Polymer Optical Fiber Liquid Level Sensor: A Review

Polymer optical fiber (POF) level sensors have a lot of potential in liquid level sensing because of their inherent safety, chemical corrosion resistance, anti-electromagnetic interference, electrical isolation, compactness, high coupling efficiency, and flexibility. In this context, a review of POF liquid level sensing is presented. Several POF materials are introduced, including polymethyl methacrylate (PMMA) and perfluorinated polymer (CYTOP). In addition, the operation principles of intensity modulation and wavelength modulation are described in general. Thereafter, contemporary POF liquid level sensing applications are discussed. For intensity modulation, the bending or polishing type and coupling type sensors are introduced. There are also some extrinsic POF level sensors based on intensity modulation. For wavelength modulation, a POF fiber Bragg grating (POFBG) and a special structure grating based POF liquid level sensors are introduced.