Single-mode fiber waveguides with losses below 1 dB/km

The modified chemical vapor deposition (MCVD) technology was used in fabrication of single-mode fiber waveguides from a quartz glass. The core was doped with germanium dioxide and the cladding deposited on it was doped with phosphorus oxide and with fluorine. The minimum losses were 0.6 dB/km at the wavelength of 1.3 µ and 0.35 dB/km at 1.5 µ. The excess losses were attributed to the presence of hydroxyl impurity groups and also due to variation of the fiber parameters along their length.