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 V{\pi}/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：高阶调制格式是提升传输系统频谱效率的最主要途径。支持此类高阶格式的相干收发机需要繁重的数字信号处理（DSP），这导致其功耗远高于强度调制直接检测（IM/DD）方案。自相干或相位恢复方法作为一种潜在解决方案应运而生，旨在结合相干技术的优势与直接检测的简洁性。本研究通过实验演示了基于直接检测的QAM调制格式接收，该方案借助循环光学频谱切片（ROSS）光子加速器，仅需极少的DSP和较低的调制器驱动电压。我们在C波段通过线性数字均衡和可编程光子器件作为循环光学频谱切片器，实验实现了32 Gbaud QAM-4/16信号在25公里、50公里及75公里距离的传输。实验展示了在驱动摆幅低于Vπ/3时仍能成功检测，而传统相干收发机则需要满摆幅驱动。我们进一步利用几何星座整形提升了系统性能。最后，探讨了下一代1.6T可插拔模块的潜在功耗改进，相较于文献报道的最轻量级相干解决方案，展示了超过40%的功耗降低。