Polymer optical fibers (POF) are mainly known as transmission fibers. Their main competitor in every field of application is the silica glass fiber. Compared to glass fibers, POF show much higher intrinsic losses. This limits POF to short range applications with fiber lengths below about 100 m for example in local area networks. Low specific weight, high flexibility, robustness and easy handling make them also very attractive for data links in vehicles like cars, ships or planes. The same characteristics and especially their high elasticity make POF also an interesting choice for fiber optic sensors [1]. Doped with organic laser dyes or lanthanide complexes POF have shown large gain which can be utilized in active optical sensors as well as fiber lasers and amplifiers [2].