A resolution-improvement scheme of a phase-shifted analog-to-digital converter (ADC) is presented and experimentally demonstrated. To improve resolution via the scheme, the optical output of each quantization channel is quantized by an electrical ADC with multiple thresholds instead of a comparator. A 9.9-GHz sinusoidal analog signal is sampled and quantized using the proposed enhancement scheme. The effective number of bits of 4.31 and the spur-free dynamic range of 40.89 dB are obtained, thus indicating an improvement of 0.66 bits and 7.47 dB, respectively.

An optical frequency comb generation scheme using time-to-frequency conversion and optical fiber-loop modulation is proposed and demonstrated experimentally. Flat-top optical pulse train from an intensity modulator is injected into a fiber loop, which includes a phase modulator and an amplifier and is cyclically modulated by the phase modulator, to generate abundant optical comb lines. A total of 110 comb lines with 3-dB spectral power variation and 10-GHz frequency spacing are obtained. The proposed scheme is relatively simple and uses only one intensity modulator and one phase modulator.

A 5-bit photonic analog-to-digital conversion under a sampling rate of 10 Gs/s is experimentally demonstrated. In the experiment, the birefringence walk-off in the scheme is compensated, and 16 high-extinction ratio optical transfer functions with different phase shifts are obtained. A 1-GHz sinusoidal analog signal is sampled and quantized by optical processing, and the effective number of bits obtained is 4.17.

提出并实验验证了一种基于光频梳的超短光脉冲的产生方法。使用强度调制器和相位调制器级联直接调制直流激光得到了29条顶部功率变化小于1.5 dB的光频梳。利用单模光纤色散将光频梳整形成重复频率为10 GHz，脉宽为2.68 ps 的光脉冲。并成功用于对1~4 GHz信号采样，系统的信噪比可达33.83 dB，等效于5.33 bit的有效比特数。

A scheme of multi-wavelength pulse generator using optical frequency comb and arrayed waveguide grating (AWG) is proposed and experimentally demonstrated. A flattop optical frequency comb is shaped into multiple narrowband Gaussian spectra by using an AWG which contains a number of Gaussian channels, and then multi-wavelength optical pulses are achieved. In the experiment, six wavelength pulses with full width at half-maximum (FWHM) of 14.6 ps at 10 GHz are obtained, and two wavelength-interleaved pulse trains at 20 GHz and four wavelength-interleaved pulse trains at 40 GHz are demonstrated by using the multi-wavelength optical pulses. This scheme has flexibility because the pulse width, the repetition rate, and time-interval can be readily controlled.

提出了一种基于锁模脉冲源和高速光开关的时分抽样模数(A/D)转换系统。使用高重复频率、窄脉宽的锁模脉冲串对射频信号进行抽样，利用高速光开关进行时分复用，将高采样率的信号转换为并行的多路低采样率信号，以适应现有的电模数转换器进行量化和编码，并且通过改变光开关的频率，可以灵活地改变解复用后每路信号的频率。系统的优点在于可扩展性高，只需一个锁模脉冲源。使用10 GHz重复频率的锁模脉冲和1.25 GHz的高速光开关验证了系统方案的可行性。利用实验中得到的采样点可以较好地恢复出时域信号，并且得到了各个频率的频谱图。其信噪比可达32.02 dB，等效于5.03 bit的有效比特数。