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New Member

Cabling-specs for Gig uplink-modules


we are planning on upgrading our 100Mbit fiber-uplinks between Cat5505-boxes to Gigabit. We would use the WS-U5534-GESX uplink-modules for this. We use 62.5 micron multimode fibers on 850nm wavelength.

I was able to find the cable specs for GBIC-modules at But I can't seem to be able to find the specs for the uplink-modules. Are they exactly the same?



Re: Cabling-specs for Gig uplink-modules

They are the same, more or less.

GBICs modules and fixed Gigabit connections are bound by the same optical restrictions in the fiber.

If you're using multimode fiber, which is rated to 2000 meters for 100-megabit Fast Ethernet full duplex, be prepared for a shock. At Gigabit Ethernet speeds, with SX GBICs (850nm wavelength) your distance shrinks to 220 to 275 meters.

You can squeeze it out to 550 meters over multimode fiber with LX GBICs (1310nm wavelength) and mode-conditioning launch/patch cables.

But if you need to go beyond that, start thinking single-mode fiber. LX GBICs can push out to 10,000 meters over single-mode. ZX GBICs (1550nm wavelength) can kick it all the way out to 70 to 100 kilometers, depending on the type of single-mode fiber used.

If running new single-mode fiber is not an option, you need more bandwidth over the same distance, and you have extra pairs of multimode fiber, then consider using Fast Ethernet media converters on copper 10/100 ports (hard-coded to 100 full duplex) and build a Fast EtherChannel connection between boxes. It will give you multiple lanes for 100-megabit traffic, but no single "conversation" over that connection will be able to exceed the 100-meg. speed limit.

Hope that helps.

New Member

Re: Cabling-specs for Gig uplink-modules

I was afraid of that. On our main site, some buildings are 300-350 meters apart and all we have are 850nm multimodes.

Thanks for the information!


Re: Cabling-specs for Gig uplink-modules

Now, having said all that about the specifications and standard distances, if you are talking about only 300-350 meters and you want to give it a try, you "might" be able to make it with SX GBICs.

The specs tell you that with an acceptable cable plant, your optics should be 100% reliable out to the specified distance. Beyond that, you're on your own.

With fiber, how far you go is primarily a matter of optical power. For example, the LX spec mentions a distance of 5km, but Cisco and others say their LX GBICs are good to 10km. I have a span that we put an OTDR on, registered a distance of 16km, but an optical loss that was still within the Cisco LX/LH GBIC's budget. The link works fine. Of course, your mileage may vary.

I remember reading about some trade show a couple years ago, probably Interop in Las Vegas, where they went past the SX spec distances and it still worked. If you have some spare equipment, you might want to try it.

If you don't have access to an OTDR, you could run some bandwidth tests across the long fiber link, then duplicate them over a local fiber link, and see if the times are the same. If the long-fiber-link times are significantly longer, you're probably fading in and out of the tolerances of the SX optics.

Pushing the SX envelope might turn out to be cheaper than pulling new single-mode fiber. Although adding single-mode fiber is the right thing to do in the long run. (I work for a fiber optic construction company, so I have to say that.)

Keep us posted...