Optical data storage using PPM and PWM.

A method for analyzing the binary signal produced by pulse position modulation (PPM) and pulse width modulation (PWM) is presented. The results are used to study the conversion of analog signals into binary waveforms. The Fourier transform is a complex analog signal. A method of using a combination of PPM and PWM to make binary Fourier transform holograms of digital data is presented. Two optical methods for reading out the optically recorded PPM signals are discussed. Experimental results demonstrate the different aspects of these modulation techniques for optical storage.