This paper reviews state-of-the-art technologies that will play important roles in high bit rate transmissionsystems. To take full advantage of fiber capacity, combined multiplexing of WDM (Wavelength Division Multiplexing) and TDM (Time Division Multiplexing) technologies is recommended. Not only device technologies, but also system-side viewpoints are emphasized in order to clarify the differences between TDM and WDM systems. Linear transmission and nonlinear ones, which includes optical soliton systems are comparedfrom such a viewpoint. Short light pulse sources, electrical and optical time-division multiplexing/demultiplexing, timing extraction, dispersion tolerant coding, equalization for second- and third-order dispersionof dispersion-shifted fiber, and optical soliton transmission technologies are described. This paper predictsthat pursuing increased transmission capacity will result in more combined designs of detailed fiberdispersion and transmitted optical signal parameters.