Abstract We have demonstrated that Raman scattering may be used to determine P and Ge concentration profiles of optical fiber preforms. For Ge, the technique has an absolute accuracy of about 0.5 mol.% Ge, and spatial resolution to 40 μm was achieved. When used in a nondestructive mode, spatial resolution of 100 μm is possible. The results clearly show that phosphorus as well as germanium burn out as the tube is collapsed, with the spatial extent of the phosphorus burnout region being about twice as great as that for germanium. Our measurements on a graded-P preform provide a determination of the Ge incorporation ratio across the preform with the surprising result that it increases toward the edge, where the temperature is higher and P content is lower. The spectra also provide clear evidence for two types of Ge sites in silica-germanium glasses, where one type of site, possibly associated with network defects, is predominantly occupied at low concentration. The 710 cm−1 line associated with these defect sites is not detected when either P or B is present, and we speculate that this may be related to the dependence of the Ge incorporation ratio on the phosphorous concentration.
[1]
A. Saissy,et al.
Diffusion Raman spontanée dans (P2O5) x-(SiO2)1-x et (B2 O3)x-(SiO2)1- x
,
1979
.
[2]
D. Kato.
Raman spectrometric determination of additive concentration in high‐silica‐content glasses
,
1976
.
[3]
D. Powers.
Kinetics of Sicl4 Oxidation
,
1978
.
[4]
R. W. Hendricks,et al.
Neutron irradiation effects and structure of noncrystalline SiO2
,
1974
.
[5]
D. Kato.
Raman spectrum and refractive index behavior of Al2O3 added high‐silica‐content glass
,
1976
.
[6]
W. French,et al.
Chemical kinetics of the reactions of tetrachlorosilane, tetrabromosilane, tetrachlorogermane, phosphoryl chloride, and trichloroborane with oxygen
,
1978
.
[7]
D. Marquardt.
An Algorithm for Least-Squares Estimation of Nonlinear Parameters
,
1963
.
[8]
J. Stone,et al.
Raman Spectral Characterization of Pure and Doped Fused Silica Optical Fibers
,
1975
.