Phase-Shifted Optical Quantization And All Optical Digital-to-Analog Conversion

Photonic analog-to-digital (ADC) and digital-to-analog conversion (DAC) are promising technologies to improve the performance of signal processing, due to its high-speed sampling, ultra-low time jitter and broad bandwidth.In this thesis, the optical quantization receiver in phase-shifted quantization system is theoretically analyzed and experimentally studied. Firstly, the influences induced by the various quantization noises are analyzed. In order to eliminate the threshold level error, a novel adaptive thresholding scheme is proposed, which is based on optical differential signal detection. According to the principle of quantization coding, the software method for correcting quantization errors is also studied. Moreover, an all-optical phase-shifted quantization system with balanced detection threshold scheme is experimentally demonstrated, achieving a sampling rate of 10GS/s and spur-free dynamic range (SFDR) of 24.2dB. Compared with the single-ended scheme, the SFDR has an improvement of 4.5 dB.In order to resolve the issues of the half-wave voltage and walk-off between polarizations in LiNbO3 electro-optic modulator, an improved phase-shifted quantization scheme is proposed, in which a novel electro-optic polarization modulator is used. In the experiment, a 9.9GHz and 10.1GHz signal is sampled and quantized by a 10GS/s, 4-bit resolution all-optical ADC, obtaining SFDR of 31.86dB and 33.49dB, respectively. According to the experimental results, the distortion induced by the chirp of sampling pulse and walk-off between polarizations is analyzed. A time- and wavelength-interleaved optical pulse source is realized to enhance the sampling rate of ADC. Using this technology, a 40GS/s multiplexed optical pulse train is obtained and used in all-optical ADC. Furthermore, a novel phase-shifted optical quantization scheme is presented, which utilizes an unbalanced Mach-Zehnder modulator (MZM) and optical filter array.In the last section of this thesis, all-optical digital-to-analog conversion technology is studied. A novel photonic digital-to-analog converter (PDAC) scheme based on summing of serial weighted multi-wavelength pulses is presented and experimentally demonstrated. Regardless of the resolution, this scheme only requires one electro-optic modulator. In the experiment, a 3-bit PDAC with a sample rate of 2.5 Gb/s and 10Gb/s is realized, respectively. This simple and compact setup could reduce the system complexity and avoid the synchronization of multiple modulators.