Infrared loss increase phenomenon of coated optical fibers at high temperatures

The loss increase phenomenon of coated optical fibers at high temperature has been studied. The wavelength dependent loss increase, observed for plastic-coated fibers at 200°C, is found to be irreversible. During heating, the absorption peak of second overtone of Ge-OH preferentially appeared. The dependence of the loss increase on temperature, heating time, and dopant is also examined. The loss increase level is strongly dependent on phosphorous concentration. The experimental results indicate that the loss increase is caused by chemical reactions between fiber constituent materials and hydrogen generated from coating materials. It is also confirmed that the heating test of secondary coated fiber is a practical, useful method to evaluate the hydroxyl loss increase of optical fibers.     

High- temperature effects of aluminum-coated fiber

High-temperature characteristics of aluminum-coated fibers have been investigated. The fibers studied are silica core fiber and germanium-doped cored fiber. it has been found that the silica core fiber is suitable for high-temperature application, although micro-bending loss change is dominant in all aluminum-coated fiber under 100°C. Germanium-doped core fiber has shown a loss increase at high temperature due to the increase of the defect centers. The loss increase at high temperature, however, can be eliminated by high-temperature annealing because the OH diffusion at high temperature will fill up the defect centers with OH. From the investigation of the germanium concentration effects, it has been found that the density of the defect center is about ten times higher at the germanium atom site than at the silicon atom site. The Rayleigh scattering coefficient of the germanium-doped fibers has been measured and clarified in a very wide temperature range.     

Thermal characteristics of jacketed optical fibers with initial imperfection

Thermal characteristics of optical loss and fiber strain in jacketed single-mode optical fibers with initial fiber axis deformation have been examined theoretically and experimentally. Fiber axis deformation due to temperature change is theoretically analyzed by applying buckling theory for a bar on an elastic foundation. Optical loss increase and fiber strain are measured for two kinds of fibers which have different initial fiber axis deformation. Experimental results approximately coincide with values calculated from the theory. It is clarified from these results that the fiber strain due to temperature change is smaller and loss increase at low temperatures is larger for the fiber with larger initial axis deformation. A design method for jacketed single-mode optical fibers to prevent loss increase at low temperatures is given.     

Studies on Loss Aging in Submarine Coaxial Cable During Storage

Attenuation loss change in submarine coaxial cables during 4 years of storage has been measured. Attenuation loss is shown to increase for one year after manufacturing. Then, loss is also shown to increase during summer (May to October) and to stay constant or to decrease during winter (November to April of the next year). This work concentrates on the causes and an estimation method of loss aging. The first part of the paper covers experimental results on the cable aging phenomenon. The second part discusses various factors affecting loss aging, and shows that fretting corrosion on the outer conductor tape will be a main factor. The third part describes an estimation method for and countermeasures to avoid loss aging during cable storage.     

非对称X结波导混合耦合器的改进型设计

为了减小非对称X结波导混合耦合器的串音和功耗,增大实现模式分离的非对称端分支角,提出了一种改进型设计.用光束传播法结合有效折射率法模拟分析了改进后的非对称X结波导混合耦合器的串音与功耗,结果表明其串音比原来有了大幅度的减小,而且功耗也得到了改善.     

Molecular hydrogen behaviour for loss increase of silica fibre in cable filled with water

Evaluation of molecular hydrogen diffusion into silica fibre, which causes a loss increase at 1.24 ?m wavelength, and the accumulation mechanism for hydrogen in cable are reported. It has been found that loss increase around 1.24 ?m wavelength due to hydrogen greatly depends on the ambient hydrogen pressure. The hydrogen pressure in LAP sheath cable easily increases due to metal corrosion and the sealing effect of the sheath.     

Wavelength-dependent optical loss increase in graded-index optical fibre transmission lines

Wavelength-dependent optical loss increase in GeO2-P2O5-doped graded-index optical fibre transmission lines has been observed. The loss increase is found to depend strongly on the P2O5 concentration. By reducing the P2O5 concentration, loss increases at 1.3 ?m can be suppressed to a sufficient extent without any hindrance for practical usage.     

