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GBIC connection to single or multimode fiber

Is it possible to connect a SX GBIC to both single-mode fiber and mulitmode fiber? What will be the effect of LX GBIC to both single-mode fiber and mulitmode fiber?

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Without using some type of mode conditioner or conversion device, single-mode fiber (SMF) transceivers (e.g. GBIC and SFP) need to attach to SMF cabling and other SMF transceivers. The same holds true for multimode fiber (MMF) transceivers and devices. Short-range or short-distance transceivers such as GBICs and SFPs (also known as SX) utilize MMF cabling unless some type of mode conditioner or conversion device is employed to attach to SMF. Long-distance transceivers (also known as LX) typically utilize SMF cabling.

The fundamental difference lies in the type of cabling and optical transceivers. SX transceivers utilize lower-powered, lower-cost optics and lower-cost, shorter-distance MMF cabling while LX utilizes higher-powered, more accurate optics for longer distance with more expensive SMF cabling.

Keep in mind that when you introduce a mode conditioner or mode conversion device, you will introduce additional degradation into the optical signal (e.g. db loss). SX and MMF should enable distances depending on speed (e.g. 1Gbit, 2Gbit, 4Gbit, 10Gbit) of the interface to a couple of hundred meters (actual distance will vary with speed). Using SMF and LX transceivers and depending upon optical cabling, repeaters and other technology including CWDM, WDM and DWDM distances of 10s to 100s of kilometers can be supported. Avoid simply looking at distance and attainable bandwidth supported and also look at effective latency and effective bandwidth over the supported distance.

This was first published in September 2005

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