The present invention provides a pulse train generator comprising: a
dual-frequency signal light source for generating a dual-frequency
signal; a soliton shaper for soliton-shaping output light from the
dual-frequency signal light source; and an adiabatic soliton compressor
for performing adiabatic soliton compression on output light from the
soliton shaper, and also provides a waveform shaper used in this pulse
train generator, including a plurality of highly nonlinear optical
transmission lines and a plurality of low-nonlinearity optical
transmission lines which has a nonlinearity coefficient lower than that
of the plurality of highly nonlinear optical transmission lines and which
has a second-order dispersion value of which an absolute value is
different from that of the plurality of highly nonlinear optical
transmission lines. Further, the present invention provides a light
source comprising a plurality of continuous light sources of which at
least one oscillates in a multimode; a multiplexer for multiplexing
output light from the continuous light sources; and a nonlinear
phenomenon producer for producing a nonlinear phenomenon on output light
from the multiplexer so as to suppress SBS (Stimulated Brillouin
Scattering).