RECENT PROGRESS IN AMPLIFIED UNDERSEA SYSTEMS

The advent of the optical amplifiers has removed the loss limitation o f the fiber in the conventional undersea systems using 3R (retiming, r eshaping, regenerating) repeaters, and it has introduced new design cr iteria for the undersea lightwave systems. The accumulation of the sma ll impairment factors that was negligible in the conventional system b ecomes significant to determine the transmission performances of the a mplified system. The fiber nonlinearity is a distinctive limitation fa ctor that dominates the transmission performance of the amplified syst em, although it was not a limitation factor in the conventional system . This paper describes the recent progress of the undersea lightwave c able systems employing optical amplifier repeaters. The limitation fac tors and the polarization dependent characteristics of the amplified s ystem are described. The system demonstrations with conventional LM-DD technology are presented using both recirculating loop and straight f iber transmission line. The system maintenance method is also explaine d briefly. Future technologies adopting the WDM or the optical soliton s are also discussed.