Interferometric Interrogation of the Inclination and Displacement of Tapered Fiber Mach-Zehnder Interferometers

Abstract

All-fiber inclinometers and displacement sensors using tunable Mach-Zehnder interferometers with an extinction ratio of > 30.4 dB are produced by introducing two abrupt tapers in a short length (<1.4 cm) of highly Er/Yb co-doped fiber. The abrupt tapers partially convert the core mode into cladding modes and interference occurs when the phase difference between the core and cladding modes accumulate to π after a certain propagation length. The maximal wavelength shift for the resonant transmission dips can reach 40.8 nm (from 1648 to 1607.2 nm) when the inclination angle, θ, varies from 0°to 32°. The wavelength shift can reach 26 nm (from 1404.4 to 1430.4 nm) when the compressive strain ε is 0.004.

Optical Fiber Inclinometer Based on a Fiber Taper Cascading a Peanut-Shape Structure

“…The measurement range can be expanded by increase the tapering diameter. The sensitivity of the inclinometer with length of 26mm is higher than the sensors proposed in [1], [4], [5], and [8], and the mechanical structure is more stable than the sensor proposed in [5] and [8]. Fig.…”

“…Usually, optical fiber inclinometer is based on fiber Bragg gratings [1]- [3], phase-shift Bragg gratings [4], taper Michelson interferometer [5], long-period fiber gratings [6], and abrupt taper [7], [8]. B. O. Guan [1] reported a vertical-pendulum based fiber Bragg grating tilt sensor, which has an accuracy of 0.1°and the resolution of 0.007°.…”

“…As the region of fiber tapering is soft and easy to bent, many inclinometers based on tapering have been proposed in recent years. N. K. Chen [8] proposed an inclinometer and displacement sensor based on highly Er/Yb co-doped fiber and abrupt tapers in short length with the sensitivity of about 1.275nm/°in the range from 0°to 32°. L. M. N. Amaral [5] demonstrated a compact fiber-optic inclinometer based on a fiber-taper Michelson interferometric sensor, which has sensitivity of 1.13 rad/°a nd angle resolution of 0.014°.…”

Plastic Optical Fiber Angle Sensor for 1-D and 2-D Based On Cascading Of TMBC

“…Yu, et al [25] proposed a temperature-insensitive fiber Bragg grating rotational angle sensor with a sensitivity of 0.743 nm/º over the rotational angle range from -21 to +21. Chen, et al [26] had designed an all-fiber inclinometer with an extinction ratio of >30.4 dB by introducing two abrupt tapers in a short length of highly Er/Yb co-doped fiber. The sensors reported in [4,27] have a complicated structure, a costly development process, and they may also have relatively low sensitivity.…”