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Re: [802.3_100GNGOPTX] 802.3_100GNGOPTX Multi Path Interference experiments

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



From: Brian Welch [mailto:bwelch@xxxxxxxxxxx]
Sent: Tuesday, March 19, 2013 6:04 PM
To: Jonathan King; STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
Subject: RE: 802.3_100GNGOPTX Multi Path Interference experiments



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)?





From: Jonathan King [mailto:jonathan.king@xxxxxxxxxxx]
Sent: Tuesday, March 19, 2013 11:24 AM
To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_100GNGOPTX] 802.3_100GNGOPTX Multi Path Interference experiments



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