Performance of improved mode diversity reception for free-space optical communication under atmospheric turbulence

This paper first proposes and verifies two simplified mode diversity receivers (MDRs) for free-space optical (FSO) communication systems under moderate-to-strong turbulence. The MDRs are designed and implemented for coherent detection of the FSO communication system based on few-mode-fiber (FMF) coupling. The first MDR replaces the coherent receiver with a Kramers-Kronig (KK) receiver, which reduces the number of photodetectors (PDs) and high-speed analog-to-digital converters by 3/4. The second MDR realizes few-mode KK detection by utilizing a few-mode local oscillator and only one PD. This method simplifies the system of a MDR to the extreme. Experimental results show that the average received power of a FSO communication system based on six-mode fiber has approximately 6 dB gain compared with the one based on single-mode fiber (SMF) under moderate-to-strong turbulence. The two proposed MDRs have approximate performance, improving by 5 dB to 6 dB compared to SMF-based heterodyne detection under moderate-to-strong turbulence. In addition, the simplified schemes reduce the volume and the cost of the optical receiver, and it has some practical significance for FSO communication. (C) 2022 Optica Publishing Group

Automated summary

This paper proposes and verifies two simplified mode diversity receivers for free-space optical communication systems under moderate-to-strong turbulence. The proposed receivers reduce the cost and volume of the optical receiver while improving system performance.