Bistability in the pump beam of one-coupler and two-coupler single-mode optical fiber ring resonators by using two different all-fiber schemes of degenerate two-wave mixing is demonstrated theoretically. The bistable behavior of the pump beam (or the input beam) can be controlled by changing the intensity of either the pump beam or the input beam. Depending on the scheme of the degenerate two-wave mixing and the controlling beam, the bistable hysteresis loop of the pump beam may be a normal type or an inverting type. The dependence of the bistability on some major parameters of the fibers and the couplers is investigated.