# A Vision of 6 th Generation of Fixed Networks (F6G): Challenges and Proposed Directions
## 5 Optical Switching: Key Challenges and Proposed Directions
### Ultra-Fast Switching
\begin{table}
\begin{tabular}{c c c} \hline \hline
**KPI** & **Inter-Factory** & **Intra-Factory** \\ \hline Capacity & Fronthaul: up to hundreds of Gb/s & End point data rate up to 2 Gb/s; \\  & Tb/s scale & P2 MP with 64 or higher end points \\ Latency & End-to-end latency: \(<\)100 \(\upmu\)s & End to end latency: 10 \(\upmu\)s \\  & End-to-end latency: \(<\)100 \(\upmu\)s & (excluding fibre propagation) \\ Reliability & Very high & 99.999\% (of packets) \\ Power Consumption & few Watts per Tb/s & few Watts per Tb/s \\ Cost & 50 cents per Gb/s & 50 cents per Gb/s \\ Electromagnetic & Required & Required \\ interference resiliency & End-to-end jitter: 30 ns to a few \(\upmu\)s & 30 ns to 50 ns \\ Jitter & depending on the application & \\ Dynamics & ms-timescale & P2 MP can be with fixed BW allocation \\ Guaranteed Delivery & End-to-end Packet loss rate: \(<\)10\({}^{-10}\) & BER: \(<\)10\({}^{-5}\) (FEC with optimized latency) \\  & Number of competing time sensitive flows: \(>\)100 & P2 MP aggregates the traffic of 64 end points into \\  & Number of machines in each edge cloud: \(\sim\)200 & a single head end—increase density \\  & Scalability could be provided by the use of WDM \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Main KPIs for intra and inter factory switches. capable solution that offers low latency, low jitter, high speed, and guaranteed delivery use cases [11]. The switching architectures of [10, 17] aim to satisfy the requirements of TSN networks. In [10], an optical wavelength, space, and time WDM cross-connect switch is employed to realize the optical metro node architecture and the Data Center Networks (DCN) architecture and consists of express and add/drop ports, photonically integrated WSS aggregation/disaggregation functions for merging/dropping the network traffic, and photonically integrated multi-cast switch (MCS). The modular approach enables one to scale the architecture in a pay-as-you-grow approach by using photonically integrated devices for wavelength and space switching. This photonic WDM switch employs SOA as an on-chip gain element for lossless operation. A significant advantage of this switch is the fast-switching time of the SOA and the high contrast ratio that make the SOA a very good candidate for fast packet-based switching operation. Next, [17] developed a novel DCN architecture utilizing OFDM and parallel signal detection technologies. The candidate architecture offers fine-grain bandwidth allocation, high switching speed, and low and uniform latency, which are vital for ultra-fast switches. This implementation has been experimentally demonstrated and verified successfully for the MIMO OFDM switching and fine-granularity flexible bandwidth sharing features. Moreover, efficient subcarrier allocation algorithms have been developed for the fine-grain bandwidth allocation. The simulation results showed that the MIMO OFDM-based architecture provides low latency and high-throughput switching. Furthermore, the implementation of the scheduler shows that it can support a high number of nodes and subcarriers offering excellent scalability capabilities. Figure 39 shows the high-level architecture of our vision on the Industry 4.0 switching architecture that aims to support both inter- and intra-factory communication. This architecture aims to connect the variety of end-points that can be found in a modern and future factory environment (including various \"things\", such as machines, sensors, robots, etc.) with a centralized control that can be seen as a micro-data center (microDC), which can be located either within the factory or at a different site. The microDC has the flexibility to host a variety of different services such as the centralized control of the machine and robots on the factory floor, centralized logistic management, digital twin functionalities, and predictive maintenance.