Abstract

A key goal of dense wavelength-division-multiplexed (WDM ) optical transmission systems is to efficiently use the available bandwidth and pack the channels as close together as possible. However, the following impairments can occur when channels are spaced very close to each other: (i) high cross talk and high induced chirp due to wavelength drifts as well as limitations in optical filtering and ( de)multiplexing technology, and (ii) increased nonlinear effects.¹ For example, it may be desirable to transmit many 10-Gb/s channels that are spaced only 12.5 GHz apart, but this tends to severely push the technology envelope. One potential solution for high spectral efficiency is to implement a bidirectional transmission link over a single fiber for which the WDM channels are interleaved in the forward and backward directions. Certainly, the requirements for the filtering technologies would be significantly relaxed. Furthermore, most of the nonlinear effects occur when channels copropagate, and these would also be reduced using this method.

© 2002 Optical Society of America