Patent ID: 6400868
Filing Date: 2002-06-04
Classification: G02B

Abstract:
A Bragg filter formed from a photosensitive optical fiber, said Bragg filter being formed in the core of said photosensitive optical fiber by irradiation with light to create a quasi-periodic succession of optically induced variations of the optical refractive index &Dgr;n1 along the length z of said fiber with a period close to &Dgr;L; said Bragg grating also having a variation &dgr;L(z) of said period &Dgr;L along the length z of said fiber; said variation &dgr;L(z) of said period &Dgr;L being a linear or quadratic variation along the length z of said fiber; said optical fiber having a core and a cladding, said core of said optical fiber having a refractive index nc and said cladding of said optical fiber having a refractive index ng, said core being doped with a photosensitive first element, said first element being Germanium, wherein the concentration CGe of Ge in the core is at least equal to 10%: CGe&gE;10%, and wherein said core is further doped with a photosensitive or non-photosensitive second element to reduce the refractive index nc of the core to reduce the refractive index difference to a value less than:&Dgr;n=ncâˆ’ng&lE;6Ã—10âˆ’3.