Performance of PM Holmium-Doped Fiber Amplifiers With Hybrid Pumps at 1150 nm & 1860 nm

We investigate the performance of polarization maintaining (PM) holmium-doped fiber amplifiers (HDFAs) in the 2-micron band with a hybrid pumping consisting of an out-of-band co-pumping at 1150nm and in-band counter-pumping at 1860nm. Our parametric studies for single stage HDFAs at 2050nm contrast the gain (G) and noise figure (NF) obtained for separate and combined pump wavelengths. Under hybrid pumping this HDFA demonstrates in saturation a combined low 3dB NF and a 34dB G, providing a 2.5W output power (Pout) for a 1mW Pin. Next, we compare the performance of the single stage hybrid pump PM-HDFA to a two stage PM-HDFA where the first stage is co-pumped by the 1150nm source while the second stage is counter pumped by the 1860nm source. This amplifier architecture delivers a 33dB G and a 3dB NF at 2050nm with a 2.1W Poutand a 25dB polarization extinction ratio (PER), performance which are comparable to our hybrid single stage design. These results confirm that hybrid pumping of a single stage PM-HDFA can combine the advantage of low noise out-of-band pumping and high gain in-band pumping