Description

Fiber optic telecommunications has seen rapid technological improvements in recent decades permitting to use the propagation support, the single-mode fiber, ever more efficiently. Key milestones have been (i) the wavelength-division multiplexing technologies allowing hundreds of wavelength channels to co-exist within the same single-mode fiber ; (ii) the optical fiber amplifier allowing great extension of transmission reach by optically re-generating attenuated signals; (iii) and most recently coherent communication technologies which is a constellation of both instrumental and digital technologies. Coherent transmitters encode data on a light field by modulating both amplitude, phase, and polarization degrees of freedom, and coherent receivers heterodyne-detect the same degrees of freedom followed by high-speed sampling and digitization, all the while advanced digital signal processing (DSP) is applied both before transmission and after reception to mitigate most impairments. Coherent communication technology is now nearing the physical limits of data transmission capacity in a single-mode fiber (around 100 Tb/s in the C-band with Erbium-dopes fiber amplifiers).

Within the PEPR project 'PLEIADES' (2025-2029) the PhLAM laboratory is working with Télécom Paris to examine the propagation support that is considered the best candidate to replace the single-mode fiber in new optical fiber communication networks : the multi-core fiber, in principle increasing fiber capacity by opening new spatial channels (one per core), but at the price of introducing a new type of impairment, inter-core cross-talk. The aim of the project is to both measure and model this impairment as well as developing DSP schemes to mitigate it.

The Phd work will be organized around the following steps:
• Literature review on multi-core fibers
• Numerical channel modeling of propagation in multi-core fibers
• Implementation and optimization of equalization and decoding schemes
• Experimentation of a high-speed coherent optical test bench for transmission over multi-core fibers.

Skills required

To be eligible for the Phd position, the candidate must hold a master’s degree in electrical engineering or a related field. The candidate must have excellent knowledge in optical communication and signal processing. Experience and skills gained through laboratory experimentation can be highly advantageous.

Bibliography

https://doi.org/10.1038/s41467-025-59037-1

Keywords

Multi-core fiber, Coherent transmission, Digital signal processing (DSP)