Measurements of gain cross-saturation and transient response in highly doped TDFAs

We report measurements of cross-saturation bandwidth on signal wavelength in single-pumped Thulium doped fiber amplifiers (TDFA) using two different pump wavelengths (1426 and 1050 nm) and a highly doped (5000 ppm) Thulium-doped fiber module. The 1050 nm pump has a lower cross-saturation effect than the 1426 nm, and an increase in cross-saturation is observed as the signal wavelength decreases within the S band. We also experimentally investigated the transient response of a single-pumped TDFA at 1050 nm, and analyze the amount of surviving channel gain, gain excursion and time-constants or the highly doped fibers.