Simpplified extended Kalman filter phase noise estimation for CO-OFDM transmissions

Area of Science:

• Optical Communications
• Signal Processing
• Digital Modulation

Background:

• Phase noise is a critical impairment in coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems, degrading signal quality.
• Existing methods for phase noise compensation, such as pilot-aided (PA) and blind phase search (BPS), have limitations in spectral efficiency and computational complexity.
• 16-Quadrature Amplitude Modulation (16-QAM) is increasingly used in high-capacity optical systems, making robust phase noise compensation essential.

Purpose of the Study:

• To propose a flexible and efficient simplified extended Kalman filter (S-EKF) scheme for phase noise compensation.
• To evaluate the performance of the S-EKF in both pilot-aided and blind modes for 16-QAM CO-OFDM systems.
• To compare the S-EKF with conventional PA and BPS methods in terms of performance, spectral efficiency, and computational complexity.

Main Methods:

• Development of a simplified extended Kalman filter (S-EKF) algorithm.
• Implementation of the S-EKF in both pilot-aided and blind operational modes.
• Extensive Monte Carlo simulations were conducted in back-to-back and dual-polarization fiber transmission configurations.

Main Results:

• The proposed S-EKF scheme achieved a low optical signal-to-noise ratio (OSNR) penalty of 1 dB for a 64-subcarrier, 32 Gbaud 16-QAM CO-OFDM system with 200 kHz laser linewidth.
• The pilot-aided mode required only 2 pilots, and the blind mode used just 4 inputs for effective phase noise compensation.
• Compared to conventional PA and BPS methods, the S-EKF demonstrated a spectral efficiency enhancement by a factor of 3 and a computational effort reduction by over 50 times.

Conclusions:

• The S-EKF offers a flexible and highly effective solution for phase noise compensation in 16-QAM CO-OFDM systems.
• The algorithm provides significant improvements in spectral efficiency and computational complexity, making it suitable for practical high-speed optical communication systems.
• The S-EKF's performance in both pilot-aided and blind modes highlights its versatility for various system configurations and constraints.