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Low-complexity mitigation of multipath interference in PAM-4 IM/DD systems via recursive filtering
Optics Express
|June 11, 2026
Summary
A new low-complexity method effectively mitigates multipath interference (MPI) in high-speed optical systems. This recursive filtering approach significantly reduces bit-error rates (BER) and enhances signal-to-interference ratio (SIR) tolerance.
Area of Science:
- Optical communication systems
- Signal processing
Background:
- Multipath interference (MPI) degrades high-speed intensity-modulation/direct-detection (IM/DD) systems.
- Existing digital signal processing (DSP) mitigation techniques often have high computational complexity.
Purpose of the Study:
- To propose and validate a low-complexity MPI mitigation method for IM/DD systems.
- To improve the performance of 32 GBaud PAM-4 systems under various signal-to-interference ratios (SIRs) and laser linewidths.
Main Methods:
- A two-stage recursive filtering approach: coarse mitigation for slow fluctuations and fine mitigation for residual distortion.
- Simulation and experimental validation on 32 GBaud PAM-4 systems.
Main Results:
- Substantial bit-error rate (BER) reduction across a wide range of SIRs and laser linewidths.
- Achieved BERs below the KP4-FEC threshold at an SIR of 22 dB.
- Improved SIR tolerance by over 8 dB for both broad- and narrow-linewidth lasers.
Conclusions:
- The proposed low-complexity recursive filtering method effectively mitigates MPI in high-speed IM/DD systems.
- Offers superior performance compared to existing digital filtering methods with significantly lower computational cost (4 multiplications, 2 additions, 2 registers per symbol).
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