Development of Optical Fiber Technology in Poland, International Journal of Electronics and Telecommunication, vol. 57, no 2, pp.191-197, July 2011

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Development of Optical Fiber Technology in Poland, International Journal of Electronics and Telecommunication, vol. 57, no 2, pp.191-197, July 2011
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  EuCARD-PUB-2011-015 European Coordination for Accelerator Research and Development PUBLICATION Development of Optical Fiber Technologyin Poland, International Journal ofElectronics and Telecommunication, vol.57, no 2, pp.191-197, July 2011 Dorosz, J (Bialystok University of Technology, Faculty of Electrical Engineering) et al 18 May 2012 The research leading to these results has received funding from the European Commissionunder the FP7 Research Infrastructures project EuCARD, grant agreement no. 227579.This work is part of EuCARD Work Package 2: DCO: Dissemination, Communication &Outreach . The electronic version of this EuCARD Publication is available via the EuCARD web site <http://cern.ch/eucard> or on the CERN Document Server at the following URL : <http://cdsweb.cern.ch/record/1449806 EuCARD-PUB-2011-015  INTL JOURNAL OF ELECTRONICS AND TELECOMMUNICATIONS, 2011, VOL. 57, NO. 2, PP. 191–197Manuscript received February 25, 2011; revised March 2011. DOI: 10.2478/v10177-011-0027-6 Development of Optical Fiber Technology in Poland Jan Dorosz and Ryszard S. Romaniuk   Abstract —In this paper, the authors, chairmen of the 13 th Con-ference on Optical Fibers and Their Applications OFA2011, andeditors of the conference proceedings summarize the developmentof optical fiber technology in Poland (during the period of 2009-2011) on the basis of papers presented there and consecutivelypublished in this volume. The digest is thus not full but coversthe periodically presented material every 18 months during themeetings on optical fibers in Białystok-Białowie˙za and Lublin-Krasnobród.  Keywords —optical fibers, optical communication systems, pho-tonic sources and detectors, photonic sensors, integrated optics,photonics applications, photonic materials. I. O PTICAL F IBERS AND T HEIR A PPLICATIONS O PTICAL fiber technology, as a part/mixture of mate-rial engineering, optics, optoelectronics, photonics andtelecommunications is intensely developed in his country inacademic communities, governmental laboratories and in theindustry. The national research community of optical fibertechnology is organized in a few professional associationsincluding: Section of Optoelectronics – Committee of Elec-tronics and Telecommunications [1]–[3] – Polish Academy of Sciences , Polish Committee of Optoelectronics – Associationof Polish Electrical Engineers (sister organizationto the IEEE),Section of Optics – Polish Physical Society and PhotonicsSociety of Poland (closely cooperating with SPIE) – andpublishing its journal Photonics Letters of Poland [4].The community is also active in the following internationalorganizations: SPIE, IEEE Photonics Society, OSA, ICO andEOS. The fiber optics part of this community meets everyyear and a half during the national conferences on ‘OpticalFibers and Their Applications’. The aim of these meetingsis to summarize the current developments in optical fiberphotonics and indicate the directions of the next research andtechnical undertakings. Similar customs prevail in the nationalcommunity of laser technology, embracing also partly opticalfiber technology, which meets cyclically, every three years,in Szczecin and´Swinouj´scie, during the National Symposiumon Optical Fiber Technology STL. The STL is organized bythe West-Pomeranian University of Technology (previouslySzczecin University of Technology) [5], [6]. Optical fibertechnology is also present during the professional conferencesorganized by the Polish Ceramic Society , Polish Society of Sensor Technology – organizer of a conference cycle on Op-toelectronic and Electronic Sensors COE, and PERG/ELHEPLaboratory at ISE WUT Warsaw University of Technology –organizer of the annual WILGA symposium cycle for young J. Dorosz is with Białystok University of Technology, Poland (e-mail:doroszjan@pb.bialystok.pl).R. S. Romaniuk is with Warsaw University of Technology, Poland (e-mail:rrom@ise.pw.edu.pl). researchers on Photonics Applications and Web Engineering[7]–[13].Białowie˙za and Krasnobród Conferences