连续调谐波长变换在正交频分复用弹性光网络中的应用

Dynamic spectrum management of optical networks is important to accommodate multiple spectrum requirements from different clients. OFDM elastic optical networks enable dynamic channel bandwidth assignment based on channel capacity and transmission distance with flexible gridding and improve spectrum utilization. Wavelength coversion, which reorganizes signals to enable new wavelengths to be added along the fiber, can be used in conjunction with optical switches to provide wavelength reconfiguration, routing and management of the optical bandwidth for reducing wavelength blocking probability. In order to match for the elastic optical networks, the wavelength conversion needs to be transparent for data modulation format and bit rate and continuously tunable for arbitrary input wavelengths. Fiber optic parametric processes have many intrinsic advantages due to the material nature of germano-silicate highly nonlinear fiber (HNLF). They are fs-order response speed, low loss, low noise, seamless (grid-less) wide operating bandwidth, phase preserving property, high dynamic range and linearity, high reliability, and low cost. Above all, the phase-preserving feature is critical for the transparency of advanced modulation formats. For OFDM signals, it is vital to have a wide guard-band between the signal and the pump to prevent the interaction of signals with sidebands from self-phase modulation and cross-phase modulation. The wide guard-band interrupts the continuum of tunable wavelength so that the wavelength conversion cannot work well with the OFDM elastic optical networks. Therefore, we propose a continuously tunable scheme based on bi-directional cascaded parametric processes of HNLF. In the first-stage parametric process, the input OFDM signal and the tunable pump is combined into a HNLF to generate a dummy signal. In the second-stage parametric process, the dummy signal and another tunable pump are launched into the same HNLF in the opposite direction by an optical circulator. Thus, the wavelength tunable gap can be eliminated and the continuously tunable wavelength conversion is able to be utilized in the OFDM elastic optical networks for arbitrary wavelength and sub-wavelength conversion.

为了满足不同用户的带宽需求，实现光网络的动态带宽管理十分重要。基于正交频分复用（OFDM）的弹性光网络，可以根据信息流量大小和传输距离，采取灵活栅格动态分配信道带宽，大幅提高了频谱的利用率。但当节点处多路信号具有相同波长时，就会造成波长竞争从而引起阻塞,因此需要将冲突的波长信号变换到其他未被占用的波长。为了确保网络弹性，所用波长变换系统必须是对信号透明，同时可实现任意波长的连续调谐。非线性光纤参量过程可以保持信号的相位信息，对信号调制格式透明，十分适合应用。但是由于高速OFDM信号具有宽的谱宽，此外泵浦和信号的自相位调制交叉相位调制会引起信号损伤，因此泵浦光和信号光之间需要一个宽的波长缺口不能实现任意波长连续调谐转换。本项目建议采取双向级联光纤参量效应，首先产生一个参考波长，然后将其再变换到需要的波长，从而可以消除波长调谐盲区，在弹性光网络中实现同波段任意波长，子波长OFDM信号波长变换。

实现光网络的动态带宽管理可以满足不同用户的带宽需求。由于正交频分复用（OFDM）的弹性光网络可以采取灵活栅格动态分配信道带宽,因此具有高频谱的利用率的特点。当节点处多路信号具有相同波长时，就会造成波长竞争从而引起阻塞，而一个对信号透明，任意波长连续调谐的波长变换系统可以解决这个问题。本项目建议采取级联光纤参量效应，消除波长调谐盲区，在弹性光网络中实现同波段任意波长，子波长的信号波长变换。本项目的研究内容包括构建全光波长变换系统；构建光OFDM 信号连续调谐波长变换系统；在OFDM 弹性光网络中演示连续调谐波长变换系统。项目的研究内容已完成。项目的研究结果包括已搭建全光波长变换实验系统，实现正交调制信号的C波段连续波长变换。已搭建OFDM 信号连续调谐波长变换及在弹性光网络中应用的仿真系统，实现利用设计的全光波长系统对OFDM弹性光网络进行频谱整合。项目执行期间已申请专利5项，发表学术论文17篇。培养研究生六名，已资助研究生参加国际会议三人次。依托项目搭建的实验系统及仿真平台可供开展光纤通信领域的实验及理论研究。