On the basis of rate equations for semiconductor lasers

an expression for the modulation characteristics of the external light injected laser source is derived by employing a small-signal analysis model

Then the expression is coded by Matlab to customize an optically injected source component for the optical simulation tool Optiwave System and the self-defined component is included in a simulation model of multi-channel transmission to evaluate the impacts of the external light injection on the transmission performances of Radio over Fiber（RoF） systems.Simulation results show that external light ejection is conducive to reducing the disturbances caused by inter-modulation distortion and improving the system performance.The impacts are still more obvious for multi-channel microwave signals at above relaxation oscillation frequencies.