Behavior of hydrogen molecules adsorbed on silica in optical fibers

It is shown that molecular hydrogen weakly adsorbed on silica in optical fibers has a dipole moment and is active in infrared spectra. This causes a loss increase at 1.3 and 1.55 μm, which are the attractive wavelengths for optical fiber communication systems. In addition, it is shown that the loss spectra are also related to the fundamental SiO4tetrahedral vibrations rather than the rotation of hydrogen molecules from the observation of the loss spectra in silica glass fibers containing hydrogen molecules and deuterium molecules. It is also shown that the loss is reversible and that the reversibility is promoted with temperature.     

Temperature dependence of second harmonic generation in germania-doped silica optical fibres

Seeded second harmonic generation (SHG) is compared between room temperature (RT) and liquid N/sub 2/ temperature (LNT) in GeO/sub 2/-doped silica fibres. At RT the SH power grows much more rapidly. The corresponding conversion efficiency after seeding for 2 h is over 20 times larger than at LNT.<>     

Concentration effect on optical amplification characteristics ofEr-doped silica single-mode fibers

Optical amplification characteristics for Er-doped silica core single-mode fiber amplifiers with different Er concentrations pumped by 1.48-μm-wavelength laser diodes are studied. Optical gain drastically depends on Er concentration, even when the Er concentration is less than 1000 p.p.m. In the case of the 40-mW incident pump power, the maximum net gain for the fiber containing 77 p.p.m. Er is higher than that for the fiber containing 970 p.p.m. Er by 11.4 dB     

石英光纤与空芯光纤损伤特性(对比)研究

高功率密度脉冲激光的光纤耦合性能一直制约着激光飞片起爆技术的工程化应用。针对106 W/cm2级功率密度脉冲激光在光纤中的耦合特性,设计了一套光纤对准夹具,用于开放光路下脉冲激光的光纤耦合。使用波长为1 064 nm,脉宽6 ns的调Q脉冲Nd:YAG激光,研究了其在大功率石英光纤和AgI/Ag空芯光纤中的能量传输效率和损伤阈值。结果显示:在焦点前后10 mm范围内,石英光纤的传输效率平均值为76.2%,AgI/Ag空芯光纤的传输效率平均值为61.8%;在焦点前2 mm处,测得石英光纤损伤阈值为22.3 mJ,AgI/Ag空芯光纤损伤阈值为29.4 mJ。通过对比结果可知,AgI/Ag空芯光纤拥有较高的损伤阈值,然而AgI/Ag空芯光纤的传输效率比石英光纤低约15%,其工程化应用潜力还有待进一步开发。     

Reduction of impurities in fluoride glass fibers

In order to realize a low-loss fluoride Optical fiber, impurity reduction is indispensable. The methods of recrystallization, extraction, chemical vapor-phase deposition, distillation, and sublimation were tried to purify the starting materials for a fluoride fiber. These purification methods were evaluated by measuring transmission loss of the fibers prepared by using the purified materials. It was found that recrystallization was useful for reducing impurities in ZrF4to the level of below 1 ppm. The extraction technique could be also applicable to purification of BaF2and GdF3. It was concluded that the sublimation was the most probable purification in order to prepare fluoride materials with less than 0.1-ppm impurities. As a result, a low-loss fiber with 8.5 dB/km at 2.12 μm was obtained by using the starting materials purified by sublimation.     

Splice loss in dispersion-modified single-mode silica fibers:effect of non-Gaussian fields

The nature of non-Gaussian fields in dispersion-modified single-mode silica fibers is examined to show the limitations of using two well-known Gaussian approximations for the theoretical prediction of splice loss caused by lateral and angular misalignments. To quantitatively evaluate this limitation, four dispersion-modified silica fiber designs were taken from the literature (a single-, a double-, a triple-, and a quadrupole-clad design) and splice losses calculated with Gaussian approximations were compared to that obtained by numerically integrating the overlap integral of the exact field distribution of the fundamental mode. The accuracy of each is discussed     

Strength and fatigue of silica optical fibers

After a brief review of early lightguide work, the authors assess advances since the mid-1970s. They note important work on strength distributions and procedures for improving strength. This is followed by a discussion of long-length strength, prooftesting and splicing. Flaw character is studied along with strength degradation, fatigue limits, aging and fatigue, and hermetic coatings     

