Roughly every two years switch silicon doubles in speed. The problem is, with every subsequent generation of switch silicon, power consumption grows exponentially outpacing bandwidth, explained Rakesh Chopra, a Cisco fellow in the common hardware group, in a blog post this week.

It’s this challenge that Cisco aims to overcome through a collaboration with Inphi to develop co-packaged optics (CPO) for the next generation of 51.2 Tb/s switches and 800 Gb/s pluggables, which are expected to begin hitting the market sometime in 2024.

CPOs aren't a new idea. For years chipmakers specializing in switching have warned that at some point the power required to achieve faster bandwidth would necessitate the development of CPO technologies, Chopra explained.

Traditionally in pluggable optics, the optical interface was located inside the pluggable module, which as its name suggests is plugged into the switch chassis. While this means pluggables can easily be replaced or swapped for higher capacity ones, it also means there is several inches of copper between the switch silicon and the optical interface.

“With CPO, the optical interface in a networking switch system moves from pluggable modules at the front of the switch enclose to optical modules that are assembled in the same package as the switch chip,” said Hugh Durdan, VP of network interconnect marketing at Inphi, in a blog post.

He explains that by reducing the distance between the switch silicon and the optics from inches to mere millimeters, power consumption can theoretically be reduced by as much as 30%m, in a 51.2 Tb/s switch configuration.

While Durdan notes that 800 Gb/s pluggables for 51.2 Tb/s switches are possible without CPO, the reduced power requirements enabled by the technology are attractive to certain customers.

“Power is a major challenge in today’s data centers, and anything that can be done to reduce the power consumption of the equipment in the data center is a benefit to the operator,” he said. “Data center operators are paid for computing and storage, not moving data. Every watt spent on networking, is a watt that can’t be used to generate revenue.”

So while 800 Gb/s pluggables for 51.2 Tb/s switches will be possible without CPO, Durdan said the industry needs to begin parallel development of CPO switches for that generation beginning around 2024 and beyond. “Over time, as the power and bandwidth challenges increase, data center operators will deploy an increasing proportion of their optical interfaces with CPO.” he explained.

Cisco isn’t the only switch chipmaker pursuing co-packaged optics. Marvell, a major manufacturer of switching silicon, announced plans to acquire Inphi in a deal worth $10 billion in October 2020.

According to Marvell CEO Matt Murphy, Inphi’s electro-optical interconnect technologies compliment the chipmaker’s existing Ethernet physical layer technologies.

In related optical news, Cisco this week paid an additional $2 billion to shore up a botched deal to acquire optical networking vendor Acacia. The network giant will now pay $4.5 billion for the company, which among other optical technologies produces digital signal processors used in pluggable optics.