Specialty Optical Fibers Handbook

before the FBG fabrication. Afterwards, the fiber was annealed at 100 8C for 24

hours to outgas any residual hydrogen in the loaded sample and to stabilize the

index modulation at room temperature. The FBGs were fabricated using an

illuminating beam at a 244-nm wavelength, having an intensity of 300 W=cm

2

.

The resulting index modulation achieved in these conditions was 1  10

3

.

The fiber had a 120-mm diameter, an NA of 0.16, a cutoff wavelength of

1500 nm, and a Tm concentration of about 1000 ppm. These preliminary results

suggest that Sb might become a promising photosensitive element for the devel-

opment of RED photosensitive fibers, which are