Improve The Technology Of The Microwave Signal Optical Adc Conversion Accuracy

In this paper, the concept of the electro-optical analog-to-digital converter (ADC) was described by firstly introduced the principle and the progress of the electronic ADC. The advantages of the electro-optical ADC were also introduced, as well as the significances and the prospects of the electro-optical ADC. Four main techniques for realizing electro-optic ADCs were briefly discussed in this thesis, e.g., phase-encoded optical sampling based technique, OTDM (optical time division multiplexing) based technique, OWDM (optical wavelength division multiplexing) based technique, and photonic time stretched based technique. After analyzing and comparing these four techniques, we summarize the processes and the developing trends of the electro-optic ADC.In this thesis, the phase-encoded optical sampling based electro-optic ADC technique was investigated. Then a novel technique that was capable of realizing high-precision ADC, by cascading Mach-Zehnder modulators was proposed. Theoretical analysis was carried out, and the functional characteristics of the electro-optic ADC were theoretically analyzed. The new scheme was compared with the classic electro-optic ADC scheme, Taylor's scheme, in terms of modulation frequency and bandwidth, and summarizes the advantages and disadvantages of the both schemes.In order to build up a five bit electro-optical ADC, a cascaded, doubling voltage and OTDM schemes were designed. The functional characteristics of these schemes, as well as the advantages and feasibilities were analyzed. For the doubling voltage scheme, the difficulties of the decreased amplitude of the output signal were analyzed. For the cascaded scheme, the five outputs of the five bit electro-optical ADC were simulated. For the OTDM scheme, four kinds of noises in the system, and their influences on the effective number of bit (ENOB) of the system were analyzed.Finally, a two bit electro-optic ADC was built up experimentally. The modulation curves of the Mach-Zehnder modulators were measured and the outputs of the Mach-Zehnder modulators were analyzed. Then a new method for doubling the frequency was proposed. The experimental investigation on the electro-optic ADC with two cascaded Mach-Zehnder modulators was also conducted. The experimental results clearly demonstrated the feasibility of the proposed scheme in this thesis.