Ultra-Wide Bandwidth and High Resolution Photonic Analog to Digital and Digital to Analog Converters

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Title: Ultra-Wide Bandwidth and High Resolution Photonic Analog to Digital and Digital to Analog Converters Abstract: Nontechnical: In today's technology driven world digital electronics and digital systems are ubiquitous. Their hardware and software are the essence of everything that touches our lives many times a day. Real life systems generate analog signals which need to be converted into digital form before they can be handled by digital technology. This is done using an Analog to Digital Converter (ADC). Almost all the existing ADCs are electronic. There are many types of ADCs with different resolution and speed. As the resolution of an ADC increases its fidelity improves significantly. Although electronic ADCs provide very high resolution they do not operate very fast. This proposal aims to develop a high speed ADC photonics technology which operates without sacrificing resolution. The same technology is used in fiber optic communication systems, is well understood and its parts are commercially available. However, a few special components need to be developed before the entire ADC can be demonstrated. This project will develop and fabricate such components and demonstrate a proof of concept operation of the ADC. Such high resolution and fast ADC will improve many applications, such as instrumentation, radar, optical fiber communication and wide bandwidth signal distribution. Technical: This proposal introduces a new and novel approach for a photonic ADC that can deliver eight bits of resolution at bandwidths of 20 GHz and higher. The proposed basic ADC resembles very much to a wavelength division multiplexed (WDM) fiber optic digital link without the fiber. It consists of a multi wavelength source, a quantizer, a sampler, a demultiplexer and receivers. The quantizer is a high-speed Mach-Zehnder modulator (MZM) with an intentional path length difference between its arms. The sampling is done after the quantizer. The sampled outputs at different wavelengths generate a code corresponding to the digitized version of the analog signal applied to the quantizer. This basic idea is improved upon using a subranging approach to improve the number of bits while reducing the component count. This requires a digital to analog converter (DAC), which can be made out of a single MZM. The practical operation of such an ADC requires low-voltage and high-speed MZM for quantizer and DAC. The required ultra-low jitter sampling can also be performed using such MZMs. The focus of this proposal is to develop these critical components, namely the quantizer, DAC and the sampler, and make a proof of concept demonstration of a scaled down version of the ADC.