Electronic Design

Wired Networking With Ethernet

Wireless is certainly getting all of the attention and much of the business today, but we're still a nation of interconnecting cables. How many times over has the world been wired now? There's electrical power, telephones, cable TV, long haul and metro networks, and LANs, with passive optical networks to the home soon being added to the mix. They won't go away and they won't be replaced by wireless in most cases. We will continue to see Ethernet dominate this space due to its breadth of coverage and range of products. It's practical and affordable, and development continues.

The most recent standards work concerns a 10-Gbit/s specification over twisted pair. I'm not making this up. Trying to get a data rate that high over a cable would seem to defy physics. Certainly, engineers of yesteryear would be tempted to laugh out loud. But with today's technology, it can happen.

Several chip companies already demonstrated that rate over 30 meters of CAT6 cable using multilevel PAM and some amazing equalization, echo canceling, and filtering. The proposed IEEE 802.3an standard seeks a speed of 10 Gbits/s over 100 meters of CAT6 twisted-pair cable. By using 12-level PAM and a raw data rate of 800 Mbits/s over all four pairs, 10-Gbit/s full duplex is possible.

This technology would target data centers that must link many high-speed servers, routers, and other fast networking. It's significantly cheaper than 10-Gbit/s optical solutions, and the installed wiring can be used in most cases. IEEE 802.3an could replace the expensive multisource-agreement (MSA) optical modules now being used in this application. Look for standard ratification in late 2005 and real products to follow on its heels-if not some pre-standard chips before that.

Ethernet has already captured the industrial networking title. While it still works with other industrial monitoring and control protocols, it has grown in usage and will continue that momentum. The older 10/100 versions of Ethernet are still viable for most industrial applications, but they aspire to have 1- and 10-Gbit/s versions. The key to industrial applications is non-deterministic, real-time response. Already, wireless Ethernet is penetrating this tough space as it solves the environmental and security issues of industrial control.

Another Ethernet development is Ethernet in the First Mile (EFM). The IEEE 802.3ah standard was ratified last year and is ready to roll. This standard provides a way to use Ethernet for fiber-to-the-home (FFTH) connections. Employing single-mode fiber, it can achieve a data rate of 1 Gbits/s up to 20 km without intermediate repeaters or other electronics. It also supports a version that permits 10-Mbit/s full duplex on up to 750 feet of single twisted pair. Chips are available now, but competition from the ITU BPON standard-the ATM-based PON being adopted by most telecom carriers-may slow deployment. Yet it's a great option that will see some action here and certainly in Asia or Europe.

Where does Ethernet go from there? With 10-Gbit/s standards in place and several fiber-optic versions to chose from, in addition to the impending arrival of 10-Gbit/s short-range copper, surely developers will turn their sights on the next speed increase. So far, Ethernet speeds have always increased in decade increments. At this time, though, 100-Gbit/s Ethernet appears unrealistic. What does seem possible is the creation of a DWDM version. Alternately, a 40-Gbit/s version may be in the future as the fiber-optic field delivers components and systems for the forthcoming 40-Gbit/s Sonet (OC-768). All of that development will obviously take more time. But who needs this right now anyway?

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