Interview with Fellows

Interview with MULTIPLY Fellow Florent Bessin

Dr. Florent Bessin received his MSc degree in physics in 2016 and his Ph.D. in 2019 from the University of Lille. Now he is a MULTIPLY Fellow at Aston Institute of Photonic Technologies, Aston University, and the title of his project is «Addressing Comb Tuneability in Optical Resonators». We asked Florent about his research group and project results.

– You are working with Prof. Nick Doran, who was one of the founders of the photonics group at Aston University. Could you please tell us more about your group’s research?

Telecommunications play a crucial role in today’s society and with the massive increase of exchange of information around the world these last decades, optical fibers and light become the main support to carry information around the globe at high data speed rate. Because of the loss of light along with the propagation in optical fiber, Erbium doped-fiber amplifiers (EDFA) are used at periodic intervals to compensate these losses. These amplifiers are robust and easy to implement but face some limits to increase the data speed rate capacity because of their bandwidth and wavelength range. Our team of 4 postdoctoral fellows coming from all over the world is working on amplifiers (fiber optical parametric amplifiers, FOPA) using a different process to amplify signals that overcome these limitations faced by EDFA. These amplifiers we are developing use nonlinear processes and can theoretically work at any wavelength, with high bandwidth and gain. Different designs are explored by my coworkers like half-loop, phase-sensitive, Mach-Zehnder configurations to improve performances, and characteristics of these FOPA.

– How your group’s research can improve the lives of people?

For now, amplifiers (FOPA) we are developing are mainly used in the research area and still need improvements for real-life applications. However, they are really promising for future applications in fiber optical telecommunications and could operate on large bandwidth at different wavelengths allowing us to follow the massive increase of data speed rate required by our society.

Florent’s working space

– What are the most important skills you improved here in AiPT?

One thing I really wanted to learn and improve my skill on when I came to AIPT was the control of instruments for lab experiments via computers and algorithms. Such control in the experiment was very important for me since a high volume of tasks can be executed with precision and accuracy avoiding human errors. It also gives more flexibility, and it allows to set and track instruments parameters/measurements with one platform. I came to AIPT with very little knowledge about these technics; however, my team at AIPT uses these kinds of systems a lot and shows me how to do that. In no time, and with help of my team’s members I was able to build my amplifier (FOPA), control, and connect all the equipment used in this setup to one computer to perform automated measurements. By having all these instruments connected to one system I was also able to go further and use a control algorithm like a feedback loop to compensate for drift of parameters in real-time (like output power measured at the output of the amplifier).

– Has your area of interest changed or expanded due to the work on your MULTIPLY project?

Yes, my interests have expanded during my fellowship, and developed some interest in electronics. During my fellowship, I worked on a new design for an optical amplifier (FOPA) promising better performance than standard ones. This design was based on an interferometer configuration (Mach-Zehnder) that is really sensitive to external sound variation in pressure and temperature creating fluctuation of the length of fibers used in the device. To overcome this issue, I had to build an active feedback loop system compensating these fluctuations in real-time. These kinds of loop use electronics to work and such equipment was not available in the lab and needed to be designed on purpose. Since I had only basic knowledge about electronics at that time, I started to read articles on electronics, follow tutorials and read books to find how to create my own system. Finally, with some difficulties and help of coworkers, of course, I was able to have a perfectly working system using components like operational amplifiers, potentiometers, resistors, and capacitors that compensate these fiber length fluctuations.

Florent’s working space

– What difficulties did you face during your MULTIPLY fellowship?

I think like most people these last 2 years, we had to adapt our work and schedule with the Covid situation and lockdowns. The first 6 months of my fellowship I was expecting to work in the lab on experiments, but because of the first lockdown, I had to adapt my plan. I decided to investigate some theoretical ideas for FOPA, like using filters to improve their performances also known as quasi-phase matching for FOPA. So, I started to read many papers, to investigate this concept and to develop some equations to predict gain provided by this kind of amplifiers. Then, I developed some applications to compare in real-time my theoretical model and numerical simulations when changing parameters of the system. I was thinking at that time to use this app to find the right parameters to build a real FOPA using this concept.

Aside from the Covid situation, I also had to face some “bad luck” with brand new faulty optical components that took me some while to identify in my setup. Some of these components designed for high power were changing from there specification at high power that needed a full analysis to be understand. For other faulty components, I should have checked them before implementing them. Next time, I will be more careful, I learned from my mistake I think.

– Your MULTIPLY project was extended due to Covid. Will there be additional research results?

Yes, these last 6 months gave me opportunities to collaborate with people from other groups in Aston. We developed new concepts (theory) on fiber cavities operating in nonlinear regimes and obtained a good agreement between the theory we developed and numerical simulations. My coworker and I started to develop an experimental setup this month to investigate this new concept. We are very excited by this new idea and expect results if everything goes well before the end of March.

Florent’s working space

– What is your plan for the future? Aston, academia, industry?

I would like to work in academia in France as a lecturer. There is a national campaign every year that starts in March to select people in multiple steps (first write a proposal, then if it is accepted there is a second round which is an oral presentation) where the 1st ranked obtains the position. I applied last year for different positions but it did not work. The process is though, like everywhere, and your profile does not always match with the position available, however, it is good training for next time and I will apply again this year.

I also plan to write and submit a proposal for a postdoctoral fellowship in France for the StaRS project (Haut de France) that targets people working in foreign countries. I would like to develop my proposal around the topics we are investigating with my coworker in Aston about fiber cavities operating in nonlinear regimes in order to study it more deeply.