on Optical Fi-bres and Their Applications gather every year and a half the majority of the academic research community from thiscountry and a number of invited guests from neighboringcountries. The paper presents considerations concerning thedevelopment directions of optical fiber technology in Polandduring the last period (2009-2011) basing on the research andtechnical material submitted to the XIII th National Symposiumon Optical Fibers and Their Applications, which was heldin Białystok and Białowie˙za on 26-29 January 2011. Thesymposium has gathered more than 80 persons from academiaand industry. There were presented 60 papers and 6 plenarypresentations.The subjects of symposium were: materials for optoelec-tronics, technologies of optical fibers, optoelectronic com-ponents and circuits, metrology of optical fibers and op-toelectronic components, applications of optical fibers andDELs. The previous XII th symposium was held in Krasnobródin October 2009 and the next one XIV th will be also inKrasnobród in October 2012. The XV th meeting on OpticalFibers and Their Applications, to be held in Białystok andBiałowie˙za is scheduled for January 2014.The XIII th Conference on Optical Fibers and Their Applica-tions was organized by the Department of Optoelectronics andLighting Technology (previously the Department of OpticalRadiation) at the Faculty of Electrical Engineering – Białystok University of Technology in cooperation with Białystok Sec-tion of PTETiS. The conference organizer – the Departmentof Optoelectronics and Lighting Technology was establishedin 1983 by prof. M.Banach (as a Department of RadiationTechnologies). The department was chaired for many years byprof. W. Dybczy´nski and now is chaired by prof. J. Dorosz.Optical fiber technology has been present in the departmentsince the mid seventies of the XX century. The subjectscovered by the conference were: materials for optoelectronics,technology of optical fibers, optoelectronic components andcircuits, metrology of optical fibers and optoelectronic circuits,applications of optical fibers, applications of modernLED lightsources.The conference cycle on ‘Optical Fibers and Their Ap-plications’ started in 1976 in the Jabłonna Palace by PolishAcademy of Sciences, under the patronage of KEiT PANand next PKOpto SEP, and Photonics Society of Poland. Theinitiators of these first conferences were professors AdamSmoli´nski from Warsaw University of Technology (WUT)and Andrzej Waksmundzki from Maria Curie-SkłodowskaUniversity in Lublin (UMCS). Now this cycle is continuedevery 18 months and organized, in an alternate way, by opticalfiber technology and research centers by Białystok University  192 J. DOROSZ, R. S. ROMANIUK of Technology (BUT) [14]–[16] in Białowie˙za and by LublinUniversity of Technology (LUT) [17] in cooperation with theUMCS [18] in Krasnobród.The 2011 Białowie˙za conference on Optical Fibers hasgathered more than 80 persons from his country, mainlyfrom the universities and from the governmental laboratories(Białystok, Gliwice, Katowice, Kraków, Lublin, Łód´z, Pozna´n,Warszawa, Wrocław). There were presented 6 plenary papers,around 20 contributed papers and 50 posters reporting ownresults from the current projects run by research teams. Theinauguration session was held at the Faculty of ElectricalEngineering of LUT. The conference was opened by prof.W.Woli´nski, member of PAS, honorary chair of the ScientificCommittee.Prof. W. Woli´nski reminded the outstanding representativesof this branch of technology in this country who passed awayduring the last year: prof. Jan Rayss and dr Jan Wójcik fromUMCS . These persons, remarkable graduates and co-workersof prof.A.Waksmundzki, were the builders of the optical fibertechnology center in Lublin at the UMCS. Prof.J.Rayss and drJ.Wojcik were the organizers of the previous XIIth conferenceon Optical Fibers and Their Applications, which was heldin Krasnobród in October 2009 [18]. During the conferenceplenary session, the rector of BUT prof T.Citko presented thecurrent development problems of the university – which is thebiggest academic institution in the North-West part of Poland.The development perspectives are huge and accompanyingdifficulties are similar as at other Polish technical universities.The plenary papers of the conference, presented during theinauguration session on fibers, sources and detectors and nextsessions on photonic material engineering and optical fibercommunications were: • R. Romaniuk (Warsaw University of Technology), Op-tical fiber technology in the future Internet [19], [20], • A. Rogalski (Military University of Technology), IRphoton detectors [21], • W. Nakwaski (Łód´z University of Technology), Electro-luminescent diodes, • E. Bere´s-Pawlik (Wrocław University of Technology),Multimode, passive optical fiber LAN networks, • W. Urba´nczyk (Wrocław University of Technology),Birefringence in photonic optical fibers – srcins, mea-surement and applications, • M.