There is provided a millimeter wave band frequency optical oscillator predicted
to be used as a millimeter wave oscillating frequency signal source in a base station
of a millimeter wave wireless transmission system. The optical oscillator has a
double resonator structure in which a pair of wavelength tunable fiber grating
mirrors are inserted into a unilateral fiber-ring laser resonator in order to internally
and additionally form a linear laser resonator. The double resonator structure
composed of the two stable laser resonators can oscillate laser of two modes. Due
to a beat phenomenon occurring between the two modes, received laser is modulated
to an ultra-speed frequency of 60 GHz or greater. A variation in the gain within
a resonator is induced by a polarization controller using the dependency of laser
modes upon polarization. A modulation frequency is consecutively changed from 60
GHz to 80 GHz by controlling the wavelength of light reflected by the fiber grating mirrors.
