Circle Polarization Shift Keying With Direct Detection for Free-Space Optical Communication

TLDR

The paper proposes a binary circle polarization shift‑keying (CPolSK) scheme using two circular polarization states. The authors analyze CPolSK beam propagation using the cross‑spectral density matrix of a circle‑polarized Gaussian Schell‑model beam. Simulations show that CPolSK preserves polarization, slightly increases the degree of polarization, achieves a 3 dB lower SNR requirement than on‑off keying, and is promising for future free‑space optical systems.

Abstract

A binary polarization shift-keying scheme with two circle polarization states, circle polarization shift keying (CPolSK), is proposed and discussed. The propagation of the circle-polarized Gaussian Schell model beam is studied based on the cross-spectral density matrix. The results show that the state of polarization remains unchanged and the degree of polarization slightly increases upon propagation in a turbulent atmosphere. The analysis of the bit-error-rate performance shows that the CPolSK system has about a 3 dB lower requirement in signal-to-noise ratio than the on–off keying system. The modulation scheme will be helpful for practical free-space optical communication systems in the future.