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Trellis-coded OAM-SK multiplexing system based on spatial indexing and a multi-task neural network for
Optics Express
|May 4, 2026
Summary
This study introduces a novel trellis-coded orbital angular momentum shift keying (OAM-SK) system using spatial indexing and a multi-task neural network (MTNN) to combat atmospheric turbulence (AT). The system enhances high-capacity optical transmission by suppressing AT effects and improving data rates.
Area of Science:
- Optical Communications
- Signal Processing
- Artificial Intelligence
Background:
- High-capacity optical transmission demands advanced modulation techniques like multi-state orbital angular momentum shift keying (OAM-SK).
- Atmospheric turbulence (AT) significantly degrades vortex beams (VBs), limiting the performance and distance of OAM-SK systems.
- Existing methods struggle to mitigate AT effects without increasing channel overhead or complexity.
Purpose of the Study:
- To propose and evaluate a novel trellis-coded OAM-SK multiplexing system robust to atmospheric turbulence.
- To leverage spatial indexing and a multi-task neural network (MTNN) for AT suppression and enhanced data transmission.
- To improve transmission capacity and distance in free-space optical communication systems.
Main Methods:
- Development of a trellis-coded OAM-SK system incorporating spatial indexing for virtual channel creation.
- Implementation of a multi-task neural network (MTNN) to suppress atmospheric turbulence effects.
- Design of a Spatial-OAM encoder to reduce the dimensionality of multi-state OAM for efficient multiplexing.
Main Results:
- The MTNN achieved over 99.28% spatial index classification accuracy for turbulence levels up to 2×10⁻¹³ m⁻²/³.
- The Spatial-OAM encoder effectively converted 16-bit multi-state OAM into 4-bit single OAM modes for multiplexing.
- A bit error rate (BER) of 1.5×10⁻³ was achieved at 1000m transmission distance with turbulence (Cn²=5×10⁻¹⁴ m⁻²/³), demonstrating long-distance potential.
Conclusions:
- The proposed system effectively utilizes spatial indexing for inter-source switching and suppresses AT effects without additional channel redundancy.
- The integration of MTNN and Spatial-OAM encoder significantly enhances transmission capacity and extends transmission distance.
- This approach shows considerable promise for future high-capacity, long-distance free-space optical communication systems.
