Abstract

Because the pulse dispersion of even the best graded-index fiber fabricated thus far is limited to only about 0.01 times that of the equivalent step-index fiber¹, with values of 0.1 being more typical, emphasis is being placed on the development of low-loss, single-mode (SM) fibers, in which mainly only source-bandwidth- dependent material dispersion sets an upper limit to the maximum permissible data rate.2 We report here on the practicality of producing SM fibers with large core diameters 2a (9 to 15μ), and having associated relative refractive index differences ∆ on the order of 0.1%. The fabrication of SM fibers with such small ∆'s became feasible through the MCVD process employing the B₂0₃-SiC>₂ system in particular3, since indications are that the volatility of B₂C>₃ at the high deposition and collapsing temperatures used is considerably less than that of other prospective dopants such as Ge0₂ or PpOp-. Furthermore, the change in refractive index difference per mole percent addition of B₂C>₃ is relatively small.

© 1977 Optical Society of America