Simplified turbo equalizer for bandwidth-limited 50G passive optical networks

Area of Science:

• Telecommunications Engineering
• Optical Networks
• Digital Signal Processing

Background:

• 50G passive optical networks (PON) enable cost-effective implementations using low-cost devices, but face performance degradation due to limited bandwidth.
• Chromatic dispersion (CD) in the O-band, while low, cumulatively impacts 50G on-off keying signals over longer distances (e.g., 40km).
• Inter-symbol interference (ISI) arises from device limitations and CD, hindering bit error ratio (BER) performance.

Purpose of the Study:

• To propose a simplified Turbo equalizer utilizing a maximum-log-maximum a posteriori (Max-Log-MAP) module for 50G PON.
• To address ISI caused by bandwidth-limited low-cost devices and cumulative chromatic dispersion.
• To reduce computational complexity compared to conventional Log-MAP modules.

Main Methods:

• Implementation of a simplified Turbo equalizer with a Max-Log-MAP module.
• Replacing complex logarithmic and exponential calculations with simple comparisons within the equalizer.
• Experimental evaluation of the equalizer's performance in 0km, 20km, and 40km access scenarios.

Main Results:

• The Max-Log-MAP module significantly decreases computational complexity without performance loss.
• Receiver sensitivity improvements of approximately 0.1dB (0km), 0.25dB (20km), and 0.5dB (40km) were achieved.
• The simplified Turbo equalizer effectively compensates for ISI in bandwidth-limited 50G PON.

Conclusions:

• The simplified Turbo equalizer is a promising solution for enhancing the performance of bandwidth-limited 50G PON.
• This approach offers a practical method to overcome ISI challenges in cost-sensitive optical network deployments.
• The proposed equalizer facilitates the deployment of 50G PON in demanding access scenarios up to 40km.