基于受激布里渊散射增强效应的超高分辨率光谱分析方法及其应用

Characteristics of optical spectra is one of the most important parameters to evaluate the optical communication systems and the optical devices. Analyzing the optical spectra with ultra-high resolution may reveal more inherent laws in them. And optical filtering components with narrow passband and large isolation play the key role in the acquisition of ultra-high resolution optical spectra. Conventional diffractive gratings have a wavelength resolution on the order of 1 GHz, which cannot meet the increasing demand. An novel active optical filter (AOF) utilizing enhanced stimulated Brillouin scattering (SBS) in high nonlinear fiber is proposed. It can be used to extract the fine spectral components of the optical signal under test, and features high wavelength resolution and wide tuning range. Frequency response of the SBS-AOF under a time-variable pumping wavelength will be studied. Subsequently the corresponding theoretical model for this optical spectrum analysis method can be derived. And the trade-off between fiber design and spectral analysis ability should also be considered comprehensively. The machenisms of noise accumulation and error propagation in the measurement system will be investigated. Meanwhile, the limitations caused by them and the approaches to improve the system performance will be discussed. An experimental setup with a spectral resolution of about 10 MHz and a dynamic range of more than 60 dB will be built to verify the feasibility of the proposed method. Therefore new phenomenon and new laws may be discovered via this setup. The research achievements can offer an effective way to obtain the optical spectra with ultra-high resolution, large dynamic range and high-accuracy.

光谱特征是评价光通信系统与光器件性能的重要参量之一。对光谱进行超高分辨率分析，有望得到更多系统与器件内在变化规律。带宽窄、隔离度大的光学滤波元件是获得超高分辨率光谱的关键。常规衍射光栅对波长分辨能力为1GHz量级，难以满足新要求。本项目创新性提出利用高非线性光纤中经增强的受激布里渊散射（SBS）效应构建一种有源光学滤波器（AOF），以实现对被测信号光谱成分的精细提取，具有波长分辨率高、调谐范围大的优点。项目将从研究泵浦光波长时变条件下SBS-AOF频率响应特性出发，建立相应光谱分析理论模型；解决高非线性光纤设计与光谱分析能力间的平衡问题；探索光谱测量中的噪声累积和误差传递机制，分析制约因素，寻求改善方法；搭建分辨率为10MHz量级、动态范围大于60dB的超高分辨率光谱分析实验演示装置，发现新现象，揭示新规律。本项目成果将为超高分辨率、大动态范围、高精度光谱测量提供有效途径。

光谱特征是评价光通信系统与光器件性能的重要参量之一。对光谱进行超高分辨率分析，有望得到更多系统与器件的内在变化规律。带宽窄、隔离度大的光学滤波元件是获得超高分辨率光谱的关键。常规衍射光栅对波长的分辨能力为1GHz量级，难以满足新要求。本项目创新性提出利用高非线性光纤中经增强的受激布里渊散射（SBS）效应构建一种有源光学滤波器（AOF），实现被测信号的超高分辨率光谱分析。项目研究了基于光模声模联合调控的布里渊增益谱（BGS）剪裁方法，通过对光纤中声/光模的激励与耦合进行操控，达到剪裁BGS的效果；设计和制备了一种SBS效应增强型高非线性光纤，其BGS具有单峰、窄带宽、高增益等特点，可用于构建超高分辨率光学滤波器件，提取超精细光谱成分；设计了一种基于分段泵浦技术的双级SBS-AOF结构，通过优化双级SBS-AOF各工作状态参量，实现对SBS-AOF线性工作区的灵活调控，从而有效减缓SBS-AOF的增益饱和效应；提出了一种基于分功率型马赫泽德干涉仪的泵浦频域消偏技术，通过优化其结构参数，能在大波长范围内显著降低泵浦光的偏振度，从而有效减小SBS-AOF的偏振相关增益；研究了泵浦光波长扫描条件下SBS-AOF频率响应特性，通过修正SBS耦合振幅方程组，建立了超高分辨率光谱分析系统传递函数的数学模型；研制了基于SBS-AOF的超高分辨率光谱分析系统，该系统光谱分辨率优于0.1pm，输入信号功率动态范围大于50dB，工作波长覆盖C波段；在此基础上开发了一种光纤信号特征识别技术，可对光纤信号的工作波长、调制格式、工作速率和光信噪比等主要特征参数进行自动识别与监测。项目成果通过了中国光学工程学会组织的科技成果鉴定，整体达到国际先进水平，并荣获第45届日内瓦国际发明展金奖、中国光学工程学会创新产品二等奖各1项，在光通信与光传感系统性能评估与监测、光电子器件特性测试与分析等领域有广阔的应用前景。