1600 Gbps PAM-4 FSO link enabled using OFCL-based WDM and OAM-multiplexing techniques

Abstract

The twisted light beams carry orbital angular momentum (OAM), which acts as additional degrees of freedom. In this work, we have proposed a free space optics (FSO) communication system employing wavelength division multiplexing (WDM), OAM multiplexing, and four-level pulse amplitude modulation (PAM-4) techniques. A 1600 Gbps data has been successfully transmitted over free space in different environmental scenarios such as clear weather, weak turbulence, moderate turbulence, and strong turbulence. The effects of atmospheric turbulence on the PAM-4 signals carrying OAM modes are examined theoretically and simulated for the first time. Optical frequency comb lines are generated by employing a single laser source and used as a broadband laser source. A sufficient low power penalty of 1.489 dB at a BER value ∼ 10-9 along with clear eye diagrams has been achieved for the proposed system. Thus, the proposed 1600 Gbps PAM-4, OAM, and WDM-based system can be a promising solution for the next generation of long-reach and high-data-rate free-space communication.

Keywords

• Orbital angular momentum of light
• Free space optics
• Wavelength division multiplexing
• PAM-4
• Optical frequency comb lines
• Atmospheric turbulence