Grating coupling is a widely adopted strategy for coupling light into optical waveguides. While this versatile approach benefits both fabrication and alignment, grating couplers are particularly sensitive to both wavelength and polarization. These drawbacks hinder its application in integrated wavelength-division-multiplexing passive optical network (WDM-PON) transceivers, where widely separated wavelength bands are utilized for upstream and downstream signals. In this letter, we propose a three-port grating coupler that enables polarization-independent receiving for the downstream signal from fiber and single-polarized coupling of the upstream signal from chip. Dual-wavelength-band operation is obtained by adding an output port to couple upstream wavelength on existing polarization-splitting grating coupler for downstream wavelength. Peak coupling efficiencies of −2.93 dB and −3.50 dB are achieved for 1266 nm and 1481 nm respectively. This grating coupler design can be adopted in transceivers for fiber-to-the-home (FTTH) networks.

中文翻译：

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用于 WDM-PON 应用的三端口双波长带光栅耦合器

光栅耦合是一种广泛采用的将光耦合到光波导中的策略。虽然这种通用方法有利于制造和对准，但光栅耦合器对波长和偏振都特别敏感。这些缺点阻碍了其在集成波分复用无源光网络 (WDM-PON) 收发器中的应用，其中广泛分离的波段用于上行和下行信号。在这封信中，我们提出了一种三端口光栅耦合器，它可以对来自光纤的下行信号进行偏振独立接收，并对来自芯片的上行信号进行单偏振耦合。双波长带操作是通过在现有的偏振分光光栅耦合器上增加一个输出端口来耦合上行波长来获得下行波长。1266 nm 和 1481 nm 的峰值耦合效率分别为 -2.93 dB 和 -3.50 dB。这种光栅耦合器设计可用于光纤到户 (FTTH) 网络的收发器。