This PDF file contains the front matter associated with SPIE Proceedings Volume 9228, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

In this paper, the authors, chairs of the 15th Conference on Optical Fibers and Their Applications OFTA2014, and editors of the conference proceedings summarize the developments of optical fiber technology in Poland (during the period of 2012-2014) on the basis of papers presented there and consecutively published in this volume. The digest covers the periodically presented work results every 18 months during the meetings on optical fibers in Białystok – Lipowy Most (with emphasis on technology and applications) and Lublin – Nałęczow (with emphasis on materials and technologies). The XVth Conference on Optical Fibers and Their Applications was held in Białystok and Lipowy Most on 29.01-01.02.2014. The first conference from this cycle was organized in Jabłonna in 1976. Conference topics were: optical fiber technology, materials for optoelectronics and photonics, rare earth doped and luminescent materials, metrology of optical fibers, components and optoelectronic circuits, applications of optical fibers, waveguides and optical fiber sensors, and lighting technology. The conference was attended by 120 participants, including international guests, and 90 papers were presented. Conference papers are traditionally published in Proceedings SPIE.

The European Technology Platform Photonics21 is an organization to coordinate common applied research and industrial activities and to realize large multibillion applied technological projects. Analogous projects of global weight are established in the USA (National Photonics Initiative) and in Asia. Photonics21 organization calls and names Photonics a key enabling technology of Europe in 21 century, and estimates that it will decide of the development of many fields of industry and civilization infrastructure during this century. It concerns such areas like: medicine, environment protection, food production and agriculture, telecommunications, transportation, civil engineering, safety, immediate human environment, etc. There is lively interest of this country and local research and industrial, economic and political communities in active participation in such large pan European industrial sectors initiatives. The paper, prepared on the basis of the public and membership materials of Photonics21, and Polish public organizations involved in Photonics presents a concise portrait of these organizations, their activities, from the perspective of abilities and ambitions of Europe and this country.

This paper provides an overview of the process of 4H-SiC pn junction fabrication and characterization. The samples used in this study were fabricated in a resistively heated horizontal hot-wall Chemical Vapor Deposition reactor. The homo-epitaxial layers were grown on commercially available 4H-SiC substrates (Cree). In order to obtain p-type epilayers, they were intentionally doped with aluminum. In this work, we present our recently developed 4H-SiC pn junctions fabrication and characterization results. The ohmic contacts were formed using evaporation, etching, lift-off and high temperature annealing. Current-voltage characteristics of the devices were demonstrated.

This contribution deals with the preparation and characterization of the silica optical fibers doped by nanocrystalline zinc silicate. The sol-gel approach was employed to prepare colloidal solution of zinc silicate precursors. Prepared sol was thermally treated to form nanocrystalline zinc silicate disperzed inside amorphous silica matrix or soaked inside the porous silica frit deposed inside the silica substrate tube which was collapsed into preform and drawn into optical fiber. Single mode optical fiber with the core diameter 15 μm and outer diamer 125 μm was prepared. Optical and waveguiding properties of the fiber were analyzed. Concentration of the zinc silicate in the fiber was 0.93 at. %. Radioluminescence properties of nanocrystalline zinc silicate powder and of the prepared optical fiber were investigated. The nanoparticle doped samples appear a emission maximum at 390 nm.

In the paper optical properties of 40TeO₂ – 20GeO₂ – 30(PbO – PbF₂)– 10(BaO – Nb₂O₅ – LaF₃) glass system co-doped with Er³⁺/Tm³⁺ ions were investigated. The maximum of phonon energy at 790cm-1 in fabricated tellurite glass which was determined by FTIR measurements. Optimisation of glass composition led to the emission at 1820 nm which was observed in results of energy transfer (ET) between Er3+and Tm3+ions under the optical exciting at 976 nm. In order to determine the optimal conditions of ET between exited energy levels of co-doped RE ionsthe dependence of the near-infrared emission upon the thulium ions concentration was studied. In result of that broadband emission in the range from1500 to 1900 nm was achieved owing to the superposition of electronic transition in Er³⁺ (⁴I_13/2 → ⁴I_15/2) and Tm³⁺ (³F₄ → ³H₆) ions.The highest efficiency of energy transfer was obtained in glass co-doped with 0.2Er₂O₃/0.3 Tm₂O₃.

