Nokia Bell Labs Publishes Research on Optical Link Synchronization

Nokia Bell Labs has published a technical review addressing new digital signal processing (DSP) methods for resolving synchronization issues in coherent optical links. The research specifically focuses on phase and frequency estimation, which has been a significant challenge in optical data transmission.

Traditionally, the synchronization requirements for transmit and local oscillator (LO) lasers in coherent optical systems, such as homodyne systems, have been stringent. This necessitated optical phase-locked loops, imposing significant demands on laser linewidth. Emerging DSP techniques enable synchronization to be performed in the digital domain, thereby reducing these requirements.

The review examines how digital signal processing can improve the performance of coherent optical receivers. The methods have been applied to both digital and analog links and allow for the synchronization of free-running LO lasers with the received optical signal. This advancement is a crucial step towards achieving more reliable and efficient optical data communication.

The publication, authored by Noriaki Kaneda, offers an in-depth look at the technical challenges and solutions in the field. It builds upon Bell Labs' long-standing research and development in optical communications. Advances in the technology now permit laboratory-scale demonstrations of DSP-assisted coherent optical receivers.