Two-dimensional bend sensing with a cantilever-mounted FBG

A technique for simultaneous measurement of a 2D bend by using a cantilever-mounted fibre Bragg grating (FBG) is experimentally demonstrated. The value of the two-dimensional deflections is acquired from the central wavelength and chirp bandwidth of the reflection spectrum via the inverse sensitivity matrix. Moreover, an interrogation system with an intensity modulator and a Mach-Zehnder interferometer structure is demonstrated, not only providing wavelength information, but also distinguishing the direction of the horizontal deflection. The measured vertical deflection sensitivity reaches 0.135 nm mm(-1) and its horizontal counterparts along the positive and negative axes achieve 0.602 nm mm(-1) and -0.572 nm mm(-1) respectively.