In earlier papers the authors have shown by XRD measurements and HRTEM imaging/SAED (selected area electron diffraction)/STEM imaging/EDS X-ray spectra that erbium or erbium/ytterbium-enriched nano-crystals are formed in erbium doped and erbium/ytterbium co-doped oxy-fluoride glass-ceramics fibers by their controlled heat-treatment. By the analysis of XRD, HRTEM and SAED patterns three crystalline compounds have been identified (Pb₅Al₃F₁₉, Er₄F2O₁₁Si₃, Er₃FO₁₀Si₃). Additionally, STEM imaging combined with EDS X-ray analysis revealed higher erbium/ytterbium content in nano-crystals than in glassy host. According to several reports on homogeneous/inhomogeneous broadening of emission lines we can expect in glass-ceramics material the distinct reduction of the 1.55 μm Er³⁺ linewidth (FWHM) as a consequence of structurally ordered (crystalline) vicinity of erbium ions in glass-ceramics fibers. Additionally the Stark splitting of Er³⁺ ions sub-levels should be observed due to the crystalline electric field surrounding the erbium ion, which lifts the atomic state degeneracy, however identified crystals possess rather low symmetry (monoclinic or triclinic unit cell).

In this paper we show preliminary experimental studies on accelerated aging-tests of tapered fiber Bragg gratings (TFBG). Examined gratings were fabricated on tapered and then hydrogenated optical fibers using uniform phase mask and scanning technique. In particular, the impact of isothermal annealing of TFBGs on their spectral and dispersion characteristics was analyzed. Experimental results show that although reflectance levels of TFBGs significantly reduce due to the aging process, slopes of the group delay characteristics remain practically unchanged. New knowledge on spectral and dispersion characteristics of TFBGs written in hydrogen loaded optical fibers is important in possible applications, where long-term stability and reliability is required.

Optical properties of Pr3+ ions in lead-free germanate glasses modified by BaF2 were investigated. Luminescence bands related to 3P₀ → ³H₄, ³P₀ → ³H₅, ¹D₂ → ³H₄, ³P₀ → ³H₆, ³P₀ → ³F₂ transitions of Pr³⁺ were registered under 450 nm excitation. The relative integrated luminescence intensities of 3P0 → 3H4 transition (blue) to the ³P₀ → ³F₂ transition (red) of Pr³⁺ ions strongly depend on fluoride modifier BaF2 in glass composition. The blue-to-red luminescence intensity ratios of Pr³⁺ are drastically reduced, when BaO is partially substituted by BaF2. The luminescence lines due to ³P₀ → ³F₂ hypersensitive transition of Pr³⁺ are blue shifted with increasing BaF₂ concentration.

Influence of M₂O₃ (M = Al, Ga) modifiers oxide on local structure and spectroscopic properties of lead phosphate glasses containing rare earth ions was studied. Among the rare earths, the trivalent europium and erbium ions were selected as an optically active dopants. The thermal properties were examined using DSC, whereas the X-ray diffraction analysis was used in order to verify the structure glass matrix. Luminescence of rare earth ions in lead phosphate glasses was registered in visible and NIR spectral region. The excitation and emission spectra of lead-based systems are presented and discussed in relation to the effect of modifiers oxide M₂O₃ (M = Al, Ga). Luminescence lifetimes (τm) for the ⁵D₀ state of Eu³⁺ ions and ⁴I_13/2 state of Er³⁺ ions were also evaluated.

