To overcome power fading induced by chromatic dispersion in optical fiber communications, optical field recovery is a promising solution for direct detection short-reach applications, such as fast-evolving data center interconnects (DCIs). To date, various direct detection schemes capable of optical field recovery have been proposed, including Kramers-Kronig (KK) and signal-signal beat interference (SSBI) iterative cancellation (IC) receivers. However, they are all restricted to the single sideband (SSB) modulation format, thus conspicuously losing half of the electrical spectral efficiency (SE) compared with double sideband (DSB) modulation. Additionally, SSB suffers from the noise folding issue, requiring a precise optical filter that complicates the receiver design. As such, it is highly desirable to investigate the field recovery of DSB signals via direct detection. In this paper, for the first time, we propose a novel receiver scheme called carrier-assisted differential detection (CADD) to realize optical field recovery of complex-valued DSB signals via direct detection. First, CADD doubles the electrical SE compared with the KK and SSBI IC receivers by adopting DSB modulation without sacrificing receiver sensitivities. Furthermore, by using direct detection without needing a precise receiver optical filter, CADD can employ cost-effective uncooled lasers as opposed to expensive temperature-controlled lasers in coherent systems. Our proposed receiver architecture opens a new class of direct detection schemes that are suitable for photonic integration analogous to homodyne receivers in coherent detection.

中文翻译：

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运营商辅助的差分检测。

为了克服光纤通信中色散引起的功率衰减，光场恢复是直接检测短距离应用（例如快速发展的数据中心互连（DCI））的有前途的解决方案。迄今为止，已经提出了能够进行光场恢复的各种直接检测方案，包括Kramers-Kronig（KK）和信号信号差拍干扰（SSBI）迭代消除（IC）接收机。但是，它们都限于单边带（SSB）调制格式，因此与双边带（DSB）调制相比，明显损失了一半的电频谱效率（SE）。此外，SSB还存在噪声折叠问题，因此需要一个精密的光学滤波器来使接收器的设计复杂化。因此，迫切需要通过直接检测研究DSB信号的现场恢复。在本文中，我们首次提出了一种新的接收器方案，称为载波辅助差分检测（CADD），以通过直接检测实现复值DSB信号的光场恢复。首先，与KK和SSBI IC接收器相比，CADD通过采用DSB调制而不会牺牲接收器灵敏度的情况下，使电子SE翻了一番。此外，通过使用直接检测而不需要精确的接收器光学滤波器，CADD可以采用经济高效的非冷却激光器，而不是相干系统中昂贵的温度控制激光器。我们提出的接收器体系结构开辟了一种新的直接检测方案，适用于与相干检测中的零差接收器类似的光子集成。