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Optical/IP

Ten Gig Meeting Sparks Optical Flap

From Jay Hoge, Principal, Firestorm Ventures: I am, in general, a big fan of Light Reading. I must, however, take exception to this article. I was, until recently, a Marketing Director with JDS Uniphase, and have been attending IEEE 802.3ae meetings since last summer. I am also the clause editor for the serial PMDs.

The split at La Jolla had nothing to do with the system vendors prefering single mode installations, as your article states, but rather how many solutions for short haul multimode fiber installations would be supported. Everyone wants to support 10GB/s operation over MMF.

The two camps were the "3 PMD Camp," including most of the system vendors, and the "5 PMD Camp", including most of the VCSEL vendors and fiber manufacturers. Both camps fully support the two SMF PMD's. The argument arises over how to support MMF.

The 802.3ae Task Force adopted a set of goals over a year ago. Among these were a set of Reach Objectives. The objectives were to support 10GB/s operation:

  • 1) Over SMF at 10 Km.
  • 2) Over SMF at 40 Km.
  • 3) Over SMF at 2 km.
  • 4) Over MMF at 300 m (note that no particular MMF is specified).
  • 5) Over 160MHz/Km 62.5u MMF at 100m.

Both camps agree that objective 3 can be subsumed into Objective 1. They also agree that Objectives 1 & 2 can be met by the 1310 nm & 1550 nm PMD's which were approved overwhelmingly at La Jolla. The question is how to meet Objectives 4 & 5.

One proposal, backed by the system vendors in the 3PMD Camp, would be to adopt a 4 Channel WWDM at 1310 nm PMD, proposed by Agilent. This device works over both SMF and MMF and meets both Objectives 4 & 5. For MMF operation, it requires an offset patchcord, like that of 1000BASE-LX. The system vendors like this solution because it offers a single PMD solution for any MMF requirement. They further argue that economies of scale resulting from having a single device (versus 3) covering the MMF application space will minimize the cost differential between the PMD's. Last, they suggest that very short reach (less than 100m)intra system links are outside the scope of Ethernet and can be implemented most cost effectively by using proprietary, vendor specific solutions.

The 5PMD Camp wants to include 850nm solutions in the standard; both serial and WWDM. They maintain that, since ~90% of 10GB/s links will be less than 300m, that the market will support 3 PMD types, each optimized for a more specific application. The 850nm WWDM would cover existing 62.5u installation to 150m plus up to 550m over new extended BW MMF. The serial 850nm would cover links to 30m over existing fiber and to 300m over the new fiber. The 1310nm WWDM would cover links to 300m over existing fiber. The 5PMD Camp believes that this will result in lower costs for each application space.

In reality, the System Vendors want to support as few PMD as possible because of logistical concerns and concerns that their customers will get confused by having to many overlapping options.

The VCSEL manufacturers plus the manufacturers of high BW MMF (Corning & Lucent) will be left with nothing to sell unless the addition 2 PMD's are adopted. This group blocked the inclusion of the 1310 WWDM, which they support as part of a set, rather than risk being left out in the cold. At present, the 2 groups are still deadlocked.

Given all of this, your report totally missed the boat.

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