Phase-shifted bandpass filter fabrication through CO2 laser irradiation

We report what is believed to be the first example of phase shifted bandpass filter written on the fiber Bragg grating (FBG) through CO2 laser irradiation. The filter is realized by fiber residual stress relaxation effect. The induced phase shifts in different position can produce multiple narrow passbands within the stopband of the FBG. The produced filter is compact, stable, cost effective, and its bandpass profile is easy to control. (C) 2005 Optical Society of America.