熔石英亚表面杂质对激光损伤概率的影响

基于Mie理论和热传导方程,结合ICP-OES对熔石英亚表面杂质粒子的主要成分测量,建立了计算吸收性杂质粒子诱导熔石英光学元件表面损伤概率的模型。通过该模型理论研究了不同种类的杂质粒子诱导损伤所需的临界能量密度随粒子尺寸的变化,以及不同尺寸分布的杂质粒子诱导熔石英表面的损伤概率。通过损伤实验测试获得了不同光斑尺寸的355 nm激光辐照作用下熔石英表面的损伤概率,与理论计算结果进行对比,在相同粒子分布参数下,分析了三种杂质粒子对损伤概率的贡献（Cu Al CeO2）。通过该模型能够分析光学基底或薄膜亚表面中不同潜在的杂质吸收性粒子对光学元件损伤概率的影响。     

The effect of various types of shallow impurities and their concentration on microhardness and photomechanical properties of semiconductors

The results of studying the influence of various types of shallow-level impurities and their concentrations on the microhardness and photomagnetic effect in silicon single crystals are reported. It is shown that an increase in impurity concentration results in a decrease of both the dark microhardness and the magnitude of the photomagnetic effect. The effect of the acceptor impurities is found to be more efficient in comparison with the donor ones. The data obtained are explained on the basis of the mechanism according to which the decrease of microhardness in semiconductors is caused by free charge carriers (antibonding quasiparticles) occurring in relevant energy bands.     

Mode coupling of microstructured optical fibers using temperature-dependent nitrogen-doped silica fibers

A promising method for the diminishing of loss upon the welding of microstructured optical fibers with suspended core is proposed. The method is based on the application of the nitrogen-doped optical fiber whose thermally expanding core serves as the mode coupler. The loss related to the welding of the conventional fiber (Corning SMF-28 and OFS Clearlite 980) and the suspended-core microstructured fiber (with a core diameter of about 2 μm at wavelengths of 1060, 1310, and 1550 nm) using a conventional welding device is experimentally studied. The welding loss (less than 0.5 dB) in a wide spectral range is several times less than the loss corresponding to the existing methods for the coupling of conventional and microstructures fibers.     

Spectral-hole burning in erbium-doped silica and fluoride fibers

Room-temperature (RT) spectral-hole burning (SHB) in erbium-doped silica and fluoride fibers is investigated and compared. SHB in a fluoride fiber is less strong than in a silica fiber and the hole widths are much wider indicating less inhomogeneity.     

Consolidation-atmosphere influence on drawing-induced defects inpure silica optical fibers

Drawing-induced paramagnetic defects (E'centers and oxygen-associated hole centers (OHCs)) and optical absorption bands at 630 nm and in the UV region are investigated for optical fibers. These fibers are drawn from pure silica glass preforms consolidated in atmospheres containing O₂ and Cl₂. UV absorption bands at 245 nm and 275 nm are clearly observed through deconvolution of the absorption spectra of optical fibers. The defects and absorption bands are influenced by the atmosphere in the consolidation process: (1) the OHCs and the absorption bands at 630 nm and 275 nm increase the intensity with increasing O₂ content and with decreasing Cl ₂ content; (2) the E' centers decrease under the same conditions; and (3) the absorption band at 245 nm is independent of the atmosphere     

Adsorption of alkali metals and their effect on electronic properties of grain boundaries in bulk of polycrystalline silicon

The adsorption of alkali metals and their effect on the electronic properties of grain boundaries in bulk of polycrystalline silicon has been studied experimentally. The results obtained show that the potential barrier grows during diffusion and adsorption of alkali metal atoms along grain boundaries.     

Polarization-maintaining fibers and their applications

Polarization-maintaining fibers and their applications are reviewed. The classification of high-birefringent fibers and low-birefringent fibers and their fabrication methods and characteristics are discussed in Section II. Analytical methods and numerical methods for fiber design on the birefringence are presented in Section III. Degradation factors of polarization maintenance expressed as crosstalk or mode-coupling parameters caused by internal origins such as structural imperfections, wavelength, and nonlinear effects, and by external origins such as temperature fluctuations, mechanical perturbations, and electromagnetic effects, are discussed in Section IV. Characterization methods on beat length, mode coupling, stress distribution, and mechanical strength are presented in Section V. Applications to the fiber devices and nonlinear effects, and splicing methods for the polarization-maintaining fibers are described in Sections VI and VII.     

