Title 1: Recent progresses in Brillouin distributed fibre sensing
Time: 10, Oct, 9:30~10:15am
Venue：国家光电实验室A101
Abstract: 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 strain can be obtained from any point along the fibre. While classical configurations have practically a spatial resolution limited by the phonon lifetime to 1 meter, novel approaches have been demonstrated these past years that can overcome this limit. This can be achieved either by the prior activation of the acoustic wave by a long lasting pre-pumping signal, leading to the optimized configuration using Brillouin echoes, or by probing a locally generated steady acoustic wave using either a ultra-short pulse propagating in the orthogonal polarization of a highly birefringent fibre or the correlation between randomly phase modulated waves. These novel configurations can offer spatial resolutions in the centimetre range, while preserving the full accuracy on the determination of temperature and strain.
Title 2: dynamic Brillouin gratings for optical signal processing and microwave photonics
Time: 10, Oct, 10:30~11:15am
Venue：国家光电实验室A101
Abstract: Abstract: The recent possibility to generate dynamic Bragg gratings by the interaction of 2 optical waves through stimulated Brillouin scattering has opened a new field to realize all-optical functions in optical fibres. A local and temporary grating can be placed at any position along an optical fibre and can be repositioned dynamically with a total flexibility. This new tool has found direct applications in all-optical delay lines, demonstrating a tunable delaying capacity of more than 1 microsecond with an ideal reconfigurable time. But it turns out that its field of application is much vaster, from optical storage and analog operations on the signal (time reversal, derivative, integration) to distributed sensing with an extreme spatial resolution, turning the optical fibre into a real sensitive nerve system.
Biography: Luc Thévenaz received the M.Sc. degree and the Ph.D. degree in physics from the University of Geneva, Switzerland. In 1988 he joined the Swiss Federal Institute of Technology of Lausanne (EPFL) where he currently leads a research group involved in photonics, namely fibre optics and optical sensing. Research topics include Brillouin-scattering fibre sensors, slow & fast light, nonlinear fibre optics and laser spectroscopy in gases.He achieved with his collaborators the first experimental demonstration of optically-controlled slow & fast light in optical fibres, realized at ambient temperature and operating at any wavelength since based on stimulated Brillouin scattering. The first negative group velocity of light in optical fibres was also realized in his lab using this approach.
During his career he stayed at Stanford University, at the Korea Advanced Institute of Science and Technology (KAIST), at Tel Aviv University and at the University of Sydney. In 2000 he co-founded the company Omnisens that is developing and commercializing advanced photonic instrumentation. He is Fellow of the Optical Society of America, Senior Member of the IEEE and Editor of Nature Scientific Reports.
