The Acacia Communications IPO doesn't have much to do with software-defined anything or data-center convergence. It's not cool like Nutanix.

But Acacia has something Nutanix doesn't: profits.

Not huge profits: $3 million on revenues of $171 million for the first nine months of 2015. But I think this makes Acacia — which, like Nutanix, filed to go public this week — worth a glance, because the optical-networking niche it's chosen is notorious for chronic losses.

Based in Maynard, Mass., Acacia makes optical modules, the plug-in devices that connect a fiber-optic cable to a piece of equipment like a switch or router. They aren't just connectors; they include the lasers and receivers that make optical communications go.

It's a market outside SDxCentral's purview, but one that means something to me. I covered optical networking for more than 10 years, most of them at Light Reading. I followed the optical components market — companies including Finisar and JDSU — through the dry years following the dotcom bust of 2001. (JDSU recently split up, with the optical business going to Lumentum.)

Losses dogged this sector. Competition was abundant, especially as Asian vendors entered. (One of them, OE Solutions, went public in Korea last year.) Manufacturing was expensive, because it required manual intervention for steps such as centering the fiber in the module. And multiservice agreements — standards, essentially — dictated much of the design, muting any differentiation.

Some of that is changing with the advent of 100-Gb/s networking in telecom and data center networks. The technique being used, coherent transmission, works by using electronics to clean up the signal on the receiving end.

This means modules can use cheaper lasers, because the level of precision can be lower. And more of the module's chips can be built from ordinary silicon — as opposed to indium phosphide, which is more expensive.

In other words, coherent technology has turned this optical module business into more of a chip business. It's a high-end chip business, to be sure, but the expertise bar is lower, so startups can sneak into this market even in difficult times — which is what Acacia did, in 2009.

Acacia raised more than $30 million in four funding rounds, but don't expect other VC-backed startups to come storming into this market. Optical modules remain a tough business. The company making the most money off them might be Cisco, which resells optical modules at markup prices.

It's a tough gig, but Acacia managed to make it a profitable one. Even in the software-defined age, there's hope for hardware. Even optical hardware.

Acacia was also profitable in 2014, when it recorded revenues of $146 million and net income of $1.7 million, or 23 cents per share, according to the prospectus. In 2013, the company had revenues of $78 million and losses of $5 million, or $1.12 per share.