specially difficult for high-speed operation. The EDC filter within the DSP electronics must be configured to match the optical fiber link. Transmitter-end EDC can be carried out via user input with a knowledge of the antici- pated dispersion in the link, by completely automated optimization, or by an intermediate approach, where the user provides a target value around which an optimum can be found. Where the optimization is completely automated, there must be a feedback channel from the receiver end. It can be provided if the communication system consists of two fibers guiding the light unidirectionally in opposite directions, which is normally the case in medium- and long-haul operations. When the EDC is at the receiver, it is performed after the detector. The main method employed, called "Maximum-Likelihood Sequence Estimation" (MLSE) (McGhan, 2006; Downie, Sauer, & Hurley, 2006), uses a fast analogue-to-digital converter to digitize raw received data samples; from them it deduces the most likely bit sequence. Receiver-end EDC can adapt dynamically to changing network conditions, such as after the reconfiguration of an optical add-drop multiplexer. Moreover, it has the advantage of not requiring expensive and lossy opto-electronic modulators. However, in 10-Gbit/s applications, receiver-end EDC tends to be limited to system spans of a few hundred kilometers because the required processing grows exponentially with the dispersion that has been accumulated in the system. Therefore, it may be most useful for cost-sensitive applications, such as long-reach PONs and metropolitan networks. In contrast, transmitter-end EDC has provided chromatic dispersion compensation for 10-Gbit/s systems of up to 5200 km that consisted entirely of G.652 fiber and use no optical dispersion compensation (McGhan et al., 2006). Furthermore, with the aid of lookup tables to provide the required phase and amplitude variations, transmitter-end EDC has also been able to compensate for a nonlinear optical effect, which is described in the l