|
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.
|
