RFOG rotation rate error reducer having resonator mode symmetrization

An error reducer for reducing rotation rate errors arising because of polarization modes coupling and differing polarization modes characteristics associated with a coiled optical fiber having a pair of principal/birefringent axes in a rotation sensor capable of sensing rotation about a symmetry axis of said coiled optical fiber forming a closed optical path having a transfer means therealong for transferring electro radiation propagating along one of said principal birefringent axes into propagating along another of said axes, said coiled optical fiber connected with at least a first coil coupler such that electromagnetic waves can be coupled between said coiled optical fiber and a first external optical fiber, said rotation sensing based on having opposing electromagnetic waves propagating through said coiled optical fiber in opposing directions so as to result in each said opposing coiled optical fiber electromagnetic wave impinging at least in part on a corresponding one of first and second photodetectors with at least one of said opposing coiled optical fiber electromagnetic waves propagating in one of said opposing directions being subject to having frequencies thereof varied by selected signals supplied to a first input of a source means capable of supplying an emitted electromagnetic wave from which that said opposing coiled optical fiber electromagnetic wave is obtained, said first photodetector providing an output signal in response to such impingement thereon of a corresponding said opposing coiled optical fiber electromagnetic wave which is representative of that wave, said error reducer comprising:

• oscillating frequency value establishment means having an output electrically connected to said first input of said source means, said oscillating frequency value establishment means being capable of providing an output signal on said output thereof sufficient to cause said source means to direct said opposing coiled optical fiber electromagnetic waves propagating in one of said opposing directions subject to having frequencies thereof varied by selected signals supplied to a first input of said source means, as aforesaid, to oscillate in frequency value between frequencies occurring substantially in opposite polarization mode resonances of those said waves.