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Dear all, I note that there was a contribution regarding Raman
interactions. I have concerns that the calculations used there do not
reflect the actual operational cases and trade-offs of fiber distance loss and Raman
interaction strength, the significant effect of intra-office losses, the use of
low-channel pre-emphasis, and so on. The bottom line is that these calculations have many
parameters, and drawing any conclusions from un-audited calculations is dangerous.
To help our progress, I have attached my calculation model
for Raman cross talk with a video channel and 2 digital waves. (This is a
slight update of the file I used to prepare my January 07 presentation on this
same topic.) There are two independent sheets. The first computes
the delivered CNR. My calculations show that a 1G launch power of 2 dBm
and a 10G launch power of 8 dBm seems to deliver more than 46 dBm (which is the
current performance spec of important operators). One must remember that
typical in-office losses are 2 dB, so the maximum launch powers of the
respective systems would be +4 and +10 dBm at the OLT face-plate. That is
a significant 3dB more than a number suggested recently. I invite others to work with the model, and provide their
own comments. As a parting comment, I note that analog overlay use is
rapidly declining. I know of only one large application of such systems,
and that user is now phasing out the support of analog. So, the entire
point may become moot. Sincerely, Dr. Frank J. Effenberger ¸¥À¼¿Ë °£·Ò²©¸ñ Huawei Technologies Office (732) 625 3002 Cell (908) 670 3889 |