Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member


When connecting 2 5509's via a WS-G5486 it says to use the above mentioned cable. As per Cisco documentation

"When using an LX/LH GBIC with 62.5-micron diameter MMF, you must install a mode-conditioning

patch cord (CAB-GELX-625 or equivalent) between the GBIC and the MMF cable on both the transmit and receive ends of the link. The mode-conditioning patch cord is required for link distances less than 328 feet (100 m)or greater than 984 feet (300 m). The mode-conditioning patch cord prevents overdriving the receiver for short lengths of MMF and reduces differential mode delay for long lengths of MMF."

My question is

Do I need this cable at each 5509 or just one end?

New Member

Re: CAB-GELX-625

Cable required at Both ends.

Long Wave will still work with a normal MMF fibre for shorter distances however. (Will not conform to standards though)

New Member

Re: CAB-GELX-625

Yes, you need a cable attached to *each* GBIC, on *both* ends.

New Member

Re: CAB-GELX-625

We have used mode-conditioning patch cables for many of our longer distance GigE links. You definitely have to have one on each end. Each transmit port has single mode fiber that is spliced to multi mode fiber to offset the laser from the center of multi mode fiber. There is a fair amount of documentation about Differential Mode Delay (DMD) effects.

The documented IEEE distances are very conservative. I have some links that are over 800M and we didn't need mode-cond cables. Then we have some under 800M that require the mode-cond. It really depends on the amount of loss in the link. I have one link that is almost 1KM.

What we do is keep a supply of mode-cond cables. Then start with GBIC-SX's. If no link, then swap to GBIC-LX's with standard fiber patch cables. If still no link, then try mode-cond cables. If still no link, then try another fiber pair. We have really been amazed with some of the links that we got up that exceed the distances for both SX and LX GBIC's.

CreatePlease login to create content