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4D modulation scheme employing concatenated multi-level coding for short-reach coherent optical communication systems
Optics Express
|June 11, 2026
Summary
We developed a novel four-dimensional (4D) modulation scheme using multi-level coding (MLC) for short-reach optical systems. This method enhances bandwidth efficiency and improves robustness against impairments like polarization-dependent loss.
Area of Science:
- Optical Communications
- Information Theory
- Signal Processing
Background:
- Coherent optical communication systems are crucial for high-speed data transmission.
- Existing modulation schemes face limitations in bandwidth efficiency and robustness against impairments.
- Short-reach systems require specialized solutions for performance optimization.
Purpose of the Study:
- To propose and demonstrate a novel four-dimensional (4D) modulation scheme for short-reach coherent optical communication.
- To enhance system bandwidth efficiency and improve tolerance to polarization-related impairments.
- To mitigate the error floor and boost cross-polarization correlation.
Main Methods:
- Implementation of a polar-based eight-level multi-level coded (MLC) architecture for 4D dual-polarization 16-ary quadrature amplitude modulation (4D-DP-16QAM).
- Utilizing an outer concatenated encoder to strengthen polarization-domain interdependence.
- Employing multi-stage decoding (MSD) for efficient soft-information exchange between polarization branches.
Main Results:
- The proposed 4D-DP-16QAM scheme achieved a 0.77 dB improvement in optical signal-to-noise ratio (OSNR) sensitivity.
- Demonstrated superior robustness against polarization-dependent loss (PDL) and in-phase and quadrature (IQ) skew.
- Outperformed conventional coherent optical DP-16QAM systems in experimental 60 GBaud tests.
Conclusions:
- The proposed 4D-MLC modulation scheme offers significant advantages for short-reach coherent optical communication.
- Enhanced polarization protection and efficient decoding lead to improved system performance and robustness.
- This approach represents a promising advancement for future high-capacity optical networks.
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