Indoor optical wireless communication with optical beamsteering capability is currently attracting a lot of attention. One major two-dimensional (2D) optical beamsteering scheme is realized by 2D grating or its active counterpart, which is usually based on a spatial light modulator (SLM). However, there is a fundamental trade-off between the field of view (FoV) and power efficiency due to the inherent feature of gratings. In this Letter, we propose a new class of 2D beamsteering, named cyclically arranged optical beamsteering (CAO-BS), which can break that trade-off. Traditional 2D gratings extend the optical beam in the Cartesian coordinates (1D grating in horizontal + 1D grating in vertical), while CAO-BS extends the optical beam in the polar coordinates (1D grating + angular rotation). Since only 1D grating is engaged, the power efficiency increases with the number of grating lobes reduced. In the polar coordinates, the angle rotation tuning in a SLM is quasi-continuous in a full $2\pi$ range. The CAO-BS is demonstrated at the receiving end in an indoor experimental system. The FoV is 18° by 360° in polar coordinates without any additional mechanical parts. Based on the CAO-BS, 40 Gbit/s on-off keying data is also successfully transmitted over 1 km single-mode fiber and 0.5 m free space.

中文翻译：

---

40 Gb / s室内光学无线系统，由周期性布置的光束转向接收器支持

具有光束控制能力的室内光无线通信目前引起了很多关注。一种主要的二维（2D）光束转向方案是通过2D光栅或其有源对等物实现的，通常基于空间光调制器（SLM）。但是，由于光栅的固有特性，因此在视场（FoV）和功率效率之间存在根本的权衡。在这封信中，我们提出了一种新的2D波束控制，称为周期性排列的波束控制（CAO-BS），可以打破这种折衷。传统的2D光栅在笛卡尔坐标中扩展光束（水平的1D光栅+垂直的1D光栅），而CAO-BS在极坐标中扩展光束（1D光栅+角旋转）。由于仅使用一维光栅，功率效率随着栅瓣数量的减少而增加。在极坐标中，SLM中的角度旋转调整在整个过程中都是准连续的$\mathrm{2个}\pi$范围。在室内实验系统的接收端演示了CAO-BS。FoV在极坐标中为18°x 360°，而无需任何其他机械部件。基于CAO-BS，还可以在1 km单模光纤和0.5 m的自由空间上成功传输40 Gbit / s的开关键控数据。