RF test methods for balanced receivers for swept source optical coherence tomography

Abstract

Optical coherence tomography (OCT) has risen as a clinical standard of diagnosis and management of ocular diseases since its development in 1991 by the MIT group and the collaborators. Since current cutting-edge OCT technology based on frequency-swept lasers has achieved scanning rate over 1,000,000 axial scans per second, the imaging speed is limited by the detection and analog-to-digital conversion stages. In order to match the rapid advancement of OCT imaging speed, a variety of balanced photoreceivers have been developed. A low-cost setup for systematic performance evaluation of the receivers in radio frequency (RF) range up to 2GHz is presented. The test procedure, including measurements of gain, bandwidth, and harmonic distortion, is automated by National Instruments Virtual Instrument Software Architecture (NI-VISA) programming using USB and GPIB interface. Since the test equipment has parasitic response, quasi-calibration using a fast biased detector is necessary. Detailed description of the equipment and the test protocol is included as well as the performance comparison of the available receiver products and prototypes.