˙Zelechower (Silesian University of Technology inKatowice), Oxide-fluoride, glass-ceramic optical fibers.Three conference sessions covered the subjects of activeoptical fibers, planar optical waveguides, mainly technologicalaspects, and modeling and simulations of technology solutionsof optical fibers and functional components. The followingparticular subjects were debated: • optical fibers with hanging core, design, characteristics,differences with classical fibers, applications, • generation of supercontinuum in optical fibers, power of levels, width of generated spectrum, damage thresholds, • multi-core active optical fibers with a super-mode, phaseconditions for generation of a supermode, • integrated optics components and porous optical glassobtained by sol-gel method, • optical fiber communication systems with super-denseWDM, ultimately dense spacing of channels, • thermally tuned liquid crystal photonic optical fiber com-ponents, optical nonlinearities, range of tenability, • liquid crystal optical fibers of low, medium and highrefraction, homogeneousand hybrid propagationof beam, • highly nonlinear photonic optical fibers with micro-structured core, role of nano-pores in the fiber core, • micro-structured,polymer optical fibers, materials, losses,spectral behavior, thermal resistance, structural solutions, • active optical fibers, amplifiers and lasers, novel solutionsto mixed and multicomponent low-loss glasses, • capillary optical fibers with noble metal nano-layers,methods of deposition, layer homogeneity, plasmonics.Two poster sessions of the conference concerned mainly themetrology and optical fiber applications. The exemplary appli-cations embraced: remote observations and optical analysis of the combustion processes of coal dust and biomass; thermal,mechanical and dilatometric measurements with optical fibersensors; distributed multi-point optical fiber vibration sensors;optical fiber broadband on-off switch, and optical fiber basedlight sources.Direct research on optical fibers concerned: modeling of chromatic dispersion in micro-structured optical fibers, op-timization of bending losses in photonic optical fibers, op-timization of solitonu optical fibers, optimization of opticalfiber wavelength converter as a light source for WDM chan-nel, wavelength conversion processes in optical fibers, dopedtelluride glasses for optical fibers, mechanical properties of polymer optical fibers, optical fiber phase demodulator withspace integration in the Fourier plane, polarization measure-ments of optical fibers.II. G LASSES AND O PTICAL F IBERS Topical Track on Optical and Photonic Materials and Op-tical Fiber Technology gathered over 30 papers. The majorsubjects were: liquid crystal photonic optical fibers, meta-glass (glass-ceramic) optical fibers, polymer photonic opticalfibers, photonic fiber sensors, and new solutions of nonlinearand active optical fibers. The strength of this topical track stems from over 35 years of research on specialty opticalfibers carried out in the optoelectronic laboratories in thiscountry. Three labs were then active: UMCS in Lublin , ITMEin Warsaw and Białystok Glass Works (next Biaglass GW)with Białystok University of Technology [14], [16], [22]–[37], cooperating with WUT and WAT. Now the work onspecialty optical fibers is spread also to Warsaw University of Technology – Faculty of Physics, Faculty of Electronics andInformation Technologies; Wrocław University of Technology,Military University of Technology and other university labs.Photonic optical fibers have been one of the major re-search subjects since around 15 years, which is caused bythe refractive and non-refractive propagation ability of thesingle mode beam of light. Non-refractive guidance is effectivein low-loss low-refraction regions of any kind confined byprohibited area, via the photonic band gap