Testing LANs optically to the Gigabit Ethernet standard

Gigabit Ethernet is a third-generation technology that builds on both the original Ethernet, with its 10-Mb/s data rate, and the second-generation, 100-Mb/s Fast Ethernet. Moving data at 1 Gb/s, Gigabit Ethernet meets the demands of emerging applications like desktop videoconferencing, high-resolution graphics, and high-speed networking in general trough the use of optical fibre links. High-speed optical communications opens up a tremendous learning opportunity for many LAN designers, introducing a host of new testing issues and techniques. For those engineers accustomed to working with lower-speed electrical transmission, the different equipment and measurements required for characterizing optical transmission may at first seem intimidating. But examined step by step, they are really not all that difficult to master. A LAN designer needs nothing more than an optical spectrum analyzer and an advanced communications oscilloscope-equipped with an optical-to-electrical converter-to ensure that the light source, the transmitter, and the system comply with the optical portions of the Gigabit Ethernet standard. To be sure, additional instruments and measurements will help refine a LAN design. But with just the optical spectrum analyser, the designer can determine that the light source's spectrum is sufficiently narrow and powerful, and with the oscilloscope, he or she can examine the data signal's potential for error from noise, jitter and attenuation.