High power Yb-free Er-doped cladding pumped fiber amplifier for L-band operation

We report a high power, highly efficient, all-fibered Erbium amplifier operating in L-band range. The amplifier is demonstrated to be suitable with both resonant and non-resonant cladding pumping. These results have been obtained thanks to the in-house fabrication of a LMA 30-130 μm Erbium doped fiber whose composition has been carefully optimized. Under 1535 nm pumping, output power up to 80 W is obtained with 51% optical-to-optical efficiency at 1590 nm with respect to the launched pump power. Moreover, we demonstrate a minimum power of 66 W (42% efficiency) within the 1570-1610 nm wavelength range, and this without bringing any modification to the amplifier. Using a non-resonant pumping at 976 nm, we achieve 50 W output power with 38% slope efficiency at 1590 nm while ensuring a minimum power of 40 W for signal wavelengths emitting between 1570 nm and 1610 nm. RMS stability over several hours is measured at less than 1%. Optical-to-noise ratio is at least 32 dB for all tested signal wavelengths. The output power of the amplifier in both pumping configurations is only limited by the available pump power as no roll-off is visible in the evolution of the output power and the thermal load throughout the entire system remains moderate.