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New Member

Gigabit Ethernet over 2000ft.

My campus has a building that is around 2000ft. from the master swtich. The runs to the building are Multi-mode fiber.

From looking at Cisco docs, I cannot do Gigabit ethernet over multi-mode fiber because the longest distance is 1800 ft. over MMF.

Is there any way around this, such as a repeater or something?

Cisco Employee

Re: Gigabit Ethernet over 2000ft.

Not sure about repeaters, but I have seen some customers use another switch such as an XL series inbetween

New Member

Re: Gigabit Ethernet over 2000ft.

You can try this

When using the LX/LH GBIC with 62.5-micron diameter MMF, you must install a mode-conditioning patch cord (Cisco product number CAB-GELX-625 or equivalent) between the GBIC and the MMF cable on both the transmit and receive ends of the link.

The patch cord is required for link distances greater than 984 feet (300 meters) and must comply with IEEE standards

Or you can get a 3550 and put it in between.



Re: Gigabit Ethernet over 2000ft.

If you can insert a switch with two SX GBICs somewhere to the middle of the span, you can use it kind of like a repeater or an amplifier.

The standard specifies that fiber installed in accordance with commonly acceptable constuction principles should be able to carry the signal reliably out to at least 550m. If your fiber plant install is better than average (near-perfect splices or no splices at all; near-perfect finish on the tips at either end; quality glass with no kinks, etc. along the way), you can probably squeeze some more distance out of it. Get an optical TDR and shoot the span for dB loss at your chosen wavelength(s) 850-nm for SX GBICs, 1300-nm for LX/LH GBICs. You might be suprised how far you can push it beyond the standard distance -- just be sure you realize that you are exceeding the standards (some people have a problem with that).

I have driven LX/LH GBICs out to 16km (Cisco rates their gear to 10km over single mode fiber, and the official standard is 5km for LX anyway, so they're already encouraging you to push it).

Of course, there are other issues to contend with, like modal dispersion I think it's called. But hey, scan it and see what you get. It's cheaper than running new SMF...