This paper describes the wavelength division multiplexing technology for the long-haul optical communication system, especially for the undersea cable system. At first, the present WDM technology for the undersea cable system is reviewed briefly. After that, some experiments using compensation of the dispersion slope of the transmission fiber are discussed as future technical options of undersea systems with over 100 Gbit/s capacity.

In this paper we review the stretched-pulse principle and discuss its inherent advantages for ultrashort pulse generation and transmission. An analytic theory of the stretched-pulse fiber laser is presented and shown to be in good agreement with experimental results. An extension of the stretched-pulse theory is applied to both fiber lasers and dispersion-allocated soliton transmission and then compared to numerical results. We also discuss the design and operation of an environmentally stable stretched-pulse fiber laser.