In the article the upconversion luminescence ofTeO₂– GeO₂ – PbO – PbF₂– BaO – Nb₂O₅ – LaF₃ glass system co-doped withYb ³⁺ /Tb ³⁺ under 976 nm laser diode excitation was investigated. The influence of Tb2O3concentration on the luminescent properties was determined. Measured strong luminescence at492, 547, 588, 622 nm correspond to ⁵D₄→⁷F_J (J=6, 4, 3) transitions. Energy transfer (ET) mechanism involved in observed emission was discussed. The highest upconversion emission intensity was obtained in the tellurite glass co-doped with 0.5 Yb₂O₃/0.5 Tb₂O₃ (mol%).

In the article an analysis of thermal and spectroscopic properties of heavy metal oxide glasses from the Bi₂O₃-Ga₂O₃- Na₂O-Ge₂O₃ system doped with rare earth elements were presented. It has been focused on the elaboration of the glass composition in terms of low phonon energy, high transparency in the range of infrared region and high thermal stability (ΔT=160 °C) required in optical fiber technology. Fabricated glasses co-doped with Er3+/Ho3+ions under 980 nm laser diode excitation exhibit emission at 1.55 μm (Er3+: ⁴I _13/2 → ⁴I_15/2) and 2.0 μm (Ho³⁺: ⁴I₇ → ⁵I₈). The emission at 2.0 μm results from the Er³⁺ → Ho3+energy transfer. Taking into account great thermal stability and good optical properties such as high transparency (up to 80%) or high refractive index (2.23), the fabricated bismuth-germanate glass co-doped with Er³⁺/Ho³⁺ is promising material for construction of active optical fibers operating in the range of mid-infrared.

This paper presents an analysis of the possibilities of producing waveguide structures of the inverted-rib type. Such structures can be produced on the basis of planar gradient strip waveguides (channel waveguides) produced in a glass substrate by the ion exchange method. The glass surface is then covered with a thin uniform optical layer with a high refractive index. The thickness of this layer is less than the cut off thickness for the used wavelength. The wave propagation is therefore possible in the gradient area only. The homogeneous sensitivity of such waveguides is much greater than in case of single-mode waveguides without a uniform layer. The paper presents the calculations of homogeneous sensitivity for single-mode waveguides of the rib type, the inverted rib waveguides and the gradient waveguides. The use of single-mode inverted rib waveguides in the design of the planar interferometer in the Young configuration was proposed.

This paper presents the design and theoretical characterization of a composite uniform-gradient planar waveguide polarimetric interferometer. Presented structure is composed of an Ag⁺↔Na⁺ ion-exchange based waveguide formed in Borosilicate 33 glass substrate and a uniform, sol-gel based, silica-titania film. Characteristics of homogeneous sensitivity difference for TE₀-TM₀, TE₀-TE₁ and TM₀-TM₁ modes in function of the uniform film refractive index and the gradient waveguide refractive index profile are given. Because thermal annealing is an inseparable part of the sol-gel process, the gradient index waveguide is subjected to a rediffusion process. The original refractive index profile is flattened. It was shown that a presence of the gradient waveguide increases sensitivity differences over values which can be obtained for single layer uniform silica-titania waveguides. Moreover, it was shown that a range of uniform film thickness values, for which sensitivity difference of the composite structure is maximized, is downshifted to a range which can be much easier obtained with a sol-gel process.

This paper presents the calculations showing the possibility of the implementation of the Long Period Waveguide Grating (LPWG) structures in glass with gradient refractive profile. As the substrate material the Pyrex glass has been chosen, which is characterized by good optical properties. Calculations were performed for the actual material properties (refraction and chromatic dispersion) of this glass. The real technological processes of the Ag⁺↔Na⁺ ion exchange in Pyrex glass used for the production of the gradient areas were also included. The obtained results showed the potential to generate such structures in Pyrex glass for applications in the visible spectrum. Simulations of ion exchange processes in this glass have been carried out taking into account experimentally determined temperature coefficients of the diffusion of exchanged ions.

