High order modulation formats constitute the most prominent way for increasing spectral efficiency in transmission systems. Coherent transceivers that support such higher order formats require heavy digital signal processing (DSP), which increases the power consumption of coherent pluggables, well above the intensity modulation and direct detection (IM/DD) counterparts. Self-coherent or phase retrieval methods have emerged as potential solutions, trying to combine the merits of coherent technology with the simplicity of direct detection. In this work, we experimentally demonstrate the reception of quadrature amplitude modulation (QAM) modulation formats based on direct detection aided by the recurrent optical spectrum slicing (ROSS) photonic accelerator, utilizing minimal DSP and low modulator driving voltages. We experimentally demonstrate 32 Gbaud QAM-4/16 for 25 km, 50 km and 75 km in the C-band aided by a linear digital equalization and the use of programmable photonics as recurrent optical spectrum slicers. We showcase successful detection with driving swings below Vπ/3 in contrast to the full swing required by conventional coherent transceivers. We further improve the system performance utilizing geometric constellation shaping. Finally, we explore the potential power consumption improvement for the next-generation 1.6T pluggables, showcasing over 40% reduction with respect to the most lightweight state of the art coherent solutions reported in literature

翻译：高阶调制格式是提高传输系统频谱效率的最重要手段。支持此类高阶格式的相干收发器需要繁重的数字信号处理（DSP），这导致相干可插拔模块的功耗远超强度调制/直接检测（IM/DD）方案。自相干或相位恢复方法作为潜在解决方案应运而生，试图结合相干技术的优势与直接检测的简易性。本工作中，我们实验验证了基于循环光谱切片（ROSS）光子加速器辅助直接检测的正交幅度调制（QAM）格式接收，仅需极简DSP和低调制器驱动电压。我们借助线性数字均衡和可编程光子器作为循环光谱切片器，在C波段25公里、50公里及75公里传输距离上实现了32 Gbaud QAM-4/16信号接收。实验证明可在驱动摆幅低于Vπ/3的条件下实现成功检测，而传统相干收发器需满摆幅驱动。通过几何星座整形进一步提升了系统性能。最后，针对下一代1.6T可插拔模块的潜在功耗改进进行了探索，结果显示相较文献报道的最轻量级相干解决方案可降低功耗逾40%。