A fiber-optic gyroscope apparatus includes a light source, an optical coupler, a photodetector and an optical circuit device having at least one input, at least two outputs and a birefringent crystal substrate waveguide as a first segment of a Lyot type depolarizer between the input and the outputs. An input fiber of polarization maintaining fiber composition operating as a second segment of a Lyot type depolarizer is located between the optical coupler and the optical circuit device. A sensing coil is coupled to the outputs of the optical circuit device. The input fiber is fixed at approximately 45 degrees to the waveguide, with the input fiber and waveguide cooperating to form a Lyot type depolarizer. Other implementations of the fiber-optic gyroscope apparatus are also disclosed.