Optical losses in single-mode and multimode fibres heavily doped with GeO2 and P2O5

Optical losses in single-mode and multimode optical fibres heavily doped with germanium oxide and phosphorus oxide are studied. Optical losses in multimode fibres in a broad spectral range are found to be much lower than in single-mode fibres with the same concentration of dopants. The study of few-mode fibres showed that the core – cladding interface is the region of excess optical losses. The reasons for the observed relation between optical losses in single-mode and multimode fibres are discussed.