Patent ID: 6014217
Filing Date: 2000-01-11
Classification: G01C

Abstract:
An error reducer for reducing rotation rate errors arising because of electromagnetic wave backscattering in a coiled optical fiber in a rotation sensor capable of sensing rotation about an axis of said coiled optical fiber formed in a closed optical path in conjunction with at least a first coil coupler which is connected therewith 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 optical fiber electromagnetic wave impinging at least in part on a corresponding one of first and second photodetectors with one of said opposing coiled optical fiber electromagnetic waves propagating in one of said opposing directions being subject to having phasing thereof varied by selected signals supplied to a first input of a first phase modulator and with that other of said opposing coiled optical fiber electromagnetic waves propagating in that one of said opposing directions remaining being subject to having phasing thereof varied by selected signals supplied to a first input of a second phase modulator, 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 compensator comprising:a first resonance determination signal generating means having an amplitude control input and an output electrically connected to said first phase modulator so as to be capable of providing a phase modulation component in a said opposing coiled optical fiber electromagnetic wave at a selected first resonance monitoring frequency, said first resonance determination signal generating means being further capable of adjusting values of amplitude of said phase modulation component provided thereby in accord with selected signals provided at said amplitude control input thereof;a second resonance determination signal generating means having an amplitude control input and an output electrically connected to said second phase modulator so as to be capable of providing a phase modulation component in a said opposing coiled optical fiber electromagnetic wave at a selected second resonance monitoring frequency differing from said first resonance monitoring frequency, said second resonance determination signal generating means being further capable of adjusting values of amplitude of said phase modulation component provided thereby in accord with selected signals provided at said amplitude control input thereof;a backscatter reduction signal generating means having an amplitude control input and an output electrically connected to a selected one of said first and second phase modulators so as to be capable of providing a phase modulation component in a selected one of said opposing coiled optical fiber electromagnetic waves at a selected backscatter reduction frequency, said backscatter reduction signal generating means being further capable of adjusting values of amplitude of said phase modulation component provided thereby in accord with selected signals provided at said amplitude control input thereof;a first resonance determination amplitude control signal generator having an output electrically connected to a selected one of said first and second resonance determination signal generating means amplitude control inputs, said first resonance determination amplitude control signal generator being capable of providing at said output thereof a signal which directs that said one of said first and second resonance determination signal generating means to which said output thereof is electrically connected to provide a phase modulation component of an amplitude value which also would result in a substantial reduction in value of error components in said first photodetector signal; anda backscatter reduction amplitude control signal generator having an output electrically connected to said backscatter reduction signal generating means amplitude control input, said backscatter reduction amplitude control signal generator being capable of providing at said output thereof a signal which directs said backscatter reduction signal generating means to provide a phase modulation component of an amplitude value which would result in a substantial reduction in value of error components in said first photodetector signal.