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Exactly what kind of fiber cable do I need.....

.....connecting 2 Cisco switches with Cisco GBICs to a fiber patch panel. Can't seem to find doc to tell me what kind of cable I need, single/multi mode, # of microns, etc Thanks a bunch!


Re: Exactly what kind of fiber cable do I need.....

It depends. What kind of GBICs? SX, LX/LH, or ZX? What kind of fiber coming off the back of that patch panel, single-mode or multimode? What kind of connectors terminating those fiber runs in the patch panel -- ST, SC, MT-RJ, FC, other?

SX GBICs take multimode fiber (usually 62.5 micron, sometimes 50 micron; usually orange in color, but can vary to others, but almost never yellow). ZX GBICs take single-mode fiber (typically 8 or 9 micron; almost always yellow). LX/LH GBICs take single-mode, sometimes multimode, and sometimes a hybrid cable called a mode-conditioning launch cable (this cable is based on multimode, but has a short section of single mode coming from the GBIC's TX port, going into an offset splice about halfway down the patch cable, to "launch" the normally single-mode type signal into the multimode fiber at an angle, so it'll bounce the photons around the potential imperfections in the center of multimode cable). The choices for the LX/LH GBIC depend on what kind of fiber you'll be using through that fiber patch panel, and how far it goes.

In any event, the connectors for the GBIC end of the link are a pair of SC connectors. You may have SC, or ST, or MT-RJ, or even FC, or some other kind of connector in the fiber patch panel. You can get cables that match whatever your connector needs are.

SX GBIC optical signal is good for 220 to 275 meters over multimode, depending on type of fiber coming off the patch panel. LX/LH GBIC will go to 550m with a mode conditioning launch cable, and out to 10km over single mode, with no in-line attenuators needed. ZX GBICs will go to 70-100km depending on the type of single mode fiber they're connected to, but they run "hot", so at shorter distances you need inline attenuators so you don't overdrive (or blind) the RX ports. Cisco says you should use a 10dB attenuator on the RX port on each side of a fiber link if you're under 25km end-to-end; a 5dB atttenuator if you're over 25 and under 50km; and no attenuator needed if over 50km.

Hope this helps.

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