This work presents results of the theoretical analysis as well as the results of experimental study on sensing structures with grating couplers. Grating couplers with a groove density of 1250g/mm were produced by us using the method of master grating embossing in a sol film. The waveguide films SiO₂:TiO₂ of high refractive index have been produced using the sol-gel method

The paper is devoted to the sensitive films for application in chemical sensors. These films, made of the sol-gel derived porous silica, were fabricated via a sol-gel dip-coating method. We have obtained silica layers of the minimum refractive index of ~ 1.22 and porosity ~47%. These layers were sensitized with a pH indocator - bromocresole purple. The indicator was introduced into porous silica layers by means of impregnation. Methods and results of characterization of porous silica films, before and after sensitization are presented in this paper. It was shown that films are very sensitive toward ammonia.

In the paper is presented optoelectronic diagnostic set for standardization the biostimulation procedures performed on cell lines. The basic functional components of the therapeutic set are two digitally controlled illuminators. They are composed of the sets of semiconductor emitters – medium power laser diodes and high power LEDs emitting radiation in wide spectral range from 600 nm to 1000 nm. Emitters are coupled with applicator by fibre optic and optical systems that provides uniform irradiation of vessel with cell culture samples. Integrated spectrometer and optical power meter allow to control the energy and spectral parameters of electromagnetic radiation during the Low Level Light Therapy procedure. Dedicated power supplies and digital controlling system allow independent power of each emitter . It was developed active temperature stabilization system to thermal adjust spectral line of emitted radiation to more efficient association with absorption spectra of biological acceptors. Using the set to controlled irradiation and allowing to measure absorption spectrum of biological medium it is possible to carry out objective assessment the impact of the exposure parameters on the state cells subjected to Low Level Light Therapy. That procedure allows comparing the biological response of cell lines after irradiation with radiation of variable spectral and energetic parameters. Researches were carried out on vascular endothelial cell lines. Cells proliferations after irradiation of LEDs: 645 nm, 680 nm, 740 nm, 780 nm, 830 nm, 870 nm, 890 nm, 970 nm and lasers 650 nm and 830 nm were examined.

Construction of endoscopes which are known for decades, in particular in small devices with the diameter of few millimetres, are based on the application of fibre optic imaging bundles or bundles of fibers in the illumination systems (usually with a halogen source). Cameras - CCD and CMOS – with the sensor size of less than 5 mm emerging commercially and high power LED solutions allow to design and construct modern endoscopes characterized by many innovative properties. These constructions offer higher resolution. They are also relatively cheaper especially in the context of the integration of the majority of the functions on a single chip. Mentioned features of the CMOS sensors reduce the cycle of introducing the newly developed instruments to the market. The paper includes a description of the concept of the endoscope with a miniature camera built on the basis of CMOS detector manufactured by Omni Vision. The set of LEDs located at the operator side works as the illuminating system. Fibre optic system and the lens of the camera are used in shaping the beam illuminating the observed tissue. Furthermore, to broaden the range of applications of the endoscope, the illuminator allows to control the spectral characteristics of emitted light. The paper presents the analysis of the basic parameters of the light-and-optical system of the endoscope. The possibility of adjusting the magnifications of the lens, the field of view of the camera and its spatial resolution is discussed. Special attention was drawn to the issues related to the selection of the light sources used for the illumination in terms of energy efficiency and the possibility of providing adjusting the colour of the emitted light in order to improve the quality of the image obtained by the camera.

The paper presents the experimental and theoretical investigations for a 2 x 2 MIMO optical communication system based on mode group diversion multiplexing over the 200m GI-MM fiber. As light sources at the system the low-cost VCSEL lasers were used. A coupling of the optical signals into the fiber at the transmitter side was done by using only a commercial optical coupler. In analogical way a ‘combined’ optical signal which was present on the fiber output was divided into two separate optical paths by using second optical coupler acting as a splitter.

