Measurement and Modeling of Emission Spectra of Er-Yb Co-doped Fibers

With the recent development of double-clad Er-Yb fibers, signals in the 1550-nm band can be amplified to powers greater than 10 W, well above the range of conventional Er-doped fiber amplifiers (EDFAs). Although conventional EDFAs have been modeled for many years and their properties can now be calculated very accurately[1,2], limited modeling and benchmarking to data have been presented in the literature for Er-Yb co-doped fibers and waveguides, let alone for cladding-pumped configurations [see 3 for references]. The additional absorption, emission and energy transfer mechanisms associated with the Yb ions as well as the larger densities and higher powers used in the cladding pumped Er-Yb fiber amplifier significantly increase the complexity of the model and the differential equations that need to be solved[3]. Accurate modeling of these amplifiers is important for optimizing performance and reducing competing effects. Here we use a recently developed model[3] 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 a low Yb inversion and a core-pumped geometry that gives a higher Yb inversion.