Patent ID: 7062140

Claim:
An optical fibre for transmission of light at a predetermined wavelength λ 0 , the optical fibre having a longitudinal direction (z), a cross-section (r,φ) perpendicular to the longitudinal direction, a length L and an outer periphery r fibre (φ) in a cross section, the optical fibre comprising: a core region, said core region having a centre axis in the longitudinal direction, said core region extending along and including said centre axis, said core region having an outer periphery r core (φ), and a refractive index n core (r,φ), and a geometrical index n g,core in a cross-section of the fibre; an inner cladding region, said inner cladding region extending along the longitudinal direction, said inner cladding region surrounding and neighbouring said core region, said inner cladding region having an inner periphery r iclad,inner (φ), that coincides with r core (φ) and an outer periphery r iclad,outer (φ) and a refractive index n iclad (r,φ) and a geometrical index n g,iclad in said cross-section of the fibre, said inner cladding region including N spaced apart voids, said voids being located in a background material and extending in the longitudinal direction, each void having a centre and an outer periphery r void,i (φ), i=1–N, in a cross-section of the fibre, and wherein N is larger than one; and an outer cladding region, said outer cladding region extending along the longitudinal direction and enclosing said inner cladding region, said outer cladding region having an inner periphery r oclad,inner (φ) that coincides with said outer periphery r iclad,outer (φ) of said inner cladding region and a refractive index n oclad (r,φ) and a geometrical refractive index n g,oclad in a cross-section of the fibre, wherein n g,oclad <n g,core and wherein a predetermined TBF-selection of Q of said voids over a certain part L fill,j extending between z fill,j-2 and z fill,j-1 of the length L of said fibre contains a substance, said substance-containing voids having a refractive index n void,fill,j (r,φ), j=1–Q in a cross-section of the fibre, Q being less than the total number of voids N, and wherein said substance, at least for one void, is filling said void over only a part L fill,j of the length L of said fibre, where L fill,j <L.