TDPA for amplification in the S-band

A new (S) band will be implemented, likely with both distributed and lumped amplification. If the thullium doped fibre amplifier (TDFA) offers almost ideal characteristics, it uses less mature technology than the lumped Raman amplifiers, which exhibit however a low power-performance in the S-band. The implementation of such an S-band may however take some time, due to the deployment first of L-band channels in the networks and the implementation of 40-Gbit/s line rate (or maybe of 25-GHz spacing in the case 10-Gbit/s systems). This time will play in favor of the TDFA, whose characteristics may still be improved and the related technology made more mature.