The Research Of Photonic Time-stretched Analog-to-digital Conversion Technology

Ultra-wide-band analog-to-digital (A/D) conversion is one of the most critical problems faced in communication, instrumentation, and radar systems. Photonic analog-to-digital has a lot of permits, such as high sampling rate, low jitter and ultra-narrow pulse, so it assumed to be the most potential technology.This paper presents a comprehensive analysis of the photonic time stretched analog-to-digital converter. Firstly, we demonstrate the principle of pulse "propagation in the dispersive fiber, then we make a fundamental-physics analysis about the analog-to-digital technology based on photonic time-stretched and the implication of time dilation on the signal-to-noise ratio. After that, we introduce and contrast much different architecture with different optical instruments, for example:Fiber Bragg grating, Arrayed Waveguide Grating (AWG) and so on.Secondly, a detailed mathematical description of the time-stretch process is constructed. It elucidates the influence of linear and nonlinear optical dispersion on the fidelity of the electrical signal in the double-side-band (DSB) and single-side-band (SSB) modulation systems. Because of the time aperture and the signal bandwidth's interaction, the time-bandwidth product (TBP) is used as a figure-of-merit. The performances of optical DSB and SSB intensity modulation are then compared, and optical SSB intensity modulation is identified as a potential solution to extend the system's time-bandwidth product.Thirdly, we improve the of time stretch structure through using Fiber Bragg grating instead of large bandwidth, which can decrease shaking of the deflection spectrum. With the new structure, we simulate the time-stretched system; it can stretch a lps Gauss pulse to800ps, with very low loss and nonlinear effects. The other merit is its very small volume. At the last, we simulate and demonstrate that the max frequency of input signal could reach about500GHz. There are several methods can be used to improve the sampling rates.Finally, it's the summation of the work. Some limitations of time stretched A/D conversion have been proposed, which give useful information for further research.