Modelling of Photonic Crystal Fibers with W - shaped Refractive Index Profile

Korišćenjem vremenski nezavisne i vremenski zavisne jednačine protoka snage, ispitivane su prenosne karakteristike fotonsko kristalnog optičkog vlakna sa W profilom indeksa prelamanja. Za različite kombinacije odabranih strukturnih parametara fotonsko kristalnog vlakna sa W indeksom prelamanja određene su dužine na kojima se uspostavljaju stacionarna i ravnotežna raspodela modova, potom gubici koji nastaju usled sprezanja modova, propusni opseg i frekventni odziv. Ispitivan je i uticaj talasne dužine i različitih uslova pobuđivanja svetlosti na ulazu u vlakno na prostiranje svetlosti i gubitke curećih modova. Za jednomodno fotonsko kristalno vlakno W tipa je ispitivan uticaj strukturnih parametara na slabljenje signala usled Rejlijevog rasejanja. Sve ispitivane parametre je značajno poznavati prilikom modelovanja i dizajniranja vlakna za određenu vrstu primene.Using the time-independent and time-dependent power flow equation, transient characteristics of W-type photonic crystal fiber were investigated. For different combinations of values of selected structural parameters of Wtype photonic crystal fiber, we have determined: the lengths of the fiber at which stationary and equilibrium mode distributions are established, coupling losses, bandwidth and frequency response. Also, the influence of wavelength and different light excitations on light transmission and leaky mode losses was examined. The influence of structural parameters on losses due to Rayleigh scattering was investigated for singlemode W-type photonic crystal fiber. All of the examined parameters are significant for modelling and designing a fiber for a specific application

Uticaj uzrasta, stepena oštećenja sluha, ocene i pola na imenovanje predmeta kod gluvih i nagluvih učenika

Difficulties in pronouncing isolated sounds, their automation in everyday speech and communication as well as the resulting scarcity of the lexicon characterize the speech and language of deaf and hard of hearing children. The stance that the aforementioned problems are overcome through written expression is outdated as it develops very slowly and with a great deal of effort - it is abstract. The sign language is a language of its own It has its own linguistic rules, lexis, semantics, syntax and grammar. It is the first language the deaf use to speak and, by learning it, children gain their first knowledge and communicative experience. The aim of this study was to examine the level of familiarity with the names of objects and defining their purpose within written, oral and sign expression, depending on the age, the level of hearing impairment, the mark in the Serbian language and the sex of students. The study was carried out on the sample of 83 third grade to eighth grade students who attend schools for deaf and hard of hearing children in Serbia. The instrument which we applied was the Linguistic Assessment of Certain Components of Dysphasic Syntax (D Blagojević) - the segment Naming objects and what they are used for. The obtained results indicate that the success in naming objects and defining their purpose increases with age (with some exceptions), the mark in the Serbian language significantly influences successful performance, while the effect of the level of hearing impairment and the sex has not been observed The study also presents specific mistakes and characteristic replies in naming each individual object.Teškoće pri izgovoru izolovanih glasova, njihova automatizacija u svakodnevnom govoru i komunikaciji, kao i oskudnost leksikona koja iz toga proizilazi, karakterišu govor i jezik gluve i nagluve dece. Mišljenje da se pisanim izrazom navedeni problemi prevazilaze je prevaziđeno, jer se on razvija izuzetno sporo i teško, apstraktan je. Znakovni jezik je jezik za sebe. Ima svoja lingvistička pravila, leksiku, semantiku, sintaksu i gramatiku. Prvi je govor gluvih i njegovim savladavanjem deca stiču prva saznanja i komunikativna iskustva. Cilj istraživanja bio je ispitati stepen poznavanja naziva predmeta i određivanje čemu oni služe u okviru pisanog, govornog i znakovnog izraza u zavisnosti od uzrasta, stepena oštećenja sluha, ocene iz srpskog jezika i pola učenika. Istraživanje je obavljeno na uzorku od 83 učenika uzrasta od trećeg do osmog razreda koji pohađaju škole za gluvu i nagluvu decu u Srbiji. Instrument koji smo koristili je Jezičko ocenjivanje pojedinih komponenata disfazične sintakse (D. Blagojević) - segment Imenovanje predmeta i čemu služe. Dobijeni rezultati ukazuju na to da sa uzrastom raste uspešnost pri imenovanju predmeta i određivanju čemu služe (sa pojedinim odstupanjima), ocena iz srpskog jezika značajno utiče na uspešnost, dok uticaj stepena oštećenja sluha i pola nije uočen. U radu su date i specifične greške i karakteristični odgovori pri imenovanju svakog pojedinačnog predmeta

Calculation of bandwidth of multimode step-index polymer photonic crystal fibers

By solving the time-dependent power flow equation, we present a novel approach for evaluating the bandwidth in a multimode step-index polymer photonic crystal fiber (SI PPCF) with a solid core. The bandwidth of such fiber is determined for various layouts of air holes and widths of Gaussian launch beam distribution. We found that the lower the NA of SI PPCF, the larger the bandwidth. The smaller launch beam leads to a higher bandwidth for short fibers. The influence of the width of the launch beam distribution on bandwidth lessens as the fiber length increases. The bandwidth tends to its launch independent value at a particular fiber length. This length denotes the onset of the steady state distribution (SSD). This information is useful for multimode SI PPCF applications in telecommunications and optical fiber sensing applications

