GLC-LH-SMD in ASR1K

[johnlloyd_13]

hi,

i'll be terminating a fiber cable to our ASR1K and use a GLC-LH-SMD SFP/GBIC.

just would like to confirm i need to use a SM fiber? can i also use MM fiber since the connection is "short distance"/same rack from fiber patch panel (SC from telco) and then LC to our ASR1K SFP.

do i use SC-LC SM or MM fiber or either will work? or is it best practice to use a compatible fiber patch cable with the SFP/GBIC? i.e. GLC-LH-SMD to only use with SC-LC SM fiber cable.

[Leo Laohoo]

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@johnlloyd_13 wrote:

can i also use MM fiber since the connection is "short distance"/same rack from fiber patch panel (SC from telco) and then LC to our ASR1K SFP.

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MM or MMD if the distance is <100 metres on OM1/OM2.  <1000 metres on OM3/OM4 (1 Gbps only).

[marce1000]

                - FYI : https://tmgmatrix.cisco.com/?npid=1541

 M.

[johnlloyd_13]

i'm not asking if SFP is compatible with ASR1K.

i'm asking SFP to fiber cable compatibility here.

[marce1000]

 - Look at column Media

 M.

[johnlloyd_13]

hi,

so only SM fiber cable works on GLC-LH-SMD?

[marce1000]

 - Yes , 

 M,

[Marvin Rhoads]

While sometimes you can get away with using multimode patch for a short length within an otherwise single mode end to end link, it is very much not recommended. The cost of a single mode patch cable is well under US$10 and well worth the headache avoidance.

Reference for my cost citation: https://www.fs.com/c/os2-9-125-single-mode-897

[johnlloyd_13]

hi marvin,

thanks for your feedback! yes, i remembered i used a MM fiber on a SM SFP and it worked. that was a long time ago.

just asking here if it's best practice to stick with SM SFP with SM fiber patch cable.

[Leo Laohoo]

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@johnlloyd_13 wrote:

just asking here if it's best practice to stick with SM SFP with SM fiber patch cable.

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It boils down to the distance.  For 1 Gbps, <100 metres on OM1/OM2 or <1000 metres of OM3/OM4.

[Tom Randstrom]

It's always best to match the fiber to the specification outlined for the optical transceiver.  If you want to use multimode fiber for a short run, use the appropriate short reach (SX) transceivers on the ends of the links. 

[johnlloyd_13]

hi tom,

thanks for your feedback! will use proper SM fiber with SM SFP.

maybe i just got away using MM fiber with SM SFP

[Tom Randstrom]

Sorry, I was not thinking straight regarding the question.  

The GLC-LH-SMD is a 1000BASE-LX/LH transceiver, thus it is a SMF based module; but can also be used with MMF (with a launch cable). So it is possible that it what your previous experience was with mixed use SMF/MMF using the same transceiver. 

https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/gigabit-ethernet-gbic-sfp-modules/datasheet-c78-366584.html