Data centers rely heavily on multimode fiber, which is perfectly adequate for networking at 10G and 40G, but isn't expected to be up to the task of networking at hundreds of gigabits a second. Traffic growth within data centers is growing at mind-boggling rates, however. Some of the biggest data center operators say traffic within their facilities is already so voluminous they would jump straight to 400G today but for the fact the technology isn't ready yet.
There are several possible options to upgrade to 100G/400G, but one of the more obvious is switching to single mode fiber, which can handle such data rates easily. There are several problems that come with the use of single mode fiber that need to be solved first, however.
One of the biggest is the difficulty of aligning the ends of optical fibers with silicon photonics chips inside the chip packages. The optical core of a single mode fiber has a diameter of 9 microns (the entire fiber, core-plus-cladding, is 125 microns). The ends of these fibers need to terminate at the waveguides on silicon photonic chips, but waveguides typically measure only 1 micron wide. Properly aligning fiber to waveguide requires specialized, high-precision equipment. The production rate is a measly ten packages an hour.
Teramount has created a module, called the Photonic Plug, that connects fiber to chip and automatically aligns them. Fibers are attached to the module using a standard v-groove, Teramount CEO Hesham Taha told Light Reading. The optics within the module ultimately focuses the beam on the waveguide on the silicon photonics chip.
The optics in the module include a series of mirrors, made with standard silicon and a standard lithographic process, Taha said. He was reluctant to dive too much deeper into the technological details, but said the technology is not based on MEMS (micro-electrical mechanical systems) mirrors.
Details of the implementation aside, the ultimate advantage the module provides is that silicon photonic packages can be assembled with standard semiconductor pick-and-place equipment, at a rate of thousands an hour.
Taha said the company has working prototypes. The first versions are a mere 700 microns thick (roughly three-hundredths of an inch), and are surface coupled. The company plans to eventually follow with an edge-coupled device.
The incredibly tight tolerances required of current silicon photonic packaging with single mode fiber dictate that the design of silicon photonics chips and production cannot be separated, Taha said, but the Photonic Plug makes it possible for even fabless companies to design silicon photonic modules. Expecting that fabless companies will take advantage of the fact, Teramount is working with several silicon foundries to introduce them to its technology, Taha said.
— Brian Santo, Senior Editor, Components, T&M, Light Reading