All Optical Fiber Keyboard Based on 2D Location Sensor With Cascade Gratings

We propose and experimentally demonstrate a compact all-fiber 2D location sensor suitable for 12-key keyboard application. The proposed sensor consists of two groups of fiber bragg gratings (FBGs) one of which is spatially arranged in 4 x 3 array. Strain-induced Bragg wavelength shifts finely adjust the stopband of incident light by pressing the crossing points of the grating array, leading to corresponding reflections from the reference group due to the one-to-one correspondence between two groups. This sensor has the features of being flexible, low insertion loss, simple structure, and also combines with the advantages of the FBG-based sensors with high sensitivity and accuracy.