Multiplication-free timing phase error detector for Nyquist and non-Nyquist optical signals

Area of Science:

• Optical Communications
• Digital Signal Processing

Background:

• Future flexible and heterogeneous coherent optical networks require versatile digital coherent receivers.
• A low-complexity timing phase error detector (TPED) that supports diverse pulse shaping schemes (PSSs) is crucial.

Purpose of the Study:

• To propose a novel TPED that is versatile for all PSSs, including Nyquist and non-Nyquist signals.
• To achieve the lowest computational complexity among existing TPEDs without receiver sensitivity penalty.

Main Methods:

• The proposed TPED requires only two samples per symbol and involves no multiplications.
• Numerical simulations and experimental validation were performed.

Main Results:

• The TPED demonstrates superior timing performance and PSS versatility in both open-loop and closed-loop conditions.
• The TPED was implemented on a field-programmable gate array (FPGA) for real-time clock recovery.

Conclusions:

• The proposed low-complexity, versatile TPED is suitable for advanced coherent optical communication systems.
• Real-time clock recovery performance was verified for 10 Gbaud Nyquist and non-Nyquist QPSK signals.