Continuous fabrication of phosphate glass fiber

A phosphate glass fiber is fabricated by continuous drawing using a quartz double crucible. The raw materials for core and cladding glass are prepared at almost 100-percent efficiency by a liquid-phase process using ultra-high-purity chloride solutions. The transmission losses of the fiber are 2.5 dB/km at 1.1μm wavelength and 5.8 dB/km at 0.85 μm. The numerical aperture of the fiber is 0.31, and the breaking stress at 50-percent failure on the Weilbull plots is 3.5 kg for a 150-μm outside diameter. The phosphate glass is sufficiently water-resistant for practical use. Costs are less than 4 cents/m when phosphate glass fiber is produced continuously in quantities greater than 10
⁵
km per year. This is approximately half the estimated cost of doped silica fiber.