Analysis on the transient response of 1.55-μm/1.4-μm dual-wavelength pumped thulium-doped fiber amplifiers

The transient response of S- and S/sup +/-band thulium-doped fiber amplifiers with 1.4-μm/1.5-μm dual-wavelength pumping scheme was investigated both experimentally and theoretically. In contrast to conventional Erbium-doped fiber amplifiers, two characteristic time-constants related with ³F₄ and ³H₄ level lifetime were observed, implying the need of much complex transient control algorithm for the future applications. The amount of surviving channel gain, gain excursion, and related time constants showed changes in their response characteristics, depending on the combinations of main pump, subsidiary pump, and signal powers. A simplified numerical approach for the analysis of transient response in thulium-doped fiber amplifiers under average inversion framework, will be provided.