Some twenty years ago the concept of IP over Wavelength Division Multiplexing (WDM) was proposed as a way to simplify the optical infrastructures. In this vision, all optical networks are connected via point-to-point mesh networks with a router at the center. The concept was elegant, but never took off because the optical technology at the time was not able to keep up with the faster innovation cycle of CMOS, driven by Moore’s law. The larger form factor of WDM optics does not allow them to be directly plugged into a router port. Adopting a larger form factor on the router in order to implement IP over WDM in a massive scale would be prohibitively expensive.

For routers to interface with the networks, a “transponder” is needed, which is connected to a router via short-reach optics on one side and WDM optics to the network on the other. The market for transponders grew quickly to become a multi-billion-dollar market.

A Star is Born

About 10 years ago, I was building a team at Inphi, where I was a co-founder, to further develop a nascent technology called silicon photonics. SiPho, as it’s called, leverages commercial CMOS foundries to develop photonics integrated circuits (PIC) that integrate hundreds of components ranging from high-speed modulators and detectors to passive devices such as couplers, waveguides, monitoring diodes, attenuators and so on. We were looking for ideas and customers to bring silicon photonics to the marketplace.

Fortunately, good technology and market need found one another. A group of Microsoft executives had been considering IP over WDM to launch a new concept of “distributed data centers,” in which multiple data centers in a region are connected by high speed WDM optics using the same form factor as shorter reach “client optics” used in switches and routers. By chance, we met at ECOC 2013 in London for the initial discussion, and then some months later, a product that enabled IP over WDM at cloud scale was born.