The efficient generation of third-harmonic blue-violet light at 440 nm in short lengths of Er3+-doped germanosilicate single-mode optical fibers pumped at 1.319 mu m is reported. Measurement indicates that the third-harmonic generation process that is due to a GeO2-SiO2 core is resonantly enhanced through the amplification of the signal light at 440 nm by population inversion of the erbium ions in the fiber core. An average signal power at 440 mn of similar to 5 mu W was observed. (C) 1995 Optical Society of America