Characteristics Of Multi-channel Hybrid Optical/electronic Analog-to-digital Converter System

As we all know, everyone’s life has been increasingly digitized andinformationized since the time has moved into the second decade of21st century. Onecan easily find out various digital terminal devices everywhere around our lives, andthis is all because of the rapid development and wide application of digital signalprocessing and storage technique. More complex and sophisticated signal processingsystems have been arisen and their application areas have also been spread out fromradars, missiles and satellite systems in military defense domain to wirelesscommunication, medical imaging and multi-media with fiber digital television inscience and technology and economy domain. One of the keys to the success of thesedomains is the development of analog-to-digital converter (ADC) which is a device thatconvert continuous-time analog signals to discrete-time and binary-coded form. Sincethe digital information age has come, the improvement speed of conventional electronicADCs is too much slower compared to that of digital signal processors (DSPs). Soelectronic ADCs have become the key bottleneck in high performance digital signalprocessing systems. Thus, the hybrid optical/electronic ADC that use opticalcomponents to improve the system performance has gradually attracted people’s interestand is considered a real potential technique.In this dissertation, two types of hybrid optical/electronic ADC system arediscussed. Firstly, multi-channel parallel time-interleaved ADC system based on OpticalTime Division Multiplexing (OTDM) technique is proposed. The principle of thesystem and the practical limits on the performance of the Effective Number of Bit(ENOB) are documented. Then a dual-channel experiment is accomplished. In theexperiment, a high accuracy variable optical delay line is used to precisely control thechannel delay time. We recorded the system’s recovered signal with four differentfrequency of the analog input radio-frequency signal, which are50MHz,100MHz,200MHz and250MHz, respectively. The ENOB of the system is obtained through IEEEstandard for digitizing waveform recorders in Matlab.Secondly, the principle of the Photonic Assisted Time-Stretched ADC system is stated. Also, the advantages of this system are documented when compared with OTDMbased system. Then the signal-to-noise ratio of the system is analyzed. The experimentincluded two respective stretch index,1.11and10, and the data is recovered byeliminating the carrier envelope. A method of combining the Photonic AssistedTime-Stretch and Optical Time Division Multiplexing to eliminate the envelope isproposed.Finally, a brief summary of this work is represented. The limits and problems thatexisted in the two types of system and useful suggestions that should be considered inthe next step of research are proposed.