Patent ID: 6243167
Filing Date: 2001-06-05
Classification: G01C

Abstract:
A multimode optical fiber gyroscope comprising:a SAGNAC interferometer having an optical fiber coil comprising a length of multimode optical fiber having a first end and a second end;a symmetrical multimode X-coupler coupled to the first end and the second end of the multimode optical fiber;a light source supplying light through the a symmetrical multimode X-coupler into the first end and the second end of the multimode optical fiber coil, the multimode optical fiber coil having an intermodal dispersion such that adjacent optical paths have a difference between co-propagating adjacent modes of any order of the supplied light that is greater than a coherence length of the light source, and a limited number of modes;an optical detector, coupled to the symmetrical multimode X-coupler, for receiving a multimode optical signal from the first and second ends of the optical fiber via the symmetrical multimode X-coupler, the multimode optical signal being generated by a first and second counter rotating multimode optical signals emitted from the first and second ends of the multimode optical fiber;the optical detector receiving the multimode optical signal which is converted to an initial electrical signal, amplified and assigned a first voltage value V.sub.1 proportional to the amplitude of the first order harmonic of the multimode optical signal, a second voltage value V.sub.2 is assigned proportional to the second order harmonic of the multimode optical signal and a third voltage value V.sub.dc is assigned proportional to the continuous incoherent component of the multimode optical signal;a processor for determining a result R based upon a mathematical relationship between assigned voltage values V.sub.1, V.sub.2 and V.sub.dc to compensate for fluctuations in the multimode optical signal caused by intensity and wavelength instabilities in the light source, variability in the X-coupler, the multimode optical fiber and the optical detector; andwherein the result R is determined for all the modes of the multimode optical signal and a statistical average result is obtained.