SLM steering-based covert communication over strong atmospheric turbulence channels

Area of Science:

• Optical Communications
• Information Security
• Signal Processing

Background:

• Secure communications focus on message content protection, while low probability of intercept (LPI) communications prioritize process privacy.
• Covert communication is the most restrictive LPI form, aiming to prevent detection entirely.
• Existing methods may not sufficiently obscure communication signals in challenging environments.

Purpose of the Study:

• To propose and experimentally validate a novel covert communication technique.
• To hide transmitted signals within solar radiation for enhanced LPI.
• To achieve a high rate of covert data transmission in free-space optical links.

Main Methods:

• Utilizing an incoherent Gaussian source modulated with phase-shift keying (PSK).
• Transmitting a portion of the unmodulated carrier to aid detection.
• Employing spatial light modulator (SLM)-based beam steering for link establishment.
• Conducting experiments over a 1.5 km free-space optical link.

Main Results:

• Demonstrated a novel method for covert optical communication.
• Achieved a record number of covert bits transmitted.
• Successfully transmitted data in both strong and saturation turbulence regimes.
• Validated the feasibility of hiding signals within solar radiation.

Conclusions:

• The proposed PSK-modulated incoherent Gaussian source is effective for covert optical communication.
• The technique offers a viable solution for LPI in free-space optical links.
• Experimental results confirm the system's robustness under various turbulence conditions.