Optical loss property of silica-based single-mode fibers

The optical loss property of silica fibers has been investigated theoretically and experimentally based on their Rayleigh scattering and absorption losses. The Rayleigh scattering loss for fibers has been estimated using Rayleigh scattering coefficients and power distribution in the fiber. The Rayleigh scattering coefficients are measured for preforms prepared for fiber fabrication and are discussed for GeO₂ -doped and F-doped glasses. The relationship between the optical loss and fiber parameters is clarified. Moreover, the loss increase due to residual stress which occurs during the drawing process is simulated. The optical loss limitations for GeO₂-doped and pure silica core fibers are shown     

An X-band small outline leaded plastic package for MMIC applications

A new small outline (SO) leaded plastic package has been developed that improves return loss, insertion loss, and isolation performance over that of a shrink small outline package (SSOP) in the same body size. A custom TRL calibration kit was developed, and prototype packages built and measured. The measured package showed an increase in the application bandwidth of SO-type packages from 5 GHz to over 8 GHz. Further investigations using full-wave electromagnetic simulations reveal a potential increase in return loss of better than 30 dB to 10 GHz, giving the package a usable bandwidth well into the X-band (8-12GHz). Applications for the new package are in microwave and RFIC applications.     

Chemical change from diffused hydrogen gas to hydroxyl ion in silica glass optical fibres

The chemical change from hydrogen gas that diffuses into silica glass for optical fibres to hydroxyl function has been investigated. Hydrogen molecules that diffuse into GeO2-doped silica glass at 500°C easily change into OH ions by thermal energy, while this chemical change does not occur in pure silica glass at 500°C. Also, germanium-doped silica fibre, in which hydrogen gas is dissolved at room temperature, shows OH ion absorption loss increase with chemical change by heat treatment at above 100°C, while pure silica core fibre shows no OH ion absorption loss increase by the same treatment.     

Loss increase in deuterium-doped VAD fibres with heat treatment

The origin of the increase in the intensity of OH bands with heat treatment has been investigated using deuterium-containing VAD fibres. Remarkable loss increases only in the absorption peaks due to the OH ions have been observed after 200?500°C heat treatment applied to three kinds of fibre: drawn from a preform prepared by a D2-O2 flame, and OD-doped in the core and in the cladding. It was confirmed that the origin of the hydrogen causing the loss increase is not in the synthesised glass materials.     

Thermal Aging Reliability of Package-Level Polymer Optical Waveguides

Polymer optical waveguides are viewed as a potential interconnect solution in board-level optoelectronic systems. In this paper, the optical loss changes in siloxane polymer waveguides during thermal aging conditions are studied for the wavelengths of 850 and 1310 nm. The optical loss in waveguides during intended operation and temperature exposure can increase due to factors such as oxidation of waveguides, increased absorption, and scattering. In addition to these inherent changes in the optical properties of the waveguides, physical failures such as delamination and cracking of waveguides will also increase the optical loss. This paper focuses on the first set of parameters that affects the optical loss and as a first step; the optical absorption of the polymer material is characterized through spectroscopy experiments. The thermal-aging dependent optical loss is determined for waveguide samples at several different accelerated temperature conditions. The temperature contours in a polymer waveguide with an embedded laser are determined from experiments as well as finite-element modeling. Using experimental data, analytical models have been developed that relate the optical loss with temperature and time, and provide a practical way of determining the reliability of the optical waveguides during field-use conditions.     

Large photosensitivity in wet tin-phosphosilicate fibres

Large refractive index modulations have been induced in a wet tin-phosphosilicate fibre under KrF excimer laser illumination. Comparison with dry and loaded tin-phosphosilicate fibres show that considerable photosensitivity increase can be achieved without any burdensome loss increase.     

Investigation on propagation properties of terahertz waveguide hollow plastic fiber

The propagation properties of terahertz (THz) waveguide plastic hollow fiber have been investigated in this paper. The effects of radiation frequency, bore diameters and dielectric coating layers on the waveguide property have been shown and discussed. The results show that the attenuation loss of TM mode increases and that of TE mode decreases as radiation frequency increases. The attenuation loss decreases with the increasing of fiber bore diameter. The attenuation loss decreases as the refractive index of dielectric coating layer and the ratio of the refractive index of outer dielectric layer to that of inner dielectric layer increase.     

