Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Innovative technique for shaping light could solve bandwidth crunch

20.10.2016

Researchers encode more than 100 channels of information in laser light; approach could greatly increase capacity of optical communications networks

As data demands continue to grow, scientists predict that it's only a matter of time before today's telecommunication networks reach capacity unless new technologies are developed for transporting data. A new technique could help avert this bandwidth crunch by allowing light-based optical networks to carry more than one hundred times more data than is possible with current technologies.


Researchers used more than 100 spatial modes of light to transmit an image pixel by pixel over a lab-based free-space optical network

Credit: Carmelo Rosales-Guzmán, University of Witwatersrand

Laser light comes in many different shapes, or spatial modes. However, today's optical networks use just one spatial mode to carry information, limiting the amount of data that can be transmitted at one time. Researchers led by Andrew Forbes, a professor at the University of Witwatersrand, South Africa, developed a technique known as spatial multiplexing that reshapes a laser beam into many spatial modes that can each carry information.

In a paper presented at the OSA Laser Congress in Boston, the researchers demonstrate optical communication with more than 100 spatial modes by combining their new spatial multiplexing approach with wavelength division multiplexing (WDM), which uses different wavelengths of light to carry information.

"We created 35 spatial modes encoded in three different wavelengths, producing 105 total modes," said Carmelo Rosales-Guzmán, research fellow and first author of the paper. "Our new method might serve as the basis for future communication technologies."

The researchers demonstrated that their technique can transmit data with 98 percent efficiency in a laboratory free-space optical network, which uses light to transmit information over the air. The scientists say the approach should also work in optical fibers, the basis for fiber-optic communications.

Increasing bandwidth with more light modes

The new technique makes use of light with an orbital angular momentum, which gives it a twisted, or helical, shape. Different spatial modes can be created by varying the number of twists, known as the azimuthal degrees of freedom. While other scientists have been exploring the use of azimuthal degrees of freedom for increasing bandwidth, recent research showed that even though, in theory, the set of modes with orbital angular momentum is infinite, in practice there aren't enough modes available to make significant improvements.

Forbes' team solved this problem by using the azimuthal degrees of freedom plus another variable known as a radial degree of freedom. Each azimuthal degree of freedom can have, in theory, an infinite amount of radial degrees of freedom, but there are practical limitations that restrict this number. Because all the modes are orthogonal to each other, the signals don't get mixed up as they travel and can be separated upon arrival at their destination. The researchers say that this is the first time two spatial degrees of freedom have been used to optically encode information.

Key to this new approach is an optical device known as a spatial light modulator. The researchers used one spatial light modulator to shape the laser light into the various modes and another to reverse the process on the receiving end.

"One of the advantages of our approach is that we only need a single detector to demultiplex all the spatial modes to recover all the information," said Rosales-Guzmán. "This is faster than other approaches for increasing bandwidth that need multiple detectors."

Sending pictures pixel by pixel

To test the new technique, the researchers used it to encode a grayscale and color image. Each image was sent across a communication link pixel by pixel and then each pixel was recovered to reconstruct the image. For the grayscale image, each gray level was linked to a separate spatial mode, allowing transmission of 105 gray levels.

"In this demonstration, sending a 10,000-pixel image took 5 to 7 minutes," said Rosales-Guzmán. "However we could increase that speed by sending two or four pixels at the same time or by using many more wavelengths."

Real-world free-space optical networks -- which can transfer information between buildings, for example -- come with many challenges that aren't present in the lab. As a next step, the researchers are partnering with experts in free-space communication to adapt their technique for practical applications.

"We are working with a company in South Africa that already makes a device that has the ability to use different spatial modes for free space communication," said Rosales-Guzmán. "We are interested in trying to increase the bandwidth of their device to four times what it is capable of now."

###

About the Presentation

Angela Dudley, an honorary academic at the University of Witwatersrand and a visiting scholar in Andrew Forbes' lab, will present "Free-space communication with over 100 spatial modes" during the Free Space Optical Communications I session of the Application of Lasers for Sensing & Free Space Communication Conference on Thursday, Nov. 3 from 9:15 to 9:30 a.m. in Room 1 of The Westin Boston Waterfront.

MEDIA REGISTRATION: Media/analyst registration for OSA Laser Congress 2016 can be arranged by emailing mediarelations@osa.org. Please visit the event website at OSA Laser Congress for additional information, including travel arrangement details.

About OSA Laser Congress

The OSA Laser Congress will be held 30 October - 03 November at the Westin Boston Waterfront in Boston, Massachusetts, USA. The Congress features the latest advances in solid state laser development and related technologies for free space laser communication, laser-based sensing, and numerous industrial applications. It provides attendees with a comprehensive view of the latest technological advances as well as applications of laser technologies for industrial products and markets. In 2016, the Congress offers three collocated meetings: Advanced Solid State Lasers Conference (ASSL), Application of Lasers for Sensing & Free Space Communication (LS&C) and Laser Applications Conference (LAC) along with the Executive Forum.

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and entrepreneurs who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit osa.org/100.

Media Contact

Rebecca Andersen
RAndersen@osa.org
202-321-5488

 @opticalsociety

http://www.osa.org 

Rebecca Andersen | EurekAlert!

More articles from Physics and Astronomy:

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

nachricht Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Behavior-influencing policies are critical for mass market success of low carbon vehicles

17.07.2018 | Power and Electrical Engineering

Plant mothers talk to their embryos via the hormone auxin

17.07.2018 | Life Sciences

Subaru Telescope helps pinpoint origin of ultra-high energy neutrino

16.07.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>