Optimal Trade-Off of Mode-Mixing Optical Filtering and Index Difference in Digital Fiber Optic Communication Systems

In a digital fiber optical communication system, the optical power required at the receiver input to achieve a desired error rate depends upon the shape of the received pulses. In systems employing multimode fibers and/or broadband sources, we can experience pulse spreading in propagation because of the group velocity differences of different modes or because of dispersion. In an effort to control or compensate for pulse spreading, we can trade off coupling efficiency between the light source and the fiber (by varying the core-cladding index difference or bandlimiting the source), scattering loss in the fiber (by introducing mode coupling), and equali sation in the receiver at baseband. This paper investigates the optimal trade-off for various fiber-source combinations.