Demonstration of an optical phase conjugation based dual‐hop PDM‐QPSK free‐space optical communication link

Abstract

The dual‐hop free‐space optical (FSO) communication link for polarization‐division multiplexing quadrature phase‐shift keying (PDM‐QPSK) signals is proposed and experimentally demonstrated in an atmospheric chamber with the optical phase conjugation (OPC) compensating the turbulence‐induced signal distortions. The phase fluctuations can be effectively reduced by the OPC, as the error vector magnitudes are 10.03% and 8.28% decreased for x‐ and y‐polarization. At the bit error rate of 1 × 10–3, the power penalty of the dual‐hop link with OPC is 2.85 or 2.34 dB lower than that of each polarization without OPC.

An integrated design for improving spectral efficiency of FSO communication system in 6G applications

“…A number of studies, including polarization division multiplexing (PDM), orthogonal carrier‐division multiple‐access (OCDMA), orthogonal frequency‐division multiplexing (OFDM), and wavelength‐division multiplexing (WDM), have been conducted to find ways to mitigate the effects of air turbulence 16–18 . However, due to noisy environments, system performance decreases, leading to overall system failure 19 . With a single FSO connection, the system's performance is enhanced since more channels can be used within a given amount of space because each carrier has its own wavelength or channel 20 .…”