Optical wireless communications

{{Short description|Use of visible, IR, or UV light to transmit a signal}}

Optical wireless communications (OWC) is a form of optical communication in which unguided light is used "in the air" (or in outer space), without an optical fiber. Visible, infrared (IR), or ultraviolet (UV) light is used to carry a wireless signal. It is generally used in short-range communication; extensions exist for long-range and ultra-long range.

OWC systems operating in the visible band (390–750 nm) are commonly referred to as visible light communication (VLC). VLC systems take advantage of light-emitting diodes (LEDs) which can be pulsed at very high speeds without a noticeable effect on the lighting output and human eye. VLC can be possibly used in a wide range of applications including wireless local area networks, wireless personal area networks and vehicular networks, among others.[https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6876267&isnumber=6876260 M. Uysal and H. Nouri, "Optical Wireless Communications – An Emerging Technology", 16th International Conference on Transparent Optical Networks (ICTON), Graz, Austria, July 2014] On the other hand, terrestrial point-to-point OWC systems, also known as the free space optical (FSO) systems,{{cite journal | doi = 10.1109/COMST.2014.2329501 | volume=16 | issue=4 | title=Survey on Free Space Optical Communication: A Communication Theory Perspective | year=2014 | journal=IEEE Communications Surveys & Tutorials | pages=2231–2258 | last1 = Ali Khalighi | first1 = Mohammad | last2 = Uysal | first2 = Murat| s2cid=3141460 | doi-access=free }} operate at the near IR frequencies (750–1600 nm). These systems typically use laser transmitters and offer a cost-effective protocol-transparent link with high data rates, i.e., 10 Gbit/s per wavelength, and provide a potential solution for the backhaul bottleneck.

There has also been a growing interest in ultraviolet communication (UVC) as a result of recent progress in solid-state optical sources/detectors operating within solar-blind UV spectrum (200–280 nm). In this so-called deep UV band, solar radiation is negligible at the ground level and this makes possible the design of photon-counting detectors with wide field-of-view receivers that increase the received energy with little additional background noise. Such designs are particularly useful for outdoor non-line-of-sight configurations to support low-power short-range UVC such as in wireless sensors and ad-hoc networks.

History

Wireless communications technologies proliferated and became essential very quickly during the last few decades of the 20th century, and the early 21st century. The wide-scale deployment of radio-frequency technologies was a key factor in the expansion of wireless devices and systems. However, the portion of the electromagnetic spectrum used by wireless systems is limited in capacity, and licenses to use parts of the spectrum are expensive. With the rise in data-heavy wireless communications, the demand for RF spectrum is outstripping supply, causing companies to consider options for using parts of the electromagnetic spectrum other than radio frequencies.

Optical wireless communication (OWC) refers to transmission in unguided propagation media through the use of optical carriers: visible, infrared (IR), and ultraviolet (UV) radiation. Signalling through beacon fires, smoke, ship flags and semaphore telegraph can be considered the historical forms of OWC.A. A. Huurdeman, The Worldwide History of Telecommunications, Wiley Interscience, 2003. Sunlight has also been used for long-distance signaling since very early times. The earliest use of sunlight for communication purposes is attributed to ancient Greeks and Romans who used polished shields to send signals by reflecting sunlight during battles.G. J. Holzmann and B. Pehrson, The Early History of Data Networks (Perspectives), Wiley, 1994.

In 1810, Carl Friedrich Gauss invented the heliograph which uses a pair of mirrors to direct a controlled beam of sunlight to a distant station. Although the original heliograph was designed for the geodetic survey, it was used extensively for military purposes during the late 19th and early 20th century. In 1880, Alexander Graham Bell invented the photophone, the world’s first wireless telephone system.

Military interest in photophones continued after Bell's time. For example, in 1935, the German Army developed a photophone where a tungsten filament lamp with an IR transmitting filter was used as a light source. Also, American and German military laboratories continued the development of high-pressure arc lamps for optical communication until the 1950s.M. Groth, "[http://www.bluehaze.com.au/modlight/GrothArticle1.htm Photophones revisited]". Modern OWC uses either lasers or light-emitting diodes (LEDs) as transmitters. In 1962, MIT Lincoln Labs built an experimental OWC link using a light-emitting GaAs diode and was able to transmit TV signals over a distance of 30 miles. After the invention of the laser, OWC was envisioned to be the main deployment area for lasers and many trials were conducted using different types of lasers and modulation schemes.E. Goodwin, "[https://ieeexplore.ieee.org/abstract/document/1449928/ A review of operational laser communication systems]," Proceedings of the IEEE, vol. 58, no. 10, pp. 1746–1752, Oct. 1970. However, the results were in general disappointing due to the large divergence of laser beams and the inability to cope with atmospheric effects. With the development of low-loss fiber optics in the 1970s, they became the obvious choice for long distance optical transmission and shifted the focus away from OWC systems.

