Direct inscription of Bragg gratings in coated fibers by an infrared femtosecond laser.

Inscription of fiber Bragg gratings through the coating of a nonphotosensitized standard telecommunication fiber is demonstrated for what is believed to be the first time. Highly reflective gratings were produced by direct point-by-point writing with an infrared femtosecond laser. The length of the gratings presented ranged from 5 to 26 mm. The technique does not require a special coating, as standard coatings are transparent to infrared radiation. Inscription through the coating improves the mechanical strength of the processed segment of fiber.