Is traffic aggregation the next role for coherent?

Ciena and Infinera have each demonstrated the transmission of 800-gigabit wavelengths over near-1,000km distances, continuing coherent's marked progress. But what next for coherent now that high-end optical transmission is approaching the theoretical limit? Can coherent compete over shorter spans and will it find new uses?

The first of several articles addressing what next for coherent.

Part 1: XR Optics

“I’m going to be a bit of a historian here,” says Dave Welch, when asked about the future of coherent.

Interest in coherent started with the idea of using electronics rather than optics to tackle dispersion in fibre. Using electronics for dispersion compensation made optical link engineering simpler.

Dave Welch

Coherent then evolved as a way to improve spectral efficiency and reduce the cost of sending traffic, measured in gigabit-per-dollar.

“By moving up the QAM (quadrature amplitude modulation) scale, you got both these benefits,” says Welch, the chief innovation officer at Infinera.

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Infinera rethinks aggregation with slices of light

An optical architecture for traffic aggregation that promises to deliver networking benefits and cost savings was unveiled by Infinera at this week’s ECOC show, held in Dublin.

Traffic aggregation is used widely in the network for applications such as fixed broadband, cellular networks, fibre-deep cable networks and business services. 

Dave Welch

Infinera has developed a class of optics, dubbed XR optics, that fits into pluggable modules for traffic aggregation. And while the company is focussing on network edge applications such as 5G, the technology could be used in thedata centre. 

Optics is inherently a point-to-point communications technology. Yet optics is applied to traffic aggregation, a point-to-multipoint architecture, resulting in inefficiencies, says Infinera.  

“The breakthrough here is that, for the first time in optics’history, we have been able to make optics work to match the needs of an aggregation network,” says Dave Welch, founder and chief innovation officer at Infinera. 

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Next-generation coherent adds sub-carriers to capabilities

Briefing: DWDM developments

Part 2: Infinera's coherent toolkit 

Source: Infinera

Infinera has detailed coherent technology enhancements implemented using its latest-generation optical transmission technology. The system vendor is still to launch its newest  photonic integrated circuit (PIC) and FlexCoherent DSP-ASIC but has detailed features the CMOS and indium phosphide ICs support.

The techniques highlight the increasing sophistication of coherent technology and an ever tighter coupling between electronics and photonics.    

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