Long-term chemical stability of organometallic reagents incorporated into polydimethylsiloxane matrix of polymer-clad
optical fibres by soaking method is investigated by means of VIS/NIR absorption spectroscopy, proton-induced X-ray
emission and electron paramagnetic resonance spectroscopy. Based on the obtained experimental results, a modified
procedure of sensing coatings preparation is proposed leading to significantly reduced decay of optical properties with
time and allowing thus fabrication of practically applicable long sensing fibres.
The kinetic parameters of a chemo-optical transducer layer sensitive to gaseous ammonia are characterized by means of
attenuation total reflection method. The tested layer consists of cross-linked polydimethylsiloxane matrix sensitized by
quinoline-based organometallic dye showing the selective chemical reaction with ammonia. Upper and lower limits of
the ammonia diffusion coefficient and the ammonia-dye reaction constant are derived from the obtained experimental
data and compared with other data available in literature and obtained from computer simulations.
Optical fibers have been used in numerous sensing applications. Specifically, polymer-clad silica optical fibers have
been employed for purposes of indirect chemical or biochemical sensors. These sensors are based on the interaction of
guided light beams with extrinsic reagents immobilized in the fiber cladding. For this demand, it is necessary to enrich
the fiber cladding with optical reagents with suitable optical properties without mechanical damage of cladding. Dipcoating
and diffusion process have been studied and compared with respect to effective incorporation of appropriate
quantities of selected organic reagents into polymer cladding. Short sections of sensitized optical fibers have been tested
for potential using in ammonia fiber optic sensors.
Polymer-clad silica optical fibers are employed for development of different absorption optic fiber sensors of gaseous analytes. In our case, the physical principles of the detection are combined with a chemical reaction between analyte and suitable opto-chemical absorption reagents. Selected organometallic complex reagents with different lengths of lateral aliphatic chains are studied with respect to the type of central ions and their coordinative conditions to surrounding ligands. The effect of solvent type on solubility and the long-term stability of the prepared reagents in solid matrix are presented and discussed. Various methods are also tested in order to achieve an effective reagent immobilization into the polymer matrix, which creates optical fiber cladding. The chemical reaction of the reagents with ammonia based on ligand exchange process is accompanied by changes of visible-near-infrared optical absorption influencing via evanescent field on the guided light intensity. Experimental results suggest that the selected reagents provide optical properties suitable for practical sensing applications and that the sensitized PCS optical fibers could be used for detection of ammonia gas.
Sharply bent optical fiber can be used as sensory systems. At first sight, application of curved optical fiber is
refractometer but after immobilizing metal layer on stripped core of optical fiber its usage can be much more
sophisticated. On the metal layer it is possible to excite surface plasmon polariton. In our case we use Drudes model of
free electron and Monte Carlo method to calculate probability and real possibility of excitation of surface plasmon
polariton on metal layer applied on the core of U-bent optical fiber. The calculated results allow for direct assessment of
appropriate positions of metal layer on semi-toroid optical fiber in dependence on system parameters.
Extremely bent optical fiber (U-optrode) is applicable as a sensing head, signal of which is govern by refractive index
and light scattering properties of the surrounding medium. The presented contribution aims to shows that when covered
with properly selected polymeric transducers, the reliable and fast thermometers covering different temperature ranges
can be constructed suitable for, e.g., measurements in environments with high level of electric or magnetic disturbances.
Obviously, the bare optrodes can be also used as sensitive analytic tools for collecting information about thermallyinduced
changes of optical and micro-structural properties of polymers.
Monte Carlo approach is applied to simulate light transmission and emission characteristics of a dielectric multimode
waveguide of a semi-toroid shape, for range of geometrical and optical parameters of the system. The physical
description of light transport is based on classical Fresnel formulas used to define probability of single photon
transmission/reflection at the core/cladding boundary. Even positional and angular distribution of 'emitters' launching
photons into the waveguide within cones defined by critical angle was employed to simulate propagation of all meridian
and skew rays. No interference effects are included in the model. The calculated results allow for direct assessment of
light leaks from and transport through the waveguide core in dependence on system parameters.
Preparation of refractometric, thermometric and chemo-optical sensing heads based on extremely curved optical fibers
(U-optrodes) is described and their sensing properties demonstrated on obtained experimental results.