January 2008

EEEL improves high-speed waveform calibrations

Researchers in EEEL and ITL have developed and validated a covariance-based uncertainty analysis for NIST's electro-optic sampling (EOS) system, which provides calibrated results for both time- and frequency-domain electronic instruments. With this EOS system, NIST presently offers photodiode calibrations to 110 GHz. The electrical response of the photodiodes is determined in the frequency domain, and the measured spectrum and phase of the photodiode's electrical output makes the NIST-calibrated photodiodes ideal for calibrating a variety of other electrical frequency-domain instruments, such as lightwave component analyzers and large-signal analyzers. The covariance-based uncertainty analysis was developed this year by Dylan Williams, Arek Lewandowski, Tracy Clement, Paul Hale, and Darryl Keenan of EEEL and Jack Wang and Andrew Dienstfrey from ITL. This approach creates a framework for maintaining the correlations in the uncertainties of the frequency-domain impedance measurements and mismatch corrections used in the electro-optic sampling system so that uncertainties in the time-domain can also be determined. Now NIST photodiodes can be used to calibrate both temporal and frequency-domain electronic instruments, making the calibrated photodiodes useful to a wider range of customers and applications than ever before. Perhaps the most important new application of the photodiodes is for the calibration of oscilloscopes and other high-speed temporal waveform measurement systems used in the digital electronics, wireless communications, and fiber optic communications industries. The work is described in D. F. Williams, A. Lewandowski, T. S. Clement, C. M. Wang, P. D. Hale, J. M. Morgan, D. Keenan, and A. Dienstfrey, "Covariance-Based Uncertainty Analysis of the NIST Electro-optic Sampling System," IEEE Trans. Microwave Theory Tech., vol. 54, no. 1, pp. 481-491, Jan. 2006.

For more information contact: Michael H. Kelley, phone 303-497-4736