June 30, 2013
Twisted Light Beam Research Could Enhance Internet Bandwidth Capacity
redOrbit Staff & Wire Reports - Your Universe Online
New fiber optic technology that transmits data along light beams that twist like a corkscrew rather than along straight lines could lead to increases in Internet bandwidth capacity, according to new research appearing in the journal Science.
According to BBC News Science and Technology Reporter Jason Palmer, more data can be encoded in differently twisted beams because of the shape of the light. The concept had previously been demonstrated over "free space," he said, but the authors of the new study are the first to demonstrate that is can effectively work over fibers as well.
"The discovery comes as internet data traffic is reaching its limit amid mounting demand for bandwidth by users of smartphones and internet-enabled devices, creating problems for network providers," ABC News Australia reported on Friday. "The new technology uses optical vortices, which are like doughnut-shaped laser light beams. Also known as orbital angular momentum (OAM) beams, they were thought to be unstable in fiber until now."
Experts from Boston University and the University of Southern California (USC) demonstrated data rates of 1.6 terabits per second (Tb/s) over one kilometer of optical fiber, Palmer said. While that falls short of the 2.5 TB/s demonstrated by these same researchers last year, it serves as an effective proof of concept for adapting the technique for use in data centers, he added.
Furthermore, according to Scientific American's Maggie McKee, the authors managed to keep the various light beam shapes separated for a record 1.1 kilometers. They designed and built a glass cable that was more than one kilometer in length which had a cross section featuring a varying index of refraction (a measurement used to describe how quickly light can travel within a specific medium). They then sent both twisted and straight light beams down the cable.
"The team found that the light output matched the input -- light beams of each shape were not getting muddled together. The varying index of refraction apparently affected each light shape uniquely, so that different shapes moved at different speeds down the cable," McKee explained.
Doing so allowed the researchers to keep the beams separated, and while they used clockwise and anticlockwise versions of twisted light during this study, they said they have conducted additional research which demonstrates that there are approximately ten different beam shapes which can be used to convey data.
"For several decades since optical fibers were deployed, the conventional assumption has been that OAM-carrying beams are inherently unstable in fibers," Boston University engineering professor Siddharth Ramachandran, who designed the new fiber, told Photonics.com.
"Our discovery of design classes in which they are stable has profound implications for a variety of scientific and technological fields that have exploited the unique properties of OAM-carrying light, including the use of such beams for enhancing data capacity in fibers," he added.