Making Single-Mode Preforms by the MCVD Process

Abstract

In the last few years, system technology has developed sufficiently to take advantage of the low-loss, high-transmission capability of single-mode fibers. First produced commercially in 1983, single-mode fiber now accounts for over 90 percent of all fiber made at AT&T Network Systems' Atlanta Works. Using the Modified Chemical Vapor Deposition (MCVD) process, glass rods, or preforms, of high-quality doped silica are created from which the fibers are then drawn. These fibers have losses below 0.40 dB/km and 0.22 dB/km at 1.31 μm and 1.55 μm, respectively, and transmission-rate capabilities in the gigabit-per-second range. Excellent concentricity of both the fiber core and outer diameter allows fibers to be joined into long lengths with a minimal additional loss. These characteristics allow single-mode fibers to be used in systems that operate at high bit rates with regenerator spacings of 30 km to 70 km apart.