Unanswered Question
Jun 30th, 2010

Hi Team,

We have a deployment wherin two sites are located at a distance of approx. 350 Mtrs.

At present we have multimode fiber which runs between two locations with 1G speed, which works fine.

With current revamp, wherin two chassis(4506) have been installed, with X2-10GB-LR Modules so that it would support 10G,

But the challenge we are facing is that the link does not turn up.

So, kindly let us know if there is any compatibility issue and what is the max distance supported by X2-10GB-LR  on MM fiber ?


Vaibhav Shirkul 

I have this problem too.
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Tom Randstrom Wed, 06/30/2010 - 07:58

The X2-10GB-LR tranceiver is designed for Singlemode fiber (SMF) operation, not the Multimode fiber (MMF) you have installed. 

Without changing out the fiber, you might try installing a pair of Mode Conditioning Patchcords.  For the transmitting end of the links, these patch cords transition the transceiver's output from SMF to MMF, and offset the fibers so the laser light is transmitted in the the correct area of the MMF's core. You order them based on the core size of your installed MMF (you didn't mention what type of MMF you had).  They are available from suppliers. 

This is not an "approved" application for the "LR" module and I am not sure it will work.  But given your limited distance, this implimentation may work.  It might be worth giving it a try versus pulling new fiber (or until you pull new fiber).

Good luck!

Tom Randstrom Wed, 06/30/2010 - 08:22

Another option is to use a third-party media converter solution between the 4506s over the current MMF.

MRV has a media converter that will support a 10G transceiver module with a 500 meter reach over MMF.

MRV Products

Media Converter

XFP transceiver module (XFP-10GD-MMX)


4506 / X2-SR -------> SFP+-SR / MRV / XFP-10GD-MMX ----------> XFP-10GD-MMX / MRV / SFP+-SR -----> X2-SR / 4506

vaib7av.shirkul Sat, 07/03/2010 - 01:29

Hi Team,

Thanks for support/

Operational Existing Scenario

6509[GLC-SX-MM] ---> LC-MM patch cable-ST --------> MM fiber ------------> ST-MM patch cable-LC-----------> 3750 Stack[GLC-SX-MM] ------> 1G

Building 1  ------------------------------------------------> Max.300 Mtr -------------------------------------------> Building 2

Unsuccessful attempt to Implement

4506-[X2-10GB-LR]------------->SC-MM patch cable-ST -------------> MM fiber ----------------->ST-MM patch cable-SC ------> 4506-[X2-10GB-LR]

Bulding 1 --------------------------------------------------------> Max.300 Mtr -------------------------------------------- > Building 2 

This diagram would help you to understand the issue faced by us.

Kindly advice,

Vaibhav Shirkul

viyuan700 Sat, 07/03/2010 - 08:00

If your 300 link is working then GLC-SX-MM is going over 50micron MM cable. (Can go upto 500 to 550m over OM2 and 1000m over Om3) Do you know what MM cable you have OM2 or Om3?

Problem at 10G is max disatnce on

OM2 MM cable is 70m for SR and 300m for LX4.

OM3 MM cable  300m for SR

If you have this module X2-10GB-LR then you have chosen a wrong module as it is meant for SMF (Single mode). Since your disatnce is 300m max then X2-10GB-LX4 could have given you the link.

You can try deppending on availability/price

1. See if you can get X2-10GB-LX4 (retrun / exchange) and check if that works

2. If you X2-10GB-LR and you cannot return/exchange then try a mode conditioning cable (http://www.cisco.com/en/US/prod/collateral/modules/ps5455/product_bulletin_c25-530836.html) mentioned in the link or similar cable. It is possible that you can get the link (not 100% sure)

Both X2-10GB-LR & X2-10GB-LX4 gives you nearly the same optical budget but i think will be limited by dispersion as LX4 have  has 4 wavelength working at 2.5Gb have EDC(electronic Dispersion Compernsation) whereas LR have 10G so dispersion will be more for LR.

3. Pull SMF cable as you have LR optics.

I dont think there is multimode extender at 10G there are at 1G but not at 10G.

mmacdonald70 Sun, 07/04/2010 - 20:05

This not neccesasarily true.  While the specs for GLC-SX-MM over 62.5micron say max 220M, we have many links that go over 300 meters (and several patches) with no problems.

viyuan700 Sun, 07/04/2010 - 22:55

This not neccesasarily true.  While the specs for GLC-SX-MM over 62.5micron say max 220M

Thanks! for sharing your expereince. It is wrong to use Max. word so will try not to use it in future. for 62.5MM fiber 200MHz.Km fiber it is possible to get distance of 275m maybe you have that one.


There are so many parameters , which tells how far you can go and those numbers are average and it is possible to get more disatnce (They are just assuring you for the least disatnce.)

Optical power for example have a very good range from (-3 to -9.5dBm)

Similary dispersion in multimode fiber depends on how good is graded index profile of the fiber if it is too good you can get more distances.

Tom Randstrom Wed, 07/07/2010 - 18:25

Thank you.... We definitely appreciate feedback from real world networks!

In many cases, the network may operate outside of the published specifications.  As viyuan700 has pointed out, the assumptions used by the specification bodies are generous so that the links will operate properly over most links.  These "loose" link losses, which include fiber, connector and system margin, plus dispersion effects, result in links that may operate over longer links than outlined by the 802.3 specifications.

There can be two problems with operating links outside the bounds of the Cisco's published specifications; if you need to contact Cisco TAC, you may not receive the support you need because you are operating the system outside the bounds of the published parameters for the device. The other is if you swap out a transceiver, the new transceiver may have a lower transmit power than the previous unit; which may result in a link that doesn't operate properly.

Again, we appreciate the real world feedback.  Keep it coming! 



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