As optical bandwidth requirements increase, system designers are turning to “coherent” modulation schemes that can place more data on the same laser light, and lower power over long connections.
A newer question is whether those savings could be achieved for short connections within data centers, as well.
“Coherent is the direction everything’s moving, because for a given system and power budget you’re trying to pack as much data as you possibly can,” said James Pond, principal product manager for photonics at Ansys. “And coherent data communications is a way to pack more data.”
In addition to its use in longer-range applications, coherent optics is poised to help reduce the power required by intra–data-center communications. That can be done by lowering individual laser power, as well as by reducing the number of lasers used, but support circuitry may make those savings harder to achieve.
Photonics in the data center
Much of today’s installed photonics are dedicated to long-haul transmission — signals that go thousands of kilometers. Power is presumably a consideration in that application, but the bigger focus on power is in the data center.
As the data center workloads grow, more data needs to move to and from more places. At present, most of that is happening over copper wire. Optics are having an impact mostly on connections across campuses or from one data center to another over shorter distances than a long-haul connection.
Beyond that, the move to disaggregate the components on today’s servers comes with a promise and a challenge. The promise is that more efficient use can be made of data-center resources. The challenge is that resources that might previously have been collocated in the same server may now need to work from a greater distance away.