Instrumentation of Stratospheric Balloon Straps with Optical Fibre for Temperature and Strain Monitoring.

This article is devoted to the instrumentation, with optical fibres, of the straps holding the envelope of stratospheric balloons. This instrumentation is motivated in the first instance by the need to validate the numerical models used in the design of balloons. It must also be used to measure the temperature along the envelope in order to deduce the pressure field. It is shown at first that the optical fibres can be inserted inside a strap during its fabrication. Different kinds of insertion are considered, none of them perturb the industrial process. The instrumented straps were then submitted to thermal and mechanical tests and the distributed Brillouin frequency shifts were measured. We thus determined the type of insertion to be used according to the parameter (temperature or strain) to be measured and assessed the performance of the measurement chain.

Local characterization of fiber-Bragg gratings through combined use of low-coherence interferometry and a layer-peeling algorithm.

The technique presented here allows us to obtain an accurate determination of the refractive index modulation amplitude, the mean effective index, and the chirp of fiber-Bragg gratings. A layer-peeling algorithm is used to extract this information from low-coherence interferometry measurements. Finally, we present a systematic study over 10 uniform and chirped gratings to proof the reliability and accuracy of this technique.