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The difference in power between the ‘clean’ and ‘MPI’ eyes is about 1dB, (At bottom left of each snapshot is shown the difference between mean ‘one’ level power and mean ‘zero’ level of 607 and 489 uW respectively). …and by all means don’t take my word for it - feel free to repeat the experiment. Best wishes jonathan From: Brian Welch [mailto:bwelch@xxxxxxxxxxx] Jonathan, Do these eye’s have the same optical power levels? It looks like the one on the right is lower. If so then how do we know it isn’t just higher RJ due to lower SNR at the receiver (stemming from increased insertion losses in the misaligned connectors)? Thanks, Brian From: Jonathan King [mailto:jonathan.king@xxxxxxxxxxx] Dear all, Here’s a few snapshots (literally) of multi path interference in a simple single mode link. It was a quick experiment, with a well isolated instrument grade laser (impervious to reflections) so that just coherent multipath effects within the low loss link are captured. It demonstrates: • Coherent Multi-path Interference penalty is real. • Near worst case penalties are observed in practice (despite a misleadingly reassuring low probability of occurrence). • Very slowly varying phenomena (minutes). – FEC can’t fix it. – EQ can’t fix it. • Need to budget for worst case. Best wishes jonathan |