Linear Drive: Potentially Huge Share Shifts in the Transceiver Market

Is Linear Drive as big of a deal as Arista Networks making it out to be?

It’s truly amazing how much technology can change over a few years. Rewind 3 years ago, and the story was how DSPs in the pluggable optics would enable higher order modulation like PAM4 and Coherent pluggable in campus reach transceivers.

But fast forward a few years, and technological change can always surprise. What has changed is that it seems like the direct linear drive will be one of the most significant cost reductions in the race to 800Gb and 1.6Tb pluggables. The linear direct drive debate will be the biggest incremental news coming out of OFC this week.

There are a few bottlenecks to driving to higher-rate modules, but energy and cost are the huge hurdles to making transceivers a reality. Arista, in particular, is excited about the direct linear drive after Nvidia and Broadcom talked about it being possible.

Arista networks this week was the real champion of this technology, and below are their slides on how to reduce optics power and enable higher 1.6TB/s networking. The key to reducing optics power in the pluggables was fourfold, but the linear drive was the biggest cost driver.

Arista also had a cost attribution slide. Linear Drive would achieve a 25% reduction in power over 400Gb optics, more efficient modulators would be 5%, and better silicon interposers would be another 10%. The clear driver is the 25% cost reduction from the linear drive.

Linear drive’s big cost reduction is from removing the DSP and relying on better components like drivers and TiAs (Transimpedance Amplifiers) to compensate for the loss of the DSP. Additionally, there are more SerDes needs on the switch to enable this change, as the SerDes on the switch compensates for the lack of DSP on the module.

This could potentially be a huge sea change in the pluggable module landscape, and I think the share and revenue impact is meaningful. This primary narrative will occupy space for the pluggable modules in the coming months.

Is the hype real? For more estimates about market sizing and its direct impact on companies and my thoughts on whether this is a big deal, please refer to my estimates behind the paywall. I have an estimate of the pricing differential between 400 GB/s and 800 GB/s pluggable as well.