RE: New 802.3ae link model
Roy,
Good question.
The "Power Budget" here is the minimum transmitted power less the nominal
receiver sensitivity. Using the 1300 nm serial example,
Tx min -4 dBm
-Rx sensitivity* -14 dBm
----
Power budget 10 dB
-Connections 2 dB
----
PwrBud.-Conn.Loss 8 dB
-Fiber att'n 5 dB
----
For impairments 3 dB
-Eye penalty ~2 dB
-Path penalty ~1/2 dB
----
Margin ~1/2 dB
----
* Note that this receiver sensitivity is measured with a good eye and so is
2-3 dB different to a receiver sensitivity measured by the telecoms way of
doing things.
To be clear, I repeat the calculation the telecoms way:
Tx min -4 dBm
-Rx sensitivity2$ ~-12 dBm
----
Power budget 8 dB
-Fiber&conn.att'n 7 dB
----
For impairments 1 dB
(Eye penalty 0 dB)
-Path penalty ~1/2 dB
----
Margin ~1/2 dB
----
$ This receiver sensitivity is measured with a worst transmitted eye.
The plan of record has effectively two patch panels - e.g. Draft 2 Subclause
52.11 Fig. 52-8. I have proposed extra text to this subclause:
" A channel may contain additional connectors or other optical elements as
long as the optical characteristics of the channel, such as attenuation,
dispersion, reflections, polarisation mode dispersion and modal bandwidth
meet the specifications."
So for example if you used 10 km of G.652.B cable at 0.4 dB/km at 1310 nm,
you would have 3 dB for connectors. Is that enough?
Piers
> -----Original Message-----
> From: Roy Bynum [mailto:rabynum@xxxxxxxxxxxxxx]
> Sent: 02 January 2001 23:17
> To: DAWE,PIERS (A-England,ex1); 'IEEE 802.3ae reflector'
> Subject: 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
>