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We report, to our knowledge, for the first time on humidity-induced Brillouin frequency shifts in perfluorinated graded index polymer optical fibers. A linear relation between Brillouin frequency shift and humidity was observed. Furthermore, the humidity coefficient of the Brillouin frequency shift is demonstrated to be a function of temperature (-107 to -64 kHz/%r.h. or -426 to -49 kHz m3/g in the range of 20 to 60 °C). An analytical description proves temperature and humidity as two mutually independent effects on the Brillouin frequency shift.
Analytical model for ball-lensed couplers to calculate the insertion loss for each optical mode. The basis for the calculation are commercial perfluorinated polymer optical (PFGI-POFs) and silica based fibres (SOFs). The modal power distribution for given misalignments are presented as well as the reflection-based losses at all optical interfaces. Additionally, the ball-lensed interconnection between PFGI-POF and SOF was theoretically demonstrated.
Possibility of post-fabrication doping of commercial PMMA fibers using well-known solution doping technique is presented. The cladding of 1 mm PMMA fiber is doped with Rhodamine B with the help of methanol-mediated diffusion of the dye molecules into the fiber material. Doping of the fiber core was not possible even at extended doping times. The proposed method represents rather simple and cheap way for preparing custom cladding-doped POFs with high flexibility of dopant choice and fiber length. Produced cladding-doped fibers have potential for various sensing or lighting applications.
One of the unique advantages of polymer optical fibres (POF) is that they can be used to measure very high strain values up to 100 % and beyond exceeding the strain limits of silica fibre-based sensor principles. In this paper the distributed strain measurement capabilities of POF based on backscatter change evaluation are summarized and distributed backscatter measurement technologies are intro-duced. Application examples in the structural health monitoring (SHM) field are presented: a promising approach is the integration into technical textiles for high-strain measurement in earthwork structures and crack detection in buildings. The potential of POF for future applications in SHM such as distributed relative humidity sensing is discussed.
We describe the fabrication of a polycarbonate (PC) micro-structured polymer optical fiber (mPOF) and the writing of fiber Bragg gratings (FBGs) in it to enable strain and temperature measurements. We demonstrate the photosensitivity of a dopant-free PC fiber by grating inscription using a UV laser. We further show that PC Bragg gratings can be extended up to at least 3% without affecting the initial functionality of the micro-structured fiber. The response of PC FBGs to temperature up to 125°C is also investigated. Polycarbonate has good mechanical properties and its high temperatureresistance might extend the range of application of polymeric FBGs.