Leaky waveguide deflector for 40 GS/s and 6 bits all-optical analog-to-digital converters

Abstract

Analog-to-digital converters (ADC) are an important part of realizing direct digital receivers in future communication systems, where broad bandwidth, high effective number of bits, and low DC power consumption are an important requirement of achieving it at microwave frequencies. Due to a number of physical limitations of electrical ADC, design of an all-optical analog-to-digital converter (AOADC) is pursued and presented here based on highly stable mode-locked laser based clock signal pulses for optical sampling, and a combination of leaky waveguide optical deflector using electro-optical (EO) polymers and stationary optical windows followed with high-speed photodetectors as optical quantizer. The reported principle of the AOADC is to convert a broadband RF signal into a spatially sampled light using optical deflection angle variation before quantizing it using either binary or Gray coded optical windows. The design and modeling of an AOADC working up to 20 GHz RF frequencies (with Nyquist sampling rate of over 40 GS/s) and for providing a resolution of better than 6 bits with under 4W of power consumption. Performance is currently limited by both optical and microwave attenuation in the available EO polymers.