A Fiber-Optic Microsensor and Probe to Measure the Index of Refraction in the Ocean

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Phase II of this SBIR research, will continue the development of two types of refraction micro-sensors, resulting in at least one calibrated prototype microsensor probe. It will also improve the accuracy and dynamic range of the spectrograph detector, largely from off-the-shelf components. An optical fiber transmission link will be developed to allow remote use of the microsensor; this development will include optimizing the reeling and unreeling techniques and minimizing the transmission link induced signal distortion. Finally, the work on the index of refraction to specific volume algorithm will continue with higher order terms in temperature and pressure included. The goal is an equation of state for the specific volume good to 1x10-5 cm 3/g at the 95% confidence level. The refraction microsensor and transmission link improvements from this research would have its most immediate commercial application in the chemical process control industry and HPLC (High Performance Liquid Chromatography). It would also have a long awaited application in oceanography, but with a longer development effort. The precise measure of seawater density in the oceans is critical to many investigations. Traditional methods for deriving density rely on independent measurements of seawater temperature, pressure, and conductivity. Differences in electronic sensor response rates and other drawbacks have become a limiting factor in making these determinations. However, the optical properties such as the index of refraction of light in seawater (and other liquids) change as a function of density. Recent advances in optical technology make it now possible to measure these changes and transmit data more effective than is presently possible using electric or electromechanical sensors.