Anyone using 50 micron for multimode?

[bbuhlman]

I want to start using 50 micron multi-mode instead of 62.5. Is anyone doing this now with Cisco equipment and what are some of the pro's and con's.

[konigl]

I personally don't know of anyone who's running new 50-micron MMF at this time. If you are set on pulling new multimode, consider the newest "next generation" MMF, which should carry 10GBase-SR out to 300m. (Note: Cisco doesn't make anything that takes advantage of this new MMF yet.)

Cisco's recommendations for people installing new cable now is to pull hybrid cable, so the MMF can handle "legacy" needs, while the SMF will be there to handle the newer technologies. See http://www.cisco.com/en/US/tech/tk389/tk214/technologies_white_paper09186a0080092958.shtml and search for the word "fiber" to get some perspective on new fiber installs.

Most of my customers who currently have 62.5-micron MMF are pulling SMF alongside if the distance to cover is greater than 550m (the max. distance for 1000Base-LX/LH over MMF, using mode conditioning launch cables) and under 2km (the max. distance for 100Base-FX over MMF). Beyond 2km, they always install SMF. If budgets are tight and they need increased bandwidth now, they're doing Fast EtherChannel with 100-megabit media converters until they can get the SMF.

The 1000Base-SX and 1000Base-LX/LH GBICs are pretty low cost, practically insignificant in fact when compared to what it costs to pull new fiber. So for Gigabit speeds, the main issues are do they really need it, and how far do they have to go.

On the other hand, electronics and optics for higher-speed 10-Gigabit Ethernet tend to be more expensive at this time. The equipment that is targeted for use over MMF is expected to be less expensive than the gear for SMF, but is severely constrained in the distance it can go. See http://www.cisco.com/warp/public/765/tools/quickreference/mediadistances.pdf for a handy chart of speeds and maximum distances by cable type.

Likewise, as you increase distance the SMF components become more expensive. In contrast to Gigabit Ethernet, however, the equipment costs cannot be ignored when making the business case for 10-Gig Ethernet. Most of my customers are opting for the SMF install today, and are content to get by with Gig Ethernet. They figure that equipment costs will come down over time, and when they really need 10-Gig the hardware that works over SMF will be more affordable.

Hope this helps.

[JEFFREY SESSLER]

We've moved to using 50 micron Cornig Infinicor SX+. You extend Gigabit SX use to a minimum of 1000 meters (lab tested as far as 2000 meters). The biggest advantage is in the cost savings of using SX vs. LX/LH Gbics. By using the Infinicor SX+, many places where you would normally need LX/LH Gbics (or even SMF) are now well within the reach of SX Gbics.

This fiber is also good for a minimum of 300 meters (lab tested as far as 600meters) at 10GigE. The idea being again that the 850 VCSEL lasers (SX) are going to cost less.

We are running this fiber in our building risers and, in building-building runs under 500 meters. For everything else over 500 meters, we are running both the SX+ and standard SMF (future use).

Jeff

[bilawson]

I have recently placed 50 micron MMF between 2 buildings in my campus network. I had originally ordered 62.5 but when the actual survey came back it was over the 900' allowed by the 5484 GBIC. By placing the 50 micron MMF in between I can go up to 1800' and still use the cheaper 5484 Gbics. I am currently running 2 strands on gig ethernet to the new building and the users are exstatic about the new speed. Hope this helps.

[bbuhlman]

I'm pretty sure but do you know if the 5484 GBIC has the LED light source? Does Cisco even use the VCSEL light source yet?

Thanks,

Bill

[konigl]

WS-G5484= "Contains a Class 1 laser of 850 nm for 1000BASESX (short wavelength) applications."

From http://www.cisco.com/en/US/products/hw/routers/ps354/products_installation_guide_chapter09186a008007e57c.html

Also, Cisco is starting to use VCSEL technology. In very-short-reach OC-192 applications and in small form-factor pluggable (SFP) Gigabit Ethernet SX optical transceivers, so far. Future plans to use it in 10-Gigabit Ethernet short links, too. Search of VCSEL on the website yielded 5 results as of this date.

Hope this helps.

[bbuhlman]

Thank you. I had trouble finding that info yesterday.

Bill