Abstract
We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip. We use Zemax modelling to find the optimum CPC tip profile and fiber length of a polymer optical fiber diabetes sensor for continuous monitoring of glucose levels. We experimentally verify the improved performance of the CPC tipped sensor and the predicted production tolerances. Due to physical size requirements when the sensor has to be inserted into the body a non-optimal fiber length of 35 mm is chosen. For this length an average improvement in efficiency of a factor of 1.7 is experimentally demonstrated and critically compared to the predicted ideal factor of 3 in terms of parameters that should be improved through production optimization.
Highlights
Fluorescence based fiber-optical sensors have been used widely to measure various physical and biological quantities of interest, such as aluminum ions [1], glucose [2], α-streptavidin and α-CRP antibodies [3,4,5]
We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip
The assay chemistry inside the membrane consists of a glucose binding protein and a glucose analog labelled with a fluorophore and a dye, respectively, which make a Fluorescence Resonance Energy Transfer (FRET) pair
Summary
Fluorescence based fiber-optical sensors have been used widely to measure various physical and biological quantities of interest, such as aluminum ions [1], glucose [2], α-streptavidin and α-CRP antibodies [3,4,5]. FRET based polymer optical fiber (POF) sensors have been used for continuous in-vivo glucose sensing before [2, 10]. A simple solution, for a fiber based FRET sensor, can be to taper the fiber tip to increase its numerical aperture and thereby allow one to increase the excitation and the fluorescence light pickup efficiency. We here propose to use a CPC (Compound Parabolic Concentrator) polymer fiber tip for FRET based glucose sensors in order to increase the florescent signal and improve the signal to noise ratio. The CPC tip can concentrate the excitation light as well as increase the numerical aperture, even when being only a few hundred micrometers long. For portable sensors measuring continuously, the increased light capturing efficiency of the CPC fiber tip can reduce power consumption. The final part compares and discusses the characterization of real CPC shapes with Zemax results
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