Speculation is swirling regarding the possible equipment suppliers to a massive optical network being built by Internet search portal firm Google.

The company's quiet plans to build a nationwide or even international fiber network have gained a great deal of attention throughout this year as the company sought to purchase large quantities of dark fiber. Industry sources say Google recently has issued a request for proposals for dense wavelength-division multiplexing (DWDM) equipment to light that network, and a note issued Monday evening from UBS Investment Research suggested two vendors in particular had become the most likely candidates to win a piece of the business.

"Industry checks suggest Google will build a DWDM network and is initially working with start-up vendor Infinera for long-haul and Adva [Optical Networking] for metro," the UBS note said.

Both Adva and Infinera declined to comment. Google did not return Telephony's request for comment.

If Google were leaning toward Adva and Infinera, it could suggest plans for a significant presence in each city its network reaches, according to Bill St. Arnaud, senior director of advanced networks for Canarie, a Canadian network development group.

"Infinera is well-suited for a lot of add/drop type of applications," St. Arnaud said. "Adva's very good also in the metro space That selection is telling me [Google is] not just trying to connect three or four data centers together. They're actually going for much deeper, richer connectivity."

Recent moves by Google into Wi-Fi have fed speculation that the company, which does not have "last-mile" infrastructure with which to reach end users, might employ wireless connections to deliver a variety of content, including video.

Infinera's unique approach to optical networks, though newer and not as widely deployed as traditional DWDM networks, was chosen earlier this year by Level 3 Communications for a nationwide network. The company uses its own microchips to do the work of more expensive optical components, thus getting the network management benefits of photonic/electric conversions at a lower price.

Adva, meanwhile, has made a deeper penetration of the North American market its primary focus for at least the past year, and recently acquired Ethernet access equipment vendor Covaro Networks to help accelerate that effort. In the third quarter, Adva gained three new customers, only one of which was American. That customer was a non-Bell incumbent carrier, an Adva spokesperson said.