面向大容量模分复用光传输的超低噪声光放大技术研究

To deal with the capacity crunch of single-mode fiber (SMF), mode-division multiplexing (MDM) based on few-mode fiber (FMF) has attracted considerable attention over the past few years. A class of active and passive devices, such as mode MUX/DEMUX and optical amplifiers, are required for realizing MDM transmission. Especially, suitable amplifiers used to compensate the fiber link loss are essential for long-haul MDM transmission. Few-mode erbium-doped fiber amplifier (FM-EDFA) and few-mode distributed Raman amplifier (FM-DRA), which are attractive amplification solutions, have been extensively investigated. Compared with EDFA, Raman amplifiers have some fundamental advantages, such as simple architecture, low noise figure (NF), and flexible gain band. In particular, profiting from the flexibility of gain band, broadband Raman amplifier can be achieved more easily than EDFA. By carefully choosing the pump wavelength and power, one can realize broadband gain-flat Raman amplifiers. . In this project, MDM ultra-low noise amplification and transmission based on high order Raman amplification over FMF will be investigated. Second and third order Raman based on random laser and bi-directional pumping will be utilized for obtaining the ultral-low noise figure as well we optimized nonlinearity distortion. Multiwavelength pumping will be adopted with algorithms for pump power distribution between wavelengths, modes and different pumping orders. Wideband amplification with small flatness and differential modal gain will be obtained. Together with the wavelength division multiplexing, MDM transmission up to 100 Tbps over few mode fiber will be achieved based on the ultra-low noise high order Raman amplification.. The applicant has demonstrated a series of MDM Raman amplification applications with up to -3-dB noise figure which is the record low noise for MDM transmission over few mode fiber. In this project, the studies will be carried out with Nokia Bell Labs who is the leading research team in large capacity optical transmission. Promising results with ultra-low noise MDM amplification and transmission can be expected based on the established research records of the applicant and the collaboration of the world-top research teams.

光纤通信趋近传输容量极限，少模光纤模分复用技术是进一步提高下一代光通信容量的重要手段。模分复用系统中，高阶调制的信噪比需求剧增，模式复用引入附加串扰，并带来倍幅增加的非线性效应，这些问题严重限制了模分复用光通信技术的发展。本课题研究模分复用超低噪声放大和传输技术，基于二阶和三阶高阶拉曼的分布式放大实现低噪声指数少模光纤放大，通过前后双向泵浦降低非线性效应的影响，通过泵浦功率的模式和波长配置，实现宽带增益平坦和低模式差分增益的少模光放大。申请人的前期研究成果处于世界领先水平，受到国内外关注。在此基础上，本课题将进一步与诺基亚贝尔实验室（美国）合作开展研究。通过本课题的研究，可以得到超低噪声指数的少模光纤放大，优化和解决模分复用光通信系统的非线性和信噪比受限问题，得到百T比特级别大容量少模传输，保持该方向技术领先优势并持续推动大容量光传输的发展。

模分复用是下一代大容量光传输的关键技术方案，发展相应的低噪声少模放大技术具有重要意义。本项目提出基于粒子群优化算法和深度神经网络的多维均衡优化方法，得到-4dB等效噪声指数、覆盖C+L带宽、平坦度小于1dB、模式差分增益小于0.3dB的100公里单跨拉曼放大传输；提出基于深度学习的多环形结构少模光纤逆向设计方法，得到弱耦合少模光纤的优化设计；基于像素化结构研制了微米级尺寸的少模波导弯曲等器件，基于简化三叉戟结构实现了2×100Gbps的少模光耦合接口，在2微米波段实现了3×80Gbps最高单波速率的片上模分复用光互连。相关成果发表Chinese Optics Letters期刊邀请和封面论文并入选COL年度十大最多下载论文、入选Photonics Research期刊的编辑精选论文以及中国光学十大进展，获得OECC最佳学生论文奖。在本项目支持下，发表SCI期刊论文16篇、会议论文11篇，培养博士毕生3人、硕士生7人，其中1人次获国家公派留学奖学金CSC、2人次入职高校、2人次获国家奖学金、1人次获上海市优秀毕业生。