Mode conditioning cables for MMF.

[forman102]

Hi,

I have a building on campus, which is connected to my core switch over obsolete MMF (the link is approx 500m, but I can't indentify what type of fibre cable it is). Recently I upgraded core switch from 4006 to the new 4506E. In the 4006 I used GBIC SX modules on both ends, but after the upgrade I can't use those anymore.It seems that I need SFP LX/LH (cisco part GLC-LH-SM) on the core side and GBIC LX/LH (cisco part WS-G5486) in the access switch. Could you advice if I need mode conditioning cables to make it work? I figured that for my set up I'd need 1x LC to ST (core to patch panel) and 1 ST to SC (patch panel to switch). Help please...

thanks,

forman

[Tom Randstrom]

I have question regarding your network.

1) Are you planning on using the installed “obsolete MMF” that you were using with the 4006 switch or is there some other fiber you will be using (what type)?

If you are using the original “obsolete” MMF, then you should be able to install a GLC-SX-MM SFP in the 4506E and connect to the original SX GBIC in the access switch.

If you will be using the original "obsolete" MMF with the 1000Base-LX/LH transceivers, then you will need a mode conditioning patch cord (MCPC) at each end.  These cables are available from many suppliers. Below is a link to a vendor that sells MCPCs that have the ST connectors you need

.

LC to ST Mode Conditioning Patch Cords for 62.5 micron fiber

http://www.fiberinstrumentsales.com/products/fiber-optic-assemblies,-cable,-and-connection-accessories_multimode-lc-st-mode-conditioning-patch-cords.html

SC to ST Mode Conditioning Patch Cords for 62.5 micron fiber

http://www.fiberinstrumentsales.com/products/fiber-optic-assemblies,-cable,-and-connection-accessories_multimode-sc-st-mode-conditioning-patch-cords.html

Hope this helps!

Tom

[forman102]

Thanks for quick respond Tom,

1) Yes, unfortunately I have to use the installed MMF. I have already tried to connect SFP SX-MM to the SX GBIC, but to no avail.

I've also tried SFP LX/LH on the core and GBIC LX/LH in the access switch (without mode conditioning cables)... the link came up for 1s, then went down, cycled up/down one more time and stayed down.

From Cisco docs I understood that I may need MCPCs on both ends to get connectivity, correct? (please see below) Tom if you could confirm this please... You suggested that I would need MCPCs for SMF, but Cisco states otherwise:

When using 1000BASE-LX/LH, 10GBASE-LX4 and 10GBASE-LRM transceivers with legacy 62.5-micron or 50-micron MMF, you must install a mode-conditioning patch cord between the transceiver and the MMF cable on both ends of the link. The patch cord is required as per IEEE standard and Cisco specification for all links over FDDI-grade, OM1 and OM2 fiber types, and should never be used for applications over OM3 and more recent fiber types.

Note We do not recommend that you use 1000BASE-LX/LH, 10GBASE-LX4 and 10GBASE-LRM transceivers with MMF and no patch cord for very short link distances (tens of meters). The result could be an elevated bit error rate (BER) and receiver damage.  

forman

[Tom Randstrom]

Forman,

I am sorry for my error. I was thinking one thing and something else typed out....

If you are using the 1000Base-LX/LH transceiver (SFP or GBIC) with the legacy MMF, then you will need the appropriate MCPC on each end.

What is confusing me is that the 1000Base-SX SFPs and GBICs have the same operating specifications and should be interoperable.  Is it possible that when you connected the new 4506 SX SFP to the fiber link that the new patch cord's connectors or patch panel's ports were dirty, the jumper cable was 50 micron MMF (versus 62.5 micron MMF), or the fiber jumper was broken/damaged?

Tom

[forman102]

Tom,

I agree. Considering the specifications it should work. I made some progress thought...After reading your post I checked the jumper cable and it turned to be 50 micron MMF. It seems that 50 micron jumper cables work fine with other switches connected thru 62.5 backbone, but not with this one (distance perhaps??). Anyway, I replace it with 62.5 cable and got link on the access switch side (up, line protocol up). Weird thing is that on the 4506E side the port is down/line protocol down.I'm not sure what's causing this. Spanning tree? Right now there are 2 fibre links from that particular access switch to 4506E, the original link is connected to my old 4006 switch, and then from 4006 to new 4506E. The other link is straight connection from access switch to new 4506E. Any suggestions?

thanks

forman

[Tom Randstrom]

Wouldn't be spanning tree if the GE port is down/down.

If you place a jumper from the Transmit port to Receive port on the 4506 GE port that is down, can you get it to show a link? 

Might review the following document to help troubleshoot the down port. 

http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a008015bfd6.shtml#backinfo

[forman102]

Swapping Tx to Rx didn't change the status of the link on 4506E. I also tried combination of LX/LH SFP(4506E) and LX/LH GBIC(access switch). Same result:

up/up on access, down/down on 4506E.Not sure what else to try. Thanks again for your help Tom.

forman

[Tom Randstrom · Accepted solution]

Forman,

Have you used these two MMFs before?  Based on the symptoms, it seems like one of the two fibers might not be functional.

Do you have any optical test equipment, specifically a power meter and light source, to test the continuity of the fibers? 

Does the fiber link have connectors between the buildings/patch panels? 

Did you place a fiber jumper from the 6509 SFP transceiver's Transmit port directly to the Receive port (loopback)?  Or did you just swap the fibers coming from the network fibers?  I wanted to see if placing a loopback at the 6509's SFP would show link, so we can verify proper operation of the SFP module slot and switch. 

This is baffling...

Tom

[forman102]

Man, it must have been bad fibre termination on patch panel.Unfortunately I don't have testing equipment, but I finally scheduled downtime and connected the patch cable using fibre pair, which was in production. Worked just fine with SX GBIC and SFP. I'm so happy this is over. What I really needed was just 62.5 micron patch cord (I originally installed 50) and good fibre pair...  Tom thanks again for your input.

forman