102 research outputs found

    Comparative measurement of Rayleigh scattering in single-mode optical fibers based on an OTDR technique

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    A new technique for comparing the Rayleigh scattering coefficients of single-mode step index fibers is described and its theoretical limitations are discussed. The validity of the technique is proven using telecommunications-grade fibers. Of particular interest is the variation of scatter found with increasing core index. In addition, the influence of small ( <0.1 percent) quantities of rare-earth dopant ions on the fiber scatter losses is analyzed for the first time

    Line narrowing and spectral hole burning in single mode Nd<sup>3+</sup>- fibre lasers

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    Line-narrowing in the output spectrum of an Nd-doped silica-fiber laser with spectrally flat reflectors is interpreted to indicate substantial homogenous contribution to the 1.09µm fluorescent linewidth. Using a fiber Bragg-reflector, frequency-stable operation with 100GHz bandwidth is obtained, dominated by power broadening and spectral hole burning

    Single-mode neodymium fibre lasers

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    A laser medium in the form of a single mode optical fibre offers a number of attractive features. For example, using a laser to end pump such a fibre provided with feedback mirrors, allows a very low oscillation threshold to be attained. In the case of Nd doped fibre a GaAs diode laser can be used as the pump, thus providing a very simple and compact laser device. The low threshold performance also suggests that other, weaker transitions may be capable of laser action eg. the 1.3µm 4F3/2 to 4I13/2 transition in Nd or transitions in other dopants which have not previously shown laser action in a glass host. Other possible applications include the use of fibres as amplifiers e.g. as an in-line amplifier in an optical communication system where it could play the role of a repeater. As a power amplifier the fibre device could have advantages over the bulk glass systems by reducing the problems of thermal distortion and thermal fracture. In this paper we report some results obtained with neodymium-doped single mode fibres

    Functional mechanisms underlying pleiotropic risk alleles at the 19p13.1 breast-ovarian cancer susceptibility locus

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    A locus at 19p13 is associated with breast cancer (BC) and ovarian cancer (OC) risk. Here we analyse 438 SNPs in this region in 46,451 BC and 15,438 OC cases, 15,252 BRCA1 mutation carriers and 73,444 controls and identify 13 candidate causal SNPs associated with serous OC (P=9.2 × 10-20), ER-negative BC (P=1.1 × 10-13), BRCA1-associated BC (P=7.7 × 10-16) and triple negative BC (P-diff=2 × 10-5). Genotype-gene expression associations are identified for candidate target genes ANKLE1 (P=2 × 10-3) and ABHD8 (P<2 × 10-3). Chromosome conformation capture identifies interactions between four candidate SNPs and ABHD8, and luciferase assays indicate six risk alleles increased transactivation of the ADHD8 promoter. Targeted deletion of a region containing risk SNP rs56069439 in a putative enhancer induces ANKLE1 downregulation; and mRNA stability assays indicate functional effects for an ANKLE1 3′-UTR SNP. Altogether, these data suggest that multiple SNPs at 19p13 regulate ABHD8 and perhaps ANKLE1 expression, and indicate common mechanisms underlying breast and ovarian cancer risk

    Self-imaging by ring-core fibers

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    A tubular dielectric waveguide of typically 100 lambda diameter and single-moded wall-thickness can produce single or multiple images of one endface on the opposite one. Applications as single-mode N x N directional couplers are possible

    Recent developments in rare-earth-doped fibres and fibre lasers

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    The development of techniques to produce single-mode rare-earth-doped fibres has led to many passive and active (laser) devices based on these fibres including distributed temperature sensors, high-rejection wavelength selective filters, and fibre lasers and amplifiers. The possibilities offered by fibre lasers and amplifiers are particularly exciting since they present a potential technique for achieving compact, tunable, diode-pumped, narrow-linewidth sources which are compatible with optical fibre technology. Recent developments include diode-pumped fibre lasers operating at 1.08µm with C.W. output powers of 6mW and Q-switched (pulsed) operation with output in excess of 13W. Single-longitudinal-mode operation with a linewidth of 1.3MHz has been demonstrated, as has single-polarisation operation with an extinction ratio of 37dB. The extension of these techniques to operation at 1.55µm will find immediate applications in coherent communications system and will be discussed, as will additional active and passive devices including in-line fibre amplifiers and bistable fibre switches

    Fabrication of Al<sub>2</sub>O<sub>3</sub> co-doped fibres by a solution-doping technique

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    A new technique for fabricating optical fibres containing Al2O3 is described. Application of the technique to single-mode and rare-earth-doped fibres is discussed

    A study of fabrication and measurement techniques for special optical fibres

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    SIGLEAvailable from British Library Document Supply Centre- DSC:D75978/87 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

    Fabrication of Al<sub>2</sub>O<sub>3</sub> co-doped optical fibres by a solution-doping technique

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    A new technique for fabricating optical fibres containing Al2O3 is described. Application of the technique to single-mode and rare-earth-doped fibres is discusse

    Extended wavelength operation of an Er<sup>3+</sup>-doped fibre laser pumped at 808nm

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    An Er3+-doped single-mode fiber laser with an extended output wavelength range around 1.55µm is reported. The laser was pumped by either a diode or dye laser and wavelength selection was by adjusting the fibre length
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