Photopolymerizable microelements manufactured on the end face of optical fibers as microtips or microbridges between two optical fibers have drawn our attention as very attractive elements for optical fiber sensors’ transducers. In our first approach we have studied feasibility of a photopolymerizable microtip as a refractive index transducer formed on the end face of a standard multimode fiber (MMF). In the paper we have shown an optimization process in which we have taken into account two important parameters, i.e., optical power and exposition time. Depending on those parameters we have got different shapes and sizes of the growing microtips what were than tested on a scanning electron microscope. In the experimental step each of manufactured microtip was immersed in liquids with known refractive indices (1.4 - 1.6) and amplitudes of the optical backscattered signals were measured by OBR4600. The minimal reflected signal was comparable to the refractive index of a microtip. This conclusion resulted from measurement of the optical fiber without photopolymer elements for which minimal signal was of 1.48, what corresponded with the core of a standard MMF. When the refractive index of external liquid was higher or lower than the mikrotip’s refractive index, then, the reflection signal increased. The linear range of reflected signal can be used to monitor refractive index changes. Described in the paper photopolymerizable microtip can be useful for optical fiber transducers due to its small size and low costs. Moreover, by modification of a photopolymer mixture we can tune refractive index of a microtip and its minimal reflected signal, as well. The aim of further research will be to manufacture a transducer for the optical fiber sensor with higher sensitivity and to prepare numerical simulations of reflection.
This paper presents the technology of performing an effective glued connection between optical fibers made from silica (SOF) and polymer (POF) and a pair of polymer optical fibers (POF-POF). This study has been undertaken in order to establish the influence of cleaving for quality of fiber preparation (its cutting in particular), type of glue, as well as joint spot protection. The prototype of a hot cleaver of POF, made in Institute of Applied Physics MUT, was minimalized and adapted to a single use of blade. Matching geometry of connected structures was optimized by adjusting optical fibers to each other. The result of this research was to define particular distance between fibers. It turned out that the optimized distance amounts to 30 μm. Experiment showed that a joint made of optical glue has given loss of less than 0.2 dB. The next step was to involve protection of the mechanical joint. It turned out that glass capillary complies with the requirements. In order to confirm the effectiveness of the chosen glue connection, measurements of technical parameters on patch cords with MMF – POF and POF – POF connections were made. It was stated that SOF – POF connections can work within the range of -40°C + 60°C workable for humidity simulation without loss change. However, connections POF – POF are unstable with respect to temperature change. Modal characteristics of near- field were also observed.
We present the process of the microtip fabrication at the LMA-10 fiber designed for near-field scanning optical microscopy probes. Facilitation of manufacturing procedure as well as proper focusing conditions of such elements are the main advantages of such microelements production.
Numerical Aperture (NA) is one of the fundamental properties of optical fibres. It determines the ability of efficient light coupling into the fibre and low loss splicing with other fibres. NA is essential when novel fibres are manufactured. Moreover, dispersive behaviour of geometrical guiding mechanisms, existing in microstructured fibres, is completely different comparing with material guiding mechanisms of classical fibres. Therefore we constructed measurement system, for characterization the dispersive properties of NA of specialty microstructured fibres in broad wavelength range. Additionally, presented setup can be applied for measurements refractive index of different materials (including highly absorbing) filling the holes of microstructured fibre in broad wavelength range.
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