Dual-wavelength (1050 nm +1550 nm) pumped thulium-doped fiber amplifier characterization by optical frequency-domain reflectometry

We present experimental results of distributed gain measurements from a dual-pumped (1050 nm +1550 nm) thulium-doped fiber amplifier using optical frequency-domain reflectometry. We show that significant reductions in total pump power and/or fiber length are realized with the addition of a few milliwatts at 1550 nm. For our experimental conditions, the addition of 5 mW of 1550 nm allows for a reduction of 100 mW of pump power at 1050 nm or a reduction of 44% of doped fiber length to reach the same gain as with 1050-nm pumping alone.