Patent ID: 7515802

Claim:
A glass fiber, comprising a core and at least two glass claddings surrounding said core, in which said core comprises a matrix glass, the matrix glass contains at least one heavy metal oxide and at least one rare earth compound, the matrix glass has a refractive index of greater than about 1.85, a refractive index change Δn from a first of the at least two glass claddings to the core is in a range from 0.001 to 0.08, the refractive index of the first glass cladding is lower than that of the core, the first glass cladding contains said at least one rare earth compound, and an outermost cladding of the at least two glass claddings contains from 5 to 5000 ppm of at least one absorbent component; in which said at least one absorbent component is at least one transition metal compound; in which the at least one heavy metal oxide is at least one oxide of Bi, Te, Se, Sb, Pb, Cd, Ga andlor As, or a mixture thereof; and in which said matrix glass contains an amount of each of said at least one rare earth compound equal to 0.05 to 5 mol %, but the first glass cladding contains only up to one half of said amount of each of said at least one rare earth compound in said matrix glass.