Georges Humbert

Characterizations at very high temperature of electric arc-induced long-period fiber gratings

Electric arc-induced long-period fiber gratings, with low insertion loss (<0.2 dB) and high isolation peaks (−24 dB), have been fabricated in standard single-mode fiber (Corning SMF28). High temperature characterizations of the fabricated gratings in the range of 30 to 1200 °C have been performed. The sensitivity are in good agreement with recent published works. Specific spectral shift of the resonance peaks with temperature have been shown. Temperature annealing of the gratings, at 200, 400 and 600 °C show high thermal stability compared with UV-induced gratings. More particularly, modal dependence of the resonance shift and time dependence during annealing cycles, have been investigated at high temperature. The evolutions of the spectra have been related to the development of internal stresses in the fiber. These temperature characterizations help to explain the writing mechanism of these gratings.

Characterizations at high temperatures of long-period gratings written in germanium-free air-silica microstructure fiber.

We report what is to our knowledge the first characterization at high temperatures of long-period fiber gratings written in Ge-free air-silica microstructure fiber. The gratings written with the electric-arc technique suffer a low shift of the resonance wavelengths when the temperature is increased from 20 degrees C to 1200 degrees C. This shift is studied and compared with that of a long-period fiber grating written in a standard single-mode fiber by the same technique. Good thermal stability of the grating and of the fiber after annealing at 1200 degrees C for 1 h is demonstrated.

Two-steps fabrication of single-mode fiber couplers with a CO2 laser source

We have used a CO2 laser as a heating source to fabricate a single-mode fiber couplers. The process consists of fusing and stretching two standard single model fibers initially maintained in lateral contact. We have fabricated 3 dB couplers at 1500 nm with insertion loss < 0.5dB. We also have fabricated multiplexers such as a 100% coupler at 1310 nm and at 1550 nm. The channel isolation of these components are > 30dB with a bandwidth of 30 nm at -30dB. Finally, a coupler with a long constant waist have been fabricated.

Electric-arc-induced long period grating filters fabricated with dual concentric core fibers

We have fabricated Long Period Grating filters in two Dual Concentric Core Fibers by an electric arc discharge technique. The gratings have induced coupling between the fundamental modes of the two cores. We have obtained filter with rejected band around 1220 nm and 1559 nm respectively, characterized by insertion loss lower than 0.5 dB. We also have investigated the inteest of using this fiber to implement a highly selective Mach-Zehnder interferometer with a 2.4 nm inter-fringe. Despite the high Ge-doping of the used fiber, thermal characterizations show a temperature sensitivity of the transmitted spectrum similar to that of the same grating written in a standard Single Mode Fiber.

Fabrication of long period grating using electric discharge in non-hydrogenated fiber

We present the fabrication of long period fiber grating, in non-hydrogenated standard telecommunication fiber, using an electric discharge. We have obtained a gratin with low insertion loss, dynamic rejection of 37.5dB at 1530 nm and bandwidth of 16.3nm at -3 dB. The performances are competitive compared to literature. We have demonstrated the flexibility of the process by fabricating band pass and compact concatenated filters.

Long period fiber grating filters fabrications and characterizations using electric arc in nonhydrogenated fibers

We have fabricated Long Period Fiber Gratings (LPFG), using non-hydrogenated standard single-mode fiber (SMF28TM), with an electric arc discharge, issued from a commercial splicer. We have obtained gratings with low insertion loss and isolation of 37.5 dB at 1530 nm. The bandwidth at -3 dB (FWHM) is evaluated to be 16 nm. Evolution of the spectral responses (peaks isolation, bandwidth) are explored. We have performed temperature characterization of the realized gratings between 0 degrees C and 750 degrees C. The gratings exhibit a robust and stable behavior to temperature annealing. We showed a spectral shift of the resonance peaks with temperature, these evolutions are worthy of note. We have studied and experimented phase-shift filters. The filters performances are competitive compared to literature. These characterizations provide a set of phenomena to help explanation of the inscription mechanism of the gratings. The fabrication is simple, it does not require to hydrogenate the fiber. The control of the filter parameters makes it possible to produce any filter profile. We have demonstrated the simplicity and flexibility of the process.

Capteurs à fibre optique pour la surveillance et l’observation du stockage de déchets radioactifs en couche géologique profonde

SONDER LA MATIERE PAR LES ONDES ELECTROMAGNETIQUES URSI 2015 104 REE N°4/2015 Par Sylvie Delepine-Lesoille1 , Stephanie Leparmentier2 , Jean-Louis Auguste2 , Georges Humbert2 Ingenieur R&D, Agence nationale pour la gestion des dechets radioactifs (Andra)1 , Laboratoire Xlim2 Andra is the French body in charge of radioactive wastes. Optical fiber sensors are attractive for their numerous advantages over traditional sensors. More precisely, ability to perform distributed sensing, without dead zones, along kilometers, would be very useful for the monitoring of Cigeo, the future deep geological repository for high and intermediate-level long-lived radioactive wastes. Andra has launched a qualification process for distributed strain and temperature measuring systems based on Rayleigh, Brillouin and Raman scattering in opti- cal fibers. It includes tests and eventually developments to reach compatibility with the harsh environment of Cigeo (radiation, hydrogen release…). Andra also contributes to research studies on optical fibers to provide distributed hydrogen and radiation measurements. As an example, the development of special optical fibers, with embedded Palladium partic