Modeling cladding-pumped Er/Yb fiber amplifiers

This paper presents a new computational strategy for efficient and stable modeling of rare-earth-doped fiber amplifiers and illustrates the strategy with results for a cladding-pumped erbium/ytterbium-doped fiber amplifier. The computational strategy allows arbitrary radial dependence for the optical fields and rare-earth densities, arbitrary wavelength resolution for amplified spontaneous emission (ASE) at pump and signal wavelengths, and arbitrary numbers of rate equations with arbitrary dependence on ground-and excited-state number density. Numerical results are presented for cladding-pumped Er/Yb-doped fiber amplifiers that illustrate how to reach the conversion efficiency limited by the quantum defect, how power conversion and the intensity of the ASE depend on operating wavelength, and how secondary loss mechanisms such as distributed loss, upconversion, and pairing/clustering affect the efficiency of the amplifier. (C) 2001 Academic Press.