J. Nagasawa, and S. Komatsu: Modulation of refractive index distribution and spectrum characteristic of chirped fiber bragg gratings, Technical Digest, MOC'08 (Brussels, Belgium, 2008), 216-217.

We propose to use the modulated reflection spectrum of a chirped fiber Bragg grating (CFBG) as the optical key for personal idetification. The reflective spectrum to be used as a key pattern is modulated by removing appropriate small parts of the clad from the CFBG with a diamond wheel saw.