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This work addresses the comprehensive viscosity measurements and assessment of fluidic materials in the range from 0.01 to 2000 Poises using a fiber optical viscometer with the long-period fiber grating (LPFG) technology. The fluidic materials used and evaluated in this study were AC-20 asphalt cement, four types of silicone oils, and sunflower seed oil. We simultaneously measured the LPFG-induced discharge time and the transmission spectra both in hot air and fluidic materials (other than the AC-20 asphalt) at six different temperatures, i.e., 30, 60, 80, 100, 135, and 170 Celsius. An electromechanical rotational viscometer was also used to measure the viscosities of fluidic materialsthe silicone oils and sunflower seed oil at the above six temperatures. Comparative analysis shows that the LPFG-induced discharge time agreed well with the viscosities obtained from the rotational viscometer. The LPFG-based viscometer was capable of measuring the viscosity (discharge time) in the range from 0.12 to 2000 Poises, which is much wider than the viscosity range of a traditional electromechanical rotational viscometer. This fiber-optic LPFG-based viscometer could be proposed and implemented in the field of road and airfield pavement technology such as the viscosity measurements of asphalt cements, emulsified asphalt binders, and other viscous materials. Hopefully, such a highly sensitive viscometer is suitable for use in various fields of applications, such as civil, food, chemical and biological, mechanical, petroleum, and aerospace engineering.

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A microfluidic system for chloride ion measurement using a long-period fiber grating (LPFG) is presented. Optical fiber sensors based on waveguide technology are promising and attractive in chemical, biotechnological, and civil engineering applications. The LPFG-based microfluidic system used to measure the transmission powers of different chloride ion concentration solutions of sea sand and seawater. The results show the relationship between transmitted light intensities and different chloride ion concentration solutions was close to linear. This system could be potentially used to discriminate the different chloride ion concentration solutions. This LPFG-based microfluidic system for chloride ion measurement reported here could hopefully benefit the development and applications in the field of civil engineering especially for concrete and raw material testing as well as infrastructure health monitoring.

Different types of objective lens (OL), i.e. circular, annular and one-dark-ring, are proposed and demonstrated to control the aspect ratio (AR) of micro-focus-region of high numerical aperture (NA) OL. Namely, the AR decreases from about 7.3 to 2.7 in case of using a circular OL with NA changes from 0.7 to 1.4, respectively. By using an annular OL, the transverse size of the focal spot of micro-focus-region decreases but its longitudinal size increases, so that the AR increases several times with respect to the case of circular OL. In particular, when using the one-dark-ring OL, one can decrease both transverse and longitudinal sizes of the focal spot or decrease only the longitudinal size, so that the AR obtained with a one-dark-ring OL is decreased to about 70% of that obtained with a circular OL. Such lenses can be useful for many applications such as sub-microfabrication and three-dimensional data storage using multi-photon absorption process.