Borosilicate clad fused silica core fiber optical waveguide with low transmission loss prepared by a high-efficiency process

A method for making fused silica core-borosilicate clad optical fiber waveguides is described. The process involves the growth of a needlelike layer of borosilicate glass onto the surface of a commercially available high-purity fused silica rod by an efficient flame reaction of boron and silicon hydrides with oxygen. The needlelike layer is subsequently heat treated at relatively low temperature to form a homogeneous bubble-free glass with a smooth surface. It is then covered with a thin protective jacket of silica and drawn into a fiber. These fibers have attenuation coefficients only slightly greater than the bulk loss of the fused silica core materials. Over the Al1−xGaxAs injection laser wavelength range, 0.82–0.88 μm, the loss is 5 dB/km, while at the YAG : Nd laser wavelength, 1.06 μm, it is 3 dB/km. The process appears to be attractive for the economical manufacture of low-loss fibers due to its simplicity and high chemical conversion efficiency.