Abstract

To cope with the rapid growth of data traffics, the transmission capacity per a line of fiber is continuously expanding. To achieve this mission, there have been extensive efforts to develop other-band amplifiers with different gain band locations than Erbium doped fiber amplifiers (EDFA). For these new approaches, Thulium doped fiber amplifiers (TDFA) has distinctive merit to compare with Raman or other Rare earth based hybrids, with its excellent positioning in the supporting band (1.46 1.51 µm : where the LD technology is mature) and high power conversion efficiency from rare earth based nature.^1–4 Out of several pumping schematics possible for the operation of TDFA, ^5–7 the recently proposed combination of 1.4 µm main pump with 1.5 µm subsidiary pump has advantages over other technologies with the readily available high power pump LDs operating in these wavelengths. Successfully enough, this lead to the latest demonstration of 11 Tbps WDM transmission experiment possible, even without the inclusion of S+ bands in the total gain bandwidths.⁸ Still, with the shortest development history among the various types of optical amplifiers, there is lack of sufficient back-up data and understandings on the dynamics of TDFA to support highly intelligent WDM networks. This includes such fundamental characteristics as transient responses, which is a must-requirement for modern EDFA to support wavelength add-drops in optically switched networks. Proper characterization and compensation techniques for this transient property would ensure the safe and stable operation of the network.

© 2002 Optical Society of America