Circuit and channel assignment plan for optical transmissions

Abstract

To support interleaving of optical channels and to provide sufficient isolation between such interleaved channels, a circulator ( ) receives, on an optical fiber ( ), a broadband signal containing a plurality of adjacent channels. The circulator selectively routes the broadband signal through a filter ( ) to isolate, on an individual basis, at least one desired channel. A filtered signal, corresponding to the at least one desired channel, is then output from the filter ( ) and reflected back into the filter by a mirror ( ) such that the at least one desired channel is subjected to a second filtering process that further improves isolation of the at least one desired channel. Following this second filtering process, the at least one desired channel is applied to the circulator ( ) for re-inserting into the optical fiber ( ), as illustrated in FIG. To mitigate the effects of four-wave mixing in each bidirectional optical fiber, a channel assignment plan ensures that pairs of adjacent channels are assigned on a mutually exclusive basis to at least one of an up-link and a down-link direction.