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US 5,491,581 AGranted
Rare earth doped optical fibre amplifiers
AssigneePirelli Cavi S.p.A.
InventorGiacomo S. Roba
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AssigneePirelli Cavi S.p.A.
InventorGiacomo S. Roba
Estimating the term…
An optical amplifier which includes an optical fiber having an erbium doped core surrounded by cladding, a pump for pumping the fiber with pump light at a pump wavelength coupled to the fiber, input means for inputting a signal to be amplified to the amplifier and output means for outputting an amplified signal from the amplifier. The fiber has a NA higher than 0.2. The difference in the coefficient of thermal expansion of the core adjacent the core/cladding interface and the coefficient of thermal expansion of the cladding at at least one radius less than 2 .mu.m from said interface is lower than a predetermined value, corresponding to a ratio of erbium loss to background loss, at said pump wavelength, and greater than a minimum ratio of about 20 when erbium loss is 0.15 dB/m and about 120 when erbium loss is 3.5 dB/m.
An optical amplifier for amplifying an optical signal having a signal wavelength, comprising an optical fibre having an erbium doped core surrounded by cladding, a pump for pumping the fibre with pump light at a pump wavelength coupled to the fibre, input means for inputting a signal to be amplified to the amplifier and output means for outputting an amplified signal from the amplifier, wherein said fibre has a NA higher than 0.2 and wherein the difference in the coefficient of thermal expansion of the core adjacent the core/cladding interface and the coefficient of thermal expansion of the cladding at at least one radius less than 2 .mu.m from said interface is lower than a predetermined value, corresponding to a ratio of erbium loss to background loss, at said pump wavelength, greater than a minimum ratio calculated by a given increasing function of the ratio erbium loss/background loss versus erbium loss, in which said minimum ratio is about 20 when erbium loss is 0.15 dB/m and about 120 when erbium loss is 3.5 dB/m.
An optical fibre having a NA higher than 0.2, comprising a rare earth doped core and cladding surrounding said core, wherein the difference in the coefficient of thermal expansion of the core adjacent the core/cladding interface and the coefficient of thermal expansion of the cladding at at least one radius less than 2 .mu.m from said interface is less than 50%.
An optical fibre having an NA higher than 0.2 comprising a silica core doped with at least one dopant from the group consisting of GeO.sub.2, Al.sub.2 O.sub.3 and P.sub.2 O.sub.5 and surrounded with a cladding, an outer annular layer of said cladding consisting essentially of silica and having a first coefficient of thermal expansion value, the core having a second coefficient of thermal expansion value, and the cladding having an annular stress relieving layer between said outer layer and said core which stress relieving layer has a coefficient of thermal expansion which varies radially inwardly from a third value to a fourth value, the third value being closer to the first value than the second value and the fourth value being closer to the second value than the first value.
Dependencies are inferred from the claim text.