We succeeded in recording broad FBG in standard single-mode fibre optic, using saturated hydrogen loading and over-exposure to the UV beam. The reflection spectra of the obtained gratings presents a FWHM line-width between 3 nm and 10 nm, and peak reflectivity in the range from 20 dB to 25 dB. The dispersion of the gratings is also measured and the dispersion coefficient results values about 2.5 ps/nm, at least 10 times smaller than that of conventional broad gratings recorded with chirped refractive index profiles.

A range of integrated fiber optic structures - lightguides, image guides, multicapillary arrays, microstructured (photonic) fibers - manufactured in the Institute of Electronic Materials Technology (ITME) is described. All these structures are made of multicomponent glasses (a part of them melted in ITME). They can be manufactured in similar multistep process that involves drawing glass or lightguide rods and tubes preparing glass performs, stacking a bundle with rods and (or) tubes, drawing multifiber or multicapillary performs. Structure formation, technological process, characterization and applications of different integrated structures are presented.

Review of the latest development in production and advanced applications of specialty fibre optics includes specialty silica fibers and IR-fibers drawn from chalcogenide glasses and extruded from crystal solutions of Silver Halides. Transmission range of these 3 types of fibers spans 0.2 to 18μm, while the power of radiation they may deliver varies from microwatts for sensing applications to several kilowatts - when silica fibers are assembled, for example, in high power cables for laser technology applications. Various probes and bundles assembled from specialty fibers are used for remote sensing of IR-emission, temperature, mechanical stress and for process-spectroscopy in very broad range - from 0.2 to 18μm.

Introduction of metal elements into the optical fiber's structure creates new possibilities of waveguides' parameters' modification especially permit to obtain polarizing fibers. A known solution is introducing of molten metal into a hole situated along a single-mode fibre's core. The alternative manner is deposition of metal layers on the internal surface of those holes. In our laboratory we manufactured new kind of optical fibers named side metal pipe (SMP) optical fiber. Its structure is similar to that of the side-hole optical fiber but the internal surface of the two open holes placed on the both sides of the core is covered with silver. The silver layers were deposited with elaborated in our laboratory static method deposition from liquid phase. The measured polarizing efficiency of this fiber of 1 m length was equal to 25% for 633nm wavelength. In the last time we manufactured the high birefringent single mode SMP fiber with elliptical core (SMK HB). Paper presents the basis of technology of SMK HB optical fiber, description of the static method of preparation of silver layers by liquid phase deposition and geometrical and optical parameters of the SMK HB optical fiber.

The properties of photonic crystal fibers are determined by the structure of photonic cladding: filling factor, type of lattice and shape of air holes. The dispersion and modal characteristics of the fiber can be modified by adding an additional lattice of glass micro-rods with a refractive index higher than the glass substrate. We have fabricated a solid-core photonic crystal fiber with a double photonic cladding composed of air holes and glass micro-rods, where a high index multicomponent glass is used for the micro-rods. As a reference a fiber with similar parameters and a single lattice of air holes is fabricated. The fiber cladding is composed of 17 x 17 air holes and micro-rods ordered in square lattice. In this paper, we study the optical properties of photonic crystal fiber with single and double lattices. FDTD method and a full-vector mode solver based on biorthonormal basis method are used for fiber analysis. Possible modifications of the structure and potential applications will be discussed.

Heavy metal oxide glasses in the system TeO₂-PbO-WO₃ doped by selected rare earth ions have been presented. The method of their preparation and physical properties were determined. Infrared luminescence of Er³⁺ and Tm³⁺ ions embedded in TeO₂-PbO-WO₃ glass hosts is reported for room and helium liquid temperatures. The substantial influence of energy transfer processes between the glass host and Er³⁺ and Tm³⁺ doped ions is shown experimentally through the dependences of photoluminescence on light polarization and excitation wavelength. The presented spectra of the rare earth doped glasses indicate on a possibility of their excitation by the Nd-YAG laser with wavelength about 1,06 um. Because of their properties this kind of glasses can be used for construction of optoelectronic devices.

In the last years rare earth doped double-clad fibers have been developed to high-power laser sources. Important progress was possible by increasing numerical aperture of the pump cladding and decreasing numerical aperture of the laser core. The high NA of the pump cladding enables the acceptance of large pump intensities whereas the low NA of the laser core makes possible to increase the core diameter and to decrease the laser power density retaining high beam quality. Here, actual challanges are discussed and possibilities are demonstrated to use microstructures for improved fiber designs which are realized by stacking and drawing of capillaries and rods. The rare earth doped parts are prepared by modified chemical vapor deposition and solution doping, but other routes of powder technology are also studied. Concerning the currently most important laser and amplifier types - Yb doped at 1.1 μm wavelength and Er/Yb doped at 1.55 μm wavelength -, the question of a high pump aperture is similar, but the limitations concerning a low core aperture are fairly different, because an efficient Er/Yb laser demands high phosphorus co-doping which naturally increases the core NA. The applied microstructures comprise "holey" fiber cross sections in form of "air clads" for the pump light and multiple hole ring structures for laser core and inner cladding. Moreover, microstructured cores made from solid parts yield new possibilities and parameters to compensate the high refractive index of the active material and to optimize the large mode area design.

