A scheme in which the bandwidth-distance product of a multimode fiber is extended, so that it can nearly support the transmission rate of single-mode systems, is studied. It is based on selective launching of lower order modes into the fiber at the transmitting end and on filtering out at the receiver the fraction of the energy that was coupled into the higher order modes throughout the propagation in the multimode fiber. The power penalty and the dispersion performance of the scheme are investigated. In particular, it is shown that the scheme carries about 6.5 dB penalty, and doubling of the bandwidth*distance value is demonstrated. The effect of splices on the performance is also presented. It is envisioned that this approach may be used to upgrade existing multimode systems without the need for rewiring. For example, it can be used to replace the FDDI (fiber distributed data interface) installations in future high-speed networks, when transmission rates increase from megabits per second to gigabits per second.
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