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Optical communication, also known as optical telecommunication, is
communication Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inqui ...
at a distance using
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the
photophone The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 ...
, invented in 1880. An optical communication system uses a
transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
, which encodes a message into an optical signal, a channel, which carries the signal to its destination, and a receiver, which reproduces the message from the received optical signal. When electronic equipment is not employed the 'receiver' is a person visually observing and interpreting a signal, which may be either simple (such as the presence of a beacon fire) or complex (such as lights using color codes or flashed in a
Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one ...
sequence). Modern communication relies on optical networking systems using
optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair Hair is a protein filament that grows ...
, optical amplifiers,
laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...
s, switches, routers, and other related technologies.
Free-space optical communication Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking. "Free space" means air, outer space, vacuum, ...
use lasers to transmit signals in space, while terrestrial forms are naturally limited by geography and weather. This article provides a basic introduction to different forms of optical communication.


Visual forms

Visual techniques such as smoke signals, beacon fires, hydraulic telegraphs, ship flags and
semaphore line An optical telegraph is a line of stations, typically towers, for the purpose of conveying textual information by means of visual signals. There are two main types of such systems; the semaphore telegraph which uses pivoted indicator arms and ...
s were the earliest forms of optical communication.Chapter 2: Semaphore Signalling
Communications: an international history of the formative years R. W. Burns, 2004
Telegraph
Vol 10, Encyclopædia Britannica, 6th Edition, 1824 pp. 645-651
Hydraulic telegraph semaphores date back to the 4th century BCE Greece. Distress flares are still used by mariners in emergencies, while
lighthouse A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses m ...
s and navigation lights are used to communicate navigation hazards. The heliograph uses a
mirror A mirror or looking glass is an object that reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the direction of the im ...
to reflect sunlight to a distant observer.Harris, J.D
Wire At War - Signals communication in the South African War 1899–1902
Retrieved on 1 June 2008. Note a discussion on the heliograph use during the Boer War.
When a signaler tilts the mirror to reflect sunlight, the distant observer sees flashes of light that can be used to transmit a prearranged signaling code. Naval
ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...
s often use signal lamps and
Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one ...
in a similar way. Aircraft pilots often use visual approach slope indicator (VASI) projected light systems to land safely, especially at night. Military aircraft landing on an
aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a ...
use a similar system to land correctly on a carrier deck. The coloured light system communicates the aircraft's height relative to a standard landing glideslope. As well, airport control towers still use Aldis lamps to transmit instructions to aircraft whose radios have failed.


Semaphore line

A 'semaphore telegraph', also called a ' semaphore line', 'optical telegraph', 'shutter telegraph chain', 'Chappe telegraph', or 'Napoleonic semaphore', is a system used for conveying information by means of visual signals, using towers with pivoting arms or shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position.Telegraph
Volume 17 of The Edinburgh encyclopaedia, pp. 664-667, 1832 David Brewster, ed.
Semaphore lines were a precursor of the
electrical telegraph Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems ...
. They were far faster than post riders for conveying a message over long distances, but far more expensive and less private than the electrical telegraph lines which would later replace them. The maximum distance that a pair of semaphore telegraph stations can bridge is limited by geography, weather and the availability of light; thus, in practical use, most optical telegraphs used lines of relay stations to bridge longer distances. Each relay station would also require its complement of skilled operator-observers to convey messages back and forth across the line. The modern design of semaphores was first foreseen by the British
polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific pro ...
Robert Hooke, who first gave a vivid and comprehensive outline of visual telegraphy in a 1684 submission to the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
. His proposal (which was motivated by military concerns following the
Battle of Vienna The Battle of Vienna; pl, odsiecz wiedeńska, lit=Relief of Vienna or ''bitwa pod Wiedniem''; ota, Beç Ḳalʿası Muḥāṣarası, lit=siege of Beç; tr, İkinci Viyana Kuşatması, lit=second siege of Vienna took place at Kahlenberg Mo ...
the preceding year) was not put into practice during his lifetime. The first operational optical semaphore line arrived in 1792, created by the French engineer
Claude Chappe Claude Chappe (; 25 December 1763 – 23 January 1805) was a French inventor who in 1792 demonstrated a practical semaphore system that eventually spanned all of France. His system consisted of a series of towers, each within line of sight of ...
and his brothers, who succeeded in covering
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
with a network of 556 stations stretching a total distance of . It was used for military and national communications until the 1850s. Many national services adopted signaling systems different from the Chappe system. For example, Britain and
Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic countries, Nordic c ...
adopted systems of shuttered panels (in contradiction to the Chappe brothers' contention that angled rods are more visible). In
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = '' Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , ...
, the engineer
Agustín de Betancourt Agustín de Betancourt y Molina ( rus, Августин Августинович де Бетанкур, r=Avgustin Avgustinovich de Betankur; french: Augustin Bétancourt; 1 February 1758 – 24 July 1824) was a prominent Spanish engineer, who wo ...
developed his own system which was adopted by that state. This system was considered by many experts in Europe better than Chappe's, even in France. These systems were popular in the late 18th to early 19th century but could not compete with the
electrical telegraph Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems ...
, and went completely out of service by 1880.


