Angle sensor based on two cascading abrupt-tapers modal interferometer in single mode fiber

In this paper, a simple-fabricated and high sensitive angel sensor based on single mode optical fiber is proposed. The sensor consists of two cascading abrupt-tapers with different sizes, manufactured by CO2 laser. The cladding modes will be excited in the first taper and interfere with the core mode in the second taper. When the angle applied on the sensor, the length between the two tapers will change. At the same time, the first taper is bend which affects the ratios and the effective indices of the core mode and the cladding modes excited by the first taper. As a consequence, the interference pattern will have a shift. By monitoring the shift of the interference pattern, the angle measurement is achieved. Experimental results show that the sensor has good linear relationships in some certain measurement range. The angle measurement sensitivity is as high as 601.8 nm/° in the measurement range of 0.0575° and 0.075°.