Coded Modulation for Fiber-Optic Networks: Toward better tradeoff between signal processing complexity and optical transparent reach

In this tutorial, we study the joint design of forward error correction (FEC) and modulation for fiber-optic communications. To this end, we use an information-theoretic design framework to investigate coded modulation (CM) techniques for standard additive white Gaussian noise (AWGN) channels and fiber-optic channels. This design guideline helps us provide a comprehensive overview of the CM schemes in the literature. Then, by invoking recent advances in optical channel modeling for nondispersion-managed links, we discuss two-dimensional (2-D) and four-dimensional (4-D) CM schemes. Moreover, we discuss the electronic computational complexity and hardware constraints of CM schemes for optical communications. Finally, we address CM schemes with signal shaping and rate-adaptation capabilities to accommodate the data transmission scheme to optical links with different signal qualities.