High-Efficiency PICs Accelerate Telecom Speeds to 40 Tbit/s

Using multiple wavelengths to deliver information — all on a single PIC — collaborators from Dublin-based Pilot Photonics and the European photonics innovation incubator ACTPHAST 4.0 have found a way to pack more data into existing internet cables, ramping up speeds to 40 Tbit/s. The speed, the collaborators say, is sufficient to download 5000 Netflix films (standard definition) in a second.

The approach is an alternative to one that may use optical fibers, and it serves as a new method for splitting up light channels.

The collaborators used optical combs — a single laser that generates a broad spectrum of equally spaced optical frequencies rather than independent lasers — to enable higher-capacity internet traffic on a single fiber without any upgrades to existing infrastructure. The work eliminates so-called guard-bands, or wasted chunks of bandwidth needed in traditional systems that prevent interference between data channels.

“A way to visualize how our photonic integrated circuits are helping the flow of information between data centers is to think of road to rail,” Frank Smyth, CTO and founder of Pilot Photonics, said. “On the road, the lanes must be much wider than the cars because the driver can veer left and right to some degree. This extra lane space represents the guard-bands between wavelengths that are used in optical systems today. With rail, you can pack trains right up side-by-side because they are on fixed tracks and cannot veer off them; this is like using an optical comb. The trains can’t bump into their neighbors because they are on fixed tracks.”

Data channels based on an optical comb cannot interfere, Smyth added; the spacing between them is physically and fundamentally fixed. The technology allows the collaborators to use multiple wavelengths at a lower speed, removing integrity pressure on a single band.

“These multiple wavelengths create a single channel known as a ‘superchannel,’ enabling longer distances to be traveled by the data and making it easier to maintain good signal integrity,” Smyth said.

The work, he said, supports bandwidth-intensive data services without significant price increases for customers and users.

Specialized Chip Technology
Pilot Photonics’ used a platform technology called monolithic indium phosphide photonic integrated circuits to develop the solution. The platform allows the comb laser, amplifiers, modulators, and coherent receivers to all be integrated. All optical functions can be placed on a single photonic chip.

According to Smyth, the methodology contrasts silicon photonics.

“Silicon does not produce light, so a laser has to be built separately and attached to a silicon photonics chip, creating challenges in manufacturing and performance,” Smyth said. Monolithic indium phosphide PICs allow total integration onto a single substrate, improving the performance of optical transceivers.

“We need high-capacity links to transfer more information than ever before between data centers and for the long-haul transmission of data between cities, countries, and continents,” Smyth said. Using a laser comb, he said, the Pilot Photonics team can combine four, eight, or 16 transceivers onto a single chip. This brings down power consumption, cost, and size.

Pan-European Support
ACTPHAST 4.0 supports and accelerates the innovation capacity of European companies by providing them with direct access to the expertise and state-of-the-art facilities of Europe’s leading photonics research centers (the ACTPHAST 4.0 Partners), enabling companies to exploit the tremendous commercial potential of applied photonics. Twenty-four research institutes make up the ACTPHAST 4.0 Partners.

The photonics innovation incubator offered Pilot Photonics’ access to research centers in Ireland (UCC Tyndall Institute), the Netherlands (Technical University of Eindhoven), and Germany (Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, HHI) for the development of its PICs.