Application of Advanced Digital Signal Processing Techniques for Noise Characterization of Optical Frequency Combs

The introduction of digital signal processing (DSP) assisted coherent detection has been a cornerstone of modern fiber-optic communication systems. The ability to digitally, after analogue-to-digital converter, compensate for chromatic dispersion, polarization mode dispersion, and phase noise has rendered traditional analog feedback loops largely obsolete. While analog techniques remain prevalent for phase noise characterization of single-frequency lasers, the phase noise characterization of optical frequency combs presents a greater challenge. This complexity arises from the multitude of fluctuating parameters, necessitating innovative measurement methods.

To fully characterize the phase noise of optical frequency combs, it is essential to separate the contributions from various phase noise sources, including 1) carrier-envelope offset, 2) repetition rate, 3) spontaneous-emission-induced phase noise, 4) chirp, 5) pulse-width fluctuations, and others. Identifying and understanding these phase noise sources can pave the way for advanced stabilization schemes, enabling even higher precision in measurements.

In this webinar, Darko Zibar will introduce a novel measurement method leveraging on coherent detection and DSP-based subspace tracking. This approach effectively decomposes phase noise into its constituent sources. Furthermore, using this method, Prof. Zibar will demonstrate that the standard phase noise model for resonant electro-optic combs fails under certain conditions.

Subject Matter Level: Intermediate - Assumes basic knowledge of the topic

What You Will Learn:
• How advanced digital signal processing techniques can be used for phase noise characterization of optical frequency combs
• The main principles behind subspace tracking and how it can be used for phase noise source separation
• The well-accepted "standard" phase noise does not hold for all combs and the importance of performing phase noise source separation

Who Should Attend the Webinar:
• Researchers working in the field of optical frequency combs 
• Researchers working in the field of phase noise measurements
• Researchers working in the field of DSP for fiber-optic communication systems

About the Presenter: Darko Zibar from Technical University of Denmark

Darko Zibar is currently Professor at the Department of Electrical and Photonics Engineering, Technical University of Denmark and the group leader of Machine Learning in Photonics Systems.  His research efforts are focused on the application of digital signal processing and machine learning techniques to advance classical and quantum optical communication and measurement systems. Some of his major scientific contributions include: record capacity hybrid optical-wireless link (2011), record sensitive optical phase noise measurement technique (2021) and record-bandwidth (S+C+L band) programmable gain Raman amplifier (2019). He is the recipient of Young Researcher Award by University of Erlangen-Nurnberg (2016), European Research Council (ERC) Consolidator Grant (2017), Alexander von Humboldt Bessel Research Award, (2021), and Villum Investigator Award (2023). Finally, he was a part of the team that won the EU HORIZON 2020 prize for breaking the optical transmission barriers (2016).