Patent ID: 6859585

Claim:
An optical filter comprising a slanted Bragg grating inscribed in an optical fiber portion comprising a core having a refractive index n 1 and a radius R core and a cladding having an average refractive index n 2 lower than n 1 and a radius R cladding , the core and the cladding of the fiber being doped with a photosensitive dopant in the fiber portion comprising the Bragg grating, which filter is characterized in that, in the fiber portion comprising the Bragg grating, the photosensitivity of the cladding is greater than the photosensitivity of the core and the cladding includes an index step area having a refractive index n 3 greater than n 2 and less than n 1 , said index step area having a width L defined by an inside radius R s1 greater than or equal to the radius R core of the core and an outside radius R s2 less than or equal to the radius R cladding of the cladding.