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Le Floch Sébastien

Professeur-e HES associé-e

Main skills

Rétrodiffusions Brillouin, Rayleigh

Main contract

Professeur-e HES associé-e

Phone: +41 32 930 22 49

Haute Ecole Arc - Ingénierie
Espace de l'Europe 11, 2000 Neuchâtel, CH

BSc HES-SO en Ingénierie et gestion industrielles - Haute Ecole Arc - Ingénierie

Métrologie
Optique
Capabilité des moyens de contrôle
Maîtrise statistique des procédés
Mathématiques

Ongoing

DISTANCE

Role: Co-applicant

Requérant(e)s: Beugnot Jean-Charles, Université de Besançon

Financement: INTERREG

Description du projet :

Réalisation d'un prototype de capteur distribué Brillouin sur de très longues distances (150km) grâce à des détecteurs à comptage de photons (Université de Besançon). La HE-Arc contribue au développement de cartes électroniques pour la synchronisation et la détection de photons ainsi qu'à l'amélioration des systèmes Brillouin classiques pour comparaison.

Research team within HES-SO: Le Floch Sébastien

Partenaires académiques: Beugnot Jean-Charles, Université de Besançon

Partenaires professionnels: Rochat Etienne, Omnisens (Morges, Suisse); Cussey Johann, Aurea (Besançon, France)

Durée du projet: 01.05.2024 - 31.10.2025

Montant global du projet: 1'102'174 CHF

Statut: Ongoing

Completed

Optimised Platform for Distributed Fibre Sensor

Role: Co-applicant

Requérant(e)s: Thévenaz Luc, EPFL

Financement: InnoSuisse

Description du projet :

Recherche et développement de nouvelles technologies appliquées aux capteurs distribués Brillouin.

Research team within HES-SO: Le Floch Sébastien

Partenaires académiques: Thévenaz Luc, EPFL

Partenaires professionnels: Rochat Etienne, Omnisens (Morges)

Durée du projet: 01.04.2020 - 01.04.2023

Statut: Completed

2025

S-BOTDA: exploiting frequency symmetry in Brillouin sensors

Scientific paper

to be published

Le Floch Sébastien

Optical Fiber Sensors (Porto), 2025

Summary:

We propose a new, simplified Brillouin Optical Time-Domain Analyzer that takes full advantage of frequency-symmetrical signals by measuring the dispersion of the probe power thanks to orthogonal polarizations of the dual-pump or probe.

2024

Brevet : Frequency tracking assisted BOTDR

Professional paper

submitted (2024)

Le Floch Sébastien

Brevet, soumis (UE), 2024

2022

Closed-loop technique based on gain balancing for real-time Brillouin optical time-domain analysis

Scientific paper ArODES

Li Zhang, Ana Gabriela Correa-Mena, Zhisheng Yang, Florian Sauser, Sébastien Le Floch, Luc Thévenaz

Optics Letters, 2022, vol. 47, no. 17, pp. 4299-4302

Link to the publication

Summary:

A closed-loop servo control based on balancing the gain of two probing frequencies is proposed for real-time Brillouin optical time-domain analysis (BOTDA) without post-processing. With the most basic BOTDA hardware setup, the system can perform measurement in 150 ms and track a sudden Brillouin frequency shift (BFS) change in excess of 300 MHz (corresponding to a temperature change of more than 250°C) over ∼5 km of fiber with a spatial resolution of 2 m. Moreover, the feedback loop is independent of the loss experienced by the probe and pump, with no requirement on the BFS uniformity along the fiber. All these advantages make the proposed system suitable for field applications in harsh environments.

2021

Few-mode elastomeric optical fibers

Scientific paper ArODES

Miguel Llera, Frédéric Flahaut, Sylvain Bergerat, Justin Benoit, Rowan Lüthi, Frédéric Mathez, Sébastien Le Floch, Yves Salvadé

Optical Materials Express, 2021, vol. 11, no. 7, pp. 2288-2299

Link to the publication

Summary:

We present a new approach for producing elastomeric optical fibers with an optical behaviour corresponding to a few-mode optical fiber. Different fibers have been produced by first fabricating thermoplastic polyurethane preforms and subsequently drawing them. The fiber attenuation has been measured by the cut-back technique and the fiber bending transmission tolerance evaluated. The fiber potential has been assessed through two basic experiments in order to highlight the benefits of elasticity and a reduced core diameter. Future potential of the proposed fiber is discussed and shows a very auspicious path towards new and unexplored applications.

