下一代光接入网光梳状谱发生器研究

This project focus on the theory and key technology of optical comb generator used in next generation optical access network such as OFDM-PON and WDM-PON, including the analysis on the advantage and disadvantage of various optical comb generation methods, the theoretic analyses on flatness and stable of comb lines and their affection to modulation signals. Through the analysis on the transfer function of system link and the characteristics of modulator, the flat optimal conditions and operating parameters of the comb lines will be studied on the Re-circulating Frequency Shifter (RFS) optical comb generator. The signal to noise ratio (SNR) degradation of comb lines caused by optical amplifier noise, and the EVM degradation of loop-back modulated OFDM signal in upstream direction by comb line noise will be researched theoretically. The methods to improve the SNR and reduce the phase noise as well as the conditions on maintaining coherent in these comb lines to reduce the complexity of digital signal processing in coherent detection optical access network will also be investgated. By optimizing the structure of the optical comb generator to make the system miniaturization, and these will be applied to as the multi-wavelength light source used in the next generation optical access network. These researches will provide some key technologies and device supports to the development of the next generation ultra-high-speed optical access network.

本项目从原理上深入研究应用于OFDM-PON、WDM-PON等下一代光接入网的光梳状谱发生器，包括各种梳状谱产生方案的优劣分析，影响谱线平坦度、稳定性及噪声等指标的因数，及对调制信号影响的理论分析。通过对系统链路传递函数的分析及对调制器特性的分析，着重研究循环移频方法（RFS）产生的梳状谱平坦的最优条件及最佳工作参数；通过理论研究光放大器噪声对谱线信噪比的影响，及谱线噪声对上行光环回调制OFDM信号解调的影响；研究提高谱线信噪比、降低相位噪声的方法；研究保持谱线相干性的条件以降低相干解调接入网系统数字信号处理的复杂度；通过优化光梳状谱发生器的结构实现系统小型化，为我国下一代超高速光纤接入网技术的发展提供关键技术及器件支持。

光梳状谱发生器是多波长光源的一种低成本实现方法，可以为OFDM-PON、WDM-PON等下一代光接入网提供中心化的梳状光源。本项目对多种结构的光梳状谱发生器进行了理论、仿真和实验研究，重点研究了基于循环移频方法（RFS）的光梳状谱发生器的相关理论及实现。研究了影响RFS方案梳状谱平坦性的多种因数，获得了最优条件及最佳工作参数；研究了光放大器噪声对谱线信噪比的影响；研究了基于梳状光源的反射式调制器RSOA相关理论，包括啁啾、动态调制特性等。项目研制了RFS方案光梳状谱发生器样机及级联IM-IM光梳状谱发生器样机，采用全保偏环路实现了模块化RFS光梳状谱发生器,获得了间隔为12.5GHz的27根稳定相干谱线输出。进行了基于中心化梳状光源的OFDM-PON上行环回调制实验，采用RSOA无色调制器实现了实时光OFDM传输；进行了基于中心化梳状光源的相干光OFDM传输实验，将光接收灵敏度提高了10dB以上。以上工作为下一代高速光纤接入网技术的发展提供了关键技术及光器件支持。