Specialty Optical Fibers Handbook

stability behavior, has been obtained in erbium-doped fibers, which did not

contain any fluorine. A new type of process that produces gratings with even

higher temperature stability has been discovered. The gratings are obtained with

large exposure doses and, therefore, large concentration of OH bondings. It is

believed that the CCG development leads to the formation of molecular water

and, hence, periodic extraction of oxygen in the irradiated cores in that case. The

strength of these gratings was basically constant at more than 1100



C for 60

minutes [105].

A totally new fabrication technique, with a huge potential, was demonstrated

in 2003. It apparently works in any type of fiber and without any pre-photo-

sensitization [106]. It consists of irradiating ...