Abstract: The present invention relates to an optical communications system performance monitoring technique which provides for detecting bit disparity within a data stream. The average power value for a data stream is ascertained by passing the data stream through a low pass filter. The data stream's average power value is then compared with a bit stream baseline power value for a one bit stream and a zero bit stream, the resulting deviation comprising a bit disparity value. An embodiment of this invention would incorporate the use of threshold alarms set for unacceptably high levels of bit disparity. The triggering of these threshold alarms could initiate the transmission of automated customer warnings such as a notification that performance cannot be guaranteed due to high bit disparity on the signal.

Abstract: A bit disparity monitor is disclosed in which a data stream is sub-sampled and logical 1's are detected in the sub-sampled stream. Within a predetermined period, the number of logical 1's is counted and the ratio of logical 1's to the number of bits is determined and compared to acceptable thresholds of bit disparity. In a second embodiment, the data stream is inverted and both the original data stream and the inverted data stream are sampled. The number of logical 1's detected in the sub-sampled original data stream and the number of logical 0's in the sub-sampled inverted data stream are correlated and mismatches, indicative of a transitional sample, are discarded before the bit disparity ratio is determined. Methods of comparing the bit disparity of a data stream to an acceptable threshold are also disclosed.