High-power single-mode fiber amplifiers using multimode fibers

Summary form only given. As the optical power levels extractable from current single-mode (SM) fiber amplifiers are reaching regions where optical nonlinearities become significant, even under cw operation, it is becoming increasingly important to develop methods for reducing these nonlinearities to further boost the amplifier performance. Here we demonstrate a simple new approach, namely the SM excitation of specially designed large-core multimode (MM) fibers. Cladding-pumped Er/Yb amplifier versions of such fibers allow the direct amplification of diffraction-limited optical soliton pulses with peak powers up to 12 kW, about one order of magnitude larger than possible with conventional fiber amplifiers.