基于频域多通道盲解卷积的模式分集复用系统解复用技术研究

In this project, a mode demultiplexing technology based on frequency domain multichannel blind deconvolution (FD-MBD) is proposed to solve the significant problem of that there exist convolution mixtures between the transmission channels of mode division multiplexing (MDM) system. The main efforts in this project will be focused on investigating the feasible FD-MBD algorithms for mode demultiplexing in MDM system, solving the permutation ambiguity of FD-MBD, and implementing the mode demultiplexing based on FD-MBD when there exists mode dependent loss in the system. On the basis of the above work, an implementation scheme of MDM system with few mode fibers (FMF) based on FD-MBD is proposed and will be verified experimentally, and the ultimate goal of this scheme is to realize a principal experiment of 2×2 MDM system in which a 112Gb/s（the overhead of FEC is 12%) signal is transmitted over 100km FMF and the bit error rate of the system is lower than 10e-9 after the demultiplexing by FD-MBD. The proposed FD-MBD can realize the mode demultiplexing only using the received signal while no need for training sequence and channel estimation, and moreover, it has low computational complexity. Furthermore, mode coupling、differential mode delay and mode dependent loss can be jointly compensated by improving the FD-MBD by using some simple approaches, and that makes the proposed FD-MBD more practical. This research has a great significance to upgrade the transmission capacity of optical transmission network and promote the development process of long-distance and high-capacity optical network.

本项目提出了一种基于频域多通道盲解卷积（FD-MBD）的解复用技术，解决模式分集复用（MDM）系统中多信道卷积性混合这一至关重要的科学问题。本项目将研究适合MDM系统解复用的FD-MBD算法，解决FD-MBD算法的次序不确定性问题，研究模式相关损耗存在条件下的FD-MBD解复用方法。提出并验证基于FD-MBD算法的MDM少模光纤通信系统的实现方案，最终实现2×2 MDM少模光纤通信系统的原理性实验，在传输速率112Gb/s（FEC开销12%）和传输距离100km条件下，FD-MBD解复用后的系统误码率小于10e-9。基于FD-MBD的解复用技术，仅利用接收信号即可实现解复用，无需训练序列和信道估计，而且算法计算复杂度低。通过简单处理手段，FD-MBD可以实现模式耦合、差分模时延和模式相关损耗的联合补偿，普适性强。课题的研究对于提升光传输网容量，推进长距离大容量光网络的发展进程有重要意义。

模分复用（MDM）技术利用相互正交的空间模式作为并行通信信道，实现多路信号同时传输，可以极大提升光纤通信系统的传输能力。然而，在实际的模分复用通信系统中存在着模式耦合、差分模式群时延和模式相关损耗等特有的损伤，这些损伤引起了信道串扰和码间干扰，严重影响着系统传输性能。在本项目中，我们提出了基于频域多通道盲解卷积（FD-MBD）的解复用方法来解决模分复用系统的损伤补偿问题。FD-MBD算法通过时频变换，将时域的卷积混合问题转换成频域的瞬时混合问题，简化了卷积问题求解的难度和复杂度，具有更好的收敛特性，且能够对高速信号进行实时有效处理，做到解复用效果和速度的双优。提出了适用于模分复用系统解复用的FD-MBD算法，并验证了该算法的解复用性能。提出了一种基于连续收敛排序的FD-MBD算法，该方法能够解决FD-MBD分离信号存在的次序不确定问题，与常用的排序算法相比，具有复杂度低、收敛速度快等优势。研究了模式相关损耗（MDL）存在条件下FD-MBD算法的解复用问题，提出了光器件联合FD-MBD算法和格基规约结合信号均衡算法的补偿方案。搭建了基于光子灯笼的模分复用通信实验系统，实现了96Gb/s QPSK信号100km的少模光纤传输，验证了FD-MBD算法的有效性，采用FEC校验后，系统误码率可优于1e-9。项目资助发表相关论文29篇，其中SCI检索论文21篇、EI检索论文8篇，获授权国家发明专利4项，培养研究生17名。