Optical fiber sensor for small angle and infinite angle detection

An optical fiber angle sensor that consists of a cam, linear displacement attenuators, and a sensitive Fabry-Perot cavity (FPC), is demonstrated to simultaneously measure small angle and infinite angle with high resolution. When the cam is driven to rotate by a fixed rotary shaft, a linear displacement transformed from an angle will be further attenuated by linear displacement attenuators and will subsequently modulate the FPC, which causes the reflected interference intensity of FPC to vary. By using the method of interferometric fringe counting, we can measure an infinite angle accurately and continuously. Moreover, a small angle measurement can be performed in a locally linear region. Experimental results show that two resolutions of 0.5 and 1.5 s in the angle range of 0.1944 degrees and 3.5496 degrees are achieved, respectively.