Kernel adaptive filtering-based phase noise compensation for pilot-free optical phase conjugated coherent systems

Area of Science:

• Optical Communications
• Signal Processing
• Nonlinear Optics

Background:

• Phase noise (PN) in dual-pump fiber-based optical phase conjugation (OPC) degrades pilot-free quadrature-amplitude modulation (QAM) signal quality.
• Deviations from ideal counter-phasing are a primary source of PN in OPC systems.

Purpose of the Study:

• To introduce a novel kernel-based adaptive filtering method for PN suppression in OPC.
• To evaluate the performance of the proposed method for 16-QAM and 64-QAM signals.

Main Methods:

• Development of a kernel-based adaptive filtering algorithm.
• Experimental and numerical validation of the proposed PN compensation scheme.
• Testing in optical back-to-back and mid-link OPC transmission configurations.

Main Results:

• The proposed method significantly improves signal-to-noise ratio compared to conventional PN compensation.
• No performance penalty was observed across various pump-phase mismatch values for 16-QAM.
• Successful application demonstrated for 64-QAM signals and in a transmission setup.

Conclusions:

• The kernel-based adaptive filtering is an effective technique for mitigating PN in pilot-free QAM signals processed by OPC.
• The method offers robust performance and broad applicability in optical communication systems utilizing OPC.