According to the deficiencies of static demodulating method of Arrayed Waveguide Grating (AWG) for Fiber Bragg
Grating (FBG) reflecting wave wavelength and the characteristic of central wavelength of tunable AWG shifting with
applied voltage, the dynamic demodulating method based on tunable AWG for FBG's central wavelength wide-range is
presented. The experiment systems are set up with tunable AWG, adjustable voltage source, photomultiplier, data
acquisition card, and computer. Experiment results show that the system can effectively resolve the problems of
measurement wide-range off-centering for the FBG, and computer can real-timely report the results of off-centering of
the FBG central wavelength. AWG with the 2nm channel-spacing is used to demodulate, and the off-centering range of
reflecting wave wavelength of the measured FBG reach 6nm, its measurement error is less than 0.02%.
Based on the Arrayed Waveguide Grating (AWG) equation and output light intensity equation, dual peaks electro-optical
AWG is presented, whose properties are analyzed in details in the paper. The experiments for the electro-optical dual
peaks AWG are simulated by Optiwave software, and the experimental results verify the theory very well.
Two novel content meters for liquid refractive index or concentration measurement are proposed based on the simple reflex fiber optic sensor configurations. One sensor exploits a reflex and concentrically arranged fiber probe structure which is very similar to the traditional intensity-modulated fiber optic displacement sensors, but the light captured by receiving fibers is modulated by the varied solute concentration, being in proportion to the liquid refractive index, instead of displacement. The other sensor works based on detecting the edge shift of the reflected light spot, which is modulated by the refractive index variation of the liquid. Theoretical analysis and simulations are carried out with the measurement range of refractive index from 1.0 to 1.5.
Water content measurement technologies are very important for quality inspection of food, medicine products, chemical products and many other industry fields. In recent years, requests for accurate low-water-content measurement in liquid are more and more exigent, and great interests have been shown from the research and experimental work. With the development and advancement of modern production and control technologies, more accurate water content technology is needed. In this paper, a novel experimental setup based on near-infrared (NIR) spectral technology and fiber-optic sensor (OFS) is presented. It has a good measurement accuracy about ∓ 0.01%, which is better, to our knowledge, than most other methods published until now. It has a high measurement resolution of 0.001% in the measurement range from zero to 0.05% for water-in-alcohol measurement, and the water-in-oil measurement is carried out as well. In addition, the advantages of this method also include pollution-free to the measured liquid, fast measurement and so on.