Abstract

Aluminum has been suggested as an alternative to germanium for doping optical fibers fabricated using MCVD.¹ The advantages of doping with AI₂O₃ Include elimination of both the layer structure and the center dip caused by thermodynamic equilibria which favor incomplete reaction of GeCl₄ to GeO₂ during deposit and conversion of GeO₂ to GeO at elevated collapse temperatures.² These features can adversely affect the multimode bandwidth,³ and the incomplete reaction also results in low doping efficiencies which lead to high material costs. AlCl₃ is thermodynamically favored to react completely to form a stable oxide resulting in a smoother doping profile and lower materials cost because of complete incorporation efficiency. Unfortunately, Al₂O₃ as a dopant in SiO₂ causes devitrification at concentrations exceeding 4 mol %. The addition of P₂O₆ has been shown to prevent this problem.⁴

© 1984 Optical Society of America