Design and construction of an optoacoustic signal processor

The design and fabrication of a prototype optoacoustic signal processor are described. This system uses a fused silica, folded acoustic path, 340-micro sec. delay line, and operates at a 30-MHz center frequency. The light source is a 200-mW GaAs LED, which is located at the focus of a 15-cm diam, f/0.33 reflecting paraboloid. The modulated light is detected by a p-i-n diode at the focus of a matching paraboloid. The entire system is housed in a chassis whose dimensions are 30 x 20 x 18 cm(3). The system performs autocorrelation of long coded sequences in which the reference is an active acoustic replica.