Abstract

This paper introduces optical disks in acousto-optic spectrum analyzers. In 2-D time and space integrating acousto-optic folded spectrum analyzers, electronic reference signals are used in the temporal spectral processing. In order to obtain complete folded spectrums, these reference signals have to be of extremely high timebandwidth product, and require extremely fast serial readout rates. It is difficult to generate these signals using electronics, and so far, only incomplete folded spectrums have been obtained. We address the signal generation problem by combining the angular motion, high storage capacity, and parallel access capability of optical disks. The disk is introduced as an optical distributed local oscillator generator and a light sampling 1-D spatial light modulator. The distributed local oscillator architecture forms the basis of a continuous wave 1-D time integrating spectrum analyzer. The reference signals are stored as concentric channels on the disk surface. When the disk spins with a constant angular velocity, each circular channel acts as a modulating light source with a specific on/off frequency. This angular motion creates an array of temporal oscillators along the radial direction of the disk. When the input test signal frequency matches one of the disk channel temporal frequencies, a positive build-up of charge occurs on the time integrating detector, indicating a frequency match. A simple disk system is demonstrated in the laboratory. The disk can also be used in a 2-D time and space integrating architecture, where radial sections of the disk are used for storing the columns of a DFT matrix used for temporal spectrum analysis.

© 1990 Optical Society of America