Optical Transport Network

About: Optical Transport Network is a research topic. Over the lifetime, 6055 publications have been published within this topic receiving 85783 citations.

Virtualization in optical networks from network level to hardware level [invited]

Abstract: Elastic optical networking is attracting much attention as a promising solution to achieve spectrum-efficient transport of higher data rates at 100 Gbits/s and beyond. If we draw an analogy to virtualization in cloud computing, it can be seen as network level resource virtualization of optical networks where spectrum resources in optical links are segmented as shareable resources and adaptively aggregated to create a wide variety of optical channels (OChs). In this paper, we discuss the benefits of introducing virtualization into the optical domain from the viewpoints of the network level and the hardware level. In elastic optical networks, a frequency slot through which an OCh is transported and the OCh itself are explicitly decoupled. While the adaptability in the frequency slot is brought about by bandwidth variable wavelength-selective switches, the adaptability in an OCh is yielded by digital coherent technology that is employed in transponders and regenerators. It is emphasized that in order to achieve transponders and regenerators that accommodate heterogeneous traffic demands in an economical manner, simply being adaptive is not enough, and being shareable is essential. We refer to this concept as hardware level virtualization. As examples, we describe a multiflow transponder and an elastic regenerator with results that show proof of concept. Based on the hardware virtualization concept, we propose an elastic optical transport system (EOTS) architecture that enables cost- and energy-efficient IP traffic offloading to the optical domain and improves programmability and automation of optical networks.

Linearization of Direct Detection Optical Channels Using Self-Coherent Subsystems

Abstract: Intensity modulation with direct detection (IM-DD) dominates the commercial short-reach optical communications. However, when upgrading the data-rate distance product to 1000 Gb/s·km per wavelength and beyond, IM-DD faces severe performance barrier. Although a linear mapping exists between the intensity of transmitter and receiver in IM-DD back-to-back system, it becomes nonlinear under fiber channel impairments; for instance, the dominant chromatic dispersion. Coherent detection overcomes this fundamental obstacle by recovering a linear replica of the optical field instead of intensity. The local oscillator provides a reference carrier which mixes with the received signal, from which both intensity and phase of the signal can be recovered. Borrowing the idea from coherent detection, in DD system, a carrier can be sent along with the signal so that the receiver utilizes the reference carrier originated from transmitter; namely, the receiver conducts self-coherent (SCOH) detection. In this paper, we review a variety of optical SCOH subsystems, and reveal how they realize linear channels, while maintaining the simple and low-cost DD. SCOH can readily reach a data-rate distance product beyond 10000 Gb/s·km, making it suitable for the future high-speed short- and medium-reach applications, such as the data center interconnect, passive access network, and metropolitan area network.

Layered switch architectures for high-capacity optical transport networks

Abstract: We propose and analyze layered switch architectures that possess high design flexibility, greatly reduced switch size, and high expandability. The improvement in loss and crosstalk due to the reduced switch size is also discussed. Theoretical models have been developed to compute the network blocking probability using these architectures. Low blocking probability and high network utilization are achieved because of the capability of communication between layers in adjacent switches. The results show that the proposed layered switch architectures are very attractive for high-capacity optical transport networks.

Traffic engineering in next-generation optical Networks

Abstract: In this article traffic-engineering issues regarding network survivability, traffic grooming, impairment-aware routing, virtual-topology engineering, and coordination among multiple layers of network architecture will be reviewed for next-generation optical networks based on wavelength-division multiplexing (WDM). Due to the recent progress and development of WDM technology, increasing traffic demands can be readily accommodated in the next-generation optical networks. In spite of the huge amount of capacity (e.g., OC-192) provided by a WDM channel, enhanced network services and network performance improvement can only be achieved with efficient traffic-engineering mechanisms. The fault-tolerant function is essential in order to provide seamless services to users by protecting their traffic against failures in the optical network because many connections can be carried on a fiber. Because the capacity of a WDM channel is very large, its bandwidth may not be efficiently utilized by a single connection. Hence, low-rate user connections need to be efficiently aggregated through the traffic-grooming scheme. An intelligent routing algorithm is especially necessary in the optical network where signal impairments due to device imperfections might degrade the signal quality. In addition, the virtual network connectivity (topology) should be flexibly maintained such that dynamic changes to the traffic demands can be easily absorbed, which can be implemented by the virtual-topology engineering method in a WDM network. As the dominant usage of Internet protocol (IP) of the Internet is expected to reside directly above the WDM layer in the future network, the coordinated traffic-engineering scheme should be deliberately designed for the multi-layer network by judiciously choosing where to put many overlapping functions in the different network layers.