Programmable Transponder, Code and Differentiated Filter Configuration in Elastic Optical Networks

Next generation optical networks will require high levels of flexibility both at the data and control planes, being able to fit rate, bandwidth, and optical reach requirements of different connections. Optical transmission should be able to support very high rates (e.g., 1 Tb/s) and to be distance adaptive while optimizing spectral efficiency (i.e., the information rate transmitted over a given bandwidth). Similarly, the control plane should be capable of performing effective routing and spectrum assignment as well as proper selection of the transmission parameters (e.g., modulation format) depending on the required optical reach. In this paper we present and demonstrate a software-defined super-channel transmission based on time frequency packing and on the proposed differentiated filter configuration (DFC). Time frequency packing is a technique able to achieve high spectral efficiency even with low-order modulation formats (e.g., quadrature phase-shift keying). It consists in sending pulses that overlap in time or frequency or both to achieve high spectral efficiency. Coding and detection are properly designed to account for the introduced inter-symbol and inter-carrier interference. We present a software defined network (SDN) controller that sets transmission parameters (e.g., code rate) both at the transmitter and the receiver side. In particular, at the transmitter side, a programmable encoder adding redundancy to the data is controlled by SDN. At the receiver side, the digital signal processing is set by SDN based on the selected transmission parameters (e.g., code rate). Thus, extensions to the OpenFlow architectures are presented to control super-channel transmission based on time frequency packing. Then, the SDN-based DFC is proposed. According to DFC, the passband of the filters traversed by the same connection can be configured to different values. Experiments including data and control planes are shown to demonstrate the feasibility of optical-reach-adaptive super-channel at 1 Tb/s controlled by extended OpenFlow. Then, the effectiveness of the proposed SDN-based DFC is demonstrated in a testbed with both wavelength selective switches and spectrum selective switches, where filters traversed by a connection requires different passband values. Extended OpenFlow messages for time frequency packing and supporting DFC have been captured and shown in the paper.