The Brillouin scattering light signal is a wideband signal containing a lot of phase noises and amplitude noises. And the
envelope of the Brillouin scattering signal will include some characteristics due to the influences of temperature and
strain change on the sensing fiber. In order to obtain the useful temperature and strain change information, the amplitude
demodulation of the noise signal should be conducted, and at the same time, it is necessary to effectively suppress the
signal noise. In this paper, Morlet wavelet has been used to do the envelope detection since it has band-pass filtering
function and signal demodulation function provided by the orthogonal characteristic between real part and imaginary part.
Moreover, the Morlet wavelet function has the characteristic of time-frequency analysis, and it can analyze envelope of
the signal and extract characteristic of the signal in the whole frequency range by changing the scale factor and
translation factor. Meanwhile, it can also suppress the signal noise effectively. The simulation model has been built to
verify the validity of envelope demodulation principle by Morlet wavelet algorithm. Theory analysis and experiment
show the algorithm is reasonable and efficient.
The optical fiber acousto-optic sensor (OFS) coated with piezoelectric ZnO has previously been investigated both theoretically and practically. While fabricating OFS, the performance of it will be affected by many parameters. Based on the equivalent circuit's model of cylindrical resonator of acoustic optic devices, an optimization method has been presented in this paper. By considering the effects towards the performance of optical fiber sensor due to some parameters, including electrode's thickness, Piezoelectric ZnO film thickness, the fiber's radius, resonator length, series impedance, and so on, the partial optimization of target functions including reflectance and coupling efficiency is programmed to produce optimized values. Also, combined with the effects of reflectance and coupling efficiency, the optimized values have been made based on the theory of multi-targets optimization.
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