Scientific Applications of Distributed Acoustic Sensing: State-of-the-Art Review and Perspective.

This work presents a detailed review of the development of distributed acoustic sensors (DAS) and their newest scientific applications. It covers most areas of human activities, such as the engineering, material, and humanitarian sciences, geophysics, culture, biology, and applied mechanics. It also provides the theoretical basis for most well-known DAS techniques and unveils the features that characterize each particular group of applications. After providing a summary of research achievements, the paper develops an initial perspective of the future work and determines the most promising DAS technologies that should be improved.

Implementation of a Mobile Platform Based on Fiber Bragg Grating Sensors for Automotive Traffic Monitoring.

Instrumentation techniques, implementation and installation methods are major concerns in today's distributed and quasi-distributed monitoring applications using fiber optic sensors. Although many successful traffic monitoring experiments have been reported using Fiber Bragg Gratings (FBGs), there has been no standardized solution proposed so far to have FBG seamlessly implemented in roads. In this work, we investigate a mobile platform including FBG sensors that can be positioned on roads for the purpose of vehicle speed measurements. The experimental results prove the efficiency of the proposed platform, providing a perspective toward weigh-in-motion systems.

Fiber Bragg grating regeneration at 450°C for improved high temperature sensing.

Type-I fiber Bragg gratings photo-inscribed in hydrogen-loaded B/Ge co-doped silica single-mode optical fibers have been regenerated efficiently at 450°C, which is the lowest temperature reported so far. The mechanical strength of the annealed fiber is preserved while ensuring temperature sensing of the regenerated gratings up to 900°C. Unlike low temperature cycles (≤600°C), an annealing process at higher temperatures revealed faster regeneration for strong gratings. Changes in grating strength were also measured before the regeneration cycle. These behaviors suggest the contribution of different mechanisms to the regeneration process with different relative dynamics.

Analysis and suppression of nonlinear frequency modulation in an optical frequency-domain reflectometer.

A new method for monitoring the nonlinearities perturbing the optical frequency sweep in high speed tunable laser sources is presented. The swept-frequency monitoring system comprises a Mach-Zehnder interferometer and simple signal processing steps. It has been implemented in a coherent optical frequency domain reflectometer which allowed to drastically reduce the effects of nonlinear sweep, resulting to a spatial resolution enhancement of 30 times.