Researchers aim to tease capacity gains from fiber with optical combs

A group of researchers inched closer to untangling the problem of how to add capacity to fiber networks in a way that’s both simple and easy to control, announcing a breakthrough in optical comb technology.

One of the researchers involved in the project, Trinity College School of Physics Professor John Donegan, told Fierce optical comb technology could be used as an alternative to today’s wavelength division multiplexing (WDM) coherent optics.

In the simplest terms, Donegan said an optical comb is a device which takes a single beam of light from a laser source and breaks it into a set of equally spaced frequency channels or lines, like the teeth on a comb. Several different types of combs exist, yielding varying numbers of channels.

He explained that WDM coherent optical technology uses multiple lasers functioning in harmony with one another, helping eliminate interference when wavelengths wander due to factors such as temperature changes. But instead of “having to make all of those 10, 20 or 30 lasers that are in the WDM system coherent with one another, you could get the coherence automatically from” a single device via the comb, he said. And with more channels, networks could also deliver more capacity, he added.

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The breakthrough Donegan’s team achieved was the development and demonstration of what is known as an octave-spanning coherent optical comb, which covers a broad frequency span of electromagnetic spectrum from deep red to deep violet without any breaks. Other team members include scientists from AMBER, the SFI Centre for Advanced Materials and BioEngineering Research, CRANN, the School of Physics at Trinity College Dublin and Huazhong University of Science and Technology.

Donegan said the team’s comb can generate more than 100 channels, opening the door to a wide range of applications across communications, astronomy and quantum computing. But he said communications applications could do with as few as 10 channels.

Asked where such combs might be applied, Donegan said he doesn’t see them being deployed for use cases like fiber-to-the-home. Instead, he believes they “will be used in areas in which there’s huge data transfer, such as within and between data centers, for stock exchange systems and to process data from hospitals.

In terms of when technology might be applied, Donegan speculated comb-based systems could be used for high-volume data transfers “within the decade” but added deployments for use cases like quantum computing are likely “even further [out], maybe another decade after that.”