Semaphore signal flags

Semaphore flags are the system for conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags, objects or arms; it is read when they are in a fixed position. Semaphores were adopted and widely used (with hand-held
flag A flag is a piece of fabric (most often rectangular or quadrilateral) with a distinctive design and colours. It is used as a symbol, a signalling device, or for decoration. The term ''flag'' is also used to refer to the graphic design empl ...
s replacing the mechanical arms of shutter semaphores) in the maritime world in the 19th century. They are still used during underway replenishment at sea and are acceptable for emergency communication in daylight or, using lighted wands instead of flags, at night. The newer flag semaphore system uses two short poles with square flags, which a signaler holds in different positions to convey letters of the alphabet and numbers. The transmitter holds one pole in each hand, and extends each arm in one of eight possible directions. Except for in the rest position, the flags cannot overlap. The flags are colored differently based on whether the signals are sent by sea or by land. At sea, the flags are colored red and yellow (the Oscar flags), while on land, they are white and blue (the Papa flags). Flags are not required, they just make the characters more obvious.


Signal lamps

Signal lamps (such as Aldis lamps), are visual signaling devices for optical communication (typically using Morse code). Modern signal lamps are a focused lamp which can produce a pulse of light. In large versions this pulse is achieved by opening and closing shutters mounted in front of the lamp, either via a manually operated pressure switch or, in later versions, automatically. With hand held lamps, a
concave mirror A curved mirror is a mirror with a curved reflecting surface. The surface may be either ''convex'' (bulging outward) or ''concave'' (recessed inward). Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are ...
is tilted by a trigger to focus the light into pulses. The lamps are usually equipped with some form of optical sight, and are most commonly deployed on naval vessels and also used in airport control towers with coded
aviation light signals In the case of a radio failure or aircraft not equipped with a radio, or in the case of a deaf pilot, air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the gro ...
.
Aviation light signals In the case of a radio failure or aircraft not equipped with a radio, or in the case of a deaf pilot, air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the gro ...
are used in the case of a radio failure, an
aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...
not equipped with a radio, or in the case of a hearing-impaired pilot. Air traffic controllers have long used signal light guns to direct such aircraft. The light gun's lamp has a focused bright beam capable of emitting three different colors: red, white and green. These colors may be flashing or steady, and provide different instructions to aircraft in flight or on the ground (for example, "cleared to land" or "cleared for takeoff"). Pilots can acknowledge the instructions by wiggling their plane's wings, moving their ailerons if they are on the ground, or by flashing their landing or navigation lights during night time. Only 12 simple standardized instructions are directed at aircraft using signal light guns as the system is not utilized with
Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one ...
.


