Low Brillouin Scattering Optical Fibers and Formation Methods Thereof

Disclosed is an optical fiber formed from a preform that includes a clad component and a core component. The core component includes one or more precursor core materials. The precursor core materials and the clad materials are selected such that that the photoelastic constants of at least one precursor core material and the clad material are of opposite sign resulting in a final glass optical fiber of tailored Brillouin performance. The clad material may include an oxide glass having a positive photoelastic constant and the core component may include a precursor core material that has a negative photoelastic constant. During formation, the precursor core material can melt and interact with clad material that precipitates into the core to form a glass of at least one tailored Brillouin property, such as very low Brillouin gain

CCR5 Haplotypes and Mother-to-Child HIV Transmission in Malawi

CCR5 and CCR2 gene polymorphisms (SNPs) have been associated with protection against HIV transmission in adults and with delayed progression to AIDS. The CCR5 Delta32 deletion and SNP -2459G are associated with reduced expression of the CCR5 protein.We investigated the association between infant CCR2/CCR5 diplotype and HIV mother to child transmission (MTCT) in Malawi. Blood samples from infants (n = 552) of HIV positive women who received nevirapine were genotyped using a post-PCR multiplex ligase detection reaction and haplotypes were identified based on 8 CCR2/CCR5 SNPs and the open reading frame 32 base pair deletion. Following verification of Hardy-Weinberg equilibrium, log linear regression was performed to examine the association between mutations and MTCT. Overall, protection against MTCT was weakly associated with two CCR5 SNPs, -2459G (Risk ratio [RR], 0.78; confidence interval [CI], 0.54-1.12), and the linked CCR5 -2135T (RR, 0.78; CI, 0.54-1.13). No child carried the CCR5 Delta32 SNP. Maternal Viral Load (MVL) was found to be an effect measure modifier. Among mothers with low MVL, statistically significant protection against MTCT was observed for -2459G (RR, 0.50; CI, 0.27-0.91), and -2135T (RR, 0.51; CI, 0.28-0.92). Statistically significant protection was not found at high MVL.Results from this study suggest that CCR5 SNPs -2459G and -2135T associated with reduced receptor expression protect against MTCT of HIV at low MVLs, whereas high MVLs may over-ride differences in coreceptor availability

Roadmap on optical sensors

Optical sensors and sensing technologies are playing a more and more important role in our modern world. From micro-probes to large devices used in such diverse areas like medical diagnosis, defence, monitoring of industrial and environmental conditions, optics can be used in a variety of ways to achieve compact, low cost, stand-off sensing with extreme sensitivity and selectivity. Actually, the challenges to the design and functioning of an optical sensor for a particular application requires intimate knowledge of the optical, material, and environmental properties that can affect its performance. This roadmap on optical sensors addresses different technologies and application areas. It is constituted by twelve contributions authored by world-leading experts, providing insight into the current state-of-the-art and the challenges their respective fields face. Two articles address the area of optical fibre sensors, encompassing both conventional and specialty optical fibres. Several other articles are dedicated to laser-based sensors, micro- and nano-engineered sensors, whispering-gallery mode and plasmonic sensors. The use of optical sensors in chemical, biological and biomedical areas is discussed in some other papers. Different approaches required to satisfy applications at visible, infrared and THz spectral regions are also discussed

Type I and II Bragg gratings made with infrared femtosecond radiation in high and low alumina content aluminosilicate optical fibers

Aluminosilicate fibers have very low Brillouin scattering gain coefficients, making them interesting fibers for nonlinear optical applications. We manufactured Bragg gratings in high (30 mol.%) and low (4 mol.%) alumina content optical fiber using 800 nm femtosecond pulse duration radiation and a phase mask. Grating spectral characteristics and thermal behavior are presented. Index modulations >10 123 were generated for fundamental pitched Bragg gratings, and >10 124 for higher-order gratings. Gratings were annealed at temperatures up to 900\ub0C. Type II gratings written in fibers with lower alumina content showed better thermal stability than gratings written in fibers with higher alumina content. Bragg gratings in these fibers would be well suited as laser cavity mirrors in high-energy laser systems, as well as in telecommunication and sensor systems where Brillouin scattering restricts power scaling.Peer reviewed: YesNRC publication: Ye

(INVITED)Investigation of intense visible defect luminescence from visible and infrared pumped barium fluorosilicate glass-core fiber

Optically active defects in silica have been studied for decades and are often indicators of network irregularities such as those that might result from optical or mechanical damage. They are well-known to be weak emitters and are usually present in relatively low concentration, thus precluding their use in a wide range of applications, including sensing and laser gain. Here, a new paradigm in intense defect emission in the visible wavelength range from a nominally passive optical fiber is presented. Optical fiber starting with 100 mol % BaF2 precursor core material and a pure silica cladding was successfully drawn utilizing the molten core method. These fibers demonstrate an intense, yet unexpected, green photoluminescence peaking near 537 nm (in addition to a second, weaker band near 704 nm) arising from relatively low-power CW pumping in the near-infrared at 976 nm. To understand the origins of this emission, absorption across the optical spectrum is analyzed and photoluminescence via excitation in both the visible and near-infrared wavelength ranges is studied. In addition, Raman spectra, decay lifetimes, magnetization curves, and temperature dependence measurements were collected. The emission spectra maintained a Pekarian-like spectral shape, suggesting an optically active defect as the mechanism behind the green emission. The results presented herein point towards the most likely origin being silanone or dioxasilyrane groups usually associated with surface defects. Importantly, such fibers, fabricated through less conventional methods and possessing novel compositions, may prove to be key in further extending the range of possibilities in defect engineering to well beyond what was previously thought possible