mechanism, of   DEVELOPMENT OF OPTICAL FIBER TECHNOLOGY IN POLAND 193 the high-refraction. The beam is compulsory confined by twodimensional Bragg structure or any other kind of periodicstructure, per analogism to the band-gap in a semiconductor.The only allowed direction of propagation is intentionallydelimited along the low-loss fiber axis, irrespective of therefraction (glass, liquid-crystal, gas or vacuum in a capillary)of this region. Isotropic photonic fibers are built of a subtleair-glass net or cobweb (depending on density) of the biggestpossible symmetry and the lowest possible perturbations of thestructure. A refractive fiber is built of this structure with filleddefects on the axis, while holey, non-refractive fiber is builtof this structure with empty defects on the axis. The defects(by removing rods from the fiber preform) may be single ormultiple, adjacent, overlapping or isolated. A beam of lightin the fundamental mode propagates in air in the holey fiber,while its evanescent fields propagate in glass. Majority of thepropagation parameters of holey fiber as dispersion, losses,and mode conversion depends on the glass-air boundary.Birefringent photonic optical fibers (refractive and non-refractive) are built by embedding asymmetry in the fiberstructure like: presence of micro-holes of different dimensions,introduction of stress agents near the core, etc. The fiberswhich are ideally axially symmetric (circular, hexagonal, etc.)can not be birefringent. Birefringence is defined as a differenceof effective refractions of two polarization sub-modes of thefundamental mode. In practice, like fiber measurements orpolarization fiber sensors, as a measure of birefringence, a beatlength is used. The beat length is defined as a ratio of the prop-agated wavelength and the birefringence at this wavelength.Large birefringence (approaching 10 − 2 ) can be induced insinglemode photonic optical fibers. This value is bigger thanthe birefringence of classical birefringent optical fibers 10 − 3 ,Bow-tie and Panda. Polarization maintaining optical fibers areused in the transmission systems for elimination of the harmfulpolarization dispersion PMD effect.Optical fibers made of glass-ceramic are investigated forphotonic components of new propagation and beam process-ing/transformation properties. They are researched for buildingof optical fiber lasers of new construction, nonlinear fibercomponents, resonant refraction/losses components, plasmonicdevices, etc. Crystalline srcinators initiated in optical fiberglass, of nanometric dimensions are generally difficult forvery precise control. To investigate the very beginning of thecrystallization processes there are used microscope methodsas well as roentgen and spectroscopic ones. There wereinvestigated mixed oxide-fluoride glasses for optical fibers,doped with mixed, energetically coupled rare earth ions likeerbium and iterbium. The aim of the optimized technologyof such glasses and fibers is to release nano-crystallizationprocess and let the crystallization radicals grow only to de-signed dimensions. The nano-crystallites should be essentiallyenriched with the active doping ions. Optical parameters of the active ions, such as quantum efficiency, life time of themetastable level, half-width of the absorption line for theoptical pump, in the monocrystals are better than in the glass.Modified, highly efficient EYDFA amplifiers may base on theglass ceramic metamaterial, where the optical activators aregathered in nano-crystallites.Active specialty optical fibers [37] are increasingly im-portant field of research in photonics. Non-telecom oriented,active optical fibers for all infrared bands, from NIR toFIR, are researched for instrumentation, functional, sensory,optical signal processing, signal amplification, improvementof the system noise performance, optical band conversion,and have various theoretical solutions, constructions, technolo-gies and applications. There were investigated the followingactive optical glasses for specialty optical fibers: alumina-silica, phosphate, oxide-fluoride, and antimonite. The glasseswere doped with with multiple activators like Nd3+, Yb3+.There were determined stability areas of these glasses forhigh doping levels and cross acceptance levels for doping.The reaction kinetics of the crystallization processes in theseglasses were analyzed with the Friedman and OFW methods.The fiber should