Abstract: The present invention provides optical compensation for a submarine optical cable optical. A dummy light module generates a dummy light signal according to a continuous spectrum in a predetermined range and a combining module combines a service signal with the dummy light signal. When the dummy light is used for the compensation, conventional problems are solved, including complicated control, difficult realization of the pre-equalization function and inflexible configuration. When service signals are increased, the adjustment for the power of the dummy light signal is avoided; therefore, the control for the dummy light is simplified. In the pre-equalization operation, power control is only performed on the dummy light signal in the single channel or the continuous dummy light signal; therefore, the realization of the pre-equalization function is easy.