Burst errors suppression for MLSE in high-speed IM/DD transmission systems using PAM.

Area of Science:

• Optical Communications
• Signal Processing

Background:

• Maximum Likelihood Sequence Estimation (MLSE) is optimal for removing inter-symbol interference (ISI).
• MLSE can cause problematic burst consecutive errors in M-ary Pulse Amplitude Modulation (PAM-M) intensity modulation/direct detection (IM/DD) systems with significant ISI.

Purpose of the Study:

• To propose and evaluate a precoding technique to suppress MLSE-induced burst consecutive errors in PAM-M IM/DD systems.
• To maintain the signal's probability distribution and Peak-to-Average Power Ratio (PAPR) using a 2M modulo operation.

Main Methods:

• A precoding scheme using a 2M modulo operation is applied before MLSE.
• A decoding process involving addition and a 2M modulo operation is implemented post-MLSE.
• Experimental validation using 112/150-Gb/s PAM-4 and over 200-Gb/s PAM-8 signals at C-band.

Main Results:

• The proposed precoding effectively breaks burst consecutive errors.
• For a 201-Gb/s PAM-8 signal, the precoding MLSE achieved a 1.4-dB receiver sensitivity gain.
• The maximum length of burst consecutive errors was reduced from 16 to 3.

Conclusions:

• The integrated precoding and MLSE approach successfully mitigates burst errors in high-speed PAM-M IM/DD systems.
• This technique offers significant improvements in receiver sensitivity and error performance for advanced optical communication systems.