Brevet : Use of the sidebands of a mach-zehnder modulator for a FMCW distance measurement

Professional paper

Le Floch Sébastien, Salvadé Yves, Marcel Rohner

Patent number: 11162773, 2021

2019

Fiber Bragg grating-based thermometer for drill bit temperature monitoring

Scientific paper ArODES

Miguel Llera, Kenny Hey Tow, Sylvain Bergerat, Yves Meyer, Serge Monnerat, Olivier Gloriod, Sébastien Le Floch, Yves Salvadé, Luc Thévenaz

Applied Optics, 2019, vol. 58, no. 22, pp. 5924-5930

Link to the publication

Summary:

The temperature measurement of a drill bit during an implantology drilling process is proposed by using a fiber Bragg grating fitted inside the drill bit. Due to the rotational nature of the drilling process, a free-space fiber-optic rotary joint is used for interrogating the fiber Bragg grating. Due to mechanical clearances and interferometric noise induced at this rotary joint, signal integrity is strongly deteriorated and is not workable without adequate measures. These measures involve a proper fiber lensing and a signal processing in order to remove the interferometric noise. Finally, a heating measurement on an implantology drill bit is performed and discussed for drilling several holes on a pork jaw sample.

2018

Unique Coded Sequence For Fast Brillouin Distributed Sensors

Scientific paper

Le Floch Sébastien

Optical Fiber Sensors (Lausanne), 2018

Link to the publication

Summary:

We present, for the first time, a colour coded sequence running in an endless loop and dedicated to ultra-fast Brillouin distributed sensors. Measurements within the whole elastic zone of single-mode optical fibers are presented.

2017

Cyclic coding for Brillouin optical time-domain analyzers using probe dithering

Scientific paper ArODES

Haritz Iribas, Alayn Loayssa, Florian Sauser, Miguel Llera, Sébastien Le Floch

Optics Express, 2017, vol. 25, no. 8, pp. 8787-8800

Link to the publication

Summary:

We study the performance limits of mono-color cyclic coding applied to Brillouin optical time-domain analysis (BOTDA) sensors that use probe wave dithering. BOTDA analyzers with dithering of the probe use a dual-probe-sideband setup in which an optical frequency modulation of the probe waves along the fiber is introduced. This avoids non-local effects while keeping the Brillouin threshold at its highest level, thus preventing the spontaneous Brillouin scattering from generating noise in the deployed sensing fiber. In these conditions, it is possible to introduce an unprecedented high probe power into the sensing fiber, which leads to an enhancement of the signal-to-noise ratio (SNR) and consequently to a performance improvement of the analyzer. The addition of cyclic coding in these set-ups can further increase the SNR and accordingly enhance the performance. However, this unprecedented probe power levels that can be employed result in the appearance of detrimental effects in the measurement that had not previously been observed in other BOTDA set-ups. In this work, we analyze the distortion in the decoding process and the errors in the measurement that this distortion causes, due to three factors: the power difference of the successive pulses of a code sequence, the appearance of first-order non-local effects and the non-linear amplification of the probe wave that results when using mono-color cyclic coding of the pump pulses. We apply the results of this study to demonstrate the performance enhancement that can be achieved in a long-range dithered dual-probe BOTDA. A 164-km fiber-loop is measured with 1-m spatial resolution, obtaining 3-MHz Brillouin frequency shift measurement precision at the worst contrast location. To the best of our knowledge, this is the longest sensing distance achieved with a BOTDA sensor using mono-color cyclic coding.

2016

Contrôle qualité et numérisation tridimensionnelle de pièces horlogères par tomographie rayons X

Professional paper ArODES

Yves Salvadé, Valentin Perez, Antoine Bueche, Sébastien Le Floch

Bulletin de la SSC (Société Suisse de Chronométrie), 2016, no. 82, pp. 33-37

Link to the publication

Summary:

La tomographie par rayons X est une technique bien connue dans le domaine médical, elle est cependant moins répandue dans le secteur industriel. Cette méthode d'imagerie très performante permet des mesures tridimensionnelles pour des pièces de géométrie complexe. Elle est en passe de devenir une méthode de mesure incontournable pour le contrôle qualité.

Liquid-air based Fabry-Pérot cavity on fiber tip sensor

Scientific paper ArODES

Miguel Llera, Thierry Aellen, javier Hervas, Yves Salvadé, Pascal Senn, Pascal Senn, Sébastien Le Floch, Herbert Keppner

Optics Express, 2016, vol. 24, no. 8, pp. 8054-8065

Link to the publication

Summary:

This paper presents a Fabry-Perot fiber tip sensor based on an air-liquid filled cavity. The cavity is sealed off by a thin gold coated membrane of parylene C, between 300 and 350 nm, creating a particularly flexible diaphragm. In order to retrieve and track the cavity of interest from other cavities formed within the sensor tip, a signal processing of the feedback signal is performed by inverse fast Fourier transform. The experimental sensor has been manufactured and tested for temperature, giving cavity length sensitivities of 6.1 nm/°C and 9.6 nm/°C for temperature increase and decrease respectively. The external gas pressure response gives a sensitivity of 15 nm/kPa. The fiber sensor has also been adapted for force sensing after silicone embedment and has shown a sensitivity of about 8.7 nm/mN. Finally, the sensor has been tested on insertion into a human temporal bone, proving that it could be an interesting candidate for insertion force monitoring for robotic cochlear implantation.

