Tech Briefs

Fiber-Optic Sensors for Measuring Oxygen Dissolved in Water

Colors of immobilized metal complexes change in the presence of dissolved oxygen.

Fiber-optic sensors for measuring concentrations of oxygen dissolved in water are undergoing development. In comparison with electrochemical dissolved-oxygen sensors, the fiber-optic sensors are expected to be easier to use and maintain. Also, unlike electrochemical dissolved-oxygen sensors, the fiber-optic dissolved-oxygen sensors are amendable to connection into networks for taking measurements at multiple sites.

The fiber-optic sensors detect oxygen through changes in color. A sensor of this type includes an optical fiber coated with an oxygen-conducting polymer matrix. Specific metal complexes that exhibit rapid and reversible binding of oxygen with associated changes in optical absorption spectra are immobilized in the polymer matrix. In operation, the coated fiber is immersed in water at a test site, and by use of optoelectronic components coupled with the optical fiber, the absorption spectrum of the metal complexes in the coating is measured. The absorption spectrum is then translated into the concentration of dissolved oxygen.

The absorption-measurement principle of the developmental fiber-optic sensors is compatible with a network of distributed sensors and results in lower costs of instrumentation.

This work was done by Michael Schwartz of Eltron Research, Inc., for Kennedy Space Center. Inquiries should be addressed to Michael T. Carter, Eltron Research, Inc., 4600 Nautilus Ct. South, Boulder, CO 80301; telephone (303) 530-0263.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to the above. Refer to KSC-11999, volume and number of this NASA Tech Briefs issue, and the page number.