Weird GigE Media Converter Behavior

Tue Aug 24 20:31:10 UTC 2004

Yes, you have experienced what is known in the field as "air gap attenuation"--not
something you want to depend on if you want a clean link!   A close relative
is "knot-in-the-fiber attenuation".

Your subject says "GigE Media converter" but you say you are deploying
an OC12.  Which is it?  

Definitely invest in a light meter that can do the usual flavors 
of single and multimode, connector types, and at least 850 and 1310nm 
wavelengths.  Then simply test strength of light on your receive port 
on each side, compare to specifications of your equipment, and add
in-line attenuators as necessary.  You'll usually find a range something
like -3 to -27 dBm, and we prefer -15 dBm as our ideal.  Also, make
sure you've got the right type of fiber jumpers--mixing up single 
(yellow) and multi (orange) mode fiber can cause similar issues.

Can't wait until more routers start to incorporate inline optical
power readings in "show interface" commands the way Procket did :-)

Cheers,
-Lane

On Tue, Aug 24, 2004 at 01:10:15PM -0400, kwallace at pcconnection.com <kwallace at pcconnection.com> wrote:

> 
> 2 quick things come to mind-
> 
> single mode vs multimode, or the signal is too hot and you need attenuators.
> 
> 
> -----Original Message-----
> From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu]
> Sent: Tuesday, August 24, 2004 12:48 PM
> To: nanog at nanog.org
> Subject: Weird GigE Media Converter Behavior
> 
> 
> 
> 
> Hello all, wondering if anyone has seen or experienced this same problem.
> Currently deploying an OC12 on a campus network and am using Netgear media
> converters. Set up the lines and had lit fiber to the building I needed it
> to go to. On one end (main drop) I had light and tested the connectivity
> which worked fine, on the other side, when I jacked up my Netgear, it
> flickered. Now, when I went to swap out the fiber, I noticed a full
> contact between the wires and the converter dropped it out. Meaning if I
> had the wires not fully plugged it lit, if I plugged them entirely in, it
> dropped.
> 
> So... I ran to the other building and tried to replicate it there, and it
> did the same. I figured bad media converter so I swapped it out, next one
> worked fine. However, I took the media converter and swapped the funky
> acting one to yet another building and it worked fine. Anyone care to
> offer a thought on this? Relevant to my media converter? Bad line,
> "Murphy's Law", etc?
> 
> 
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