Tsuneo Suganuma

Low-loss single polarization fibers

Low-loss single polarization fibers that maintain a state of linear polarization well are proposed. This fiber is composed of four regions: the concentric circular GeO2- and/or P2O5-doped core and pure silica clad regions for constructing the low-loss waveguide, and the B2O3-doped elliptical-jacket and the silica outer support regions for introducing the large nonsymmetric stress in the core. Theoretical and experimental studies on the coupling length of the two fundamental modes of orthogonal polarization and transmission loss have been carried out. An extinction ratio of less than −33 dB at 1-km fiber length and a loss of <0.8 dB/km at 1.5 μm were achieved.

Optical fiber drawing method with gas flow controlling system

A method for reducing the diameter variation of optical fibers during fiber drawing is described. The method is based on the control of gas flow and drawing speed. Rapid fluctuations in diameter are suppressed by adjusting the gas flow rate, and slower ones are controlled by changing the drawing speed. The efficiency of this method has been tested by applying stepwise disturbance of +or-63% in preform feeding speed. Fluctuations of fiber diameter are controlled within +or-1 mu m despite the forced disturbance. By applying this method to high-speed drawing (30 m/min), a high-tensile-strength fiber, with diameter fluctuations within +or-1 mu m and transmission losses near the 0.85- mu m wavelength region of approximately 3 dB/km, is achieved. >

Reduction of chlorine content in sol-gel derived silica glass

Abstract The undesirable influence of chlorine gas in the production of hydroxyl-free and bubble-free silica glass by the sol-gel method was minimized by introducing a dechlorination treatment of the gel during a sintering process. The dechlorination treatment can be effectively carried out in an oxygen atmosphere at 1000 to 1100°C after the gel is chlorinated at 800°C to remove the hydroxyl. The dechlorination reaction seems to be rate-determined by a diffusion process which is probably governed by the adsorption and desorption of chlorine atoms. The reduction of the specific surface area by a pre-sintering process is useful for the reduction of both the hydroxyl and chlorine content in the densified silica glass. The behaviors of adsorbed chlorine and hydroxyl groups are discussed in relation to the densification mechanism.

Rapid Measuremnent of the Deterioration of Oil-Immersed Paper

A rapid measurement of thermal deterioration of oil-immersed papers by mass spectrometer and gas chromatograph is described. A special assembly was developed using a mercury diffusion pump and automatic Topler pump to extract a very small quantity of generated gas from the oil and to collect it in a reservoir. The gas collected by the above assembly is analyzed by mass spectrometer and gas chromatograph. Logarithm of the generation rate of (CO + CO2) [log (CO + CO2)] is proportional to the reciprocal of absolute temperature (1/T). This linear relationship can be explained by chemical reaction-rate theory and it is shown that the thermal endurance and the thermal life of insulating papers in oil can be estimated by the generation rate of (CO + CO2) in a few weeks as was reported previously for air and vacuum. But the change of the slope of the line log (CO + CO2) versus 1/T at the temperature near 130°C was observed. This is a new mechanism of thermal deterioration of insulating paper in oil, which is apparently unexplained.

Propagation characteristics of single polarization fibers

Detailed studies have been carried out for various dopants on the coupling length (L) of the two fundamental modes of orthogonal polarization to preserve a state of linear polarization over long lengths. Theoretical calculations indicate that L < 2.3 mm is essential to maintain good polarization. Two fundamental single polarization fibers, the elliptical-core and elliptical-clad fibers, have been prepared by CVD. Experimental results show that a B2O3 dopant yields a substantially large anisotropic birefringence than does GeO2 and P2O5. The effects of noncircularity and normalized frequency of the fiber on L have been experimentally considered.

Reduced pressure collapsing MCVD method for single polarization optical fibers

A simple fabrication method of single polarization optical fibers has been proposed. Core, clad, and jacket layers are deposited in a silica tube. The tube is then collapsed while the inner pressure of the tube is reduced. The core circularity and the jacket ellipticity are controlled by the careful selection of the softening points of core/clad and jacket materials, and the inner pressure. The pressure reduction and the softening points of the constituent glasses play an important role in fabricating single polarization optical fibers.

High ionic conductivity of Na‐βGa2O3 thin film.

Sodium β‐gallate thin films are prepared by rf sputtering and subsequent heat treatment. These thin films exhibit ionic conductivity as high as 4.2×10−2 Ω, cm−1 at 3000C and 7.0×10−6 Ω cm−1 at room temperature. Their ionic conductivity above 2000 C is only one order of magnitude less than that of single crystals. The activation energy of ionic conduction is 0.23 eV, that is, almost the same as that of single crystals. This ionic conductivity is high enough to be applied to thin‐film devices of solid electrolytes.

Refractive index behavior of SiO2-P2O5 glass in optical fiber application

Abstract The refractive index of SiO2-P2O5 glass prepared by a modified chemical vapor deposition method is measured using an interference microscope. It is found that the refractive index in bulk form increases linearly at 9.5×10-4 (mol.%)-1 as the P2O5 concentration increases. It is also found that quenching at extremely high speed reduces the refractive index over 2 mol.% P2O5. The wavelength dispersion of the refractive index dn/dλ is constant up to 5 mol.% P2O5 producing a refractive index difference of 5×10-3 compared with fused silica. Consequently, this glass materials is thought to be suitable for wide band-width optical fiber applications.

Transmission characteristics of VAD fibers using a multiple burner with single source gas nozzle

Abstract A vapor phase axial deposition (VAD) method using a multiple burner with single source gas nozzle is presented. Fibers fabricated by this technique feature very low loss and wide bandwidth characteristics, although the refractive index profile slightly deviates from the ideal, on the outer side of the core part. This technique is expected to provide a simple method of fabricating low loss and wide bandwidth fibers.

Chlorination reduction in sol—gel-derived porous silica gels

Abstract Chlorine dehydroxylation in plate-like silica gels prepared by hydrolysis of Si(OCH3)4 was investigated for gels treated in chlorine at 800°C. The infrared absorption spectrum of OH on the open pore surface of the gel was measured. The exchange reaction between OH and Cl was found to decrease linearly with the square root of treatment time and with reciprocal gel thickness. The dependence of the dehydroxylation rate on gel thickness indicated that the exchange between OH and Cl is limited by Cl2 diffusion into the gel.