LX SFPs are spec'ed to work back-to-back and don't need attenuation.
Tx dBm: -3 to -9.5 (max to min)
Rx dBm: -3 to -20 (max to min)
(ie. max Tx = Max Rx).
On 17/09/2010, at 9:52 AM, <email@example.com<mailto:firstname.lastname@example.org>>
I'm wondering what sort of equipment people are using as their physical
connection to the network; we are having some issues getting some cheap
and cheerful media converters to work that are connected at 100mb to a
Catalyst 2960, their current thoughts are that the TX power is too high
(28db measured at South Dunedin, we are Central) and we may need to look
at putting an attenuator on to drop it down to the 8db they see on their
other customer links. Before we go out and source an SFP to suit one of
the other switches I want to get an idea of what other people are using.
Ah, that explains the e-mail I had in my inbox the other day from a
Delta engineer :-)
For our layer 2 service, we use a Cisco LX SFP (GLC-LH-SM) straight
into a Catalyst 3750 switch.
That appears to work OK without attenuation (if I'm one of the other
8dB links :-)); we are about 700m from South City peering point, so
distance should be around the same as to you from there.
Also have a DLink DMC-810SC 1000Base-LX to 1000Base-T media convertor
on one end connected to another GLC-LH-SM on the 3750 via our dark
fibre pair to our upstream provider, around 4km, also works fine. I
have the test results for that pair somewhere.
No problems to report with either service in 2 years.
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