The present invention relates to a transmission optical fiber. The
transmission optical fiber including a core and a cladding made of
SiO.sub.2 is characterized in that GeO.sub.2 and F are doped in SiO.sub.2
of the core and the cladding. Therefore, a high Raman gain coefficient
could be obtained while a desired dispersion value and a non-linearity are
maintained, by controlling the refractive index of the core and the
cladding. Further, the pump power of the laser diode could be reduced and
the cost of the laser diode could be lowered accordingly. In addition, the
life of the laser diode is extended since the laser diode needs not to be
operated at a high output.
