Breakthrough in wireless communications
Communication signals, including high-definition video broadcast, could soon be wirelessly transmitted via a device that converts ultra fast laser pulses into bursts of radio-frequency signals. Researchers at Purdue University, Indiana, USA say the miniature device uses “microring resonators” to allow all communications to be transmitted from a single base station. The team claims the development has the potential to make wires obsolete for communications within offices.
"Of course, ideas about specific uses of our technology are futuristic and speculative, but we envision a single base station and everything else would be wireless," Minghao Qi, an assistant professor of electrical and computer engineering, said. "This base station would be sort of a computer by itself, perhaps a card inserted into one of the expansion slots in a central computer. The central computer would take charge of all the information processing, a single point of contact that interacts with the external world in receiving and sending information."
Ordinarily, the continuous waves of conventional radio-frequency transmissions encounter interference from stray signals reflecting off of the walls and objects inside a house or office. However, the pulsing nature of the signals produced by the new "chip-based spectral shaper" reduces the interference that normally plagues radio frequency communications, said Andrew Weiner, Purdue's Scifres Family Distinguished Professor of Electrical and Computer Engineering.
Each laser pulse lasts about 100 femtoseconds, or one-tenth of a trillionth of a second. These pulses are processed using "optical arbitrary waveform technology" pioneered by Purdue researchers led by Weiner.
Findings have appeared online in the journal Nature Photonics and were published in the February print issue of the magazine. The research is based at Purdue's Birck Nanotechnology Center in the university's Discovery Park.
"What enables this technology is that our devices generate ultrabroad bandwidth radio frequencies needed to transmit the high data rates required for high resolution displays," Weiner said.
Such a technology might eventually be developed to both receive and transmit signals.
"But initially, industry will commercialise devices that only receive signals, for 'one-way' traffic, such as television sets, projectors, monitors and printers," Qi said. "This is because the sending unit for transmitting data is currently still a little bulky. Later, if the sending unit can be integrated into the devices, we could enjoy full two-way traffic."
The researchers first create laser pulses with specific "shapes" that characterise the changing intensity of light from the beginning to end of each pulse. The pulses are then converted into radio frequency signals.
A key factor making the advance potentially useful is that the pulses transmit radio frequencies of up to 60 gigahertz, a frequency included in the window of the radio spectrum not reserved for military communications.
The Federal Communications Commission does not require a license to transmit signals from 57-64 gigahertz. This unlicensed band also is permitted globally, meaning systems using 60 gigahertz could be compatible worldwide.
"There is only a very limited window for civil operations, and 60 gigahertz falls within this window," Qi said.
Purdue filed a provisional patent in January for the technology, which is at least five years away from being ready for commercialisation, Qi said.