Maximization of Coupled Power in Plastic Fiber Probe for Light Reflection Measurement

This paper demonstrates design and development of low-cost optical probes for measuring reflected/ scattered spectrum using plastic optical fiber (POF) towards non-invasive medical applications. The work focuses on maximizing the collected power through controlling the number of fibers as well as the spacing to the sample. Three designs are included: single emitting-single collecting bifurcated fiber probe, ten emitting-single collecting fiber bundle, and single emitting-ten collecting fiber bundle. In the experiment, cool white LED and optical power meter are used to validate the fabricated probes. The fabricated POF-bifurcated fiber has coupling efficiency of $\sim2 -4$% which is comparable to an available commercial silica bifurcated fiber. Adding nine more collecting fibers, the coupling efficiency is enhanced up to four folds of the case of single collecting fiber. This implementation guarantees a low-cost probe design using a plastic fiber. That can be applied in many of optical instruments.