Abstract

As the bandwidth of high-frequency optical detectors reaches beyond 20 GHz, it becomes increasingly difficult to measure the frequency response of these devices. Swept frequency measurements require either an intensity modulated laser or an external modulator both with a known response greater than that of the detector¹; time domain measurements require picosecond optical pulses and are easily affected by sampling and computational errors²; and the beat frequency method requires two narrow linewidth (usually external cavity) semiconductor lasers with excellent temperature control and no optical feedback.³ These three techniques can be experimentally difficult or are limited in frequency response. We present a new method, the FM sideband technique, for measuring detector frequency response. FM sidebands are generated in a directly modulated semiconductor laser and then converted to intensity modulation using an interferometer. The detector response is obtained by measuring the ratio of the various sidebands. This technique does not require a flat, or even a known, laser frequency response and, most important, measures the detector response well above the modulation frequency applied to the laser.

© 1987 Optical Society of America