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Theoretical results on the extinction ratio (ER) improvement in ultralong semiconductor optical amplifiers (UL-SOAs) are presented indicating a Bogatov-like effect in the saturated section. Starting from general nonlinear gain equations, an analytic description of the Bogatov-like effect is derived in terms of gain coefficients. These equations are used to explain the results of fully numerical simulations. The data signal's ER improves because of a two-step process. First, the data signal cross-gain modulates the additionally injected CW signal. Second, due to this inverse modulation, the data signal's states are differently amplified via the Bogatov-like effect. Since the ER improvement is caused by the fast intraband effects, this simple scheme has the potential for high-speed regeneration.