Optical transceiver modules are commonly used in telecommunication and data communication systems, and are among the most troublesome electromagnetic interference (EMI) problems for regulatory compliance at their operation frequencies and/or harmonics. In this study, simulations and measurements are performed on an optical subassembly module, including the silicon photonics submodule assembly, in order to identify and characterize the EMI coupling paths. The total radiated power is measured and computed. Through simulation and corroborating measurements, the dominant EMI coupling paths at high frequencies above 10 GHz are identified and characterized, and currents on the silicon photonic subassembly conductor housing and optical fiber connection ferrule are a dominant radiating source. EMI mitigation methods are developed and shown to be effective in reducing the radiated emissions from real product hardware.