Theoretical Investigation of Bandwidth in Multimode Step-Index Silica Photonic Crystal Fibers

Solving the time-dependent power flow equation (PFE) provides a useful method to study the transmission bandwidth of step-index silica photonic crystal fibers (SI SPCFs). The transmission bandwidth of these kinds of fibers is determined for different air-hole structures (different numerical apertures (NAs)) and different distribution widths of the Gaussian launch beam. The results indicate that the lower the NA of SI SPCFs, the higher the bandwidth (for example, for a lower NA of SI SPCFs, a bandwidth that is eight times larger is obtained at a fiber length of 3500 m). The narrower launch beam at short fiber lengths results in a wider bandwidth. The longer the fiber (>300 m), the much less the effect of the launch beam width on the bandwidth. The bandwidth becomes independent of the width of the launch beam distribution at the fiber length at which a steady-state distribution (SSD) is reached. These results are useful for some potential applications, such as high capacity transmission optical fiber systems

Theoretical Investigation of Bandwidth in Multimode Step-Index Silica Photonic Crystal Fibers

Solving the time-dependent power flow equation (PFE) provides a useful method to study the transmission bandwidth of step-index silica photonic crystal fibers (SI SPCFs). The transmission bandwidth of these kinds of fibers is determined for different air-hole structures (different numerical apertures (NAs)) and different distribution widths of the Gaussian launch beam. The results indicate that the lower the NA of SI SPCFs, the higher the bandwidth (for example, for a lower NA of SI SPCFs, a bandwidth that is eight times larger is obtained at a fiber length of 3500 m). The narrower launch beam at short fiber lengths results in a wider bandwidth. The longer the fiber (>300 m), the much less the effect of the launch beam width on the bandwidth. The bandwidth becomes independent of the width of the launch beam distribution at the fiber length at which a steady-state distribution (SSD) is reached. These results are useful for some potential applications, such as high capacity transmission optical fiber systems

Microwave synthesis of novel chenodeoxycholic acid esters and comparative study of chromatographic behavior and lipophilicity

In this study, eco-friendly microwave-assisted esterification reactions of chenodeoxycholic acid with medium-chain diols (1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol) or tetraethylene glycol were accomplished. The synthesized bile acid esters were obtained with high yields (up to 81 %) and purity in a short reaction time (15 min). It is shown that the microwave technique is a suitable method for the preparation of chenodeoxycholic acid esters. In order to obtain detailed insight into the lipophilic behavior of the studied chenodeoxycholic acid esters, a comparative study of chromatographic behavior and lipophilicity was performed. Also, the present study deals with the estimation of pH – logD profiles in order to get an overview of the changes in lipophilicity related to the pH value changes. The obtained results indicate that studied compounds have logD values in the range acceptable for potential drug candidates. Chromatographic lipophilicity of synthesized chenodeoxycholic acid esters successfully correlate with in silico lipophilicity descriptors

Wavelength dependent equilibrium mode distribution and steady-state distribution in double-clad W-type microstructured polymer optical fibers

This paper investigates wavelength dependence of equilibrium mode distribution and steady-state distribution in W-type (double-clad) microstructured polymer optical fibers (mPOFs) with a solid core for parametrically varied refractive index and width of the intermediate layer (IL) (inner cladding) by solving the time-independent power flow equation (TI PFE). In the case of wider IL, independent of wavelength, the lengths for establishing the equilibrium mode distribution and steady-state distribution are larger. We have demonstrated that the wavelength has no effect on these lengths for IL’s width that is larger. These lengths drop in a wavelength-dependent manner as the IL's width decreases. Equilibrium mode distribution and steady-state distribution occur at shorter optical fiber lengths as the depth of the IL diminishes, which is due to the similarly declining number of leaky modes. The smaller the depth of the IL, the shorter the fiber length is required for completion of the coupling process. These programmable characteristics allow double-clad W-type mPOFs to be easier customized for a particular use in optical fiber sensors and communications at various wavelengths

High bandwidth performance of multimode graded-index microstructured polymer optical fibers

The investigation of the bandwidth in multimode graded-index microstructured polymer optical fiber (GI mPOF) with a solid core is proposed using a modal diffusion approach. For a variety of launch radial offsets of multimode GI mPOF, bandwidth is reported by numerically solving the time-dependent power flow equation (TD PFE) using the explicit finite difference method (EFDM) and physics-informed neural networks (PINN). The decline in bandwidth with fiber length becomes slower at fiber lengths close to the coupling length Lc at which an equilibrium mode distribution (EMD) is attained, showing that mode coupling enhances bandwidth at longer fiber lengths. As fiber length is increased, bandwidth approaches complete independence from radial offset, suggesting the steady-state distribution (SSD) has been reached. We compare multimode GI mPOF performance in terms of bandwidth with that of traditional multimode GI POFs made of the same material. Higher bandwidth performance and quicker bandwidth improvement are displayed by the GI mPOF. To enhance fiber performance in GI mPOF links, such a fiber characterization can be used