2015

Brevet : Brillouin optoelectronic measurement method and apparatus

Professional paper

Le Floch Sébastien

Patent number: 9116119, 2015

2001

Etude de la rétrodiffusion Brillouin dans les fibres optiques. Application aux capteurs de température et de pression.

Doctoral thesis

Le Floch Sébastien

2001, Brest : Université de Bretagne Occidentale

Link to the publication

2017

Brillouin optical time-domain analyzer for extended sensing range using probe dithering and cyclic coding

Conference ArODES

Haritz Iribas, Alayn Loayssa, Florian Sauser, Miguel Llera, Sébastien Le Floch

Proceedings of the 25th International Conference on Optical Fiber Sensors, 24-28 April 2017, Jeju, Korea, Republic of

Link to the conference

Summary:

We present an enhanced performance Brillouin optical time-domain analysis sensor that uses dual probes waves with optical frequency modulation and cyclic coding. The frequency modulation serves to increase the probe power that can be injected in the fiber before the onset of non-local effects and noise generated by spontaneous Brillouin scattering. This leads to higher detected signal-to-noise ratio (SNR), which is further increased by the coding gain. The enhanced SNR translates to extended range for the sensor, with experiments demonstrating 1-m spatial resolution over a 164 km fiber loop with a 3-MHz Brillouin frequency shift measurement precision at the worst contrast position. In addition, we introduce a study of the power limits that can be injected in the fiber with cyclic coding before the appearance of distortions in the decoded signal.

Enhancement of signal-to-noise ratio in Brillouin optical time domain analyzers by dual-probe detection

Conference ArODES

Haritz Iribas, Alayn Loayssa, Florian Sauser, Miguel Llera, Sébastien Le Floch

Proceedings of the 25th International Conference on Optical Fiber Sensors, 24-28 April 2017, Jeju, Korea, Republic of

Link to the conference

Summary:

We demonstrate a simple technique to enhance the signal-to-noise ratio (SNR) in Brillouin optical time-domain analysis sensors by the addition of gain and loss processes. The technique is based on the shift of the pump pulse optical frequency in a double-sideband probe system, so that the gain and loss processes take place at different frequencies. In this manner, the loss and the gain do not cancel each other out, and it makes possible to take advantage of both informations at the same time, obtaining an improvement of 3 dB on the SNR. Furthermore, the technique does not need an optical filtering, so that larger improvement on SNR and a simplification of the setup are obtained. The method is experimentally demonstrated in a 101 km fiber spool, obtaining a measurement uncertainty of 2.6 MHz (2σ) at the worst-contrast position for 2 m spatial resolution. This leads, to the best of our knowledge, to the highest figure-of-merit in a BOTDA without using coding or raman amplification.

New improvements for Brillouin optical time-domain reflectometry

Conference ArODES

Sébastien Le Floch, Florian Sauser

Proceedings of the 25th International Conference on Optical Fiber Sensors, 24-28 April 2017, Jeju, Korea, Republic of

Link to the conference

Summary:

This paper presents new techniques designed to improve the performances of a BOTDR. The first one introduces a second pump to the sensor, thus doubling the Brillouin signal on the receiver. The second one uses image processing with a two-dimensional Gaussian filter whose parameters are defined. The last technique explores the possibilities offered by colour codes. The benefits of each, in terms of signal-to-noise ratio, is presented by comparing measurements over a distance range of 50km with a spatial resolution of 5m. These techniques can easily be combined and the global improvement is estimated at 10dB, compared to conventional sensors.

Achievements

PEOPLE@HES-SO
Directory and Skills inventory

Le Floch Sébastien

Professeur-e HES associé-e

Main skills

Optique

Métrologie

Capteurs fibrés

Rétrodiffusions Brillouin, Rayleigh

Professeur-e HES associé-e

PEOPLE@HES-SO Directory and Skills inventory

Le Floch Sébastien

Professeur-e HES associé-e

Main skills

Optique

Métrologie

Capteurs fibrés

Rétrodiffusions Brillouin, Rayleigh

Professeur-e HES associé-e

PEOPLE@HES-SO
Directory and Skills inventory