CdZnTe substrate impurities and their effects on liquid phase epitaxy HgCdTe

Impurity levels were tracked through the stages of substrate and liquid phase epitaxy (LPE) layer processing to identify sources of elements which degrade infrared photodetector performance. Chemical analysis by glow discharge mass spectrometry and Zeeman corrected graphite furnace atomic absorption effectively showed the levels of impurities introduced into CdZnTe substrate material from the raw materials and the crystal growth processes. A new purification process(in situ distillation zone refining) for raw materials was developed, resulting in improved CdZnTe substrate purity. Substrate copper contamination was found to degrade the LPE layer and device electrical properties, in the case of lightly doped HgCdTe. Anomalous HgCdTe carrier type conversion was correlated to certain CdZnTe and CdTe substrate ingots.     

Acid stripping of fused silica optical fibers without strengthdegradation

Glass optical fibers are almost always coated with a polymer immediately after drawing to protect them from subsequent handling damage. When studying the strength and fatigue properties of the fibers, it is useful to be able to remove this coating in order to directly observe the fatigue properties of the glass in immediate contact with the environment. Fused silica optical fibers are frequently stripped by immersion in hot (~200°C) concentrated sulfuric acid. Two recent papers have claimed that hot acid stripping significantly degrades the strength and increases the width of the strength distribution. However, there is a large literature that implies that, at least for most coating systems, acid stripping does not degrade the strength provided sufficient care is taken to protect the bare fiber surface during stripping and subsequent testing. This paper explicitly proves this result, showing that careful complete stripping has little or no effect on the strength of fiber tested in both tension and bending. It is also shown that the immersion time in the hot acid has no noticeable effect on the strength. Experimental protocols are described that minimize the likelihood of accidental damage to the fiber during stripping     

Investigation on chalcogenide and silica based photonic crystal fibers with circular and octagonal core

In this paper, a novel chalcogenide and silica photonic crystal fiber (PCF) structure is designed with circular air-holes located in the cladding and the various optical properties, namely, dispersion, nonlinearity and group velocity dispersion parameters are compared for two different core structures, namely, circular and octagonal. The objective is to obtain high nonlinearity with dispersion flattened PCF. The prime focus is to obtain high non-linear effects as it plays great role in speed and capacity of optical communications. The proposed chalcogenide octagonal and circular PCF exhibits a dispersion of +77.55 ps/(nm km) and +77.34 ps/(nm km), respectively, whereas, the nonlinearity is in the order of 4506 W⁻¹ km⁻¹ and 4498 W⁻¹ km⁻¹, respectively. Also, the silica octagonal and circular PCF exhibits a dispersion of +19.03 ps/(nm km) and +0.97 ps/(nm km) respectively, whereas the nonlinearity is in the order of 169.41 W⁻¹ km⁻¹ and 182.41 W⁻¹ km⁻¹ respectively.     

Experimental performance of silica GIO fibers with a highlyelliptic core

A silica graded-index oval-core fiber with a highly elliptic core has been successfully fabricated for the first time. The core radii along the major and minor axes are 50 and 12 μm, respectively, giving a core aspect ratio of 4.2. Experiments show that a circular modal field of a standard single-mode fiber operating at a wavelength of 980 mm could be transformed into an elliptic field having an aspect ratio of up to 8.0. A numerical investigation was also performed and the results agreed closely with those obtained by the experiments     

掺Yb~(3+)石英光纤的制作

利用一种新型的环形石墨炉加热的改进的化学汽相沉积(MCVD)车床制作出了高吸收、低背景损耗单包层高掺Yb3 石英光纤,并对其几何参数和吸收谱进行了测量、分析和讨论,得出了高掺Yb3 石英光纤的制作要点在于高质量疏松层的制作的结论,并分析了疏松层中掺P有助于提高掺Yb3 量的机理.制作出的高掺Yb3 单包层石英光纤样品在976 nm波长下的吸收可达594 dB/m,而背景损耗只有0.1 dB/m.