Experimental demonstration of low-complexity trigonometric-memory-polynomial decision-feedback equalizer for...

Area of Science:

• Optical Communications
• Signal Processing
• Nonlinear Optics

Background:

• Intensity-modulation direct-detection (IM/DD) systems face performance limitations due to nonlinear distortions.
• Existing equalization techniques like Volterra-based methods can be computationally complex.
• High-speed optical transmission, such as 56-80 Gbit/s PAM-4, requires efficient solutions for signal integrity.

Purpose of the Study:

• To propose a novel and high-performance trigonometric-memory-polynomial decision-feedback equalizer (TMP-DFE) for IM/DD systems.
• To develop an improved version, TMP-IWDFE, to mitigate error propagation in decision feedback.
• To evaluate the performance and complexity of these schemes against conventional equalizers.

Main Methods:

• The TMP-DFE utilizes sine and cosine operations on received samples, implementable via the CORDIC algorithm with additions and shifts.
• It effectively models odd and even-order nonlinearities, with adjustable nonlinear factors.
• The TMP-IWDFE enhances the decision feedback mechanism to reduce error propagation.

Main Results:

• Experimental results in a 56-80 Gbit/s PAM-4 IM/DD system over 30-50 km SSMF show TMP-DFE outperforms V-DFE, DP-V-DFE, and DPAT-V-DFE in bit error rate (BER).
• TMP-DFE requires significantly fewer real multiplications compared to conventional schemes (20.04%-74.12% less).
• TMP-IWDFE demonstrates superior performance and lower complexity than V-IWDFE, DP-V-IWDFE, and DPAT-V-IWDFE.

Conclusions:

• The proposed TMP-DFE and TMP-IWDFE offer a high-performance and computationally efficient solution for nonlinear distortions in IM/DD systems.
• These schemes present a promising approach for future high-speed, low-cost optical transmission systems.
• The CORDIC-based implementation of TMP-DFE contributes to reduced hardware complexity.