GLC-LH-SMD - use SM or MM fiber?

[johnlloyd_13]

hi,

will be using GLC-LH-SMD SFP in one of our ASR router.

just need an advice on which type of fiber patch cord to use.

the telco will run a SM fiber in their rack which is in another room, all the way to our DC rack which the patch panel hand off is LC.

the patch panel (LC termination) is found on the top most of the rack and the ASR is all the way at the bottom.

my question is, do we use a SM LC-LC fiber cable between the ASR GLC-LH-SMD SFP and the patch panel (LC)? or use MM LC-LC fiber instead?

[PatrickBixler22547]

It is always best to match the patch cable with the fiber plant cable.  Your optics should also match to the fiber plant.  

Since your fiber plant is SM and your optic is SM (LH), it is best to use SM patch cables.

[Giuseppe Larosa]

Hello @johnlloyd_13 ,

I recommend to use a single mode fiber cable because as already noted everything is single mode your SFP and the fiber of the provider and the cabling.

You shouldn't have saturation issues on the receiver that would require the use of an optical attenuator.

Hope to help

Giuseppe

[stephen2024]

In case anyone else runs across this, it should be clarified. The other answers are correct. However, using the correct patch cable is a requirement, not a recommendation or best practice. The type of patch cable and transceivers should always match the type of fiber. It must be the same mode from end to end. Keep in mind, there are modes within Multimode as well (OM#). Mixing cable modes will lead to packet loss, or in many cases, no connectivity at all. The reason is the glass sizes in the fiber cable are different. It's similar to trying to connect a water hose to a 4" PVC pipe. 90+% of the water will flow out of the 4" pipe and not enter the water hose.