We compare four different sensing solutions suitable for distributed fiber optic humidity sensing in peruorinatedgraded-index polymer optical fibers (PFGI-POFs). Compared to silica fibers, polymer optical fibers offer advantageousbenefits including significantly higher break down strain, fracture toughness and humidity sensitivity.Various humidity-related effects in PFGI-POFs have been reported in the last years including measured attenuationand length changes as well as Brillouin frequency and Bragg wavelength shifts. The four aforementionedmethods could serve as a basis for distributed and quasi-distributed humidity sensing and are described hereclosely with an emphasis on plausible cross effects to temperature and strain. The main focus of this paper lies onthe comparison of four approaches with regard to method complexity, sensitivity to humidity, spatial resolution,real-time capability and e ort to compensate for cross e ects.
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