Key requirements for specialty optical fibers engaged in various aerospace applications are extended lifetime and superb performance combined with small fiber diameter, minimal bend radius and ease of terminations. To address these requirements, the use of novel inorganic -organic materials called hybrid glass was proposed as single and double coats. Several types of hybrid glass candidate materials were applied on line on silica fibers as 7-35 μm thick single- or double -layer coats. The hybrid glass applied on silica fibers formed a non-strippable glasslike layer that was permanently bonded to the fiber surface. SEM analysis showed smooth, crack-free surfaces of the coatings and their strong adherence to the glass surface. To evaluate the protective ability of the hybrid coatings, the 2-point bending testing (dynamic fatigue) was controlled in a controlled temperature and humidity environment. Dynamic fatigue plots, the stress corrosion parameter n, Weibull strength distribution plots and average bending strength were calculated from the 2-point bending test data for each type of coated fiber tested. Two polymer coated fibers were used as reference and were tested as well. The hybrid glass coatings offered higher values for both fiber strength and n than those found for reference fibers. The UV induced photopolymerization of coating materials crosslinked the inorganic- network. The UV curing contributed also to the condensation process of inorganic constituents of the coatings and their permanent bonding to the silica fiber surface.

The distribution of light emitted from the sol-gel coated fiberoptic applicator for interstitial laser therapy was examined. The silica sol-gel coatings were prepared from silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid catalyzed hydrolysis. The applicator was produced with ratio R = 20, whereas R denotes the number of solvent moles (ethanol) to the number of TEOS moles. Then, the light pattern was captured by means of CCD camera and statistical pattern recognition method was applied to study the repeatability of light distribution. Two methods were applied: Fisher Linear Discriminant Analysis (FLDA) and Principal Component Analysis (PCA). The top match characteristic TM as calculated by statistical pattern recognition methods was taken as a factor corresponding to the performance repeatability. It was demonstrated that is possible to produce the sol-gel applicators with more than 92% repeatability.

The scattering matrix formalism, extensively used for the analysis of microwave networks can be easily extended to the optical domain if the optical signal is represented by Jones vectors to account for the different polarizations. The polarization properties of optical components are characterized by Jones matrices which can be easily combined with the scattering matrix formalism. We show in this paper, that the scattering matrices of polarization dependent fiber optic couplers can be calculated by combining their theoretical vector modes with simple measurements. The complete theoretical description of the polarization properties of fiber optic couplers is important for the simulation of interferometric fiber optic sensors, which are very sensitive to polarization and to estimate PDL and PMD in fiber optic communication networks.

Equations expressing electromagnetic fields in the core, first and second cladding regions of W profile optical fiber in terms of eight constants will be presented. These constants will be determined by applying the boundary condition that the tangential components of electric and magnetic field must be continuous across the core - first cladding and first cladding - second cladding interfaces. By requiring the continuity of appropriate tangential components set of eight homogeneous equations will be obtained. These equations have nontrivial solution only if determinant of the coefficient matrix vanishes. This condition leads to the compact eigenvalue equation of the W profile optical fiber.

Optical fibres made from heavy metal oxide glasses doped by Dy³⁺ ions with the numerical aperture 0,4 - 0,9 are presented. Heavy metal oxide glasses in the system PbO-Ga₂O₃-Bi₂O₃-CdO doped by 1500 ppm Dy³⁺ ions were used. The method of their preparation and physical properties as well the results of luminescence investigations of Dy³⁺ ions embedded in glass hosts are reported. Double-crucible drawing technique was applied to obtain optical fibre doped by Dy³⁺ ions. Core and cladding glasses have been obtained by modification the base glass with small amounts of cadmium and gallium. In such a way these glasses possessed the same technological parameters which can be controlled in a wide range.

Plastic optical fiber (POF) can be taken as short distance transmission system medium for replacing of coaxial cable because of its many excellent characteristics. The bandwidth characteristics of graded-index POF is strongly influenced by the differential mode attenuation (DMA). In this paper, a comprehensive bandwidth calculation model of POF is given. The analytical expression of DMA is fitted by eighth order polynomial from the experimental data, and is used for the calculation of fiber bandwidth. The frequency response function of graded-index plastic optical fiber(GIPOF) is calculated numerically under selective mode excitation condition, and the fiber bandwidth is studied. The calculated results indicated that the selective mode excitation could improve efficiently the fiber 3dB bandwidth. The influence of light source linewidth on fiber bandwidth is also investigated.

