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Least-squares-assisted BCJR algorithm for severe ISI mitigation in bandwidth-limited IM/DD optical interconnection
Optics Express
|August 13, 2025
Summary
A new least-square-assisted Bahl, Cocke, Jelinek, and Raviv (LS-BCJR) algorithm enhances optical interconnection systems. This method significantly improves receiver sensitivity for 160 Gb/s pulse amplitude modulation signals, mitigating inter-symbol interference.
Area of Science:
- Optical communication systems
- Signal processing
Background:
- Inter-symbol interference (ISI) severely degrades performance in bandwidth-limited optical interconnections.
- Pulse amplitude modulation (PAM4) is crucial for high-speed optical data transmission.
- Accurate symbol detection is vital for maintaining signal integrity.
Purpose of the Study:
- To propose and experimentally validate a novel detection algorithm for mitigating ISI in intensity-modulation direct-detection (IM/DD) PAM4 systems.
- To enhance receiver sensitivity and overall system performance in high-speed optical interconnections.
Main Methods:
- Development of a least-square-assisted Bahl, Cocke, Jelinek, and Raviv (LS-BCJR) detection algorithm.
- Utilizing a training-based short-tap least-square (LS) equalizer to reconstruct the channel response.
- Assisting the BCJR estimator with optimized transition metric calculation for soft-symbol decisions.
Main Results:
- Experimental demonstration on a 160 Gb/s PAM4 signal within a 19-GHz bandwidth.
- LS-BCJR scheme improved receiver optical power sensitivity by 1.2 dB (vs. MLSE) and 0.9 dB (vs. conventional BCJR) at a BER of 2.4e-2.
- Achieved optimal receiver sensitivity improvement of 3 dB over the conventional BCJR scheme at a BER of 3.8e-3.
Conclusions:
- The proposed LS-BCJR algorithm effectively mitigates ISI in IM/DD PAM4 optical systems.
- Significant improvements in receiver sensitivity and system performance are achieved.
- LS-BCJR offers a superior solution compared to conventional BCJR and MLSE for high-speed optical interconnections.
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