Nonlinear distortion mitigation of DML-based OFDM optical systems with non-orthogonal DFT-precoding

Area of Science:

• Optical Communications
• Signal Processing

Background:

• Directly modulated lasers (DMLs) in orthogonal frequency division multiplexing (OFDM) systems face nonlinear distortion from laser chirp and fiber dispersion.
• This distortion degrades transmission performance and limits system reach.

Purpose of the Study:

• To propose a non-orthogonal Discrete Fourier Transform (DFT) matrix precoding scheme to mitigate nonlinear distortion in DML-based OFDM systems.
• To reduce peak-to-average power ratio (PAPR) and nonlinear distortion without compromising spectral efficiency (SE).

Main Methods:

• A non-orthogonal DFT matrix precoding scheme is employed.
• The cascaded binary-phase-shift-keying iterative detection (CBID) algorithm is utilized to manage induced inter-carrier interference (ICI).

Main Results:

• The proposed scheme experimentally achieved approximately 0.4-dB sensitivity improvement at the KP4-forward error correction (FEC) threshold.
• It outperformed the third-order Volterra nonlinear equalizer (VNLE).

Conclusions:

• The non-orthogonal DFT precoding scheme effectively mitigates nonlinear distortion in DML-OFDM systems.
• Significant reductions in computational complexity (90% multiplication, 88.32% addition) were achieved compared to VNLE.