# New 802.3ae link model

All,
There is a new version of the link model at
http://www.ieee802.org/3/ae/public/email_attach/10GEPBud2_4_1.xls
This updated spreadsheet contains:
Proposal for 850 nm,
OMA definition of transmit power,
RIN and RIN(OMA) are distinguished,
Worst extinction ratio is calculated,
1550 nm powers raised by 2 dB,
A simple Polarisation Mode Dispersion formula.
The new features can be overridden as explained in the notes page.
For those who like equations, some detail follows.
Piers
The PMD (Polarisation Mode Dispersion) formula uses an input parameter
DGDmax, which the equalization ad hoc tell me is 19 ps for 1550nm. I have
taken a guesstimate of 10 ps for 1300 nm. The calculation I used is as
follows:
If DGDmax is used (box E7)
Effective BW1(MHz.km) = 10^6*Ltarget(km)/(3*DGDmax(ps))
else
Effective BW1(MHz.km) = BWm(MHz.km)
endif
Effective BW2(MHz) = Effective BW1(MHz.km)/L(km) (column E)
Notice two quantities with identical names but different units.
You can get the factor of 3*DGDmax by considering
sin(2pi.f.t+a) + sin(2pi.f.t-a) = sin(2.pi.f.t)
where f is the bandwidth and 2a represents the phase splitting of a pulse
caused by DGDmax. This result was known to the 802.3z community. You can
get a very similar result by working through the standard deviation of a
pair of Gaussian pulses.
The effect of Polarisation Mode Dispersion seems to be less than we had
feared.
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