# Time Shared Optical Network (TSON): A Programmable Network Edge Solution for Multi-Access Support
## 2 TSON, the Past
### Evolution Stage 4: TSON Multi Haul  
The fourth stage of the TSON evolution is building a state-of-the-art disaggregated edge node to support both metro and long-haul networks [14]. The reason behind creating such a disaggregated edge node for the first time is the need for a flexible and programmable edge node architecture providing an interface between the 5G access and transport network. This requirement is due to the plethora of applications, their KPIs, and the diversity of 5G access network technologies that will share common transport network solutions.  
Figure 10 presents the proposed disaggregated edge node data plane architecture comprising the TSON solution, Voyager [15], and wavelength selective switches (WSS) [16]. This architecture is highly programmable using SDN. As the heart of the architecture, the TSON solution follows the TSON multi-protocol legacy presented in the previous sub-section, as well as supporting both metro and long-haul networks on demand on the basis of the operator or service provider requirements. The TSON edge node aggregates/dis-aggregates any input access traffic to/from a highly synchronous and bandwidth granular optical transport on the basis of time slot switching in a programmable way. In addition, it provides access to a highly programmable coherent variable bandwidth transponder suitable for spectrally elastic long-haul transmission. The Voyager is a Broadcom Tomahawk-based switch with added dense wavelength division multiplexing (DWDM) ports, acting as a disaggregated optical transponder [14]. It hosts multiple BVTs that are capable of dynamically allocating variable spectral width and reach by modifying the device parameters. This is achieved through the support of three types of modulation formats, namely polarisation multiplexed quadrature phase-shift keying (PM-QPSK), 8-ary quadrature-amplitude modulation (8-QAM), and 16-ary quadrature-amplitude modulation (16-QAM) that allow different line rates of up to 200 Gbps. The WSS provides filtering and switching of the optical signal [15]. The WSS is used in this architecture as a programmable \(4\times 16\) optical switch that multiplexes and demultiplexes the optical signals to specific ports. As can be seen in Figure 10, one WSS is connected to the Voyager and another to the TSON output ports. WSS'multiplex and demultiplex four wavelengths with different bandwidths from the Voyager/TSON ports.  
Figure 9: The TSON data plane architecture supporting NC.  
Figure 11 presents the TSON data plane architecture in support of the disaggregated edge node. The functions for the operation of TSON domains has been implemented in internal modules, within the SDN controller, which collaborate for the on-demand provisioning of connectivity between TSON nodes. The data plane functionality of this architecture is the same as the previous architecture. The 10 Gbs wavelengths are dedicated for metro networks. The extended pipelines with 40 Gbs, which are marked in Figure 11, are to support long-haul networks with only Ethernet mode. In the extension scenario, the ingress TSON edge nodes are responsible for parsing, aggregation, and mapping of any input traffic combination with different bandwidth into converged 40 Gbps Ethernet output, whereas the egress edge nodes have the reverse functionality. The disaggregated edge nodes are evaluated at the same time for both 8 km metro and 200 km long-haul networks and the evaluation results are available in [14]. Results showed that low latency and power penalty for both metro and long-haul networks.