Featured Research

from universities, journals, and other organizations

Multi-rate Laser Pulses Could Boost Outdoor Optical Wireless Performance

Date:
October 27, 2004
Source:
Penn State
Summary:
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.

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.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Multi-rate Laser Pulses Could Boost Outdoor Optical Wireless Performance." ScienceDaily. ScienceDaily, 27 October 2004. <www.sciencedaily.com/releases/2004/10/041027102152.htm>.
Penn State. (2004, October 27). Multi-rate Laser Pulses Could Boost Outdoor Optical Wireless Performance. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2004/10/041027102152.htm
Penn State. "Multi-rate Laser Pulses Could Boost Outdoor Optical Wireless Performance." ScienceDaily. www.sciencedaily.com/releases/2004/10/041027102152.htm (accessed July 22, 2014).

Share This




More Matter & Energy News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins