Abstract

All types of birefringent (but not polarizing) fiber ring resonators present environmentally-induced variations in the fringe shape that cannot be eliminated passively.¹ A fringe shape stabilization system has been constructed, for use with fiber ring resonators with power exchange between the birefringent axes.^2-4 The system works by keeping the depth of successive resonant dips equal, through a feedback loop that controls the fiber birefringence Δn. Two schemes for controlling Δn are investigated: in the first less efficient scheme, the entire loop is subjected to stretching, causing a fringe drift of more than 100 fringes. In the second scheme, the fiber is subjected to a localized compression, which changes Δn while having only a small effect on the average refractive index, thus causing a smaller fringe drift. When the resonator is used as a high-resolution spectrum analyzer, either stabilization scheme can be used; but the second scheme allows the resonator to be also used as a sensor, as it interferes little with the signal recovery system. With this stabilization system the resonator can operate in a variable environment with minimal deterioration in performance.

© 1993 Optical Society of America