In the paper the genesis, current stage and perspectives of the OPTIME project are described. The main goal of the project is to demonstrate that the newdeveloped at AGH technology of fiber optic transfer of the atomic clocks reference signals is ready to be used in building the domestic Time and Frequency distribution network. In the first part we summarize the two-year continuous operation of 420 kmlong link connecting the Laboratory of Time and Frequency at Central Office of Measures GUM in Warsaw and Time Service Laboratory at Astrogeodynamic Obserwatory AOS in Borowiec near Poznan. For the first time, we are reporting the two year comparison of UTC(PL) and UTC(AOS) atomic timescales with this link, and we refer it to the results of comparisons performed by GPS-based methods. We also address some practical aspects of maintaining time and frequency dissemination over fiber optical network. In the second part of the paper the concept of the general architecture of the distribution network with two Reference Time and Frequency Laboratories and local repositories is proposed. Moreover the brief project of the second branch connecting repositories in Poznan Polish Supercomputing and Networking Center and Torun Nicolaus Copernicus University with the first end-users in Torun such as National Laboratory of Atomic, Molecular and Optical Physics and Nicolaus Copernicus Astronomical Center is described. In the final part the perspective of developing the network both in the domestic range as far as extention with the international connections possibilities are presented.

Side optical fibers developed at the University of Technology in Bialystok allow the absorption of light. This enables the construction of safe sensors with a distributed detection surface and unique properties. Rotationally - symmetric geometry of the fiber allows the construction of measuring heads for mean cylindrical and semi-cylindrical illuminance . This article presents the construction and measurement results for the application of side optical fiber in measurements of cylindrical and semi-cylindrical illuminance.

The basic, well-known of the fiber task is to transmit the optical signal along an optical fiber. To achieve this, you should reduce energy losses which result from reflections on the border of core - clad. However, in some cases, the light output can be derived by side surface the fiber. Luminous flux through side surface of optical fiber is realized in many ways. It is possible to change local shape of cylindrical fiber or scattering light on border between core and clad. Side optical fiber with helical spiral core have a different way of side emission. It is the result of controlled scattering inside the optical fiber [1].

The paper presents application of fiber optic flame monitoring system and its signals analysis for estimation thermal power and air-fuel ratio of single burner that are hard to determine. To achieve this, several combustion tests were conducted for nine different settings of the laboratory combustion facility, where thermal power and excess air coefficient were kept constant and set independently for known biomass content. Thermal power was regulated by adjusting fuel flow rate knowing the heating value of the known fuel blend. The fiber optic probe was capable to monitor several zones of the flame located along the axis of the flame. The k-NN regression algorithm was applied to determine thermal power and air-fuel ratio.

Due to the growing demand for transmission capacity, it has become essential to utilize multiple wavelength domains in one transmission system. To take full advantage of parallel 1550/1310 nm transmission, efficient 1310 nm amplification techniques are needed, such as the 1310 nm Raman amplifier. In the paper, we present detailed studies regarding the design of the 1310 nm Raman amplifier. Based on numerical simulations, we propose an efficient 1310 nm Raman amplifier design, utilizing the 1240 nm quantum-dot pumping lasers. The designed Raman amplifier is built and characterized. The achieved gain in a QD-laser pumped 1310 nm Raman amplifier was 19.5 dB. The presented results open the way for enhanced utilization of the 1310 nm Raman amplifier in the opto-telecommunication systems.

This paper presents fiber optic illumination sensor based on composition of detecting special shape optical fibers. The proposed optical fibre system was used for illumination measurements. The experimentally obtained characteristics of designed detection head are presented and compared to standard illumination measurement equipment for inclination angles from 0^o to 90^o. The good agreement of characteristics of proposed system with commercial available devices was obtained. The potential applications of illumination optical fibre sensor are presented.

Presented is a compact, all-PCF modal interferometer made by fusion splicing. The splices were performed in such a way as to cause the holes of the PCF to collapse over the length of the splice. The modal interferometer is created by the segment of a birefringent PCF, including the micro-collapses at the ends, and SMF-28 pigtails spliced to it. Obtained spectra of the interferometer and an estimation of its parameters are presented. The effect of tensile strain on the spectrum is illustrated. The application possibilities of the constructed interferometer for sensors are given.

