40-Gbps and 100-Gbps Ethernet coming into focus
By Martin Rowe, Senior Technical Editor -- Test & Measurement World, 3/1/2009 2:00:00 AM
Today's 10-Gbps optical and electrical links are running out of steam. To address the problem, engineers are working on IEEE P802.3ba, a standard that will define an architecture for 40-Gbps and 100-Gbps Ethernet (Ref. 1).
Although IEEE P802.3ba is still in the works, engineers around the world are beginning to develop products for the high-speed links, and those products will need testing. While much of the testing for IEEE P802.3ba will leverage 10-Gbps technology, some tests will require new equipment and techniques.
| To learn more about 40-Gbps and 100-Gbps testing, read the article “40-Gbps and 100-Gbps Ethernet will bring new test challenges.” There, you'll find diagrams of the IEEE P802.3ba sublayer architecture and links to several relevant technical papers. In addition, engineers from Agilent Technologies, Anritsu, Force10 Networks, Spirent Communications, and the University of New Hampshire Interoperability Lab share their insights on this emerging technology. |
IEEE P802.3ba defines an architecture that can support 40-Gbps and 100-Gbps transmission over single-mode and multimode fibers. The key to the architecture is its flexibility. It uses multiple lanes to carry signals on a single fiber or multiple fibers over several specified distances (table). The standard also defines an architecture that supports copper connections over cables and backplanes.
Both 40-Gbps and 100-Gbps implementations can use existing 10-Gbps fiber PHYs (physical links). In the future, the same architecture will support 100-Gbps links using four 25-Gbps lanes.
For 40-Gbps links, the IEEE P802.3ba protocol sublayers create four 10-Gbps lanes, while for 100 Gbps, the standard defines sublayers for ten 10-Gbps lanes. Because these implementations will use 10-Gbps lanes, you can use existing optical test equipment such as oscilloscopes, spectrum analyzers, power meters, and BER (bit-error rate) testers to test individual lanes.
IEEE P802.3ba also defines 100-Gbps transmission using four 25-Gbps lanes, but those implementations will take a few more years to develop. When they do, test equipment will need to support those data rates. In fact, some new equipment has already begun to appear.
 Figure 1. Ixia used its 100 GE Development Accelerator System to demonstrate a 100-Gbps data link. Courtesy of Ixia. |
Ixia has used its 100 GE Development Accelerator System (Figure 1) together with equipment from Avago Technologies and Infinera to prove that multilane, 100-Gbps optical transmission is possible (Ref. 2). The demonstration, which took place in June 2008 in Las Vegas, used the Ixia system to generate 100 Gbps of Ethernet traffic.
Earlier this year, Anritsu introduced cards for its MP1800A signal analyzer that can generate modulated signals at rates up to 28 Gbps. That's enough to test future implementations of 100-Gbps Ethernet running on four 25-Gbps lanes.
What's still needed?
Although existing 10-Gbps Ethernet test equipment will get things started, IEEE P802.3ba will likely give rise to new test equipment. For example, a four-lane or 10-lane BER tester will reduce test time over using a single-channel instrument.
Protocol analyzers that decode the 66-bit data blocks into Ethernet packets will also help. In addition, testers that inject unexpected alignment blocks and remove expected alignment blocks will help you test your network link under stressed conditions.
The 25-Gbps data rate will require manufacturers to develop electrical and optical components capable of reaching that speed, and test equipment will need to keep up. For example, real-time oscilloscopes will need even more bandwidth than the current 30-GHz state-of-the-art.
You'll also need BER testers, clock-recovery units, optical spectrum analyzers, and other equipment capable of working with signals at those speeds and with multiple lanes of traffic. Stressed-eye testers will let you test optical receivers for the added signal distortion that will occur at the higher bit rate.
To learn more about 40-Gbps and 100-Gbps testing, read the article “40-Gbps and 100-Gbps Ethernet will bring new test challenges.” There, you'll find diagrams of the IEEE P802.3ba sublayer architecture and links to several relevant technical papers. In addition, engineers from Agilent Technologies, Anritsu, Force10 Networks, Spirent Communications, and the University of New Hampshire Interoperability Lab share their insights on this emerging technology.
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