C.Z. Shi

Improving the performance of a FBG sensor network using a genetic algorithm

Genetic algorithm is used to improve the performance of FBG sensors within in a wavelength-division multiplexed sensor network. Simulations and experiments demonstrated wavelength detection accuracy of a few microstrains even when the spectrums of FBGs within the network are partially or completely overlapped.

Cantilever optical vibrometer using fiber Bragg grating

A cantilever optical vibrometer using a fiber Bragg grating (FBG) is developed. The sensor head is made by attaching an FBG to a triangular beam to provide position-independent strain for the purpose of acceleration measurement. The vibrometer demonstrates a noise-limited acceleration resolution of 2.8×10 –4 √Hz with repeatability error of less than 2.4%.

Improving the wavelength detection accuracy of FBG sensors using an ADALINE network

We report the use of an adaptive linear network for enhancing the wavelength detection accuracy in fiber Bragg grating sensors. A wavelength detection accuracy of /spl sim/10 pm is experimentally achieved when the unwanted interferometric signals are presented.

Improving the performance of FBG sensors in a WDM network using a simulated annealing technique

Simulated annealing technique is used to improve the performance of fiber Bragg grating (FBG) sensors in a wavelength-division-multiplexed network. Experiments demonstrated strain detection accuracy of /spl sim/2.5 /spl mu//spl epsiv/ when the spectrums of FBGs are fully or partially overlapped.

Improving measurement accuracy of fiber Bragg grating sensor using digital matched filter

Fiber Bragg grating (FBG) sensors are promising candidates for strain measurements in smart structures. The wavelength-encoded nature of the reflected signals from FBGs allows for absolute strain measurement and for multi-point operation based on wavelength division multiplexing (WDM). To measure strain variation with good accuracy, detection of the small shift in the Bragg wavelength is essential. In this paper, we report the use of a digital matched filter (DMF) for improving the wavelength detection accuracy. The DMF technique has been used extensively in image processing and pattern recognition for the detection of weak signals in a noisy environment. We apply it here for the detection of Bragg wavelength in FBG sensors when the SNR is low.

Enhancement of the measurement range of FBG sensors in a WDM network using a minimum variance shift technique coupled with amplitude-wavelength dual coding

The measurement range of fiber Bragg grating sensors within a WDM network is extended by the use of a combination of amplitude-wavelength dual coding and a minimum variance shift technique. The crosstalk between sensors can be minimized even when the spectrums of FBGs within in network are partially or fully overlapped.

Diaphragm-type fiber-optic interferometric acoustic sensor

A diaphragm-type fiber-optic acoustic sensor is developed. In such a sensor, the sound-induced strain is imposed on the fiber on the diaphragm-type sensing element, and can be measured by the use of a Mach-Zehnder interferometer. The diaphragm structure can provide di- rectional response with high sensitivity. The experimental measurement frequency range is from 100 Hz to 5 kHz. The sensitivity and minimum detectable acoustic pressure of the system are 2139 dB re V/mPa and 82 dB re mPa, respectively.