Mode mixing in fiber optic oximeter

Varoujan David Amirkhanian; Wylie I. Lee

doi:10.1117/12.17554

1 July 1990 Mode mixing in fiber optic oximeter

Varoujan David Amirkhanian, Wylie I. Lee

Proceedings Volume 1201, Optical Fibers in Medicine V; (1990) https://doi.org/10.1117/12.17554
Event: OE/LASE '90, 1990, Los Angeles, CA, United States

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.

Citation Download Citation

Varoujan David Amirkhanian and Wylie I. Lee "Mode mixing in fiber optic oximeter", Proc. SPIE 1201, Optical Fibers in Medicine V, (1 July 1990); https://doi.org/10.1117/12.17554

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