A novel digital PPM receiver using an acoustooptic deflector

A novel receiver for optical digital PPM signals using an acoustooptic deflector (AOD) is presented. The error performance of this receiver in the presence of AWGN is the same as that in conventional digital PPM receivers. However, the presented receiver saves the hardware complexity encountered in conventional receivers, especially for large number of time slots. In digital PPM, larger number of slots is required in order to reduce the power requirements. The presented receiver may require no slot recovery and block or frame recovery can be achieved at the expense of very small reduction in transmission efficiency. The AO PPM receiver also provides less interference from neighboring symbols, which results in improved error performance. The intersymbol interference can be reduced using pulse shaping or increasing the spatial separation between pulses. Commercially available AODs can demodulate digital PPM signals with number of slots M as large as one thousand. The geometry, design, and operation of an AO DPPM receiver is introduced, error performance is discussed, and interference analysis is presented. Computer simulation for an AO DPPM receiver with M=128 is presented and results are shown.