Journal of the Optical Society of Korea

Optical Society of Korea (한국광학회)
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A Fiber Optic Sensor for Measurements of Solute Concentration in Fluids

  • Kim, Chang-Bong (Department of Information and Communication Engineering, Kongju National University) ;
  • Su, C.B. (Department of Electrical Engineering, Texas A&M University)
  • Received : 2003.03.18
  • Published : 2003.06.01
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Abstract

A new and simple calibration technique that greatly enhances the measurement sensitivity of conventional fiber-optic reflectometry based on Fresnel reflection from the tip of a fiber is used for demonstrating the feasibility of measuring solute concentrations and index changes in fluids to very high precision. The amplitude of pulses originating from reflection from the fiber-fluid interface is compared in real-time with the amplitude of reference pulses from a fiber-air interface such that errors caused by pulse amplitude fluctuations and slightly varying detector responses are corrected. Using solutions of salt and water, it is demonstrated that the technique is capable of measuring index changes of about $1 {\times} 10^{-5}$ corresponding to a salt concentrations of 0.01 %.

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References

  1. H. B. Fisher, E. J. List, R. C. Koh, J. Imberger, and N. H. Brooks, Mixing in Inland and Coastal Waters (Academic Press, New York,1997).
  2. S. D. Woodruff and B. S. Yeung, “Double-beam Fabry-Perot interferometer as a refractive index detector in liquid chromatography,” Anal. Chem., vol. 54, pp. 2124-2125, 1982. https://doi.org/10.1021/ac00249a055
  3. Brandemburg, “Differential refractometry by an integrated-optical Young interferometer,” Sensors & Actuators B38-39, pp. 266-271, 1997. https://doi.org/10.1016/S0925-4005(97)80216-X
  4. T. A.Wilson and W. F. Read, “Low cost interferometric differential refractometer,” Am. J. Phys., vol. 61, pp. 1046, 1993. https://doi.org/10.1119/1.17338
  5. V. Krishna, C. H. Fan, and J. P. Longtin, “Real-time precision concentration measurement for flowing liquid solutions,” Rev. Scientific Instruments, vol. 71, pp. 3864-3868, 2000. https://doi.org/10.1063/1.1288236
  6. C. H. Fan and J. P. Longtin, “Laser-based measurement of liquid temperature or concentration at a solidliquid interface,” Exp. Thermal Fluid Science, vol. 23, pp. 1-9, 2000. https://doi.org/10.1016/S0894-1777(00)00019-4
  7. J. Lin and C. W. Brown, “Spectroscopic measurement of NaCl and seawater salinity in the near-IR region of 680-1230 nm,” Applied Spectrosc., vol. 47, pp. 239-241, 1993. https://doi.org/10.1366/0003702934048208
  8. J. Lin and C. W. Brown, “Near-IR fibre-optic probe for electrolytes in aqueous solution,” Anal. Chem., vol. 65, pp. 287-292, 1993. https://doi.org/10.1021/ac00051a017
  9. M. Born and E. Wolf, Principle of optics, 3 Ed. (Pergamon Press, New York, 1965), p. 38.
  10. Y. M. Yunus, “Temperature dependence of refractiveindex and absorption of NaCL $MgCl_2$ and $Na_2SO_4$ solution as major component in natural seawater,” Appl. Optic., vol. 31, pp. 2963-2964, 1992. https://doi.org/10.1364/AO.31.002963