Estimation of long-term transmission loss increase in silica-basedoptical fibers under hydrogen atmosphere

The irreversible loss increase in silica-based optical fibers due to hydrogen is discussed on the basis of results of various high-temperature tests. The results show that germanium-doped-core fibers have different behavior with respect to irreversible loss increase, and that a pure-silica-core fiber fabricated under optimum conditions is very stable against irreversible loss increase. The estimation of long-term transmission loss stability is also discussed, and high-temperature testing is certified to be effective for estimating the long-term loss stability under low temperature     

Design issues for the transformer in a low-voltage power supplywith high efficiency and high power density

Circuit model, design feasibility, and design tradeoffs are investigated for the transformer in 1.5-5 V power supplies with high efficiency and high power density. The transformer is constructed from a single or a matrix of pot cores and from interleaved planar windings. It has been determined theoretically and verified experimentally that such a transformer is realizable as long as the loss constraint is not severe (e.g. less than 0.5 W transformer loss per 100 W output). The primary source of loss is the winding, not the core, in 1.5 V/turn design. Measures to reduce the transformer height tend to increase transformer loss or volume     

Stress and temperature effects on optical loss increase for phosphor-doped silica fibre in the long wavelength region

Irreversible loss increase in the long-wavelength region is first observed for phosphor-doped silica fibres with silicone resin layer by applying the stress at high temperature. The loss increment becomes larger for longer wavelengths. Experimental results show that the loss increase is strongly dependent on stress and temperature.     

Long-term loss stability of single-mode optical fibres exposed to hydrogen

The rate of increase in loss in single-mode optical fibres exposed to hydrogen at temperatures up to 150°C has been determined. Extrapolation down to ambient temperature of effects other than that due to interstitial hydrogen indicates that slow long-term loss increments at 1310 nm will remain less than 0.02 dB/km after 25 yr at 20°C in one atmosphere of hydrogen.     

Loss increase for optical fibers exposed to hydrogen atmosphere

Loss spectrum changes for optical fibers exposed to a hydrogen atmosphere in the15-200degC temperature range are measured. Loss increase due to molecular hydrogen dissolved into fibers is investigated from the loss peak at 1.24 μm, and that due to hydroxyl group formation from the loss peak at 1.41 μm. The loss increase due to molecular hydrogen is fully explained by physical solubility theory and diffusion equation. The empirical formula for time, temperature, and hydrogen-pressure dependences of the loss increase due to hydroxyl group formation is evaluated from the experimental results. The loss increase at 1.3- and 1.5-μm wavelength band at room temperature are estimated.     

A 5-μm-wide 18-cm-long low-loss YBa2Cu3O7-δ coplanar line for future multichip moduletechnology

Narrow and low-loss YBa₂Cu₃O_7-δ (YBCO) coplanar lines, which can be used in multichip module technology for future high-density and high-speed digital circuits, have been developed. Etch-back planarization and a patterning process combining Ar-ion milling and wet-etching enabled us to form an 18-cm-long 5-μm-wide YBCO coplanar line without electrical shorts, even for the narrow spacing of 2.5 μm. The surface resistance of this line was kept at a level comparable to that of 10- or 25-μm-wide YBCO coplanar lines and also comparable to that of unpatterned films. This indicates successful fabrication of the 5-μm-wide YBCO coplanar line without notable loss increase resulting from process damage. The 5-μm-wide line showed a low-transmission loss of 0.49 dB at 10 GHz and 55 K. This level of loss is similar to that in Cu coaxial cables. No significant increase in transmission loss was observed up to an input power level of 16 mW at 10 GHz and 55 K. This input power is comparable to the power-handling capability required for transmitting high-speed digital signals through the lines with characteristic impedance of 50 Ω. These results show that the narrow 5-μm-wide YBCO coplanar line has great potential for high-density and high-speed digital circuits