A POF ALKANE SENSOR EMPLOYING ANTIOXIDANT-ADDED SWELLABLE POLYMER CLADDING

摘要

We have developed leaky/waveguide conversion-type plastic optical fiber (POF) alkane sensors. These sensors take advantage of the refractive index change caused by the swelling of the polymer cladding due to alkane gas. In our previous works, blend polymers used as sensing cladding were created by adding polyvinylidene fluoride (PVDF) or plasticizing agents--low refractive index materials--to polyisoprene (PIP), which exhibits swelling in the presence of alkane gas. These POF sensors had a strong sensitivity and a fast response time. However, the oxidation of the cladding polymer causes a deterioration of sensitivity over time. Therefore, as an alternative to using PVDF to regulate the refractive index of the cladding, this study aimed at improving sensitivity and reducing the time-dependent changes of the sensor by using the antioxidants sebacic acid bis(2,2,6,6-tetramethyl-4-piperidyl) ester and dibutylhydroxytoluene. No sensitivity decrease of the POF sensors with the antioxidant-doped cladding were observed, even after more than a month. We thus demonstrated the effectiveness in sensitivity preservation of the addition of antioxidants to sensor cladding.