Current status

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Over the decades, interest in OWC was mainly limited to covert military applications,D. L. Begley, "[https://ieeexplore.ieee.org/abstract/document/1159343/ Free-space laser communications: a historical perspective]," Annual Meeting of the IEEE, Lasers and Electro-Optics Society (LEOS), vol. 2, pp. 391–392, Nov. 2002, Glasgow, Scotland. and space applications including inter-satellite and deep-space links.H. Hemmati, Deep Space Optical Communications, Wiley-Interscience, 2006 OWC’s mass market penetration has been so far limited with the exception of IrDA which is a highly successful wireless short-range transmission solution.{{Update inline|reason=Is this still true?|?=yes|date=September 2018}}

Applications

Variations of OWC can be potentially employed in a diverse range of communication applications ranging from optical interconnects within integrated circuits through outdoor inter-building links to satellite communications.

OWC can be divided into five categories based on the transmission range:

  1. Ultra-short range: chip-to-chip communications in stacked and closely packed multi-chip packages.{{cite journal |first1=Christoforos |last1=Kachris |first2=Ioannis |last2=Tomkos |title=A survey on optical interconnects for data centers |journal=IEEE Communications Surveys & Tutorials |volume=14 |issue=4 |pages=1021–1036 |date=Oct 2012 |doi=10.1109/SURV.2011.122111.00069|s2cid=1771021 }}
  2. Short range: wireless body area network (WBAN) and wireless personal area network (WPAN) applications under standard IEEE 802.15.7, underwater communications.{{cite journal |last1=Bhowal |first1=A. |last2=Kshetrimayum |first2=R.S. |title= Performance Analysis of One-way and Two-way relay for Underwater Optical Wireless Communications |journal= OSA Continuum |date=2018 |volume=1 |issue=4 |pages=1400–1413 |doi=10.1364/OSAC.1.001400|doi-access=free }}{{cite journal |first1=F. |last1=Hanson |first2=S. |last2=Radic |title=High bandwidth underwater optical communication |journal=Applied Optics |volume=47 |issue=2 |pages=277–83 |date=Jan 2008 |doi=10.1364/AO.47.000277|pmid=18188210 |bibcode=2008ApOpt..47..277H }}
  3. Medium range: indoor IR and visible light communications (VLC) for wireless local area networks (WLANs) and inter-vehicular and vehicle-to-infrastructure communications.
  4. Long range: inter-building connections, also called free-space optical communications (FSO).
  5. Ultra-long range: Laser communication in space especially for inter-satellite links and establishment of satellite constellations.

References

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Further reading

  • {{cite journal |url= http://www.osa-opn.org/opn/media/Images/PDF/2014/0314/34-41_Daukantas-Mar14.pdf?ext=.pdf |title= Optical Wireless Communications: The New Hot Spot |date= March 2014 |journal= Optics and Photonics News |first= Patricia |last= Daukantas |volume= 25 |issue= 3 |pages= 34–41 |doi= 10.1364/OPN.25.3.000034 |bibcode= 2014OptPN..25...34D }}
  • {{cite book |display-editors= 1 |editor1-last= Arnon |editor1-first= Shlomi |editor2-first= John |editor2-last= Barry |editor3-first= George |editor3-last= Karagiannidis |editor4-first= Robert |editor4-last= Schober |editor5-first= Murat |editor5-last= Uysal |doi= 10.1017/CBO9780511979187 |isbn= 9780511979187 |title= Advanced Optical Wireless Communication Systems |edition= 1st |location= Cambridge |publisher= Cambridge University Press |date= 2012 }}
  • {{cite book |first1= Z. |last1= Ghassemlooy |first2= W. |last2= Popoola |first3= S. |last3= Rajbhandari |date= 2012 |url= http://www.crcpress.com/product/isbn/9781439851883 |isbn= 9781439851883 |title= Optical Wireless Communications: System and Channel Modelling with MATLAB |edition= 1st |publisher= CRC Press, Inc. |location= Boca Raton, FL }}

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Category:Optical communications

Category:Wireless communication systems