Comparison of distributed gain in two dual-wavelength pumping schemes for thulium-doped fibre amplifiers

Using the coherent optical frequency domain reflectometry technique, a non-invasive study has been made of the distributed gain in two pumping schemes for thulium-doped fibre amplifiers. The compared schemes employed 800+1050 nm or 800+1400 nm pump wavelengths, and it was concluded that the former is advantageous over the latter primarily due to the ground-state absorption and pumping mechanism.