Temporal and spectral coding over amplified spontaneous emission for secure optical coherent communications

Area of Science:

• Optical Communications
• Information Security
• Signal Processing

Background:

• Traditional optical communication security is vulnerable to advanced eavesdropping techniques.
• Physical-layer security offers a robust solution by leveraging inherent signal characteristics.
• Amplified spontaneous emission (ASE) noise presents a unique opportunity for secure data transmission.

Purpose of the Study:

• To demonstrate secure optical coherent communications using low-coherence matched detection.
• To achieve two-level physical-layer optical encryption via temporal and spectral coding of ASE noise.
• To analyze and investigate the impact of chromatic dispersion on the proposed system.

Main Methods:

• Utilizing a broadband amplified spontaneous emission (ASE) source for signal generation.
• Employing polarization multiplexing for an ASE-carried signal and unmodulated carrier.
• Implementing polarization tracking and matched detection at the receiver.
• Experimentally investigating the effects of chromatic dispersion.

Main Results:

• Successfully demonstrated secure optical communication with physical-layer encryption.
• Achieved optically coded 20 Gbaud Quadrature Phase Shift Keying (QPSK) and 8-Phase Shift Keying (8-PSK) signal transmission.
• Transmitted signals over a 43 km single-mode fiber (SMF) span.
• Reached a maximum line rate of 60 Gbits/s.

Conclusions:

• Low-coherence matched detection based on ASE noise randomness enables secure optical communications.
• Temporal and spectral coding effectively provide two-level physical-layer encryption.
• The system is robust against chromatic dispersion, enabling high-speed transmission over standard SMF.