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Catalyst 3550 & Single Mode Fiber Card Config

We have some offsite locations across town that will be connecting to us via single mode fiber, I have not ever configured a single mode fiber card for use with a switch(3500) I did read that it was possible with this switch. Just wondering if there is any special config or certain type of card to buy.



Re: Catalyst 3550 & Single Mode Fiber Card Config

Catalyst 3550 takes Gigabit Interface Converters (GBICs). There are two versions for single mode fiber:

* 1000BASE-LX/LH (Cisco part WS-G5486=), list price US$995.

* 1000BASE-ZX (Cisco part WS-G5487=), list price US$3,995.

You need a pair for each point-to-point connection.

The LX/LH GBIC operates at the 1300nm wavelength, and is good to 10km (6.2 miles). No special attenuation requirements -- just plug it in at both ends and it works.

The ZX GBIC operates at the 1550nm wavelength, and is intended for longer distances. It's good to 70km (43.4 miles) over standard single mode fiber, and to 100km (62.1 miles) over dispersion-shifted single mode fiber.

CAUTION: The ZX GBIC laser is pretty powerful; unless your single mode fiber distance is greater than 50km (31.0 miles), you are going to need inline attenuators to put into the Rx port of each ZX GBIC. Between 25km and 50km, Cisco recommends a 5dB attenuator; under 25km, Cisco recommends a 10dB attenuator. If you are going to test equipment with ZX GBICs in a lab setting prior to deployment, it's OK to use the 10dB attenuators and a 2m two-strand single mode patch cable.

WARNING: Do not look directly into the uncapped or "business end" of any fiber cable. Likewise, do not look into the Tx port of a GBIC, especially the ZX ones. It's not good for your eyes. Unless you want to practice do-it-yourself laser eye surgery. (Actually, it's not really that bad, but it is certainly not good for you; just trying to keep you from developing a bad habit.)

Patch cable should have SC connectors for the end that goes into the GBIC; and appropriate connectors for plugging into the long-haul fiber (usually also SC). If when you plug in the patches at both ends you don't get a link light, you're probably patched in Tx to Tx, and Rx to Rx. Swap the connectors on one GBIC, so that it creates a Tx to Rx, and Rx to Tx connection; link light should come on. (If no link light, re-insert all connectors and try again; if still no link light, you may have a bad GBIC, a bad patch cable, or the long-haul fiber may have a problem.)

It's always a good idea to test the stuff in a lab setting so you know the patch cables and GBICs are working BEFORE you drive the equipment out to a remote site. (Learned that the hard way, first time I worked with single mode fiber.)

BTW, there are no special configuration parameters for the optical GBICs, if you're going Cisco switch to Cisco switch: just plug them in and it should go. You still have to tell the port what access VLAN to belong to, or make it a VLAN trunk port, same as you would have to on a copper port.

Hope this helps.

Community Member

Re: Catalyst 3550 & Single Mode Fiber Card Config

Thanks a bunch, that gives me the answer.



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