Can I go from SM fiber to MM?

[olsonc0510]

Hi,

I am new to fiber connections. We are have a SM fiber comming into our data center. It will terminate with Single Mode SC Unicam connectors in the fiber panel. I want to connect these to a 3760 GB switch using Cisco GLC-SX-MM Gbics. I'm guessing all I need is a SC to LC fiber connection. My question is this; is there any issue going from Single mode to Multi-mode? Do I need an adapter or do I need to find SM GBICS? The distance between the patch panel and switch is only about 10 feet.

Thanks

Fiber-newbie

[paolo bevilacqua]

You cannot use MM optics on SM fiber.

You will need to buy the correct SFP module.

[vmiller]

Mode conditioning cables are available to accomplish what you want.

Personally I would avoid it. just stay Single mode and remove one variable.

Here is one of many links available.

http://www.cisco.com/en/US/products/hw/switches/ps679/products_installation_and_configuration_guide09186a008007d1cb.html

[paolo bevilacqua]

vmiller wrote:
Mode conditioning cables are available to accomplish what you want. 
Personally I would avoid it. just stay Single mode and remove one variable.
Here is one of many links available.
http://www.cisco.com/en/US/products/hw/switches/ps679/products_installation_and_configuration_guide09186a008007d1cb.html

You cannot use mode conditioning cable for MM optics on SM fiber.

Only the opposite is possible, subject to distance limitations, as indicated in the referenced document.

[Jonathancert_2]

The GLC-LH-SM can do SM and MM.  I would not recommend doing SM for such a short distance.  The laser in the SM SFP could cause problem with the interfaces.  See the link below for more advice.

1000BASE-LX/LH SFP for Both Multimode and Single-Mode Fibers

The  1000BASE-LX/LH SFP, compatible with the IEEE 802.3z 1000BASE-LX  standard, operates on standard single-mode fiber-optic link spans of up  to 10 km and up to 550 m on any multimode fibers. When used over legacy  multimode fiber type, the transmitter should be coupled through a mode  conditioning patch cable. For details on this implementation, refer to http://www.cisco.com/en/US/customer/prod/collateral/modules/ps5455/product_bulletin_c25-530836.html.

Jonathan,

[paolo bevilacqua · Accepted solution]

Jonathancert wrote:
The GLC-LH-SM can do SM and MM.  I would not recommend doing SM for such a short distance.  The laser in the SM SFP could cause problem with the interfaces.  See the link below for more advice.

Nowhere the OP hsd indicated that his fiber circuit is of short distance, He has indicated that it is coming from the ISP into their facilities, consequenly it can potentially be of many miles. The ISP is the right subject to ask for the correct optical module to use.

[olsonc0510]

Thanks very much. You are right, MM will not work. I am 37 floors above the vendor demarc so we have to use SM up to the data center. I was hoping we wouldn't have to purchase SM GBICS but it looks like I'm going to have to. Can you make a recommendation as to the model. I can't find anything when looking for GLC-SX -SM.

Thanks again!

[olsonc0510]

Now the hard part, there are many different GBICS out there. Does Cisco support ONLY Cisco brand GBIC's?

[Leo Laohoo]

 Does Cisco support ONLY Cisco brand GBIC's?

Yes.

[paolo bevilacqua · Accepted solution]

leolaohoo wrote:
 Does Cisco support ONLY Cisco brand GBIC's?
Yes.

Officialy, yes. But I don't think I will commit a mortal sin mentioning that there are alternatives.

For the OP: see, that is the point of using a reputable consultant instead of a DYI approach. He will know everything and will take care of anything in your best interest, for you to go home at 5pm happy and relaxed.