High precision fiber-optic inclinometer based on abrupt-tapered Mach-Zehnder interferometers

We demonstrate all-fiber inclinometer using tunable Mach-Zehnder interferometers with an extinction ratio of above 30.4 dB by introducing two points of abruptly tapering in a short length (< 1.4 cm) of highly Er/Yb co-doped fiber (EYDF). The abrupt tapers can transfer partial core mode into cladding modes and the interference occurs when the phase difference between core and cladding modes are accumulated to π after a certain propagation length. The wavelength shift can reach 40.8 nm (from 1607.2 to 1648 nm) when the inclination angle θ varying from 0° to 32°. The wavelength shift can reach 26 nm (from 1404.4 to 1430.4 nm) when the inward compression displacement D is 260 µm.