have an intentionally introduced asymmetryfor building of fiber amplifiers and lasers - to enable efficientoptical power coupling into the active core from the oversizedor double cladding excited by external optical pump. Thereare used fibers with special optical cladding or with a helicalcore.Polarization state of light propagating in liquid crystalphotonic fibers [38]is used for optical sensing purposes or foron-line processing of the propagated optical beam. A micro-structured optical fiber is impregnated with liquid crystal,which enables dynamic tuning of its propagation charac-teristics. Three basic cases can be distinguished for threebasic refraction values of the fiber core in reference to therefraction of the liquid crystal. Low refraction optical fibersallow for selective light propagation, where the localizationof the transmission bands depends on light polarization. Formedium refraction optical fibers, where the core refraction laysin-between the ordinary and extraordinary refractions of theliquid crystal, a hybrid propagation may be obtained. One of the polarizations is propagated refractively while the other,orthogonal non-refractively (photonic). Low-loss optical fibersof high refraction allow for wide tuning of the birefringencefrom 0 to above 10-4. Reorientation of the liquid crystalmolecules may be done by the external electric field. Per-manent orientation of the molecules inside the fiber may beenforced by orienting polymer layers.III. D ETECTORS Near infrared detectors are generally divided to two maingroups: thermal and photon. Thermal detector is built of anabsorber which is isolated from the base and coupled toa thermometer. The radiation signal to be detected, increasesthe temperature of the absorber. The photon detector is a semi-conductor component. The radiation signal enforces intra bandelectron transits. The sensitivity of thermal detectors does notdepend on the wavelength, while is quite selective in case of proton detectors. The following semiconductors are used forphoton detectors in the visible: AlGaN, CdS, CdSe, GaAs, andfirst of all Si. The materials used for IR photon detectors are:HgCdTe, LiTaO 3 , PbS, PbSe, InSb, PtSi, InGaAs, InGaAsP,Ge, Si:Ga, Si:As, Si:Sb, Ge:Au, Ge:Cu, Ge:Zn. On the otherhand, thermal detectors are thermocouples and bolometers.  194 J. DOROSZ, R. S. ROMANIUK Out of the listed materials, a straight band gap possess thefollowing ones: InSb, InAs, GaAs, GaN, ZnS, CdS, CdSe,and the skew one Si, Ge, GaP, AlAs. Si has ∼ 1,1eV bandgapwhat is equivalent to the absorption edge at 1,1 µ m. Carriermobility in Si is 1500cm 2  /Vs. GaAs has the bandgap of 1,5eV,absorption edge at 0,8 µ m and carrier mobility 8500cm 2  /Vs.GaAs devices can be in principle faster than Si ones.The simplest photodetector is a photoresistor. The basictechnical parameter of a photodiode considered by a user isdetectability. It is measured in [cmHz1/2/W]. The detectabilityis confined by background radiation noise and thermal noise.Photodiodes are made with the following types of junctions:p-n, m-s, m-n (Schottky), pin, avalanche n + -p- π -p + , m-s-m.The m-s junction has several advantages over the classical p-n junction: simpler technology, larger saturation current becausethermoelectric emission is more effective than diffusion, andfaster response. The response time is a sum of the followingfactors: diffusion time of carriers from the place they were gen-erated to the area of space charge, flight time through the spacecharge region, time constant of charging the junction capacity.The RF photodiodes have the capacitance below a few pF.InGaAs photodiodes are used for the long-wavelength bandsof optical fiber communication systems. They have maximumof spectral characteristic in the area of 1,1 – 1,7 µ m.IV. S OURCES Electroluminescent diodes are expected to replace, in notso distant future, other light sources for lighting purposes.This is due to their large quantum efficiency measured by theratio of emitted photons to the electrons passing by the p-n junction during a second. The user is interested, however, inthe energy efficiency which is a ratio of the emitted opticalpower to the electrical energy provided to the LED. Now theLEDs are generating from the IR (GaInNAs, GaInNAsSb, In-GaAsP, InAs/GaAs, AlGaAs) to UV (AlN, AlGaN, AlGaInN,GaN, ZnO), including the visible range: red 610-760nm(AlGaAs, GaAsP, AlGaInP, Gap:ZnO), orange 