Minimization of Rayleigh scattering, α_s, and absorption, α_abs, losses in glasses for fiber drawing is considered in the study. Glasses were studied with high temperature (to 1500°C) ultrasonic acoustics, Rayleigh and Mandel'shtam-Brillouin scattering, Raman scattering (RS) and absorption spectroscopy. Contributions into αs from "frozen-in" density and concentration fluctuations were separated. The α_s (multi component glass) < α_s (silica glass) relationship is realized in glasses built from structural units of a single type found from RS and characterized by low glass transition temperature. Chemical inhomogeneities can be made optically invisible by means of prompt choice of glass composition. Selective entering of multi electron ions into concentration fluctuations of glass melt (doped ion segregation) causes excessive Rayleigh scattering by glass. To shift minimum α_abs of low scattering glass to longer wavelengths it is necessary to dope it by randomly distributed heavy metal ions or components decreasing modifier cation-anion bond strength of a glass network.

In this paper we present results of research on fiber Bragg gratings (FBGs) fabricated on hydrogen-loaded fibers using scanning phase mask method. The influence of temperature on Bragg wavelength, reflectivity and FWHM for various exposure time and hydrogenation time was investigated. We also have carried out aging tests of fiber Bragg gratings using climatic chamber. Results of these tests can be useful for optimization of FBGs fabrication. We have estimated of fiber Bragg gratings usability as wavelength standards for calibration of fiber optics devices especially optical spectrum analyzers (OSA).

Special photosensitive high germanium boron-codoped fibers are too expensive for every-day application in the research laboratory. To lower the running costs of the fibers high-pressure hydrogenation unit was realized in form of special piping system with pressure control, easy handling and all safety requirements fulfilled. The technology and special procedures of hydrogen loading into single-mode fibers were developed and tested. Available standard single mode fiber samples used by the telecom cable companies (lengths of 2-3m) were inserted into hydrogen for different static diffusion time periods under the pressure 100-140 bar in the room temperature. The optimal hydrogenation procedures for best quality gratings were found. The post-hydrogenation low-temperature storage conditions were also controlled and gratings spectral characteristics measured. No Bragg grating formation was seen in unloaded fibers under the same laser illumination.

The numerical analysis of the efficiency of the side pumping method using special asymmetrical couplers for the high-power double-clad fiber lasers is presented in the paper.

UV-curable hybrid glass materials, when applied as thin coatings on optical fibers are already known to result in fibers enhanced mechanical strength as well as thermal and environmental stability [1]. These materials, when fully cured offer refractive index in the range 1.470-1.50 measured at 1300 nm. In search for low optical loss and lower refractive index claddings the hybrid glass composition was altered to result in UV curable two component formulation HG-LI (1+2) of refractive index 1. 380 The goal of this study was fabrication and valuation of the optical, mechanical and thermal properties of the silica fibers cladded with this novel hybrid glass material. The silica fibers were drawn and cladded by HG-LI-(1+2) and HG-LI-2. For control fibers, soft silicone resin and hard silicone resin were used as cladding for the same silica preform rod. The basic optical (spectral attenuation) and mechanical characteristics (tensile strength, n parameter) for hybrid glass cladded fibers were performed. Thermo Gravimetric Analysis (TGA) was performed as well. The results showed that hybrid glass cladding has the onset decomposition temperature exceeding 300 °C, whereas the NA values of the silica fiber cladded by HG-LI-(1+2) and HG-Li-2 were 0.31 and 0.33, respectively.

The one of the manners of change or introduce birefringence of manufactured optical fibers is placed it into electrical field. In accordance with description of Kerr effect the change of birefringence is proportional to the square of the electrical field. However the electrical field is proportional to the distance between electrodes. In standard optical fibers the change of birefringence through the Kerr effect required to use high voltage. In our laboratory the two new types of optical fibers were manufactured. One of them has structure similar to that of the side-hole optical fiber but the internal surface of the two open holes placed on the both sides of the core is covered with silver. The other has four open holes placed symmetrically around the core. It is named single mode quadruple (SMK) optical fiber. The open holes with silver layers are placed a long distance from the core so as to they haven't influence on the light goes through the core. In those fibers the change of direction of polarization was measured. For the fiber with two holes the change was equal to 8 degree for the change of voltage equal to 500V. Paper presents basics of the technology of those fibers, description of the silver layers deposition process from liquid phase and geometrical and optical characteristics of fibers.