# Design of Optical Tunnel Switching Networks for Big Data Applications
###### Abstract
For example, under a 100 Gbps link, if the frame size is 1.25 Kbytes, optical switching components with a switching time of 100 nanoseconds or less are required, such as the Semiconductor Optical Amplifier (SOA) optical switching components with switch time to 1 nanosecond. The widely used MEMS and LCoS technologies are all millisecond-level switching speeds, so the frame size of the optical frame switch is very large. For example, under a 100 Gbps link, the frame size should be at least 12.5 Mbytes, which will cause a large delay in the optical frame switch, thus affecting the performance of the optical frame switch. Therefore, an optical tunnel switch is proposed in this paper. This technology mainly uses Dense Wavelength Division Multiplexer (DWDM) technology to establish many tunnels with multiple wavelengths to provide point-to-point connections. Therefore, optical tunnel switches require many wavelengths to make point-to-point, non-blocking connections. The proposed architecture of the optical tunnel switching network in this paper is to establish a wavelength tunnel between nodes. This wavelength tunnel is not used by different nodes in time sharing, but the tunnel can be shared by multiple nodes. When the traffic volume of the nodes which are monitored exceeds the traffic volume of the wavelength tunnel, the wavelengths of other nodes with less traffic volume can be scheduled for use. Therefore, we calculate the traffic volume between nodes, and the average available traffic of the server. When the average available traffic is exceeded, wavelength scheduling is performed. For example, if the two plan optical tunnel switching network is adopted, there are two direct tunnels between nodes. The two direct tunnels can be used to communicate between nodes, and they are responsibility to establish some relay tunnels for other nodes, because tunnels must be established between all nodes in our proposed architecture. If the optical tunnel switching network has 49 nodes, then \(49\times 48\) tunnels are required to be established between all nodes. Therefore, if a tunnel traffic is exceeded, we can assign other tunnels with less traffic to support this busy tunnel. All of the operations will be handled by a smart scheduler which may be a Software Defined Networking (SDN) controller, including an algorithm or methodology. The optical frame switching network allows each wavelength channel to be used by different nodes at different times. Therefore, a scheduling algorithm must be used to control the usage of every node and simulate its performance, as shown in [12]. Its performance is related to the frame size. Because of the smaller frame with the better performance, therefore, high-speed switching elements, such as SOA switching elements, are required. The optical tunnel switching network is only used for wavelength tunnel scheduling, and does not require high-speed switching elements. Therefore, the performance of the optical tunnel switching network is necessary that the average throughput of traffic reaches to 100% at least. However, the performance of the optical frame switching network ensures that average throughput is less than 100%, because the aggregation algorithm is adopted. This is because, when much traffic is sent to the same node, some traffic will be dropped. In the optical tunnel switching network, when a lot of traffic gets sent to the same node, we can schedule the wavelength tunnel to avoid traffic loss. The advantages of the optical tunnel switching network is that it does not require high-speed switching elements and flexible channel scheduling to avoid data loss when the traffic volume is changed. The brief descriptions of other sections are presented as follows. In Section 2, we describe the operations of a multi-plane Torus topology optical tunnel switching network. In Section 3, a two-plane Torus topology optical tunnel switching network with 25 nodes is presented, and its performance is discussed.