ABSTRACT
This chapter aims to discuss channel coding and coded modulation techniques for fiber-optics communication systems. It describes different codes on graphs of interest for optical communications including turbo-product and low-density parity-check (LDPC) codes. The chapter shows how to perform the code rate adaptation, based on optical channel conditions by shortening, partial reconfiguration of the parity-check matrix of a template regular quasi-cyclic-LDPC code, puncturing, and re-encoding approach introduced in. The most obvious way to design LDPC codes is to construct a low-density parity-check matrix with prescribed properties. Nonbinary LDPC-coded modulation has been shown to outperform its corresponding multilevel coding with parallel independent decoding and iterative detection and decodingscheme with performance gaps increasing as the underlying signal constellation size increases. The chapter also describes different codes on graphs of interest for optical communications including turbo-product and LDPC codes. The sum-product algorithm is an iterative decoding algorithm based on Tanner graph description of an LDPC code.