590-610nm(GaAsP, AlGaInP, Gap:ZnO), yellow 570-590nm (GaAsP, Al-GaInP, GaP:N), green 600-570nm (GaP:N,AlGaInP, AlGaP,InGaN), blue 450-500nm (InGa, ZnSe), violet 400-450 (In-GaN) and white. The radiation is generated efficiently insemiconductors with the straight bandgap, and in some withskew bandgap doped with iso-electron substances (GaP:N,GaP:ZnO, GaP:CdO).Modern LEDs have active regions doped intermediately oreven lightly, in order not to introduce defects to the crystallinestructure. The defects usually increase the level of non-radiantprocesses. Proper concentrationof carriers in nearly non-dopedregions is obtained by dynamic injection of n and p carriers.The junctions in LEDs have the following constructions:homo-junction, bi- and multi-hetero-junction, super-lattice andquantum wells. The most important problems in LEDs leadingto the increase of the energy efficiency are avoidance of factorswhich increase the losses and decrease particular factorsof the overall efficiency: decrease nonradiant recombination,absorption, mask the outgoing radiation, reflections, increaseextraction efficiency – output taper, reflecting mirrors in thesubstrate, periodic micro-scribing of the substrate, outputmicro-lenses, output of the beam via the thinned substrate,matted emitting substrate, optimization of current flow in thecomponent between the electrodes.The LEDs are constructed as classical components, witha luminophore (radiation converter), superluminescent (usingASE – amplified spontaneous emission), resonant (with Fabry-Perot cavity), white (cichromatic, trichromatic, ttrachromatic,pentachromatic, multi-chromatic). The bichromatic sourceshave to mix two waves, longer and shorter, in a proper balance,to excite, in the human eye a feeling of the white light.The balance in multi-chromatic sources between the colorcomponents is approximately 1:1:1. A mixture of the waves470nm and 570nm in proportions 1:1 give a feeling of thewhite light. Dichromatic LEDs are made of GaN-AlGaN-GaInN, have multi-quantum well structure, are manufacturedas monolithic components on a sapphire substrate. Multi-colorLEDs are also build with a luminophore. A basic parameterof a white LED is the CRI – color rendering index. It isequal to 60-95% for LEDs. CRI for sunlight and incandescentbulbs is assumed to be 100. The basic advantages of LEDs forillumination purposes are: long lifetime – above 50000 h, andhigh efficiency – over 50-150 [lm/W]. The relevant parametersfor a tungsten bulb are around ten times smaller.A considerable progress is also observed in the developmentof organic LEDs. OLEDS are build of organic semiconductorsof two categories – polymer and molecular. The principle of work is similar as in classical LEDs.The carriers are passingbetween the two molecular orbits HOMO and LUMO. Theseorbits play the role analogous to valence and conductionbands in a semiconductor. The electrons are injected from thecathode to LUMO and the holes are injected from the anodeto HOMO. OLEDs promise for building flexible planar lightsources with tuned colors, transparent light sources, effectivescreens and displays of high dynamic and static contrast.V. O PTICAL S UPERCONTINUUM Generation of optical supercontinuum is photonic opticalfibers serves for building broadband sources of light. The laseris a very bright source but narrowband. Natural source of light is broadband but dim. A supercontinuum fiber source isbroadband (for example 400-1600nm), very bright and white.During the nonlinear process of broadband excitation of highintensity in a fiber, there are generated new optical frequencies.This phenomenon is combined with electron reaction in theglass. The refraction depends on the intensity of excitation.The photons are interacting strongly with phonons. Typicalexcitation conditions for a dispersive optical fiber with anintense laser pulse are: pulse duration 100 fs, pulse energy1nJ, peak Power 10 kW. The resulting peak intensity of theelectric field in fiber core is 1kW/  µ m 2 .The dispersion in a fiber, which is required to generatethe optical supercontinuum, causes that different frequencycomponents of the exciting pulse propagate in the fiber withdifferent group velocities. Simultaneously, there are manynonlinear effects present at the same time: self-shifting of theRaman frequency, solitonu fusion, and self-phase modulation.
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