Engelbert Hartl

Passive fiber optic gyroscope.

A fiber optic gyroscope different from the standard concept is presented. A fused fiber 3 x 3 directional coupler provides a constant phase shift thus enabling the detection of rotation rate at the quadrature point without phase modulation. Bias errors due to birefringent coupling centers in the fiber coil are avoided by using an unpolarized light source. A contrast insensitive signal recovery scheme eliminates the influence of polarization fluctuations on the scale factor. First measurements with a prototype gyroscope (90 mm in diameter and 23 mm in height) show a bias stability of <4.7 degrees /h and scale factor accuracy of <0.1% in the range of +/-200 degrees /s.

Low-cost passive fiber optic gyroscope

This paper presents a passive fiber optic gyroscope without nonreciprocal phase modulation. A fused fiber 3 X 3 directional coupler provides a constant phase shift, thus enabling the detection of rotation rate at the quadrature point. Bias and scale factor errors due to indeterministically changing birefringent coupling centers in the non-polarization preserving monomode fiber coil are eliminated by using a contrast insensitive signal recovery scheme. A simple temperature compensation procedure has been implemented in the gyro software which yields a bias stability < 0.04 deg/sec and scale factor errors < 0.5% in the whole temperature range between -40

Fiber-optic depolarizer

DEGC and +70 degree(s)C.