oDAC: Boosting data centre speeds with less power

Academics have developed an optical digital-to-analogue converter (oDAC) that promises to rethink how high-speed optical transmission is done.

Professor Ioannis Tomkos

Conceived under the European Commission-funded Flex-Scale project for 6G front-haul, the oDAC also promises terabit links inside the data centre.

The oDAC is expected to deliver a 40 per cent power savings for a 1.6 terabit optical transmitter, which is the ‘send’ path of an optical module.

“It might not be not 50 or 60 per cent, but in this field, even a 25 per cent power saving turns heads,” says Ioannis Tomkos, a professor at the Department of Electrical and Computer Engineering at the University of Patras, Greece, one of the researchers leading the work.

The first proof-of-concept oDAC photonic integrated circuit (PIC) has sent 250 gigabits per second (Gbps) over a single wavelength as part of the European Proteus programme.

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Do optical DACs have a role in future coherent modems?

• A proposed optical digital-to-analogue converter (oDAC) concept offers several system benefits, including better signal performance, higher bit rates and lower power consumption.
• The oDAC design benefits coherent optics but can also be used in direct-detect designs. This article focusses on coherent optics.
• Coherent system vendors are aware of oDAC technology but it is not part of their current roadmaps. 

A 256-QAM constellation using a conventional coherent transmitter (left) and using the oDAC. Note there is no modulator loss (the full area is used) nor any optical warping using the oDAC. Source: Tomkos and Nazarathy.

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