Optical error diffusion coding for analog-to-digital conversion

Abstract

We propose an alternative to classical interferometric optical analog-to-digital conversion based on oversampling and error diffusion coding techniques that employs optical threshold and arithmetic operators, and describe a noninterferometric realization using multiple quantum well SEED devices, photodetectors, common optical components, and a novel approach to achieve noninterferometric optical subtraction. The analog input signal is first optically sampled at a rate much greater than the Nyquist frequency and is then quantized by a modulator that incorporates one-bit quantizers and linear filters in a negative feedback architecture for the purpose of reducing the in-band quantization noise. The output of the modulator is subsequently processed by a digital decimation filter that removes the out-of-band noise and generates a high resolution digital approximation to the analog input signal at the signal’s Nyquist rate. In the proposed realization, quantization is performed by optically bistable S-SEEDs while noninterferometric optical subtraction is accomplished by SEEDs using a technique known as optical level shifting.