Photobleaching of fiber bragg gratings written through the fiber coating

A system for providing a low absorption Bragg grating along a grating region of an optical fiber, comprising:

• a light generator generating a writing light beam of ultrafast optical pulses;
• an optical assembly configured to impinge the ultrafast light pulses on the grating region of the optical fiber to write the Bragg grating along said grating region by multiphoton absorption of the ultrafast light pulses while also inducing defects in the grating region;
• a photobleaching light source for photobleaching the Bragg grating by propagating a photobleaching light beam along the optical fiber, the photobleaching light beam interacting with the grating region so as to reduce the defects induced by the ultrafast light pulses in a substantially non-thermal regime.