result is well agreed with the numerical simulation, and shows the maximum displacement sensitivity of 66 nm/ $\mu $ m which is at least forty times higher than that of the previous displacement fiber-optic sensors. Furthermore, the proposed sensor has the potential for higher sensitivity by enlarging the wavelength range of both optical source and signal detector.