[128368] in North American Network Operators' Group
AW: Recommended 1Gb SFP for ~115km?
daemon@ATHENA.MIT.EDU (Thomas Weible)
Wed Aug 4 12:59:03 2010
Date: Wed, 4 Aug 2010 18:58:51 +0200
In-Reply-To: <A47E89A512E4FF4492CA4DE10D7B7C9002BE5D4CE3@pscdalpexmb02.perotsystems.net>
From: "Thomas Weible" <Thomas.Weible@flexoptix.net>
To: <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Hi,
the setup with two media-converters works but has a major drawback. If =
you want to see the overall line (digital diagnostic) you always have to =
take into consideration that there are actually 3 physical links =
involved in the overall link. Looking from your routers you only see the =
SX link (basically 2 meters via patchcord). The potential trouble making =
long distance link is hidden - or you have to look on the =
media-converters (if management is implemented).
Cisco did a quite good job on implementing the DDM characteristics of =
the optics. So why not to take a 32dB or even 41dB power budget SFP and =
make it workable in the switch / router. Works like charm in some setups =
and you see straight the actual line.
cheers
Thomas
PS: hello to NANOG from my site. I just got invited to the list because =
of this topic here. My field are the fibre optic networks based on =
pluggable technology.
-----Urspr=FCngliche Nachricht-----
Von: Abello, Vinny [mailto:Vinny_Abello@dell.com]=20
Gesendet: Mittwoch, 4. August 2010 18:27
An: Justin M. Streiner
Cc: nanog@nanog.org
Betreff: RE: Recommended 1Gb SFP for ~115km?
Thanks for the input, Justin. I'm familiar with Transition Networks and =
have used their solutions in other scenarios (as well as MRV). I'm aware =
of the fiber characteristics being a major factor of the link budget and =
dispersion, etc. I am waiting on measurements from the company who is =
finishing the splicing of the fiber for us so I know what I have to work =
with.
Thanks again!
-Vinny
-----Original Message-----
From: Justin M. Streiner [mailto:streiner@cluebyfour.org]
Sent: Wednesday, August 04, 2010 7:46 AM
To: Abello, Vinny
Cc: nanog@nanog.org
Subject: Re: Recommended 1Gb SFP for ~115km?
On Wed, 4 Aug 2010, Abello, Vinny wrote:
> Any pointers on real world experience on this topic would greatly be=20
> appreciated. What are people using successfully out there as far as=20
> third party SFP's go to hit a distance of approximately 115km? This=20
> would be for
a
> Catalyst 6506. Cisco's solution was a much more costly EDFA solution,=20
> but
I
> see plenty of vendors that make SFP's for Gigabit Ethernet that range=20
> from 115km to 150km and more. I know these are not supported by Cisco=20
> and TAC won't troubleshoot if they are in the switch. I'm willing to=20
> work around that should I need TAC assistance on the switch. What=20
> works well for a single wavelength solution at this distance without=20
> having to switch to DWDM? This circuit will have duplex fibers.
I just lit a ~110km fiber span with gigabit gear in the last few weeks, =
and I ended up going with an external line driver because the native =
Cisco options wouldn't work, for a variety of reasons. I would have =
preferred to plug directly into the 6509s I have at each end, but it =
wasn't feasible.
I ended up going with gear from Transition Networks. Pricing was pretty =
reasonable and their customer service has been great so far. There are =
some things with the management interface that I'm not too crazy about, =
but nothing that was a show-stopper. The driver has a 2-port SFP module =
that takes the LX12 long-haul signal in one side we drop it out the =
other side as 1000baseSX to drop into the 6509s. Works like a charm.
I also looked at kit from MRV and Metrobility. The MRV stuff looked =
good too.
Having said all that, you need to take into account the engineering =
characteristics of the fiber span, to make sure you choose gear that =
will live within the attenuation and dispersion limits that physics, =
fiber quality, splice quality, etc will impose upon you.
On the 110km span I just lit, I used the G.652 spec as a guide and =
figured for 0.2 dB/km of attenuation at 1550 nm and 0.5 dB of loss for =
each connector, which got me an estimated loss budget of about 23 db, =
and the span tested out better than that. With an additional =
cross-connect at the one end I'm still at about 22.5 dB end to end. The =
LX12 optics I used from Transition have a link budget of 32 dB, so we =
have a bit of headroom.
jms
