New Developments In Fiberoptic Gyroscopes

Abstract

F. Zarinetchi, S.P. Smith, and S. EzekielResearch Laboratory of ElectronicsMassachusetts Institute of TechnologyCambridge, MA 02139Fiberoptic inertial rotation sensors (or gyroscopes) so far are based on the Sagnac effect in eithera multiturn interferometers or a resonator2. Both these approaches constitute the fiberopticimplementation of previously demonstrated Sagnac interferometer3 gyroscopes and resonator4gyroscopes employing bulkoptic components. However, there has not yet been a fiberoptic analog ofthe ring laser gyroscope5'6, which has always been a bulk -optic device. In this paper, we presentpreliminary data on a fiberoptic ring laser gyroscope using stimulated Brillouin7 scattering as the lasergain medium. To our knowledge, this is the first demonstration of a solid state ring laser gyroscope orRLG.Figure 1 shows a simplified diagram of a stimulated Brillouin fiberoptic gyroscope. A singlefrequency laser, He -Ne at 1.15 pm, is coupled into opposite directions of a non -polarization maintainingfiberoptic ring resonator (length 25 m; finesse - 250; coil diameter 7.5 cm) and acts as the pump forthe stimulated Brillouin laser. The frequency of the Brillouin laser$ -11 is downshifted from that of thepump by the acoustic frequency in the fiber which is about 15 GHz at 1.15 pm. The direction of theBrillouin laser is opposite to that of the pump because that is the direction that experiences the highestBrillouin gain. The clockwise pump in the resonator is denoted by P- and the counterclockwise pumpby P. The corresponding stimulated Brillouin lasers that are created by the pumps are denoted by B-