Growing demand for more bandwidth has led to extensive research in the field of optical communication. Optical communication systems are divided in two categories, fiber optic communication systems in which light is propagated in leading channels as ordinary single and multimode optical fibers and Free Space Optical communication which uses the air as communication channel. High speed, affordable cost to implement, does not require a spectrum license, safe communication, light weight and immunity to electromagnetic interference (EMI) are the most advantages of the fiber optical communication systems. The biggest problem in free space optical communication is due to its propagated channel. Atmosphere channel is unstable and the channel characteristics change by time, season and weather conditions. Fiber-optic communication systems have a quasi-stable channel but in these systems to have an acceptable optical power in the fiber, a good coupling between the light source and fiber in transmitter side and between fiber and detector in receiver side should be created. Using Silicon Optical Bench is a practical method to assembly transmitter and receiver side with a suitable coupling efficiency. In this thesis, fiber-optic communications systems and silicon optical benches are fully introduced and a 6 × 8× 0.5 mm 3 silicon optical bench includes four v-grooves in transmitter side for parallel coupling between Multi Mode Fibers and VCSEL array and four v-grooves in receiver side for parallel coupling between the Multi Mode Fibers and PIN photodiodes is designed and implemented. Wave propagation and ray tracing method are used to investigate such systems. Wave propagation method is more accurate and sophisticated than ray tracing. Since the dimension of multi mode fiber is much larger than the VCSEL wavelength, results of simulation with ray tracing are also an acceptable accuracy. Therefore by using ray tracing method, VCSEL to MMF and PIN photodiode to MMF coupling in the transmitter and receiver side, respectively are investigated. Different misalignment as, longitudinal, transversal and angular misalignment and fiber angular rotation and fiber end facet angle misalignment are considered in our simulation. Design and Implantation process of Silicon Optical Bench is explained in detail. Finally, data of simulation results were compared with the measurement results. Keywords: Silicon Optical Bench, Active Alignment, Passive Alignment, Ray tracing, VCSEL, Photodiode, Multi Mode Fiber, Coupling efficiency