Mode Conditioning Patch Cables – Will They Help with This Issue?

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I have been having problems with a link flapping only when working with the AXM763 Module, but when I change 1G module it works without problems. Also there other 2 links with the same configuration working with the AXM763 10G.

I understand that the distance between my buildings is avobe the maximum distance, But How can I explain that 2 of those links work and only one fails.

I was reading cisco documentation and fiber specs and I found Mode Conditioning Patch cables are required for 10GBASE-LRM SFPs working on OM1 MMF because those cables reduce the effect called differential mode delay (DMD).

And I was thinking that this might help me with my problem, Can anybody help me with this problem? If it could work or not or if I missunderstood the Mode Conditioning Patch Cables.( I am not an expert in fiber)

Current Topology

Test Topology

Thank you!

Best Answer

10GBASE-LRM will only go so far over legacy multi-mode fiber. Officially, its reach is 220 m over 500 MHz·km fiber, 243 m could just about work when everything else is perfect.

A mode conditioning patch is worth a shot but I wouldn't bet on it - 10G-LRM is designed for MMF and should already launch accordingly. If you've got some 10G-LR transceivers at hand it's also worth a try with mode conditioning.

Edit: As ilkkachu has pointed out, MCPs should be used with FDDI and OM1/2 MMF fiber as specified in IEEE 802.3 Table 68-3 and by various vendors. 802.3 alternatively suggests launching into those fibers without MCP but with a pretty focused "encircled flux" (at least 30% power within 5 µm radius, 81% within 11 µm) - the same as with OM3/4. I guess that clears up why using MC patches helped in your case. It seems you need the right kind of mode-conditioning patches as well. Only OM3/4 "laser optimized" fiber seems to be good w/o MCP for full reach.

If everything fails and redeploying modern fiber is not an option you should look out for 10GBASE-LX4 transceivers - they're expensive but if you can get them they're pretty much guaranteed to work (official reach is 300 m over legacy fiber).

Also, redeployment may be much cheaper when it's possible to pull preterminated fiber - you can get that very reasonably priced from many vendors. Use either OM4, OM5, or switch to OS2 altogether, especially when using budget transceivers.

Another (suboptimal) approach is to use aggregated gigabit links with or without WDM.

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