In fiber transmission systems, optical signals can be degraded by noise light such as amplified spontaneous emission from optical amplifiers and coherent crosstalk light leaking from other channels due to imperfections in switches and/or filters in photonic network nodes. In this paper, we propose a feed-forward control circuit that mitigates such signal degradation in intensity-modulated signals. Our scheme is an optical/electrical hybrid circuit consisting of an optical coupler, photo-detector, and Mach-Zehnder intensity modulator (MZ-mod). The transmissivity of the MZ-mod is used to suppress fluctuations in the ??on?? signal state. In addition, the proposed circuit also improves the extinction ratio by adjusting the operating conditions.