Pressure-dependent Sellmeier coefficients and material dispersions for silica fiber glass

Abstract

The pressure-dependent Sellmeier coefficients are essential to characterize the optical design parameters for the optical fiber communication systems under deep sea environmental conditions. These coefficients are calculated for densified silica glass for the first time to compute the pressure dependence of material dispersion at any wavelength from the ultraviolet (UV) to 1.71 /spl mu/m. The zero dispersion wavelength /spl lambda//sub 0/ (1.2725 /spl mu/m at 0.1 10/sup 6/ N m/sup -2/) varies linearly with pressure, and d/spl lambda//sub 0//dP is 0.0027 nm/(10/sup 6/ N m/sup -2/). The calculated value is approximately one-third of the experimental value of 0.0076 nm/(10/sup 6/ N m/sup -2/) for a germanium-doped dispersion shifted fiber having /spl lambda//sub 0/=1.5484 /spl mu/m and -0.0070 nm/(10/sup 6/ N m/sup -2/) for a pure silica-core fiber cable having /spl lambda//sub 0/=1.2860 /spl mu/m. Since, the refractive indexes are increased with pressure, the negative value of shift of the zero-dispersion wavelength is erroneous. The explanations are due to Ge-doping in silica glass, a possible temperature fluctuation of 0.16/spl deg/C in the pressure-dependent measurement system of the zero dispersion wavelength and different experimental conditions of the silica glass and the optical fibers. This anomaly can also be attributed to the internal strain development at the core-cladding and fiber-jacketing boundaries due to pressure, which shows a larger experimental value. It accounts for the experimental values satisfactorily.