基于光纤级联参量过程的宽带低噪声光频梳及应用基础研究

Optic frequency comb (OFC) with low cost and high performance can substantially improve the capacity of fiber optical transmission, as well as reduce the cost and complexity of dense wavelength division multiplexing (DWDM) fiber-optical transmission. Meanwhile, all optical signal processing can overcome the bottleneck of electronic signal processing, reduce the power consumption, and achieve agile optical networking. In order to satisfy linear phase matching condition over a wide frequency span, we design and fabricate photonic crystal fiber (PCF) with ultra-low flat dispersion and high nonlinearity, based on double-ring heterogeneous structure. Taking advanced modulation formats into account, we experimentally demonstrate a broadband and low noise OFC using cascaded parametric process, which cover the C+L bands with tunable frequency spacing from 50GHz to 400GHz together with more than 40dB optical signal to noise ratio (OSNR). We carry out comprehensive investigation on generation model, parameter optimization and experimental characterization. Furthermore, we verify that the proposed OFC can be used for DWDM transmission of (D)QPSK, 8PSK and 16QSM signal. Next, we demonstrate all-optical signal regenerator and wavelength multicasting, using cascaded parametric process based phase sensitive amplification (PSA), and verify the function through practical fiber-optical transmission. At the end of project, we are able to demonstrate simultaneous amplitude and phase regeneration of 25Gbaud (D)QPSK signal after transmission through 100km standard single mode fiber(SSMF). Furthermore, we verify the application of one-to-nine wavelength multicasting for (D)QPSK signal on the condition of 100GHz frequency spacing.

低成本高性能光频梳可以提高光纤通信系统的传输容量，降低密集波分复用传输的成本和复杂性。全光信号处理技术可以克服电子处理速度瓶颈，降低能耗，提高光网络的灵活性。项目设计并研制异质双环结构的超低色散平坦高非线性光子晶体光纤，在宽频范围内满足线性相位匹配条件。针对广泛采用的高阶相位调制码型，项目创新性地提出利用光纤级联参量过程产生覆盖C+L波段，50-400GHz频率间隔可调，光信噪比大于40dB的宽带低噪声光频梳，对光频梳产生过程开展理论建模、参数优化和实验测试三个方面的研究，验证所研制的光频梳可用于（D）QPSK、8PSK及16QAM信号的密集波分复用光传输。研究基于参量光频梳的相敏放大过程实现(D)QPSK信号的全光再生和波长组播应用，最终实现25GBaud (D)QPSK信号在100公里单模光纤传输后同时实现全光相位和幅度再生，及100GHz波长间隔条件下一至九路全光组播应用。

为了简化DWDM光传输系统结构，降低成本，需要可调谐可配置的光频梳光源。同时，为了满足超大容量高频谱效率光传输要求，需要采用适用于先进调制码型的全光信号再生、波长转换及组播技术，克服电子处理速度瓶颈，降低功耗，提高光网络灵活性。光纤中的级联参量过程，覆盖光传输常用的C+L波段，是产生光频梳的必要条件，其包含丰富的作用机理，尤其是参量过程中对相互作用光束的相位敏感放大特性，决定了它可有效实现对相位调制信号的再生和处理功能。同时通过其级联特性产生多束光波可实现全光组播功能。因此光纤中的级联参量过程是满足以上需求的最佳技术选择。光纤中级联参量过程，既包括多段不同特性的光纤级联，每段光纤中不同的参量过程发生相互作用完成特定的功能；同时也包括在同一段光纤内多个不同参量过程相互作用进而产生更多光束的效应级联。因此光纤中的级联参量过程被广泛应用于宽带高增益参量放大及全光信号处理中。项目从超低色散平坦高非线性光子晶体光纤的设计出发，通过结构参数优化以满足产生宽带低噪声光频梳的要求。在高非线性超低色散平坦光纤的基础上对参量光频梳的产生机理即光纤级联参量过程开展理论建模、特性分析和实验测试三个方面的研究，同时验证参量光频梳作为频率间隔稳定和幅度平坦的多波长光源可以应用于DWDM 光传输中，并将宽带低噪声的参量光频梳应用到(D)QPSK 等高阶调制格式光信号的全光再生、波长转换和组播等功能实现。

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