Photopolymer coating of tapered optical fiber for chemical sensors

Photopolymerization process is present in the optical fiber technology since its beginning. Organic coatings preventing degradation of an optical fiber was the most important implementation of this process which ensured its practical industry application in telecommunication. However, this process can be implemented to design specialty transducers related to both optical and chemical sensors, as well. Simple optical transducer can be a microtip being an extinction of the optical fiber core as a polymer microelement. A chemical transducer can be a thin polymer layer manufactured on the tapered part of optical fiber. The second type of transducer can be applied to chromatography measurements as a solid phase microextraction fiber. In the paper, technology of the tapered optical fiber and photopolymer sensing layer formations were described. In the first step a standard heat and pull technique was used to taper an optical fiber which, then, was cleaved in two symmetric pieces. Light was launched to such a single element and output optical power from tapered part of the fiber was measured to optimize the photopolymerization process. Placing this element in a photopolymerizable monomer mixture and using a specially selected holder allow for manufacturing a polymer sorption layer applicable as a solid phase microextraction fiber. Extended description of technology of this chemical transducer type and preliminary experimental results displaying its feasibility were presented.