Improved emission silicate waveguide compositions for enhanced L-band and S-band emission and method for its manufacture

A method for manufacturing an optical fiber, the method including the steps of providing a substrate tube; depositing a boron-free cladding layer; depositing a core comprising a glass including silica, and oxides of Al, Ge, Er, and Tm; collapsing the substrate tube to form a preform: and drawing the preform-to yield optical fiber. A co-doped silicate optical waveguide having a core including silica, aluminum, germanium, erbium and thulium. The composition concentrations are: Er from 15 ppm to 3000 ppm; Al from 0.5 mol% to 12 mol%; Tm from 15 ppm to 10000 ppm; and Ge from 1 mol% to 20 mol%. In a specific embodiment, the concentration of Er is from 150 ppm to 1500 ppm; Al is from 2 mol% to 8 mol%; and Tm is from 15 ppm to 3000 ppm.