Data centres to give silicon photonics its chance

Part 4: A large data centre operator’s perspective

The scale of modern data centres and the volumes of transceivers they will use are going to have a significant impact on the optical industry. So claims Facebook, the social networking company.

Katharine Schmidtke

Facebook has been vocal in outlining the optical requirements it needs for its large data centres.

The company will use duplex single-mode fibre and has chosen the 2 km mid-reach 100 gigabit CWDM4 interface to connect its equipment.

But the company remains open regarding the photonics used inside transceivers. “Facebook is agnostic to technology,“ says Katharine Schmidtke, strategic sourcing manager, optical technology at Facebook. “There are multiple technologies that meet our requirements.” 

That said, Facebook says silicon photonics has characteristics that are appealing. 

Silicon photonics can produce integrated designs, with all the required functions placed in one or two chips. Such designs will also be needed in volume, given that a large data centre uses hundred of thousands of optical transceivers, and that requires a high-yielding process. This is a manufacturing model the chip industry excels at, and one that silicon photonics, which uses a CMOS-compatible process, can exploit.

When you bring up a data centre, you don’t just deploy, you deploy a data centre

New business model

What data centres brings to optics is scale. Optical transceiver volumes used by data centres are growing, and growing fast, and will account for half the industry’s demand for Ethernet transceivers by 2020, according to LightCounting Market Research.

Transceivers must be designed with high-volume, low-cost manufacturing in mind from the start. This is different to what the market has done traditionally. “With the telecom industry, you step into volume in more manageable, digestible chunks,” says Schmidtke. “When you bring up a data centre, you don’t just deploy, you deploy a data centre.”

Silicon photonics has already proven it can achieve the required optical performance, says Facebook, what remains open is whether the technology can meet the manufacturing demands of the data centre. What helps its cause is that the data centre provides the volumes needed to achieve such a manufacturing maturity. 

Schmidtke is upbeat about silicon photonics’ prospects. 

“Why silicon photonics is attractive is integration; you are reducing the number of components and the bill of materials significantly, and that reduces cost,” she says. “Then there is all the alignment and assembly cost reductions; that is what makes this technology appealing.”

Her expectation is that the industry will demonstrate the required level of manufacturing maturity in the coming year. Then the role silicon photonics will play for this market will become clearer.  

“Within a year it will be very obvious,” she says.