The advancement of digital coherent technologies has dramatically increased the system capacity per single-core single-mode fiber to the point that we can now approach the Shannon limit by utilizing high-order modulation formats and high-coding gain forward error correction (FEC) codes. Because the required energy per bit increases exponentially the closer we get to the Shannon limit, extending the available optical bandwidth by using ultrawideband wavelength-division multiplexing (WDM) and/or spatial-division multiplexing (SDM) is indispensable for increasing the system capacity with high energy efficiency. However, simple extensions of wavelength resources and spatial parallelization dramatically increase the number of transceivers (TxRxs) in proportion to the wavelength/spatial multiplicity. The key to achieving cost- and energy-efficient systems is to reduce the system complexity by using high-density integration and broadband optelectronics. In this article, we overview and discuss the recent advances of coherent optical transceivers integrated with an optical front end and digital signal processing (DSP)/application-specific integrated circuit (ASIC). We then present the transponder architectures and the challenges involved in applying them for massive parallelized transmission systems.

中文翻译：

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相干光收发器的扩展和集成挑战


数字相干技术的进步极大地提高了每根单芯单模光纤的系统容量，以至于我们现在可以通过利用高阶调制格式和高编码增益前向纠错（FEC）码来接近香农极限。由于越接近香农极限，所需的每比特能量呈指数增长，因此通过使用超宽带波分复用 (WDM) 和/或空分复用 (SDM) 来扩展可用光带宽对于提高系统容量是必不可少的高能源效率。然而，波长资源的简单扩展和空间并行化会与波长/空间多重性成比例地显着增加收发器（TxRx）的数量。实现高成本和高能效系统的关键是通过使用高密度集成和宽带光电器件来降低系统复杂性。在本文中，我们概述并讨论了集成光前端和数字信号处理 (DSP)/专用集成电路 (ASIC) 的相干光收发器的最新进展。然后，我们介绍转发器架构以及将其应用于大规模并行传输系统所涉及的挑战。