Hybrid pendulum-based 2-D tilt sensor with two fiber Bragg gratings

A novel two-dimensional (2-D) tilt sensor is demonstrated by incorporating only two fiber Bragg gratings (FBGs) with a hybrid pendulum transducer. The pendulum is specially designed with hollow half at the upper side and solid half at the lower side. Two FBGs were attached on the surface separated by one fourth of the circumference of the rod of pendulum and across the interface of its hollow and solid parts. Reflection peaks of FBGs split by the applied tilt angle. 2-D tilt angle can be determined by monitoring the wavelength separations of the split peak in two FBGs which is inherently insensitive to temperature. In the experiment, a sensitivity of 0.054 nm/^o over a range of 0° to 20° has been achieved, with the accuracy of 0.27°.