Nist researchers report special test of high-speed photoreceiver to 110 GHz. (General Developments).

NIST researchers have provided the first special test of the modulation response magnitude and phase of a commercially available photoreceiver to 110 GHz. High-speed photoreceivers are commonly used in fiber optic test equipment and communications systems operating at bit rates up to 40 Gbit/s. Measurement of both the magnitude and phase response of a photoreceiver over a frequency range much larger than the receiver s bandwidth is necessary for accurately modeling its response in the time-domain, thus providing critical information for digital communications systems. Prior to this work, calibration of the magnitude response above 50 GHz was not available, and calibration of the phase response was not available at any frequency.

The NIST researchers developed an electro-optic sampling system to perform the measurements. The system uses the electro-optic effect to sample highspeed electrical waveforms on a coplanar waveguide with ultrashort laser pulses. The researchers used standard microwave techniques to calibrate the response of the photoreceiver at its 1 mm coaxial electrical port, which was physically removed from the sampling plane on the coplanar waveguide where the waveforms were measured.

Using knowledge of the fundamental physics of the electro-optic sampling system, the NIST researchers have determined a preliminary uncertainty analysis of the system. The analysis showed typical expanded uncertainties (95 % confidence) less than 30 for phase and 0.4 dB for normalized magnitude. They checked the measurements and uncertainty analysis by comparing the results to the magnitude measured by a heterodyne method up to 50 GHz; the agreement was well within the combined uncertainty of the two measurement systems.

CONTACT: Paul Hale, [phone]; [e-mail] or Dylan Williams, [phone]; [e-mail].