Fiber Brillouin Ring Laser for Active Inertial Rotation Sensing

Abstract

Passive inertial rotation sensors based on the ring cavity suffer from error sources, such as frequency lock-in, mode pulling and null shift at low rotation rates. Fiber ring lasers used as active rotation sensors can remove some of these error sources, if the fiber Brillouin ring laser scheme is employed. Since stimulated Brillouin scattering gain has directional sensitivity, it is possible to support two simultaneous Brillouin lasers in the same ring resonator, yet decoupled, thus eliminating lock-in error and facilitating measurements of low input rates. Mode pulling errors should also be reduced. Laser sources powering such sensors may be subjected to Zeeman splitting under terrestrial or environmental magnetic fields, leading to magnetic field intensity dependent frequency shifts in the pump wave, of the order of the Sagnac shift. Such terrestrial dependence of laser rotation sensors may be removed by the Brillouin fiber ring scheme, since only a single pump wave can generate the two Brillouin ring lasers at one time, whichever is dominant. Demonstration of gyro application of the fiber Brillouin ring laser will add to the already abundant versatility of this device for optical amplification, channel selection, optical switching, optical noise suppression or amplification, leading to application both in fiber-optic communication and fiber-optic embedded structural sensing.