[c-nsp] 10GBase-LX4 and OM2 fibre -- MCP?

[Justin M. Streiner]

On Wed, 4 Aug 2010, Cisco NSP wrote:

> Hi all,
>
> I'm not very fibre-savvy, so if anybody could help me, I'd very much
> appreciate it!
>
> I have two Cisco 6500s about 250 meters apart in two separate buildings.
> Between those two buildings I have OM2 grade fibre. and both Cisco have an
> 10GBase-LX4 X2 interface.

>From what I recall, the recommended maximum distance on 10GBASE-LX4 on 
<OM3 fiber is 300 meters.

> When I measure the fibre end-to-end it has about 1,9dB attenuation in the
> 1300nm spectrum but when I connect the fibre to the interface, I don't get
> link-up.

That is well within the published link budget for the LX4 spec.  Are you 
sure that 1. both X2 modules are functional and 2. all of your jumpers 
and connectors are in good shape (clean end faces, no kinks/micro-bends), 
etc?

> A little troubleshooting pointed me to mode conditioning patches (a piece of
> SM and MM welded together) but I find it very hard to believe that this
> patch will solve my problem.

A mode-conditioning patch can extend the distance and reduce the dispersion
penalty you pay on multimode fiber by admitting only one mode of light 
into the fiber from the transmit side of the optics at each end.

Do you have any singlemode fiber between the buildings, or do you just 
have OM2 grade multimode?

jms

>
>
> Before I invest 800$ for 2 patch-fibers, Is this the way I should go, or am
> I overlooking anything?
>
>
> Thanks in advance,
> Dirk-Jan van Helmond
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