What is the open packet optical switch, Voyager?

1. What is the open packet optical switch, Voyager? Modern web-scale data centres are thirsty for bandwidth. Popular applications such as video and virtual reality are increasing in demand, causing data centres to require higher and higher bandwidths — both within data centres and between data centres. In this blog post, we will briefly discuss the current challenges in the optics space as well as some of the key technical aspects of the Voyager’s DWDM transponders. In part two of this series, we will cover why Voyager is a unique, powerful and robust solution. The challenges to accommodate longer distances Within a data centre, organizations are adding higher and higher bandwidth ports and connections to accommodate the need for more bandwidth. However, connections that accommodate longer distances between data centres may be limited and expensive.Therefore, a critical requirement for businesses with this challenge is how to support longer distance spans at higher bandwidths over a small amount of fibre pairs The optical industry solves the bandwidth problem using Dense Wave Division Multiplexing (DWDM). DWDM allows many separate connections on one fibre pair by sending them over different wavelengths. Although the wavelengths are sent on the same physical fibre, they act as “ships in the night” and don’t interact with each other, similar to VLANs on a trunk. Each wavelength can transport very high speeds (hundreds of Gigabits per second) over very long distances. While this is an incredible feat, today’s DWDM systems are typically closed and expensive. The transponders (which I’ll be explaining in more detail below) are generally the most expensive part of the closed DWDM network. Announcing Voyager early access Back in November, we announced the partnership between Cumulus and the open packet DWDM platform Facebook brought to the Telecom Infra Project (TIP), called Voyager, bringing the first open packet optical product to the industry. Voyager is a Broadcom Tomahawk-based switch, similar to Facebook’s Wedge 100, but with added DWDM ports that can connect to another switch tens, hundreds or thousands of kilometers away by adding transponders. What is a DWDM transponder? For reference, a typical active DWDM network is depicted below. Depending upon the use case, all elements below are not required for Voyager deployment. For example, Voyager can also be deployed over dark fiber with no ROADMs. Voyager is the transponder (TPDR) in the below scenario and is also a Layer2/3 switch with all the functionality of a Broadcom Tomahawk switch with Cumulus Linux. The transponder lives primarily at the edge of the DWDM network (with some exceptions, like when back- to-back transponders are used as a regenerator) and has a port to connect to a switch or router and a port to connect to the DWDM line system facing the remote end. In some cases, such as Voyager, the transponder could be located within a switch or router (i.e. the same box does switching, routing and transponding). A muxponder is similar to a transponder, only it also performs time division multiplexing (TDM) over a pre- specified wavelength. For example, with a muxponder, you can send ten 10GigE links over a single 100G wavelength. Voyager will support this functionality as well. What does a transponder do? A transponder performs an optical-electrical-optical conversion and is primarily responsible for three tasks: Converting the “grey” wavelength (850nm, 1310nm or 1550nm) to a pre-specified C-band wavelength and back Encapsulating/decapsulating the ethernet frame into a layer 1 OTN or OTN-like frame and providing performance monitoring and forward error correction (FEC) Modulating, transmitting, receiving, demodulating and controlling signal power •Voyager combines the transponder with L2/L3 —doing the “ethernet handoff” internally to Voyager itself. • • •

2. •What is a C-band wavelength? •The ITU-T divides the fiber optic communication spectrum (part of the infrared section of the full electromagnetic spectrum) into 6 bands: O, E, S, C, L and U. The attenuation across a single mode fiber optic cable is lowest (0.20-0.25dB/km) at the C-band (or conventional band), so it is primarily used for DWDM communications. Also, low cost Erbium Doped Fiber Amplifiers (EDFAs) help boost signals operating at this range. Voyager will support transmitting/receiving on the C-band. What is an OTN or OTN-like frame? An Optical Transport Network (OTN) frame (or the like) is used with DWDM. An ethernet frame is run inside it for this application. As you can see, an OTN frame (which is in the electrical domain) consists of three overhead layers and they are analogous to SONET Line, Section and Path overheads: •Optical Transport Unit (OTU): Between optical network elements •Optical Data Unit (ODU): Network level •Optical Path Unit (OPU): Responsible for end-to-end What is modulation and transmitting? A transponder/muxponder is also responsible for modulating the signal and transmitting the signal at the appropriate power level. Transmitting at too little power won’t drive very far, and transmitting at too much power can distort the signal. Voyager will be able to effectively transmit up to +2.5dBm. Therefore, the signal needs to be “cleaner” and have less noise in order to read it effectively. This leads to shorter supported distances and the need for more complex FEC algorithms, such as SD-FEC. For more details please visit the following website: https://www.cbo-it.de/ https://www.gbic-shop.de