Numerical analysis of high power ytterbium-doped segmented-cladding fiber amplifier

We analyze numerically an ytterbium-doped segmented-cladding fiber (SCF) for optical amplification. The analysis combines a full-vector finite-element method with propagation rate equations to calculate mode-field distributions and longitudinal power distribution. The results show that optimal parameters depend directly on the depletion position of the pump power. With a typical ytterbium-ion concentration of 4.0×10²⁵ ions/m³, an launched pump power of 5 W, and an input signal power of 1 μW, the maximum achievable gain is around 33 dB with an optimal fiber length of 0.6 m. The threshold pump power is about 500 mW for input signal power below 0.3 mW and the saturation output signal power is about the order of 300 mW at the pump power of 5 W. The results reveal that, by using appropriate pump power, a few meters of ytterbium-doped ultra-large-core SCF can provide much higher gain by its large core than that of a conventional ytterbium-doped fiber while maintaining the flexibility of length and dynamic range. © 2009 Copyright SPIE - The International Society for Optical Engineering.