L-band optical amplifier based on thulium-doped silica fiber with cut-off

摘要

A Thulium-doped silica fiber normally has its strongest gain at 1.9 microns and thus is not suitable for communication use. By engineering a W-profile or depressed cladding fiber with an appropriate index profile having a fundamental mode cut-off between 1.9 microns and the shorter wavelength of desired operation, an optical amplifier based on the W-profile Thulium-doped silica fiber operates at wavelengths shorter than conventional amplifiers, just above what is currently called the Erbium L-band. In a preferred embodiment, the cut-off wavelength is at or near 1.7 &mgr;m, eliminating longer wavelengths from the fiber. Amplifiers engineered according to the principles and techniques of the present invention can operate in the wavelength range between about 1.6 to 1.8 microns, which is particularly useful for telecommunications.