The past decade has seen intense activity in the field of microwave photonics in which optical components are used to generate, distribute, control and process microwave and millimeter-wave signals. This has led to the co-existence of electrical and optical components at the level of the integrated circuit. The existence of electrical and optical devices at the same design level requires design tools that can handle components belonging to both physical domains simultaneously for performing system simulation. The technique presented in this thesis addresses this need by presenting a method to perform steady-state simulation of optical-electrical systems using Harmonic Balance (HB). One of the unique features of this method is that it includes phase of the optical signal in finding the steady-state solution of the system. Several examples are presented that demonstrate the feasibility of the proposed method and where possible the results are compared with existing techniques.