We constructed a FBG (fiber Bragg grating) sensor system based on a fiber-optic Sagnac interferometer. A fiber-optic
laser source is used as a strong light source to attain high signal-to-noise ratio. However the unstable output power and
coherence noises of the fiber laser made it hard to separate the FBG signals from the interference signals of the fiber
coils. To reduce noises and extract FBG sensor signals, we used a Gaussian curve-fitting and a wavelet transform. The
wavelet transform is a useful tool for analyzing and denoising output signals. The feasibility of the wavelet transform
denoising process is presented with the preliminary experimental results, which showed much better accuracy than the
case with only the Gaussian curve-fitting algorithm.
The aim of this work is to design and fabricate a flow sensor using an artificial hair cell (AHC) inspired by biological
hair cells of fish. The sensor consists of a single cilium structure with high aspect ratio and a mechanoreceptor using
force sensitive resistor (FSR). The cilium structure is designed for capturing a drag force with direction due to flow field
around the sensor and the mechanoreceptor is designed for sensing the drag force with direction from the cilium structure
and converting it into an electric signal. The mechanoreceptor has a symmetric four electrodes to sense the drag force
and its direction. To fabricate the single cilium structure with high aspect ratio, we have proposed a new design concept
using a separated micro mold system (SMS) fabricated by the LIGA process. For a successful replication of the cilium
structure, we used the hot embossing process with the help of a double-sided mold system. We used a composite of
multiwall carbon nanotube and polydimethylsiloxane (MWCNT-PDMS). The performance of the mechanoreceptors was
measured by a computer-controlled nanoindenter. We carried out several experiments with the sensor in the different
flow rate and direction using the experimental test apparatus. To calibrate the sensor and calculate the velocity with
direction based the signal from the sensor, we analyzed the coupled phenomena between flow field and the cilium
structure to calculate the deflection of the cilium structure and the drag force applying to the cilium structure due to the
flow field around sensor.
We propose a fiber-optic interferometric CT that uses a time-delayed sampling signal processing to extract
the current-induced phase information. The interference signal of the reflection type Sagnac sensor coil is
sampled with a carefully adjusted time delay. And the phase is extracted by using an arctangent
demodulation. The accuracy comparison between the proposed and a lock-in amplifier demodulation showed
the feasibility of the proposed technique. Also the outputs from a flint glass sensor coil and a standard fiber
sensor coil were compared in the same condition, proving the low birefringence of the flint glass shows the
better performance. The phase measurement accuracy of the proposed demodulation technique was about
8.09 mrad.
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