Experimental and numerical demonstration of the acousto-optic effect applied in long period grating by means of
flexural waves is presented. The interaction between acoustic and optical waves is modeled with help of the method of
assumed modes, which delivers the strain field inside the grating and the transfer matrix method, which, given the strain
field as input, calculate the resultant grating spectrum. The experimental and theoretical results are found to be in good
agreement. The main effect of the bends in the grating is the break of degeneracy of the circular cladding modes, leading
the attenuation band to be changed. Among all the applications of this methodology, it is important to mention the
possibility of use as a tunable filter, laser cavity gain controller, switching device and transducer in sensing systems.
The development of a fiber extrinsic Fabry-Perot interferometer for measuring vibration amplitude and resonances of
piezoelectric elements is reported. The signal demodulation method based on the use of an optical spectrum analyzer
allows the measurement of displacements and resonances with high resolution. The technique consists basically in
monitoring changes in the intensity or the wavelength of a single interferometric fringe at a point of high sensitivity in
the sensor response curve. For sensor calibration, three signal processing techniques were employed. Vibration
amplitude measurement with 0.84 nm/V sensitivity and the characterization of the piezo resonance is demonstrated.
Acoustic waves, generated by exploiting the acousto-optic effect within silica optical fibres, were used to enhance the
sensitivity of a long period grating. Most of the physical parameters measured by using an LPG involve simple linear and
passive transformations of spectral shifts. However, by adding a temporal element using acoustic waves, parameters that
require dynamic assessment become accessible. In this work we demonstrate the measurement of fluid viscosity by
measuring the rise time and acousto-optic efficiency. We show results of sensor characterization and suggest the
possibility of monitoring a chemical reaction in real time.
The measurement of the tuning speed in fiber Bragg gratings is an increasingly important parameter for characterizing the dynamics of
tunable devices. Optical spectrum analyzers and wavelength meters are not suitable due to their slow response for measuring the
wavelength shift in time. In this paper we report on a technique for estimating the tuning speed of a fiber Bragg grating which is based
on accessing the wavelength shift through a calibration curve and measuring the time in which the shift occurs with the help of a fast