Optical Fiber Tag Based on an Encoded Fiber Bragg Grating Fabricated by Femtosecond Laser

A type of encoded FBG array for use as an optical fiber tag is inscribed using a femtosecond laser line-by-line technique. Each tag included two labels and several codes formed by grating fragments with a predetermined length. Encoded information was characterized by measuring the backscattered optical signal. Local spectra from the internal grating fragments were then used to enlarge the encoding capacity or encrypt the encoded FBG. The insertion loss of the device is as low as <; 0.1 dB.