High speed optical networks require optical transmission to be robust to noise as well as linear and non-linear distortions. Robustness to the time evolution and reconfiguration of the optical channel is also required. In this tutorial we discuss traditional optical modem and line technologies which have been deployed and, their relation to the above considerations. In addition, the significance of emerging digital optical-modem technology is explored.
Transport fiber deployed in metro and long-haul networks exhibit chromatic dispersion which if not addressed closes the receive eye. At 10Gbps line rates, dispersion management strategies are required to allow reaches to surpass their dispersion limited values. Several solutions exist which resolve this limitation. A survey of these is presented. Since dispersion is a linear operator acting upon the E-field of the transmitter, precompensation is one such dispersion management strategy. This paper presents the implementation of a transmitter which enables tunable electronic precompensation by E-field modulation. The key technology considerations brought to bear on the realization of this precompensation are discussed. The compensation of additional impairments and new capabilities of this transmitter are discussed. Experimental results, with standard single-mode fiber (G.652), without any optical compensators, demonstrate the capabilities of this new dispersion management strategy.