OM4 Multimode Fiber and supported distance for 10G Ethernet
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OM4 Multimode Fiber and supported distance for 10G EthernetExpand / Collapse
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Posted Wednesday, September 01, 2010 7:36 PM
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I have a client in a large facility ((2.6Msqft building with redundant ERs) where each TR has redundant connections. They installed OM4 fiber to support 10G Ethernet links to the TRs. The two ERs are diversely located so the fiber links can be very long. We are trying to bring up the network in the first half of the installation and the equipment manufacturer will not support the OM4 fiber for extended distances (over 300 meters). Both the fiber optic cabling manufacturer and the active equipment manufacturer are major firms in the market. The fiber was home run from one ER and field terminated with LC connectors at each end. We have a 96SM/144MM fiber between the two ERs as we expected many of the redundant links to require SM as the total length will exceed 550 meters.

 

After 4 weeks of communications, it appears the maximum distance the active equipment manufacturer will support with 10GBASE-SR transceivers is limited to 400 meters over OM4. They have stated that it may work up to 550 meters but they will not be responsible for these links. We can try the longer distance and if they work, fine, if not then don’t call them. They will also not be responsible for repairing a link over 400 meters that originally worked but eventually fail.

I am disappointed with the support from the fiber manufacturer who seems to feel that their press releases are all the proof required. This project has links with a calculated connector loss of 0.3db so they should be well within the guidelines for 550 meters. Since I have over 100 links that could exceed 400 meters and the single mode NIC is twice the cost of the multimode NIC, this could have a significant cost impact.

Has anyone else tried to push 10G Ethernet over 400 meters on OM4? I would like to hear from any OM4 product manufacturers that can actually backup their claims as I have another 10G project under design and more in the pipeline that may need the extended distances.

Note: I have documentation from Commscope that does warrant their OM4 for the full 550 meters with standards compliant 10GBASE-SR transceivers.

Post #5191
Posted Thursday, September 02, 2010 9:26 AM


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What is the model of electronics you are using? OM4 (defined in TIA-492-AAAD) was finalized in August 2009, and was published by the end of 2009 by the TIA. As long as the electronics manufacturer follows the 802.3 10GBASE-SR Standard it should be capable of 10G up to 550 Meters. This is what I thought?
Post #5194
Posted Thursday, September 02, 2010 12:37 PM
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The client is using Cisco X2-10GB-SR modules in 3750E and NEXUS boxes. Cisco has stated that they will support a maximum distance of 400 meters. Anything over that may work but don't call them if it doesn't.
Post #5195
Posted Thursday, September 02, 2010 1:28 PM


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Then I would assume other manufacturers would take the same stance, I just assumed it wasn't Cisco. So if this is the case why are cabling manufacturers clamining 550? Why would I go beyond 300 if the electronics manufacturer designed using the IEEE standard when making their electronics, and 300 is the limit. I wouldnt support it either. I emailed a couple of fiber manufactueres and sales reps, will post with their responses.
Post #5196
Posted Thursday, September 02, 2010 4:58 PM
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Just to clarify.

The cabling company certifies their cabling. This certification will/may include application garuntee's, ie. 10G SX for 550m.

The electronic manufacture certifies their products to applications, ie. 10G SX.

The application has certain perametres that products must meet to be certified in that application. 10G SX was a done deal before OM4 was ratified. You will need to wait until the IEEE revisits the 10G SX application standard for it to include the use of OM4 and therefore the distance it will travel.

However, I don't see what the big deal is about. The cabling manufacturer has certified the application for a certain distance. If the application doesn't work you go back to the cabling manufacturer and get them to fix it.

Post #5197
Posted Thursday, September 02, 2010 6:22 PM
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That is something that I had considered but i wanted something in writing for the client's records. When i asked for support from the fiber manfacturer I actually expected a them to warrant the 10G application. Since my initial request for assistance, I have received a confirmation that Cisco will limit support to 400 meters and copies of old press releases. 
Post #5198
Posted Friday, September 03, 2010 3:47 PM


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Bucket23 (9/2/2010)
Just to clarify.

The cabling company certifies their cabling. This certification will/may include application garuntee's, ie. 10G SX for 550m.

The electronic manufacture certifies their products to applications, ie. 10G SX.

The application has certain perametres thatproducts must meet to be certified in that application. 10G SX was a done deal before OM4 was ratified. You will need to wait until the IEEE revisits the 10G SX application standard for it to include the use of OM4 and therefore the distance it will travel.

However, I don't see what the big deal is about. The cabling manufacturer has certified the application for a certain distance. If the application doesn't work you go back to the cabling manufacturer and get them to fix it.


Excellent response. IEEE 802.3 has yet to officially state a distance for 10GBASE-SR over OM4 fiber.

550 m seems to be the common distance quoted by cabling vendors but I have been hearing values closer to 500 m and sometimes "up to 550 m". Not quite sure what "up to 550 m" means. Anyone want to jump in on that one; "up to 550 m"?


Kind regards

Adrian Young
Senior Technical Support Engineer
Fluke Networks Technical Assistance Center

You can test short Cat 6A links, if you've installed the right connector. This video explains why.
Post #5204
Posted Monday, September 06, 2010 2:25 AM
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If the fibre manufacturer claims to support 10G SX to 550m but does not warrant the application then go to another fibre manufacturer. If the manufacturer has always stated "upto" 550m then you need to go to single mode and/or LX modules to garuntee the application to work.
Post #5211
Posted Tuesday, September 07, 2010 10:22 AM


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Heres a response I got from a manufacturer. Are they saying that ANSI/TIA-492-AAD is "Hype"? OM4 was rattified? Why are we sugesting singlemode over 300 if this standard came out? are there Long range multimode applications?

"You have to remember that 10GBase-SR stands for “short reach”.  I don’t know any SFP+ Manufacture that guarantees this type of signaling out to 550 meters.

The transmit power is typically -7 dBm and receiver sensitivity is typically -10 dBm.  Yes, loss of the cabling plant is critical.  However, as you reach the limitations of the short reach laser, differential modal dispersion is the biggest factor.

The spectral width of the VCSEL is only around .5 nanometers (+/- .15 nm) which means that it is directly proportional to the power levels to ensure DMD does not occur.  Sounds like the Specifier found out that 400 meters was where the two curves – power and DMD met.

They should be deploying 10GBase-LR over single mode if they needed guarantees beyond 300 meters.  Or, they should have received guarantees from their SFP+ Manufacturer that their laser will work out to 550 meter.  Don’t buy into the hype from cable Manufacturers like Corning.  That is why Specifiers are paid to do their homework.

Tough way to learn."

Post #5221
Posted Tuesday, September 07, 2010 1:15 PM
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We have the budget and the SM so we can move to it. I did ask the question to a representative of Corning engineering management about Cisco support for the 550 meter distance at a meeting and was told that Cisco was 'on-board' with the distance and that he skope with Cisco weekly. I do find it interesting that Commscope will warrant their fiber for the 10G application (waited 2 days while they tested the Cisco GBICs) but Corning has not offered to do the same after 5 weeks.
Post #5223
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