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：

---

使用半码率带宽的单端光接收器重建实值调制的光场

与单相光电检测器相比，基于异端检测的异端检测与完整的相干检测器相比，简化了接收器前端的复杂性，同时又保留了数字色散（CD）补偿的能力。然而，单端外差检测方案通常需要发射机，该发射机具有与相干系统相似的复杂性。此外，当使用单端光电检测器时，复数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器结构，并在支持数字CD补偿的同时将接收器带宽减小到远低于符号率的值。在我们的实验中 实值信号来自发射机的单驱动Mach-Zehnder调制器。带宽受限的接收器抑制了输入信号的一个边带，但是接收器数字信号处理（DSP）基于实值信号频谱的Hermitian对称性来重构丢失的边带。要求接收器带宽略大于符号率的一半。借助我们的新型DSP，我们在C波段进行了80 km的光纤传输之后，利用发射器和接收器上的33 GHz电气带宽成功地恢复了60 Gbaud PAM-4信号，而无需进行光学滤波或放大。然而，接收机数字信号处理（DSP）基于实值信号频谱的Hermitian对称性来重建丢失的边带。要求接收器带宽略大于符号率的一半。借助我们的新型DSP，我们在C波段进行了80 km的光纤传输之后，利用发射器和接收器上的33 GHz电气带宽成功地恢复了60 Gbaud PAM-4信号，而无需进行光学滤波或放大。然而，接收机数字信号处理（DSP）基于实值信号频谱的Hermitian对称性来重建丢失的边带。要求接收器带宽略大于符号率的一半。借助我们的新型DSP，我们在C波段进行了80 km的光纤传输之后，利用发射器和接收器上的33 GHz电气带宽成功地恢复了60 Gbaud PAM-4信号，而无需进行光学滤波或放大。