Dispersion and equalization in fiber optic communication systems

The additional optical power required at the repeater input in a fiber optic communication system due to intersymbol interference is experimentally measured. In the experiment, the intersymbol interference which results from differential mode delay in multimode fibers is minimized with a five-tap transversal equalizer. Error rate measurements are performed using five fibers ranging from 0.01 km to 1.25 km in length. In this manner, the additional optical power required to achieve a given error rate is found as a function of pulse width. The measured values compare favorably with the power penalties predicted by Personick. The trade-off between excess optical power and equalization penalty in dispersion-limited fiber systems is discussed.