Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Multi-rate laser pulses could boost outdoor optical wireless performance

27.10.2004


Multi-rate, ultra-short laser pulses -- with wave forms shaped like dolphin chirps -- offer a new approach to help optical wireless signals penetrate clouds, fog and other adverse weather conditions, say Penn State engineers.



The new approach could help bring optical bandwidth, capable of carrying huge amounts of information, to applications ranging from wireless communication between air and ground vehicles on the battlefield to short links between college campus buildings to metropolitan area networks that connect all the buildings in a city.

Dr. Mohsen Kavehrad, the W. L. Weiss professor of electrical engineering and director of the Center for Information and Communications Technology Research, leads the study. He says, "The multi-rate approach offers many advantages. For example, lower rate signals can get through clouds or fog when high rate signals can’t. By sending the same message at several different rates, one of them can probably get through."


Rather than slowing communication down, the multi-rate approach has been shown in tests to achieve an average bit rate higher than conventional optical wireless links operating at 2.5 Gbps as well as providing an increased level of communication reliability by maintaining a minimum of one active link throughout channel conditions, he adds.

Kavehrad outlined his team’s new approach at the Optics East 2004 Conference in Philadelphia, Oct. 27, in a paper, "Ultra-short Pulsed FSO Communications System with Wavelet Fractal Modulation." He will also describe the system at the IEEE MILCOM conference in Monterey, California, on Nov. 1. His co-author is Belal Hamzeh, doctoral candidate in electrical engineering.

In optical wireless systems, also known as free-space optics (FSO), voice, video and/or data information is carried on line-of-sight, point-to-point laser beams. Outdoor FSO systems have been in use for over 30 years but are hampered by weather and other obstructions that prevent the transmitter and receiver from "seeing" each other.

Kavehrad explains that clouds and fog often clear abruptly providing brief windows for transmission, making pulsed delivery better suited to FSO. The new Penn State approach embeds data in ultra-short pulses of laser light, shaped via fractal modulation as wavelets, and then transmits the wavelets at various rates.

Belal says the wavelets are easy to generate. "We use holography to generate and separate the wavelets. You just generate the mother wavelet and then the others can be generated as a fraction of the transmission bit rate of the mother. They can all co-exist in the channel without interference," he notes.

The wavelets used by the Penn State team are Meyer’s Type which look like dolphin chirps. The wavelets minimize bandwidth waste and the ultra-short pulses are less likely to interact with rain or fog that could degrade the signal.

The researchers note that their proposed system ensures on-the-fly operation without the need for significant electronic processing. The project is supported by the Air Force Research Laboratory.

Barbara Hale | EurekAlert!
Further information:
http://www.psu.edu

More articles from Information Technology:

nachricht Fingerprints of quantum entanglement
16.02.2018 | University of Vienna

nachricht Simple in the Cloud: The digitalization of brownfield systems made easy
07.02.2018 | Deutsches Forschungszentrum für Künstliche Intelligenz GmbH, DFKI

All articles from Information Technology >>>

The most recent press releases about innovation >>>

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

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>