[c-nsp] No Link between SFP-10G-LRM and X2-10GB-LX4?

[Mack McBride]

That older fiber is probably not rated at 500 Mhz Modal BW suggested by Cisco.
Older fiber is usually 200 Mhz.
The LX4 would be a better choice (more dispersion resistant) and max distance of 300M.
Your distance limitation is probably going to be much less than the rated value
if the dispersion characteristics of the fiber don't meet the spec.
Of course you will still get connectivity but you will increment errors.
For dorms it probably doesn't matter much.  If the streaming music and video is effected
by errors it will probably save you money since the students won't stream as much.

Mack

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Jeroen van Ingen
Sent: Friday, October 07, 2011 4:49 AM
To: sthaug at nethelp.no
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] No Link between SFP-10G-LRM and X2-10GB-LX4?

On Fri, 2011-10-07 at 10:51 +0200, sthaug at nethelp.no wrote:
> > > Much better to stick to standard transceivers (SR, LR, ER, ZR or DWDM).
> > 
> > That's easier said than done; if you need 10 Gbps but you only have old
> > MMF available, your only choices for >30 meters are LX4 and LRM.
> 
> As we get to capacities higher than 10 Gbps you should not expect old
> MMF to be usable...
> 
> SMF is well worth the extra expense, IMHO.

I agree, but again, I was talking about corner cases :)

We're in the process of an upgrade where we need 10 Gbps but can't
replace the existing FDDI-grade MMF: all links to the dorms on our
Campus were installed in the early '90s, when (afaik) SMF wasn't common
yet for distances < 500m, nor were ducts & blown fiber. We have the
budget to use LRM transceivers but not to dig up the cables and put SMF
in the ground.

The 10 Gbps LRM links we're now putting in will probably suffice for the
next 5 - 10 years; perhaps then replacing the fibers will be an option,
or if we're lucky, there may be other digging activities in the mean
time that we can take advantage of...

Of course, now SMF is the standard for us, even for short distances. But
sometimes you have to cope with the limitations imposed by history ;)


Regards,

Jeroen van Ingen
ICT Service Centre
University of Twente, P.O.Box 217, 7500 AE Enschede, The Netherlands


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