Superchannels leverage the flexibility of elastic optical networks and pave the way to higher capacity channels in space division multiplexing (SDM) networks. A superchannel consists of subchannels to which continuous spectral grid slots are assigned. To guarantee superchannel operation, we need to account for soft failures, e.g., laser drifts causing interference between subchannels, wavelength-dependent performance variations, and filter misalignments affecting the edge subchannels. This is achieved by reserving spectral guardband between subchannels or by employing a lower modulation format. We propose a process that dynamically retunes the subchannel transmitter (TX) lasers to compensate for soft failures during operation and optimizes the total capacity or the minimum subchannel quality of transmission (QoT) performance. We use an iterative stochastic subgradient method that at each iteration probes the network and leverages monitoring information, particularly subchannels signal-to-noise ratio (SNR) values, to optimize the TX frequencies. Our results indicate that our proposed method always approaches the optima found with an exhaustive search technique, unsuitable for operating networks, irrespective of the subchannel number, modulation format, roll-off factor, filters bandwidth, and starting frequencies. Considering a four-subchannel superchannel, the proposed method achieves 2.47 dB and 3.73 dB improvements for a typical soft failure of +/- 2 GHz subchannel frequency drifts around the optimum, for the two examined objectives.

翻译：超信道利用弹性光网络的灵活性，为空分复用（SDM）网络中的更高容量信道铺平了道路。超信道由连续频谱网格时隙分配的子信道组成。为保证超信道运行，需考虑软故障，例如子信道间因激光漂移引起的干扰、波长相关性能变化以及影响边缘子信道的滤波器失准。目前通过预留子信道间保护频带或采用更低阶调制格式来应对这些问题。我们提出一种动态重调子信道发射机（TX）激光器的流程，以补偿运行中的软故障，并优化总容量或最小子信道传输质量（QoT）性能。该方法采用迭代随机次梯度算法，每次迭代通过探测网络并利用监控信息（特别是子信道信噪比（SNR）值）来优化发射机频率。结果表明，无论子信道数量、调制格式、滚降因子、滤波器带宽及起始频率如何，所提方法始终趋近于穷举搜索技术（不适用于运行网络）找到的最优解。以四子信道超信道为例，针对±2 GHz子信道频率漂移的典型软故障，本方法在两种优化目标下分别实现了2.47 dB和3.73 dB的改善。