Unanswered Question
Aug 3rd, 2009


does the GLC-SX-MM work over single mode fiber, short distance?


I have this problem too.
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Peter Paluch Mon, 08/03/2009 - 11:37


According to the data sheet, that module is designed for multimode fiber, 850 nm wavelength. As a rule, combining an optical transceiver module with an improper fiber type can only lead to trouble. Though I have never tried it, I doubt it will work. Even if it happens to work somehow, the transceivers are operating outside their specifications and no guarantees about the data transfer reliability can be made.

Best regards,


anasmomo Mon, 08/03/2009 - 11:41

but why the LX work over both multimode and single mode with two different distances?

Peter Paluch Mon, 08/03/2009 - 12:07


The module you are talking about is probably the GLC-LH-SM. According to the document at

a MMF is allowed for use with GLC-LH-SM but you need to use a mode conditioning patch cord with MMF (see the Table 4 in that document). Generally, the LX modules were designed with the possibility of both SMF and MMF in mind, requiring the mode conditioning patch for MMF.

However, the module GLC-SX-MM you are asking about uses a different wavelength and the datasheet does not discuss this option. In fact, the document

explicitely states: MCP should never be used in 1000BASE-SX links in the 850-nm window.

Best regards,


Jiler2008 Mon, 08/03/2009 - 12:31

Hello Anasmomo,

It seems that you are trying to use a multimode fiber SFP for single mode fiber over short distance. Why exactly are you trying to accomplish with this? As previous posts said the GLC-SX-MM is a multimode fiber module for shortwave length fiber connections.

anasmomo Mon, 08/03/2009 - 12:34


because i have single mode fiber already installed and the distance is less than 200Meter. and i will have SX SFPs.

so i want to check if SX will operate with this SMF?


Jiler2008 Mon, 08/03/2009 - 12:48

To answer your question, from my knowledge GLC-SX-MM won't work with single mode fiber, if need be you can order some single mode fiber SFPs. If you wanted to do something cheaper, what about just running Cat 5e the 200ft distance, would that be viable?

iyde Thu, 08/06/2009 - 02:44

Jason, it was 200 meters, not 200 feet. That means Cat5e is out of the question...


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