Stenio Magalhães Ranzini


Stenio is pursuing a Ph.D. in optical communications at the Technical University of Denmark in the Machine Learning in Photonic Systems group. He received his bachelor’s degree at the University of Sao Paulo, Brazil, and in 2016 his master’s degree at the State University of Campinas, Brazil. From 2011 to 2018, he was working at CPqD Foundation, Campinas, Brazil. At CPqD, he developed and implemented state-of-art digital signal processing algorithms to be employed in a commercial physical layer ASIC for high speed (400G) optical communication transceivers. He also helped to found the Brazilian photonic society (SBFoton) in 2017, where he was the administrative director. Currently, he is in the fiscal council of the organization and a Marie-Curie Fellow.
Stenio acted as ESR representative in FONTE 2018-2019.




Stenio’s Blog – the home of his blog is here

Moving on!

After completing his PhD and leaving FONTE in August 2021, Stenio has immediately found a prestigeous position as Senior Development Engineer at Infinera, Nuremberg, where he is responsible for the development of signal processing algorithms for optical communication systems.

PhD thesis

On his time in the FONTE Consortium and its impact on his career Stenio writes:

‘One of the first benefits of FONTE that attracted my interest is being able to stay 50% of the time in the world-leading telecommunication center — Nokia Bell Labs (NBL) Germany. I was hoping to see how an industry researcher would answer some of the problems that are also treated in academia,  as each institution has different constraints. Now that I am finishing my Ph.D., I am happy to say my expectations were exceeded.

I have learned so much in only 3 years of the project. It was only possible because of the expertise I have found at the Technical University of Denmark (DTU) and at NBL. Since the first day, we have had excellent communication with frequent meetings with everyone involved in the project. The talks were exciting and more than enough to keep me motivated! Not only we had the interaction with the industry partner NBL, but I was also able to know and talk with other research in the consortium. In my case, it was with Aston University (UK), Delft University of Technology (Netherlands), and Télécom ParisTech (France). I think interacting with other research centers, and the industry simultaneously is one of the things I will miss from my Ph.D.

FONTE also prepared different training events such as workshops, summer/winter schools, and bespoke events. I learned how to organize my CV, write papers, prepare my Linking, open a business, improve self-organization, make a presentation, and many more. I was also able to participate in many conferences, which exponentially increased my network!

FONTE also incentive outreach activity so anyone could learn what we were doing and our goals, which typically is only known to other research in the field. I participated in a massive event in Copenhagen called “Culture night” (before Covid-19) and talked to kids, adults, anyone who stopped to have a talk. It was a different perspective from the one I was used to, and I had to adapt so everyone could understand. The FONTE training came as a great help here as well.

In summary, I am genuinely grateful for being select for such a fantastic project! I am leaving FONTE with many new skills, an amazing professional network, and a Ph.D. project which has also generated a Patent!

On his main Scientific Achievements in FONTE, Stenio writes:

‘As one of the main scientific highlights, I am happy to say that we have produced 5 conference papers, 3 journal publications, and 1 patent during my Ph.D. Among the publications, 2 of the 3 journal publications and 2 of the 5 conference papers were invited papers, indicating recognition in the academic field (find all of them here). The publications also include published articles at the European Conference on Optical Communication (ECOC) and the Optical Fiber Communication Conference (OFC), the 2 biggest global conferences for optical communications and networking professionals, and journal publications of some of the best journals in the field — Journal of lightwave technology (JLT) and Journal of Selected Topics in Quantum Electronics (JQSTE). I have also talked at the conference about our research and exchange ideas with other researchers.

Besides the published works, I was also able to participate in 1 summer school and 2 winter schools that expanded my knowledge and my professional network. Moreover, I participated in many seminars with high-profile researchers in my field and asked direct questions. In some of these events, I was also able to create and present a poster about our study.

The industry partner, Nokia Bell Labs (NBL), was also very prepared to receive students in their research labs. In the summer, NBL has prepared an event called Nokia Bell Labs Global Intern Program. This program was fantastic as it showed me all the research areas within NBL. Each presentation was done by the field’s leading researchers, with a lot of time for questions and discussion. Besides NBL events, the researchers who have received me treated me like a team member.  Because of this environment, we were able to create a fantastic patent together.’

