Method to eliminate fiber interferometer reflections
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorMatthew N. McLandrich
Life of this patent
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Abstract
Improved performance in a fiber interferometer gyro results from eliminat signals attributed to unwanted reflections from the fiber ends and the coupling lenses. A coiled single-mode fiber bidirectionally transmits beams radiating from a continuous wave laser to a detector. A fixed frequency oscillator amplitude modulates the laser output and provides a reference signal at the same frequency to enable synchronous detection of the detector output signals. Shifting the reference signal .pi./2 radians from the modulating signal eliminates the detector output signals which are attributed to reflections from the fiber ends and coupling lenses. By properly selecting the modulating frequency and reference phase, the information validity of beam signals passing through the coiled single-mode fiber is enhanced.
Claims5
In a fiber interferometer gyro having a looped single-mode fiber coupled to bidirectionally transmit beams of light from a laser to a detector, an improvement therfor is provided comprising:
- means disposed external the light beam paths and coupled to the laser and the detector for amplitude modulating the laser output and synchronously detecting the detector output with a reference signal of the same frequency as the amplitude modulating signal .pi./2 phase shifted with respect to the amplitude modulating signal to eliminate gyro reflections attributed to fiber ends and coupling lenses.
A method of eliminating reflection signals in a fiber interferometer gyro having a looped single-mode fiber coupled to bidirectionally transmit beams of light from a laser to a detector comprising:
- amplitude modulating the laser output and synchronously detecting the detector output with a phase shifted reference signal coming from a common signal source to eliminate gyro reflections attributed to fiber ends and coupling lenses.
Dependencies are inferred from the claim text.