Publications de Stella Foaleng Mafang

Effect of pulse depletion in a Brillouin optical time-domain analysis system

Luc Thévenaz, Stella Foaleng Mafang, Jie Lin

Energy transfer between the interacting waves in a distributed Brillouin sensor can result in a distorted measurement of the local Brillouin gain spectrum, leading to systematic errors. It is demonstrated that this depletion effect can be precisely modelle ...

Optical Society of America2013

Opto-acoustic coupling and Brillouin phenomena in microstructure optical fibers

Luc Thévenaz, Stella Foaleng Mafang, Duc Minh Nguyen

Like photonic crystals have revolutionized the way of manipulating optical waves at the sub-micron scale, phononic crystals have more recently played similar decisive role for sound waves, or more generally elastic waves. Then, the idea of coupling light a ...

IEEE2012

Brillouin Echoes for Advanced Distributed Sensing in Optical Fibres

Stella Foaleng Mafang

Brillouin scattering is particularly efficient and attractive for the implementation of strain and temperature distributed sensing in optical fibres. Recently a trend has been observed that modern advanced applications require a substantial step towards be ...

EPFL2011

Distributed Brillouin sensing with sub-meter spatial resolution: modeling and processing

Luc Thévenaz, Stella Foaleng Mafang

A general analytic solution for Brillouin distributed sensing in optical fibers with sub-meter spatial resolution is obtained by solving the acoustical-optical coupled wave equations by a perturbation method. The Brillouin interaction of a triad of square ...

Optical Society of America2011

Impact of pump depletion on the determination of the Brillouin gain frequency in distributed fiber sensors

Luc Thévenaz, Stella Foaleng Mafang, Jie Lin

The energy transfer between the two interacting optical waves in a distributed sensor based on stimulated Brillouin scattering can lead to a non-uniform spectral distribution of the pumping power after a long propagation. This results in a spectrally disto ...

SPIE2011

Detrimental effect of self-phase modulation on the performance of Brillouin distributed fiber sensors

Luc Thévenaz, Stella Foaleng Mafang

We show that the spectral broadening of the pump pulse through self-phase modulation in a time-domain distributed Brillouin sensor has a considerably detrimental effect in the measurement, especially in the case of long distances and high-resolution pulses ...

Optical Society of America2011

High Spatial and Spectral Resolution Long-Range Sensing Using Brillouin Echoes

Luc Thévenaz, Stella Foaleng Mafang, Kwang-Yong Song, Sang Hoon Chin, Nikolay Primerov

While classical configurations have a practical spatial resolution of 1 meter, novel approaches have been demonstrated that can overcome this limit to offer spatial resolutions in the centimetre range, while preserving full measurand accuracy. ...

Optical Society of America2011

Depletion in a distributed Brillouin fiber sensor: practical limitation and strategy to avoid it

Luc Thévenaz, Stella Foaleng Mafang, Jie Lin

Energy transfer between the interacting waves in a distributed Brillouin sensor can result in a distorted measurement of the local Brillouin gain spectrum, leading to systematic error. We demonstrate here that this behavior can be fully and precisely model ...

SPIE2011

Impact of Raman scattering and modulation instability on the performances of Brillouin sensors

Luc Thévenaz, Stella Foaleng Mafang

The impact of Raman scattering and modulation instability is studied in Brillouin time-domain analysis systems. It turns out to be very detrimental for long-range sensing as a result of the extended interaction length combined to the high pump peak pulse p ...

SPIE2011

Photonic crystal fiber mapping using Brillouin echoes distributed sensing

Luc Thévenaz, Stella Foaleng Mafang

In this paper we investigate the effect of microstructure irregularities and applied strain on backward Brillouin scattering by comparing two photonic crystal fibers drawn with different parameters in order to minimize diameter and microstructure fluctuati ...

Optical Society of America2010

Recent progress towards centimetric spatial resolution in distributed fibre sensing

Luc Thévenaz, Stella Foaleng Mafang, Kwang-Yong Song, Sang Hoon Chin, Nikolay Primerov

Optical fibre sensors based on stimulated Brillouin scattering have now clearly demonstrated their excellent capability for long-range distributed strain and temperature measurements. The fibre is used as sensing element and a value for temperature and/or ...

The International Society for Optical Engineering2010

High spatial and spectral resolution long-range sensing using Brillouin echoes

Luc Thévenaz, Stella Foaleng Mafang

High spatial (~cm) and spectral (~MHz) resolution Brillouin sensing is realized with enhanced signal to noise ratio using a pre-activated acoustic field and an optical phase control over the interrogating pulse. Pre-activation of the acoustic field preserv ...

IEEE Institute of Electrical and Electronics Engineers2010

Observation of Brillouin linewidth broadening and decay time in photonic crystal fiber

Luc Thévenaz, Stella Foaleng Mafang

We present a novel distributed sensing technique that allows for the observation of Brillouin gain spectral distribution and acoustic decay time in photonic crystal fiber as well as in standard single-mode fiber. ...

IEEE2010

Experimental observation of Brillouin linewidth broadening and decay time in photonic crystal fiber

Luc Thévenaz, Stella Foaleng Mafang

We present a novel distributed sensing technique that makes possible the observation of Brillouin gain spectral distribution and acoustic decay time in photonic crystal fiber as well as in standard single-mode fiber. ...

IEEE2010

Advanced Brillouin-based distributed optical fibre sensors with sub-meter scale spatial resolution

Luc Thévenaz, Stella Foaleng Mafang, Kwang-Yong Song, Sang Hoon Chin, Nikolay Primerov

Classical configurations of Brillouin distributed optical fibre sensors show a spatial resolution limited by the phonon lifetime to 1 meter. Novel approaches can substantially overcome this limit through the prior activation of the acoustic wave. ...

IEEE2010

Impact of self phase modulation on the performance of Brillouin distributed fibre sensors

Luc Thévenaz, Stella Foaleng Mafang

The spectral broadening of the pump pulse through self phase modulation in a time domain distributed Brillouin sensor is demonstrated to have a non-negligible detrimental effect, leading to a doubling of the effective gain linewidth after some 20 km in sta ...

The International Society for Optical Engineering2010

Experimental verification of the effect of slow light on molecular absorption

Luc Thévenaz, Stella Foaleng Mafang, Sang Hoon Chin, Isabelle Dicaire

The absorption of light by a gas molecule has been measured comparatively using light propagating in normal conditions and in a slow light regime. The experiment is designed to make the 2 measurements possible without modifying the interaction conditions, ...

SPIE2009

Study of a progressive failure in soil using BEDS

Luc Thévenaz, Stella Foaleng Mafang

In Geotechnical Engineering, progressive failure in soil-structure interaction is one of the least understood problems. It is difficult to study this phenomenon at laboratory scale, because of the large amount of strain gages required per unit length/area ...

SPIE2009

Optical sampling technique applied to high resolution distributed fibre sensors

Luc Thévenaz, Stella Foaleng Mafang

A technique developed to acquire fast optical signals using low frequency detection and acquisition is presented here. It is based on optical sampling that creates a replica of the fast signal on a much slower time scale by a simple strobe effect. High ban ...

SPIE2009

Optimized configuration for high resolution distributed sensing using Brillouin echoes

Luc Thévenaz, Stella Foaleng Mafang

A novel configuration has been developed to optimize the response of Brillouin echoes for distributed fibre sensing. Fully resolved measurements of the Brillouin frequency shift of a 5cm spot perturbation have been performed using a 500 ps (5cm) pulse widt ...

SPIE2009