Free space optics has been a subject of interest since few decades ago due to its huge unlicensed spectrum, huge data carrying capacity and immunity to electromagnetic interference among other reasons. In this paper a novel technique for conveying 40 GHz frequency doubled Optical Carrier Suppressed (OCS) millimeter wave radio signals over free space has been proposed and simulated. After suppression of the carrier frequency the baseband data was modulated using Modified Duobinary Return to Zero in the electrical domain onto the lower sideband. A coupler was then used to combine the sidebands and such wavelengths from 8 transmitters were multiplexed and launched in free space through diversity technique. The maximum distance in the downstream (towards receiver) was 4.609 km in clear weather. The proposed architecture was very effective for upstream data transmission. It greatly improves the upstream bit error rate as compared to an architecture were all the sidebands were carrying data in the downstream.

中文翻译：

---

自由空间系统上的混合OCS / MDRZ波分复用毫米波无线电

自几十年前以来，自由空间光学一直是人们关注的主题，这是由于其巨大的无执照频谱，巨大的数据承载能力以及对电磁干扰的抵抗力以及其他原因。在本文中，提出并模拟了一种在自由空间上传输40 GHz倍频光载波抑制（OCS）毫米波无线电信号的新技术。抑制载波频率后，在电域中使用修改后的双二进制归零功能将基带数据调制到下边带。然后使用耦合器组合边带，并通过分集技术将来自8个发射器的此类波长复用并在自由空间中发射。在晴朗天气中，下游（朝向接收器）的最大距离为4.609 km。所提出的体系结构对于上游数据传输非常有效。与所有边带都在下游传输数据的体系结构相比，它大大提高了上游误码率。