Digital Transmission Systems

This chapter discusses the basic concepts of digital optical transmission systems. In particular, the key components and structure of digital transmitters and receivers for coherent optical fiber transmission are addressed. This includes modulation formats, digital pulse shaping, and optical modulation at the transmitter side. At the receiver side, digital dispersion compensation, including the use of overlap and save techniques, is first described. Timing and carrier recovery techniques for optical signals are also reviewed, along with polarization demultiplexing through the use of multiple-input and multiple-output subsystems. The description includes the use of the constant modulus algorithm, as well as decision-directed and data-aided least mean squares algorithms.