Measurement and modeling of emission spectra of Er-Yb co-doped fibers

We use a recently developed model to calculate amplified spontaneous emission (ASE) spectra in the Yb and Er bands and compare these results to direct measurements. The measurements were conducted using a cladding-pumped geometry that yields low Yb inversion and a core-pumped geometry that gives a higher Yb inversion. The model used for the Er-Yb fiber amplifier includes equations for the power in the pump and the ASE in the Yb and Er bands, and for the fractional inversions of both ions