Research And Realization Of High Repetition Rate Multi-wavelength Optical Sampling Technics

Analog-to-digital conversion (ADC) is a fundamental technology for information processing. It plays an important role in both communications and non-communication areas. Limited by "electronic bottleneck", the highest sampling rate of a commercial single-chip electronic ADC is about 2 Gs/s. Higher analog to digital conversion speed is mostly achieved through parallel processing by using several low speed electronic ADC (sigma-delta circuit), whose cost is very high. Since the 1970s, the concept of optical sampling is proposed by S. Wright and others and the technology has attracted a lot of attention. There are many realization methods proposed, such as optical interferometer, optical-assisted electronic sampling. However, the practically applicable method did not become feasible until the 1990s as the development and mature of the optical communication technologies and devices. The optical ADC employing WDM (Wavelength Division Multiplexing) and OTDM (Optical Time Division Multiplexing) technologies can greatly improve the sampling rate of the system with flexibility. Also the bandwidth of the optical sampling systems can be improved due to the wide bandwidth feature of opto-electronic devices.In this thesis, we mainly study the multi-wavelength high-speed optical sampling system. Based on the analysis of current technologies, related opto-electronic devices, and the foregoing work of our lab, we investigated theoretically and experimentally the impact of every part on system performance of sampling and quantization followed. We proposed measures to increase the delay precision of the fiber delay lines and to decrease the fiber dispersion. Such measures significantly increase the sampling rate of the system.The performance of 3?3 coupler based OTDM is analyzed theoretically and experimentally. In order to improve the power uniformity and the precision of the fiber delay lines, we proposed and implemented OTDM based on broadband high-precision 2?2 couplers. The general scheme to realize the fiber delay lines of OTDM is presented. We realized 64? and 128? OTDMs which increase the repetition rate of MLFL from 36.4MS/s to 2.3GS/s and 4.7GS/s, respectively. Experimental results were given.We successfully implemented a high precision tunable mechanical fiber stretcher, which can be used to adjust the delay of the fiber delay lines and hence improve the time precision of the WDM part. Using a commercial WDM device, we realized an 18 wavelength time and wavelength interweaved sampling clock. Combined with the OTDM, the rate of the sampling clock was increased to about 41.9G/s and 83.8G/s, respectively. The power uniformity between different channels of the WDM was also studied and method to solve the problem was proposed.The effect of dispersion on the fiber-based high-speed optical sampling system was analyzed. The dispersion-induced jitter in the WDM,OTDM and EDFA part, which affects the ENOB of the system, was calculated. Compensation method was proposed and experimentally verified. For the sampling gate realized by EOM, we analyzed the relationship between the polarization of the sampling clock and the bias voltage of the EOM. At last, we demonstrated the sampling of RF signals with different frequencies and preliminary results were presented.