The closed loop fiber optic gyroscopes (FOGs) are-solid-state devices which offer a combination long life and high reliability along with the potential of low mass-production cost. the fundamental principle is based on Sagnac effect. Our FOGs have so-called minimun configuration that provides reciprocal optical paths for two beams counter-propagating in a fiber loop.
     The FOGs consist of the one Light Source at 1550 nm wavelengths (SLD),Depolarizer(DP),one or three Photodetectors (PD),fiber Splitters(FS) to divide the light into two or three parts, one or three sets of ring interferometers to sense one or three sets of ring interferometers to sense one or three orthogonal angular rate,and printed circuit boards installed signal processing circuits.In this design a multifunction integrated optic chip (MIOC),fabricated by High Temperature Proton Exchange processs is used for splitting the light into clockwise and counterclockwise waves, light polarization and for electro-optically imparting a phase modulation to the lightwaves in the loop. The signal processing design is based on conversion of the phpotodetector signal to a digital representation of the detected light intensity, followed by digital demodulation and integration. the loop is closed by driving the integrated optical phase modulator with a voltage ramp whose slope is proportional to rotation rate.