Diversity coding for subcarrier multiplexing on multimode fibers

The bandwidth-distance product limitations of multimode fiber caused by intermodal dispersion may be overcome by using subcarrier multiplexing. Since there are deep nulls in the frequency response within the frequency band of interest, it is necessary either to avoid these frequencies adaptively or to use an appropriate coding technique. We consider the case of using a training sequence to identify the subcarriers to be discarded, and also diversity coding in which the information may be recovered in the presence of the loss of a fixed number of subcarriers. Simulation results indicate that diversity coding, which is less complex than the use of training sequences, provides very good performance over a wide range of channel conditions.