Stenio Magalhães Ranzini, Sept 2021

State-of-play: Update on Stenio’s research in FONTE

  • Performance analysis of monitoring techniques based on machine learning

    The constant increase in information due to inventions coming from internet-of-things, autonomous cars, and others, forces the network to re-inventing itself to keep demand efficiently. Optical performance monitor (OPM) techniques ensure that communication in an optical link, where most of the information goes through, is reliable. The current OPM techniques require full signal demodulation, which is too complex and expensive. Therefore, it is desirable to create a simple and cheaper mechanism to extract the necessary information. Using only photodetectors (PDs) to measure the power of the signal might be an alternative solution. However, due to the square-law detection, the phase information is lost in the process. In this scenario, machine learning (ML) techniques might be used to overcome this challenge. ML working as regression is a powerful tool that can determine a nonlinear relationship between input and output. Hence, a good promise in learning the relationship between the power signal and the channel parameters.
    We show some of the state-of-art solutions to address the topic highlighted previously and report a new approach using an optoelectronic receiver with ML to mitigate the CD in the direct detected system. Although this technique is used for mitigation, the idea of using an optical pre-processing might be extendable to OPM. The optoelectronic receiver consists of slicing the spectrum and detecting each of them with a photodetector, followed by an ML technique to reconstruct the transmitted information. Through this process, our previous works showed an increase in the transmission reach compare to a single PD receiver. (from: FONTE Deliverable D3.3)


  • System identification and parameter estimation
    System identification is the field that studies techniques to build mathematical models of dynamic systems. It can be used when no previous information is available from the system or when there is a model, but some parameters are unknown. The latter can also be called parameter identification. This is a powerful tool to simulate and understand real complex devices. The basic steps to build a model of a real system starts by collecting information (data) about it. Followed by choosing a structure that will represent the desired system. An error function is defined to measure the difference between the collected information and the estimative from the model. The difference between both systems is used to improve the model and approximate it from the real system as close as possible. One of the most important step of building a model is the choice of the structure that will represent the system. This can be a hard limitation of the model. For example, trying to model a nonlinear system with a linear model. Over the years, many different approaches were developed in the literature for system identification. A possible classification between the varieties of possibilities in structure is dividing them by linear and nonlinear models. We give a general idea in how to apply system identification for linear system using a finite impulse response (FIR) filter and for a nonlinear system using Volterra filter. (from: FONTE Deliverable D3.2)


  • Survey of machine learning algorithms for optical performance monitoring
    An incredible 4.8 zettabytes of total yearly IP traffic data has been predicted by Cisco for 2022. New applications of internet of things, the increasing number of smartphones, Ultra High Definition (4K) streaming videos and many other applications are driving the necessity for higher transmission rates to support this increasing need for data. Since fiber-optic communications are the backbone of the telecommunications systems, new solutions to cope with this ever-increasing need for transmission speed are critical. Nowadays, nonlinear effects in optical fibers are one of the major limiting factors for optical communications. Different technologies have attempted to address these impairments for optical transmission. Nonlinearity mitigation through digital signal processing (DSP), optical phase conjugation (OPC) and nonlinear frequency division multiplexing (NFDM) are the most known topics in this area. Although great results show the increase of the transmission data rate and reach, the implementation costs of any of them are still prohibitive. It is also worth to mention that all the mentioned techniques require full knowledge of the fiber transmission parameters to work properly. Optical performance monitoring (OPM) techniques estimates the parameter of the optical fiber channel, which is required at multiples point along the link. The multiple uses of this technology imply the necessity of simpler and cheaper solutions.
    Machine learning (ML) techniques may help solve the fiber nonlinearities for optical transmission and OPM, potentially reducing implementation costs. ML tools has a broad area of application and are very well known for being extremely effective for classification problems, typically for image classification and speech detection. Nonetheless, ML implementations with central processing units (CPU) are suboptimal in terms of speed and power efficiency. Considering the optical communication field, it also implies the necessity to convert the signal from optical domain to electrical/digital domain. In other words, an expensive solution. Alternatively, several researches using hybrid optical-electronic systems with reservoir computing (RC) and full optical neural networks (ONN) with programmable nanophotonic processor (PNP) have been demonstrated. We review these algorithms and point out potential advantages and disadvantages. (from: FONTE Deliverable D3.1)