Hiroshi Hihara

Fracture origins of optical fibers fabricated by hybridized process

Fracture origins of single-mode optical fibers that were produced by the CIP hybridized process consisting of overcladding a VAD-derived core rod with silica glass made from commercial silica powder were studied. It was found that there were many inclusions that caused failure of the fiber at the screening test. To identify the inclusions, the EPMA technique was successfully used and new internal defects such as a Cr, a Cr-Fe, and a Zr inclusions were found. By investigating the manufacturing process precisely, stainless steel particles and Cr/sub 2/O/sub 3/ particles in the silica powder were found to become origins of the fractures. Further, the removal of Cr/sub 2/O/sub 3/ particles by the reaction with chlorine gas at high temperature was studied, and its dependence on the reaction temperature and on the chlorine content was clarified. It was also suggested that the initial particle size of a Cr/sub 2/O/sub 3/ particle was an important factor for its elimination. The results obtained by this study should be used to remove both the Cr and the Cr-Fe inclusions.

Studies on the strength of optical fiber fabricated by a hybridized process

Strength of single-mode optical fibers that were produced by a hybridized process consisting of overcladding a VAD-derived core rod with silica glass made from commercial silica powder was studied. There were such defects as a Zr-containing inclusion (Zr-inclusion), a bubble and two kinds of Cr-containing inclusions (Cr-inclusions) found in the fiber. These defects caused failure of the fiber at a proof test. In order to make a strong fiber, removal of the defects were studied and the following results were obtained as follows. 1) The Zr-inclusion could be removed by decanting an aqueous suspension of silica powder having an average diameter of 10 /spl mu/m (Silica A). 2) The bubble could be removed by using the decanted Silica A only or by purifying at 1000/spl deg/C. 3). The Cr-inclusions could be removed by purifying at 1000/spl deg/C in helium gas containing more than 30 vol.% chlorine. The strongest fiber fabricated had a break probability as low as 0.01/km in a proof test of 0.7% elongation for 1 s.