Specialty Optical Fibers Handbook

Whereas the Er system is well understood and can be simulated with excellent

accuracy, the Er/Yb system is more complicated and modeling of amplifier

performance is more uncertain. Simulation involves treatment of more energy

levels and the details of energy transfer, but the higher RE concentration also

brings more ion–ion interactions into play. At the same time, because the goal of

the Er/Yb system is to allow operation at higher power, additional excited state

phenomena begin to dominate. Despite this complexity, current models now

have adequate accuracy for most high-power applications.

There is limited use for Er/Yb fiber lasers or amplifiers ...