Measuring the difference in group delays between the cores of a multicore optical fiber by means of time-domain interferometry

A way of measuring the difference in group delays between the cores of multi-core optical fiber is proposed. The method is based on a low-coherence Mach–Zehnder interferometer and a broadband radiation source. The corresponding experimental setup is constructed and a seven-core optical fiber with identical cores manufactured at the Fiber Optics Research Center, Russian Academy of Sciences, is studied.     

Advanced polyimide varnish for optical fiber coating fabrication

Using one-step high-temperature polycondensation, soluble polyimide based on 9,9-bis-(4’-aminophenyl) fluorene and 3,3’, 4,4’-diphenyl oxide tetracarboxylic acid dianhydride is synthesized. Polyimide varnishes inN-methyl-2-pyrrolidone are prepared, and technological conditions of their deposition during fiber drawing are studied. A polymer coating thickness over 6 μm is achieved for a single application. It is demonstrated that the developed coating almost does not degrade for a long time at temperatures to 250 °C and completely protects the optical fiber surface from water penetration.     

Elastic scattering of heavy ions and a modified liquid drop model

Zeitschrift für Physik A Hadrons and nuclei - The repulsion due to the nonlinearity of a Schrödinger equation for the elastic scattering of heavy ions is approximated by the compression...     

Highly dispersive large mode area photonic bandgap fiber

An all-silica photonic bandgap fiber composed of a low-index core surrounded by alternating high- and low-index rings allows us to achieve a large mode area (500 microm(2)) and large chromatic dispersion. Sharp resonances from the even Bragg mode to odd ring modes theoretically lead to 20,000 ps/(nm km) chromatic dispersion when large bends are applied. By nature, sharp resonances are sensitive to inhomogeneities along the fiber length. Under experimental conditions, the resonances are broadened and the dispersion coefficient is decreased to 1000 ps/(nm km). However, to the best of our knowledge, this is the largest dispersion coefficient reported using a large mode area fiber.     

All-Glass Single-Mode Microstructured Fibers with a Large Mode Area

Doklady Physics - A new design of all-glass microstructured fibers with a large mode area is presented. The numerical analysis of the fibers was performed using the finite element method....     

Synthesis of porphyrinoids with silane anchors and their covalent self-assembling and metallation on solid surface

We have synthesized a set of porphyrin and phthalocyanine compounds with two different silane anchors. Syntheses of the anchor-substituted chromophores have been carried out via hydrosilylation of alkene derivatives, catalyzed by platinum complexes. The reduction side-process was suppressed using specific anchor/catalyst pairs, and the silane-containing compounds were successfully isolated from hydrogenated by-products in pure form with good yields. The target porphyrinoids having stable reactive silane anchors possess the ability to self-assemble on metal oxides and quartz surfaces and optical fibers. Covalent attachment is done in one-step, which makes the bonding process fast and easy. Immobilized chromophores were further converted by on-surface reactions into Zn(II) and Mg(II) metal complexes. The metallation time was found to be as fast as 1 min for Zn ion. Bonding densities calculated from the absorbances of the deposited layers give rough estimations for packing of the molecules on various substrates and evidence for monomolecular layers formation.     

Stable isotopic studies of earthworm feeding ecology in tropical ecosystems of Puerto Rico

Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used (13)C and (15)N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less (15)N enrichment ((15)N = 3-6 per thousand) than exotic Pontoscolex corethrurus ((15)N =7-9 per thousand) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in (15)N enrichment ((15)N = 6-9 per thousand), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in (15)N than those in the forest sites, but more highly enriched in (13)C suggesting assimilation of C from the predominant C(4) grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright 1999 John Wiley & Sons, Ltd.     

A potential for the description of alpha-alpha interactions

In an investigation into the α-α and α-nucleus interaction the former is studied employing for the effective interaction a potential with a repulsive core embedded into a long range attractive part. Calculations with this potential reproduce the energies and widths of the levels of the α-α system⁸Be and the phases for α-α scattering quite well thus pointing to an applicability of the model to α-α and α-nucleus scattering for light nuclei.