Guest Editorial Next-Generation Spectrum-Efficient and Elastic Optical Transport Networks

IMPROVING capacity utilization of the optical transport network has been an important research challenge for many years. Extensive research efforts have been devoted to developing approaches of grooming subwavelength traffic demand onto large wavelength capacity pipes. These efforts, however, only focus on efficiently utilizing the capacity pipes, without addressing the issue of fixed ITU-T grid and frequency spacing in the DWDM layer. Under the fixed frequency spacing, optical spectrum is often over-provisioned for a low-rate optical channel, and this inefficiency becomes even prominent when more advanced modulation formats are employed. Advanced optical transmission and networking techniques are needed to provide flexibilities for optical channel spectrum allocation and to develop the related network control system so as to cater to the bandwidth elasticity of Internet traffic and improve fiber optical spectral usage. Significant attention has been given to develop spectrumefficient and elastic optical transport networks in both academia and industry in the past few years, and currently there are many research efforts underway targeting at the development of appropriate solutions for future dynamic elastic and scalable photonic infrastructures and network architectures, efficient new algorithms that determine how optical frequency resources can be matched to traffic demands in an optimized way, and a more flexible control and management plane. The technical issues that remain open for such elastic optical transport networks include efficient architecture, spectrum-efficient transmission technique, reconfigurable optical add/drop multiplexer (ROADM), routing and spectrum assignment (RSA), spectrum de-fragmentation, traffic grooming, new protocols and control plane, and more. Our objective of this special issue is to identify various challenges posed by the spectrum-efficient and elastic optical transport networks and explore research avenues for addressing them. We have received a total of 27 papers, and after multi-round careful reviews by both reviewers and guesteditors, we have accepted six papers for this special issue.