Rockley demos a silicon photonics switch prototype

Part 1: Rockley Photonics

Rockley Photonics has made a prototype switch to help grow the number of servers that can be linked in a data centre. The issue with interconnection networks inside a data centre is that they do not scale linearly as more servers are added.  

Dr. Andrew Rickman

“If you double the number of servers connected in a mega data centre, you don’t just double the complexity of the network, it goes up exponentially,” explains Andrew Rickman, co-founder, chairman and CEO at Rockley Photonics. “That is the problem we are addressing.”

By 2017 and 2018, it will still be possible to build the networks that large-scale data centre network operators require, says Rickman, but at an ever increasing cost and with a growing power consumption. “The basic principles of what they are doing needs to be rethought,” he says.

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Choosing paths to future Gigabit Ethernet speeds

Industry discussions are being planned in the coming months to determine how Ethernet standards can be accelerated to better serve industry needs, including how existing work can be used to speed up the creation of new Ethernet speeds.

The y-axis shows the number of lanes while the x-axis is the speed per lane. Each red dot shows the Ethernet rate at which the signalling (optical or electrical) was introduced. One challenge that John D'Ambrosia highlights is handling overlapping speeds. "What do we do about 100 Gig based on 4x25, 2x50 and 1x100 and ensure interoperability, and do that for every multiple where you have a crossover?" Source: Dell

One catalyst for these discussions has been the progress made in the emerging 400 Gigabit Ethernet (GbE) standard which is now at the first specification draft stage.

“If you look at what is happening at 400 Gig, the decisions that were made there do have potential repercussions for new speeds as well as new signalling rates and technologies,” says John D’Ambrosia, chairman of the Ethernet Alliance.

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Verizon prepares its next-gen PON request for proposal

Verizon will publish its next-generation passive optical network (PON) requirements for equipment makers in the coming month.

Vincent O'Byrne

The NG-PON2 request for proposal (RFP) is being issued after the US operator completed a field test that showed a 40 gigabit NG-PON2 system working alongside Verizon’s existing GPON customer traffic.  

The field test involved installing a NG-PON2 optical line terminal (OLT) at a Verizon central office and linking it to a FiOS customer’s home 5 km away. A nearby business location was also included in the trial.

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US invests $610 million to spur integrated photonics

The US government has set up its latest manufacturing initiative, the sixth of nine, to address photonic integrated circuits (PICs). The $610 million venture is a combination of public and private funding: $110 million from the Department of Defense, $250 million from the state of New York and the rest private contributions.

Prof. Duncan Moore

Dubbed the American Institute for Manufacturing Integrated Photonics (AIM Photonics), the venture has attracted 124 partners includes 20 universities and over 50 companies.

The manufacturing innovation institute will be based in Rochester, New York, and will be led by the Research Foundation for the State University of New York. A key goal is that the manufacturing institute will continue after the initiative is completed in early 2021.

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Micro QSFP module to boost equipment port densities

Twelve companies are developing a compact Quad Small-Form-Factor Pluggable (QSFP) module. Dubbed the Micro QSFP (μQSFP), the multi-source agreement (MSA) will improve by a third the port count on a platform's face plate compared to the current QSFP.

Nathan Tracy

The μQSFP will support both copper and optical cabling, and will have an improved thermal performance, benefitting interfaces and platforms.

“There is always a quest for greater port density or aggregate bandwidth,” says Nathan Tracy, technologist at TE Connectivity and chair of the μQSFP MSA.

The challenge for the module makers is to provide denser form factors to increase overall system traffic. “As we go to higher densities, we are also increasing the thermal load,” says Tracy. “And so now it is a mechanical and a thermal [design] problem, and both need to be solved jointly.”

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Data centres to give silicon photonics its chance

Part 4: A large data centre operator’s perspective

The scale of modern data centres and the volumes of transceivers they will use are going to have a significant impact on the optical industry. So claims Facebook, the social networking company.

Katharine Schmidtke

Facebook has been vocal in outlining the optical requirements it needs for its large data centres.

The company will use duplex single-mode fibre and has chosen the 2 km mid-reach 100 gigabit CWDM4 interface to connect its equipment.

But the company remains open regarding the photonics used inside transceivers. “Facebook is agnostic to technology,“ says Katharine Schmidtke, strategic sourcing manager, optical technology at Facebook. “There are multiple technologies that meet our requirements.” 

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Verizon tips silicon photonics as a key systems enabler

Verizon's director of optical transport network architecture and design, Glenn Wellbrock, shares the operator’s thoughts regarding silicon photonics.

Part 3: An operator view

Glenn Wellbrock is upbeat about silicon photonics’ prospects. Challenges remain, he says, but the industry is making progress. “Fundamentally, we believe silicon photonics is a real enabler,” he says. “It is the only way to get to the densities that we want.”

Glenn Wellbrock

Wellbrock adds that indium phosphide-based photonic integrated circuits (PICs) can also achieve such densities.

But there are many potential silicon photonics suppliers because of its relatively low barrier to entry, unlike indium phosphide. "To date, Infinera has been the only real [indium phosphide] PIC company and they build only for their own platform,” says Wellbrock.

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