Reseach On Key Tecgnologies Of The All-optical Analog-to-digital Conversion With High Resolution

With the development of science and technology, we have entered the digital age. The digital technology has become the sign and direction of information-based society, whose application areas include electricity, magnetic, sound and optic, even bioscience. The great progress of digitization puts forward higher requirements at bandwidth and switching rate of analog-to-digital converter(ADC). In recent years, all-optical analog-to-digital conversion has attracted much attention, because it can overcome the physical limits of traditional electronic companion. However, how to achieve a high resolution for all-optical ADC is still a hot issue.In this thesis, we started with intensity-to-wavelength conversion based on soliton self-frequency shift(SSFS). We proposed a high resolution quantization scheme for all-optical ADC. Firstly, based on the propagation rules of femtosecond pulse in highly nonlinearly fibers(HNLFs), we analyzed the intensity-to-wavelength conversion of femtosecond pulse and spectral compression after SSFS, and simulated the quantization scheme applying highly nonlinear photonic crystal fibers(PCFs). We obtained that the amount of frequency shift was 150 nm and the spectral width after SSFS was compressed to 1.5nm. Secondly, we verified the highly quantization scheme experimentally by combining HNLF and PCF. We used a fiber laser with 20 MHz repetition rate as a light source. The pulse width and the center wavelength were 330 fs and 1550 nm, respectively. In the experiment, we realized the intensity-to-wavelength conversion of optical pulse and the amount of frequency shift was 150nm; applying two-stage compression method, spectral widths after SSFS(wavelength ranging from 1570 nm to 1700nm) were compressed less than 2nm and quantization resolution was 6 bits. In addition, we applied fiber lasers with high repetition rate(higher than 300MHz) to verify the quantization scheme and obtained the same results.At last, applying multistage spectral compression method, we proposed a new approach to optimize the quantization resolution. Using the theory of average soliton propagation in crystal fiber, we designed a fiber using SMF and HNLFs with different parameters to realize spectral compression after SSFS. We simulated the propagation of femtosecond pulse in this designed fiber and the results showed that spectral widths after SSFS were successfully compressed to less than 1.2 nm, which was of significance to realize high resolution for all-optical ADC.