Traffic grooming is the name given to a family of optical network design problems that has attracted significant attention from both academia and industry in the last decade or so. The huge bandwidth of fiber optical networking is much larger than the typical bandwidth demands experienced by network service providers. This mismatch creates a need for multiplexing the low rate traffic demands into optical wavelength channels, but this requires costly electronic switching equipment, potentially offsetting the benefit of cheap optical transport. Traffic grooming refers to network design and resource allocation algorithms that can enable cost-efficient use of both network bandwidth and electronic switching. Due to the increasing bandwidth of optical communication on the one hand, and the growing variety of traffic demand magnitudes on the other, traffic grooming has grown from a narrow research area to a mainstream requirement for real world practitioners. This book presents the practical motivation, theoretical description, and extant techniques for traffic grooming in optical networks. The description of the various topics of research will be authored by leading researchers in this area, and will contain comprehensive description of related literature for each area. This book is intended to be a definitive reference and text for traffic grooming both for the practitioner in industry and the student in academia.