- The latest fiber optic technology is multi-core fiber in which four cores are fused together in one fiber strand
- This is important because it reduces the size of fiber optic cables in data centers
- Multi-core provides 4x capacity but not 4x cost
LOS ANGELES — Fiber optic glass is created in a fascinating process where optical engineers design the glass by creating a thick glass rod called a preform. It’s basically a giant version of the ultimately hair-thin fiber. The center of the preform is the core, and this is surrounded by cladding. Together they contain all the engineered optical properties of the fiber. The preform is then placed at the top of a tall drawing tower — from 30-65 feet tall — and heated to about 2,000 degrees Celsius. This allows for a thin strand to be pulled downward, becoming the fiber optic strand.
For demonstration purposes, fiber manufacturers can cut the preform rod into cross-sections to show the core. Fierce was able to see one of these cross-sections at the Corning booth at the Optical Fiber Communications (OFC) conference this week.
In recent years, the fiber optic industry has advanced its technology from single-core fiber to multi-core fiber. This means that each fiber contains multiple cores within a single cladding, and each core can carry an independent optical signal, allowing parallel data transmission in the same fiber.
The industry has determined that four cores is the most optimal ratio for multi-core fiber (as opposed to two-core or three-core), and it’s working on standardizing four-core fiber.
STL talks about multi-core
STL was also at the OFC conference this week, and it’s also working on multi-core fiber. Badri Gomatam, STL's CTO for Telecom said, “Our aim is to move this from early stage to standardized production.”
An executive from STL holds the vice chair position at the International Telecommunications Union (ITU), which is part of the United Nations, and sets global standards. Gomatam said single core fiber has been standardized for 20 years, and multi-core fiber is just four exact copies of what’s already been standardized. The only difference is that the four cores are within the same cladding.
“Right now, cost versus performance is hitting a sweet spot," he said. "It’s four times the capacity but not four times as expensive.”
Speaking of capacity and cost, there was definitely a theme at this week’s OFC show. There are four variables that everyone in the fiber optic industry seems to be chasing: more density, less space, less cost and less power.
Fierce asked if more density and taking up less space were really so critical that we need to be reducing the size of fiber optic strands, which are literally as thin as a strand of hair.
In answer to the question, Gomatam showed a typical fiber optic cable that is used inside data centers — it contained 6,912 fiber strands. It was surprisingly large and heavy. And one cabinet in a data center might be connected with as many as six of these cables.
“At the end of the day it’s just all about real estate,” said STL's CEO Rahul Puri.
STL has conducted a pilot of multi-core fiber with Colt Technologies. The trial was conducted within the London Metro network between two Colt PoPs, covering distances of 9 km and 63 km.
Puri said multi-core fiber technology “will take a while for mass adoption.” But things are moving much faster in the optical industry than they used to (thank you, hyperscalers!)
“Traditionally it would have taken a decade, but I feel this is the year of multi-core,” said Gomatam.