50-GHz-bandwidth, sequential-sampling DSOs test 10-Gbps network components
-- EDN, January 20, 2000
Of all digital scopes, only sequential equivalent-time-sampling instruments offer bandwidths as high as 50 GHz. This capability makes such scopes the instruments of choice in applications of rapidly growing importance-electro-optics, for example. Yet, because these scopes work only with repetitive waveforms and take just one sample during each input-signal iteration, they lack the quick response of lower bandwidth, real-time- and random-sampling instruments. This characteristic limits sequential-sampling scopes largely to applications that need extraordinary bandwidth.
To address the requirements of engineers who develop components for networks that transmit data at speeds as high as 10 Gbps, Tektronix has introduced a family of sequential-sampling scopes (Picture). These units replace Tek's venerable CSA800 and 11800 series. Because of their low measurement uncertainty, the new CSA8000 communications signal analyzer and TDS8000 sampling oscilloscope can extract signals from noise where other instruments fail. The low uncertainty results from low trigger jitter (typically less than 1 psec short term), low timebase instability (less than 0.1 ppm), high optical sensitivity (using optical-sampling heads), and high SNR.
The new scopes provide a Windows 98 user interface via standard PC hardware hidden within their benchtop enclosures. Each scope accommodates four sampling modules. Five modules provide a variety of electrical interfaces. Three more optical-sampling modules support the OC-12/STM4, OC-48/STM16, OC-192/STM64, Gigabit Ethernet, and Fibre Channel standards. Each optical module tests compliance with several communications standards. Integrated optical-reference receivers, a power meter, and clock-recovery circuits perform functions that, with earlier instruments, required additional cabling and accessories.
The CSA8000 and TDS-8000 each cost $19,500. Prices for electrical-sampling modules begin at $10,500 each; prices for optical-sampling modules begin at $17,100 each.
Tektronix Inc, 1-800-426-2200, www.tektronix.com.
-by Dan Strassberg
