Heterodyne detection based on a single-ended photodetector is of great interest to simplify the receiver frontend complexity compared to a full coherent one, while retaining the ability of digital chromatic dispersion (CD) compensation. Nevertheless, single-ended heterodyne detection schemes typically require a transmitter, which has similar complexity as in coherent systems. Moreover, a receiver bandwidth equal to at least the symbol rate of the signal is required for the complex-valued signal recovery when using a single-ended photodetector. In this article, we study a novel heterodyne detection scheme, which allows to use a simple transmitter structure, and to reduce the receiver bandwidth to a value well below the symbol rate, while supporting digital CD compensation. In our experiment, a real-valued signal originates from a single-drive Mach-Zehnder modulator at the transmitter. A bandwidth-limited receiver suppresses one sideband of the incoming signal, however the receiver digital signal processing (DSP) reconstructs the missing sideband based on the Hermitian symmetry of a real-valued signal spectrum. A receiver bandwidth slightly larger than half of the symbol rate is required. With our novel DSP, we successfully recover 60 Gbaud PAM-4 signal after 80 km of fiber transmission in C-band, using 33 GHz electrical bandwidth at both transmitter and receiver, without optical filtering or amplification.

中文翻译：

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使用半符号速率带宽的单端光接收器进行实值调制的光场重建


与全相干检测器相比，基于单端光电检测器的外差检测对于简化接收器前端复杂性非常有意义，同时保留数字色散 (CD) 补偿的能力。然而，单端外差检测方案通常需要发射机，其复杂性与相干系统相似。此外，当使用单端光电探测器时，复值信号恢复需要至少等于信号符号率的接收器带宽。在本文中，我们研究了一种新颖的外差检测方案，该方案允许使用简单的发射机结构，并将接收机带宽降低到远低于符号率的值，同时支持数字 CD 补偿。在我们的实验中，实值信号源自发射器处的单驱动马赫曾德调制器。带宽有限的接收器会抑制输入信号的一个边带，但接收器数字信号处理 (DSP) 会根据实值信号频谱的埃尔米特对称性重建丢失的边带。需要略大于符号率一半的接收器带宽。借助我们的新型 DSP，我们在 C 频段光纤传输 80 公里后成功恢复了 60 Gbaud PAM-4 信号，在发射器和接收器上均使用 33 GHz 电气带宽，无需光学滤波或放大。