We experimentally study a fiber loop laser in a figure-8 configuration and explore the dependency of the degree of polarization on controlled parameters. To account for the experimental observations, a mapping is derived to evaluate the polarization time evolution. The nonlinearity induced by the Kerr effect and gain saturation gives rise to rich dynamics. We find that the degree of polarization can be increased by tuning the system into a region where the mapping has a locally stable fixed point.
