Abstract: A distortion-compensation circuit for use on a wideband optical-fiber communication system is provided. This distortion-compensation circuit can compensate for the CSO/CTB (composite second order and composite third beat) distortions in the transmitted signals that are caused due to the intermodulation of undesired harmonics that are caused by nonlinear devices in the system. The distortion-compensation circuit includes splitting means, such as a directional coupler, for splitting the input signal into a first signal and a second signal. The first signal is directed to a first path, while the second signal is directed to a second path. A featured CSO/CTB generator is coupled on the second path to receive the second signal for selectively generating a compensating CSO/CTB output from the second signal. Further, combining means, such as another directional coupler, is arranged at the end of the first and second paths, for combining the compensating CSO/CTB output of the CSO/CTB generator with the first signal.