Pulse Dispersion Properties of Fibers With Various Material Constituents

Dispersive refractive index differences between material constituents (Ge02, B2O3, and Si02) for germania borosilicate core fibers cause modal group velocity differences to depend on the source wavelength (profile dispersion). Therefore, nonparabolic profile gradients are generally required to minimize pulse dispersion. Previous time-domain transmission measurements 1,2 were used to direct the fabrication of a nearly optimal borosilicate fiber. This paper compares more recent and extensive data for germania borosilicate fibers and borosilicate fibers at X = 907.5 nm wavelength corresponding to a GaAs injection laser. We have also characterized small profile undulations about a nearly optimal power law shape which degrade intermodal dispersion characteristics. Another paper 3 describes how profile dispersion influences fiber bandwidth properties at other wavelengths. 1653 (a) (b) Fig. 1--Refractive-index profiles derived from interference micrographs: (a) a borosilicate graded-core fiber; (b) a germania borosilicate core fiber. The fitted curves are determined from a weighted [eq. (1)] nonlinear least-squares fit to the data ©. II. FIBER FABRICATION AND PROFILE EVALUATION