Frequency offset drift monitoring: enabling simultaneously optimum performance and minimum cost of frequency offset...

Area of Science:

• Optical communication systems
• Signal processing for telecommunications

Background:

• Frequency offset (FO) is a critical impairment in coherent transmission systems caused by laser wavelength mismatch.
• Fast Fourier Transform-based FO estimation (FFT-FOE) is standard but computationally intensive, leading to high energy use if operated continuously.
• Laser frequency drift (FOD) necessitates periodic FOE to track variations and ensure system performance.

Purpose of the Study:

• To address the challenge of determining optimal FFT-FOE operation frequency for minimal complexity and energy consumption.
• To propose a novel scheme for monitoring frequency drift (FOD) to enable efficient FOE.
• To experimentally validate the proposed method in a high-speed coherent system.

Main Methods:

• Development of a frequency drift monitoring (FOD) scheme utilizing sparse fast Fourier transform (SFFT).
• Integration of a downsampling process to further reduce the computational complexity of subsequent FFT-based FO estimation (FFT-FOE).
• Experimental verification using 28 Gbaud coherent transmission systems.

Main Results:

• The proposed sparse FFT-based FOD monitoring scheme achieves simultaneous optimization of system performance and reduction in FOE cost.
• A downsampling technique effectively lowers the complexity of subsequent FFT-FOE operations.
• Experimental results confirm the efficacy of the proposed methods in a practical 28 Gbaud coherent system.

Conclusions:

• The sparse FFT-based FOD monitoring scheme provides an efficient solution for managing frequency offset in coherent systems.
• This approach balances the need for accurate FO tracking with the demand for reduced computational complexity and energy efficiency.
• The proposed method offers a practical strategy for optimizing FOE operations in high-speed optical communication.