Hybrid BOFDA/BOCDA system for distributed static and dynamic strain measurements.

We present a distributed optical fiber sensor based on a hybrid Brillouin optical frequency/correlation-domain analysis (BOFDA/BOCDA) configuration for both static and dynamic strain measurements. Distributed static strain (or temperature) measurements are realized using the conventional BOFDA method, i.e.

Distributed Temperature Sensing through Network Analysis Frequency-Domain Reflectometry.

In this paper, we propose and demonstrate a network analysis optical frequency domain reflectometer (NA-OFDR) for distributed temperature measurements at high spatial (down to ≈3 cm) and temperature resolution. The system makes use of a frequency-stepped, continuous-wave (cw) laser whose output light is modulated using a vector network analyzer. The latter is also used to demodulate the amplitude of the beat signal formed by coherently mixing the Rayleigh backscattered light with a local oscillator.

Tuning of the Brillouin scattering properties in microstructured optical fibers by liquid infiltration.

We demonstrate the possibility to modify the Brillouin scattering properties of a microstructured pure-silica core optical fiber, by infiltrating a liquid inside its holes. In particular, we show that the dependence of the Brillouin frequency shift (BFS) on the temperature can be reduced by infiltration, owing to the large negative thermo-optic coefficient of the liquid. Infiltrating a chloroform-acetonitrile mixture with a refractive index of 1.

Automated Damage Detection Using Lamb Wave-Based Phase-Sensitive OTDR and Support Vector Machines.

In this paper, we propose and demonstrate a damage detection technique based on the automatic classification of the Lamb wave signals acquired on a metallic plate. In the reported experiments, Lamb waves are excited in an aluminum plate through a piezoelectric transducer glued onto the monitored structure. The response of the monitored structure is detected through a high-resolution phase-sensitive optical time-domain reflectometer (ϕ-OTDR).

Brillouin scattering for refractive index sensing in non-adiabatic tapers.

We demonstrate the use of non-adiabatic tapers for refractive index sensing in optical fibers based on Brillouin scattering. By exciting higher order optical modes along the taper, the Brillouin gain spectrum becomes multipeaked, where each peak exhibits a different sensitivity to the refractive index of the surrounding medium. By this method, we demonstrate a sensitivity enhancement of the Brillouin frequency shift to refractive index changes by a factor of ≈ 4, compared to an adiabatic taper with the same waist diameter.