This paper presents a luminescence sensor for real-time pH measurements. The emission spectra of mixture consisted of tested and base solution of fluorescein is used for analysis of the pH of aqueous solutions. The proposed microfluidic mixing system with integrated optical fibers allows pH measurement in the range 7.6 – 2.8. The developed sensor can be used in automatic pH control systems that work with aqueous solutions. The optimization of fluorescein concentration in base solution allowed to obtain linear characteristic of sensor response. The practical realization of the sensor with continuous monitoring of the pH of liquids and its potential applications are presented.

In this work, numerical model of tapered fiber Bragg grating (TFBG) based on transfer matrix method (TMM) and coupled mode theory (CMT) is presented. It describes the behavior of TFBG when the axial strain is applied. In particular, the influence of various tensile forces on dispersion characteristics of tapered fiber Bragg gratings as fiber optic components with variable group delay were examined. Besides the numerical results, measured group delay characteristics are presented as well and compared with theoretical ones.

A possibility to estimate parameters of the first order model of PMD in a fiber of a communication line is shown. The suggested estimator is based on the maximum likelihood principle. The appropriate measures for quality of the estimator are proposed and used for its characterization.

In the article a microstructural active optical fiber for sensing application was presented. Construction consists of three hexagonal rings and a core made of SiO₂ - Al₂O₃ - Sb₂O₃ glass co-doped with 1Yb₂O₃/0.1Tm₂O₃ [mol%]. Developed optical fiber is characterized by upconversion luminescence (λp=980nm) at 480nm (Tm³⁺: ¹G₄→³H₆) and 650 nm (Tm³⁺ : ¹G₄→³F₄). Population of thulium levels was attained in result of the Yb ³⁺→Tm³⁺ upconversion energy transfer. Sensing application of elaborated active photonic structure was presented on the example of aqueous fluorescein solution. Fabricated microstructural optical fiber enables to measure of the fluorescein solutions with the concentration of (0.25 - 5.42)·10^-4 [mol%]. Sensitivity of the elaborated measurement setup is 1.51·10⁴ [1/mol%].

This paper presents properties of all-optical bistable fibre switch using two fibre Bragg gratings and rare earth elements doped optical fiber. It is not possible to obtain bistable properties at low switching power level in case of a single fibre grating. In this article the method of optical switching that uses all-optical switch has been proposed. It has been achieved by varying the refractive index of nonlinear optical material as a result of light signal amplitude changes. Presented optical bistable device can be used both in contemporary optically switched networks as well as in optoelectronic sensors, owing to their high achievable resolution.

This paper presents properties of all-optical bistable fibre switch using two fibre Bragg gratings and rare earth elements doped optical fiber. It is not possible to obtain bistable properties at low switching power level in case of a single fibre grating. In this article the method of optical switching that uses all-optical switch has been proposed. It has been achieved by varying the refractive index of nonlinear optical material as a result of light signal amplitude changes. Presented optical bistable device can be used both in contemporary optically switched networks as well as in optoelectronic sensors, owing to their high achievable resolution.

This paper has been withdrawn. The following nearly identical paper is available in this conference proceedings: Jarosław Piotr Turkiewicz and Paweł Czyżak, "The high gain 1310nm Raman amplifier," Proc. SPIE 9228, Optical Fibers and Their Applications 2014, 92280P (May 12, 2014); doi:10.1117/12.2067055.

Semiconductor optical amplifiers (SOAs) are key components in the short and medium range 1310 nm wavelength domain optical transmission systems utilized in e.g. high speed Ethernet. In this paper, by means of simulation we investigate the influence of an SOA on the transmission quality in the 1310 nm wavelength domain high capacity 10×40 Gbit/s wavelength division multiplexed (WDM) system. It occurs, that the maximal channel spacing for such system is 400 GHz for which the differences in gain of the channels do not exceed 1.5 dB, and the sensitivity differences resulting from the SOA bandwidth are below 1 dB.