The Foton Institute invites you to the presentation of doctoral thesis work:
Improving optical access networks through analog equalization
Dylan Chevalier
under the supervision of Monique Thual and Pascal Scalart
This public defense will occur wednesday 26 november 2025 at 10h00 in Enssat room 020G.
Zoom link to attend the Defense online :
https://univ-rennes1-fr.zoom.us/j/61652406667
meeting ID: 616 5240 6667
key: 292235
Jury members:
- *Prof. Ghaya Rekaya-Ben Othman, *Institut Polytechnique de Paris,
Reviewer - *Assoc. Prof. Yannis Le Guennec, *Université Grenoble Alpes, Reviewer
- *Prof. Catherine Lepers, Télécom SudParis, *Committee Member
- *Prof. Monique Thual, Université de Rennes, *Thesis directress
- *Prof. Pascal Scalart, Université de Rennes, *Thesis co-director
- *Dr. Gaël Simon, Senior Researcher, Orange Innovation, *Supervisor
- *Dr. Laurent Bramerie, Senior Researcher, Institut FOTON, *Supervisor
Keywords: Analog equalization, FFE, 50G-PON, FEC, LDPC
Summary:
In the context of passive optical networks (PON), the move towards
50G-PON, which targets data rates of up to 50 Gbit/s, is accompanied by
technical challenges linked to the interference between symbols created
by chromatic dispersion and the reduced bandwidth of the low-cost
components used. To compensate for these degradations, channel
equalization is essential, and can be implemented using either Digital
Signal Processing (DSP) or Analog Signal Processing (ASP). More
economical and less energy-intensive, the analog solution avoids the
need for costly high-rate analog-to-digital converters, but must contend
with certain imperfections specific to analog solutions. This thesis
proposes a method for optimizing an analog FeedForward Equalizer (FFE)
based on the minimum mean square error criterion, with experimental
validation in the electrical and optical domains. Results show a
significant reduction in the bit error rate and an improvement in the
eye diagram. Secondly, the study examines the combination of an analog
FFE with a Hard-Input Forward Error Correction (HI-FEC), in order to
compare this approach with the digital one. It is shown that an analog
FFE combined with HI-FEC can offer performance close to that of a
digital solution based on Soft-Input FEC (SI-FEC), while being more
affordable and less power-hungry. These results underline the relevance
of the analog approach in meeting 50G-PON requirements.