Re: New 802.3ae link model
Piers,
As a prospective customer to deploy 1300nm serial PHY, I took a look at
that specific link model. Is the total link budget the 10db (Power Budget)
plus the 2db (Connector Budget) or is it only the 10db (Power Budget)? If
it is only the 10db (Power Budget), then the total fiber attenuation budget
is 8db. What was the physical connector definition that was used to make
the determination of the number of connectors used to determine the
Connector Budget? Was it one each connector at the 802.3ae port interfaces
on each end of the link and a total of only two patch panels? If so, this
may not be enough connections. There will normally be a total of four
patch panels in addition to the connections at the interface port, as well
as an internal patch from the optical transceiver and the interface surface
bulkhead.
Thank you,
Roy Bynum
At 08:00 PM 1/2/01 +0100, DAWE,PIERS (A-England,ex1) wrote:
>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.
>--
> Phone +44 (0)1473 465654 or Telnet (31)25654
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