To generate frequency sweep light having a wide band width with simple control in an optical frequency sweeper using an optical modulator utilizing electrooptic effects as an optical frequency shifter, to provide a wavelength packet generator which uses the optical frequency sweeper to generate a wavelength packet, and to provide a wavelength packet communication network using the wavelength packet generator.

The optical frequency sweeper is provided with the optical modulator utilizing electrooptic effects instead of an optical frequency shifter utilizing acoustooptic effects, and the optical path length of an optical resonator is adjusted to adjust phase change C of a modulation signal per round in the optical resonator, and thus the optical frequency sweeper is so set that matching of the phase of a modulation side-band in lower orders of the optical modulator may not occur.