Quartz glass optical fibers with radial variations of the boron and phosphorus concentrations

Low-loss optical fibers were prepared as follows. Halide vapors were oxidized inside a quartz jacket tube placed in a traveling hot zone. The tube was then collapsed into a rod blank and fibers were drawn. The deposited halide films were doped with boron and phosphorus in accordance with a selected program. The losses in a "gradient" fiber of this kind were 4 dB/km at λ = 0.85 μ and the numerical aperture was 0.22.