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Proceedings Paper

Mode mixing in fiber optic oximeter
Author(s): Varoujan David Amirkhanian; Wylie I. Lee
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Paper Abstract

Most catheter based oximeters use optical fiber to deliver two M more colors of light to the blood and collect the reflected lights with another optical fiber. Oxygen saturation of the blood is calculated from intensity of the returned lights. The coupling efficiency of this type of two-fiber sensor depends on the separation of fibers, the numerical aperture (NA) of the fibers, and the launching condition of lights from LED's to the transmission fiber. A micro-optical integrator was designed to combine outputs from two LED's into a multimode step-index fiber pig-tail through a high NA microball lens. The mismatch in the modes of propagation between red and IR lights was corrected by looping and sine-wave bending the fiber before it was coupled to an NA limiting GRIN lens, which also serves as an exit window. A far-field scan of two lights shows these two lights have spatial overlap of 92% or better. The overlap at the tip of the catheter, after it was coupled to the mode mixing pig-tail, is better than 98%. The addition of this simple method of mode-mixing has improved the overlap by nearly 30% and has substantially improved the accuracy of the oximeter, especially when in vitro calibration is used before taking the measurement in blood.

Paper Details

Date Published: 1 July 1990
PDF: 8 pages
Proc. SPIE 1201, Optical Fibers in Medicine V, (1 July 1990);
Show Author Affiliations
Varoujan David Amirkhanian, Baxter Edwards MDS Div. (United States)
Wylie I. Lee, Baxter Edwards MDS Div. (United States)

Published in SPIE Proceedings Vol. 1201:
Optical Fibers in Medicine V
Abraham Katzir, Editor(s)

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