Optimum Linear Equalization in Digital Fiber-Optic Systems

We exhibit an optimum linear equalizer that maximizes the signal-to-noise ratio while mitigating the effects of intersymbol interference, in the case of dispersion limited operation of a digital fiber-optic transmission system. The simultaneous presence of signal-dependent noise, thermal noise, and blue noise reduces the problem to seeking a solution of an inhomogeneous linear second-order differential equation with a time-varying coefficient. Relative to detection in a channel free of intersymbol interference, we calculate power penalties at different transmission rates and compare the results to those of the integrate-and-dump and the raised-cosine-output systems.