Cisco, Nvidia team up to build fatter, faster pluggable

AI datacenters are a rats nest of fiber optic cables stitching together thousands of AI accelerators, NICs, switches, and everything else required to train and run the latest and greatest modes.

Cisco hopes to untangle this mess with a new pluggable optic developed in collaboration with Nvidia that will pack between four and eight times the bandwidth of existing pluggables into a single port.

Announced at the Open Compute Project (OCP) global summit this week, the ultra-dense small form factor pluggable (USFP) promises to pack up to 32, 400 Gbps lanes into a pluggable roughly the size of existing OSFP modules.

Each of these pluggables would boast 12.8 Tbps of Ethernet bandwidth, as much as a high-end enterprise switch just a few years ago.

To put that in perspective, the most sophisticated pluggable optics today cap out at around 1.6 Tbps using eight 200 Gbps links.

Such a pluggable has the potential to significantly simplify cabling across AI datacenters where it isn't uncommon for each GPU to be paired with an 800 Gbps and soon 1.6 Tbps NIC.

A single USFP pluggable could consolidate eight GPUs worth of cabling into a single fiber optic bundle.

Meanwhile, on the switch side, a future 204.8 Tbps switch would only require 16 USFP ports to support 128 1.6 Tbps endpoints.

Cramming all that connectivity into a single pluggable won't be easy.

Today a high-end pluggable optic might pull on the order of 20 watts.

Cisco's USFP spec calls for up to 100 watts per pluggable.

There are also design constraints that have to be taken into consideration.

Four times as many links per pluggable means 4x as many electrical contacts that have to be perfectly seated.

Because of this Cisco says USFP modules will employ a two phase insertion mechanism in which the pluggable is first inserted into the cage and then a second mechanism is actuated to make the electrical connection.