Chapter 15 provides an overview of fabrication techniques of integrated guidedwave photonic modulators, basic principles of modulation schemes and transmission medium, and single mode or few mode fibers. This chapter also investigates Si-integrated photonic circuits (Si-PIC), which are currently attracting significant interest because of their integrability with CMOS micro-electronics. This technology may emerge as an essential technique to integrate electronics and photonics on the same chip e-PIC (electro-photonic integrated circuits), leading to significant reduction of the total product cost using automatic CMOS technology production line. Chapter 15 gives a brief account of the design of optical transmission systems, especially in bi-directional optical fiber transmission links. Several examples are given for bidirectional optical transmission. Readers who need to revise their basic understanding of designs of optical fiber transmission will find this chapter useful.