Optical switched networks have the potential to reduce latency and  power consumption but that potential is jeopardised by the problems of re-scheduling and re-synchronisation of the data stream. Cool Optics is developing  a solution in combination with its Lock & Link technology

High bit rate transmission must be matched by switching capacity. But switches are a big spender concerning energy and latency. This can be better! Click image to read more..

Today all switching is done in Store-and-forward Switches. A packet has a size between 72 up to appr. 2000 Bytes for an extended packet. Every packet has first to be stored and then forwarded to the other connection after the destination address has been read and understood. Since the switch makes forwarding decisions amongst others based on the destination address which is at the header of the packet, the switch can make the forwarding decision before receiving the complete packet, this process is called cut-through, the switch forwards part of the packet before receiving the complete packet. Cut-through allows lower latency and saves buffer space, but if an error occurred in the packet while utilizing cut-through, the packet will be forwarded with an error, alternatively, utilizing store-and-forward allows the switch to drop erroneous packets. For Cut-through, the incoming line and the outgoing line must have the same speed. If the speeds are different, normal store-and-forward technology has to be applied.

A state-of-the-art switch has a cut-through latency of 300 nanoseconds. In case of e.g. a switch with 10 Gbps servers and 40 Gbps interconnect lanes, the average delay per packet (no cut-through) will be 1000 nsec for store-and-forward, and 300 nanoseconds for the processing, totaling to 1.3 μsec.

Not only the latency is substantial, performing these tasks of identifying the address, store-and-forward the information, translating from optical to electrical and back again, costs a lot of energy and requires cooling.

Although the new generation all-optical switches are becoming faster, re-scheduling the switching architecture and re-synchronization of the data stream comes at the cost of latency which may end up in milliseconds.

Most networking equipment today is based on electronic-signals, meaning that the optical signals have to be converted to electrical ones, to be amplified, switched, and then reconverted to optical signals. The latter is referred to as an ‘optical-to-electronic-to-optical’ (OEO) conversion and is one of the bottlenecks in transmission.

Currently, developments are mainly focused at the optical part of the switch, where the source and nature of the optical signals are sort of taken for granted. Development is more focused on the physical elements of the switch, rather than on the control of the switch and the optical data stream to and from the switch.

Most optical switches contain some form of OEO conversion to identify the address to send to, to maintain the synchronization in the network and so on. This results in latency and power comparable to classical store and forward switches.

Cool Optics is working on a concept in which its Lock & Link technology, combined with an ALL Optical switch, can provide a solution to that problem.

The optical communication and networking market has a high potential and is expected to be worth USD 24 Billion by 2023, growing at a CAGR of 8.1% from USD 15.11 Billion in 2017. Some of the key factors driving the growth of this market are the growing adoption of cloud-based services and virtualization, and growing data center deployments.

(ref: Markets and Markets).

Klik hier om uw eigen tekst toe te voegen