Fabrication study of single-mode optical fibers with P/F-doped cladding

In previous fabrication studies of silica-based single-mode optical fibers for long wavelength, glass compositions of Ge-doped core and pure silica cladding,1 P-doped cladding,2 and P/F-doped cladding3 were investigated. Among those three glass compositions, P/F-doped cladding is considered to be most promising because of lowered deposition temperatures of the cladding glass, which makes it possible to achieve low loss and long length. However, the reported loss value of 0.7 dB/km in Ref. 3 is not sufficiently low in comparison with those reported in Refs. 1 and 2.