The objective of this dissertation is to develop heterogeneous photonic platforms and device architectures that improve the performance of electro-photonic devices and interconnects for next-generation optical communications. The research focuses on achieving low optical loss, high-speed operation, compact footprint, and low power consumption through the integration of various material platforms. Conventional single-material photonic platforms often require tradeoffs between passive optical performance and active electro-optic modulation performance, motivating the development of heterogeneous architectures that leverage the unique properties of different materials. Heterogeneous silicon nitride (SiN)- on -lithium niobate (LN) platform are investigated and demonstrated using multiple kinds of SiN materials along with various integration approaches. These platforms enable the development of high-performance photonic devices for communications systems, including a high-efficiency, low-cost frequency converter and a high-speed, low-loss coupling modulator. The results demonstrate the potential of heterogeneous SiN–LN integration to simultaneously enhance passive and active electro-optic functionality. It also presents the researches of CMOS-compatible silicon photonics in multi-project-wafer (MPW) tapeout through monolithic integration of electronics and photonics on a heterogeneous platform. Building on this platform, CMOS-photonic-based thermal-optic tuning and low-loss electro-photonic co-packaging are demonstrated for optical communication applications. Together, these developments establish heterogeneous integration as a promising pathway toward high-performance, energy-efficient, and scalable electro-photonic systems for next-generation communications.