Low-loss fiber waveguide prepared by the axial deposition method

The first Soviet low-loss glass fiber waveguide was prepared by the axial deposition method and its properties were investigated. The material used was germanium-doped quartz glass. The total diameter of the waveguide was 130 $\mu m$, the core diameter was 75 $\mu m$, and the effective numerical aperture was 0.16. Dehydration and vitrification of a porous preform in vacuum at 1600 degree C reduced the residual hydroxyl concentration to $4\cdot10^{-5}$. In the highest transparency bands at 0.85 and 1.03 $\mu m$, the losses were 8.4 and 8.0 dB/km, respectively. The preforms were designed for production of fibers 3 km long with the transverse dimensions specified above. The refractive index profile was determined and the dispersion properties of a fiber-optical line were studied.