High-quality waveforms and analysis for DWDM, high-speed SONET/SDH and optical transmission applications are claimed for D3186/D3286 BERT, a high-performance bit error rate tester for the telecomm public network industry. The instrument characterizes and analyzes high-speed digital network devices, such as ICs and high-speed optical components, as well as dense-wavelength division multiplexing and high-speed SONET/SDH transmission systems. Designers can use the unit to evaluate and analyze high-speed communication systems, including logic devices, multiplexers, repeaters, and digital transmission systems processing data at rates of up to 12 Gbits/s.