Abstract

Fiber ring resonators made from polarization preserving fiber suffer from well-known polarization mode splitting problems, caused by small amounts of crosstalk at the coupler. The output of such a resonator is generally unsuitable for spectrum analysis or sensing. A solution to this problem has been recently described in the form of a ring resonator in which there is deliberate power exchange between the two birefringent axes. Polarization modal splitting is eliminated, and a significant signal improvement is further possible by separating the output power along the two axes. The resulting device presents simultaneous resonant peaks and resonant dips, and is simple and relatively inexpensive to construct. There are, however, some signal instabilities that are inherent in this type of resonator. These instabilities are quantified, and means of overcoming them are discussed. The resulting stabilized output is useful in very high resolution spectroscopy, since a long loop can be constructed without mechanical alignment problems. The use of the device as a spectrum analyzer is demonstrated.

© 1991 Optical Society of America