Heliograph

A heliograph ( ''
helios In ancient Greek religion and mythology, Helios (; grc, , , Sun; Homeric Greek: ) is the god and personification of the Sun (Solar deity). His name is also Latinized as Helius, and he is often given the epithets Hyperion ("the one above") an ...
'', meaning "sun", and '' graphein'', meaning "write") is a wireless solar
telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas ...
that signals by flashes of
sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when ...
(generally using
Morse code Morse code is a method used in telecommunication to encode text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code is named after Samuel Morse, one ...
) reflected by a
mirror A mirror or looking glass is an object that reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the direction of the im ...
. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter. The heliograph was a simple but effective instrument for instantaneous optical communication over long distances during the late 19th and early 20th century. Its main uses were in military, surveys and forest protection work. They were standard issue in the British and Australian armies until the 1960s, and were used by the Pakistani army as late as 1975.


Electronic forms

In the present day a variety of electronic systems optically transmit and receive information carried by pulses of light.
Fiber-optic communication Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared light through an optical fiber. The light is a form of carrier wave that is modulated to carry information. Fiber is pr ...
cables are employed to carry electronic data and telephone traffic.
Free-space optical communication Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking. "Free space" means air, outer space, vacuum, ...
s are also used every day in various applications.


Optical fiber

Optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair Hair is a protein filament that grows ...
is the most common type of channel for optical communications. The transmitters in optical fiber links are generally
light-emitting diode A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
s (LEDs) or
laser diode The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with ...
s.
Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
light is used more commonly than
visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
, because optical fibers transmit infrared wavelengths with less
attenuation In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at var ...
and
dispersion Dispersion may refer to: Economics and finance *Dispersion (finance), a measure for the statistical distribution of portfolio returns *Price dispersion, a variation in prices across sellers of the same item *Wage dispersion, the amount of variatio ...
. The signal encoding is typically simple
intensity modulation In optical communications, intensity modulation (IM) is a form of modulation in which the optical power output of a source is varied in accordance with some characteristic of the modulating signal. The envelope of the modulated optical signal is ...
, although historically optical phase and
frequency modulation Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing. In analog ...
have been demonstrated in the lab. The need for periodic signal regeneration was largely superseded by the introduction of the
erbium-doped fiber amplifier An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from ...
, which extended link distances at significantly lower cost. The commercial introduction of dense wavelength-division multiplexing (WDM) in 1996 by Ciena Corp was the real start of optical networking. WDM is now the common basis nearly every high-capacity optical system in the world The first optical communication systems were designed and delivered to the U.S. Army and Chevron by Optelecom, Inc., the venture co-founded by Gordon Gould, the inventor of the optical amplifier and the laser.


Photophone

The
photophone The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 ...
(originally given an alternate name,
radiophone A radiotelephone (or radiophone), abbreviated RT, is a radio communication system for conducting a conversation; radiotelephony means telephony by radio. It is in contrast to '' radiotelegraphy'', which is radio transmission of telegrams (mess ...
) is a communication device which allowed for the transmission of speech on a beam of
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
. It was invented jointly by
Alexander Graham Bell Alexander Graham Bell (, born Alexander Bell; March 3, 1847 – August 2, 1922) was a Scottish-born inventor, scientist and engineer who is credited with patenting the first practical telephone. He also co-founded the American Telephone and T ...
and his assistant
Charles Sumner Tainter Charles Sumner Tainter (April 25, 1854 – April 20, 1940) was an American scientific instrument maker, engineer and inventor, best known for his collaborations with Alexander Graham Bell, Chichester Bell, Alexander's father-in-law Gardiner Hubba ...
on February 19, 1880, at Bell's 1325 'L' Street laboratory in Washington, D.C.Jones, Newell
First 'Radio' Built by San Diego Resident Partner of Inventor of Telephone: Keeps Notebook of Experiences With Bell
, San Diego Evening Tribune, July 31, 1937. Retrieved from the University of San Diego History Department website, November 26, 2009.
Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell. On June 21, 1880, Bell's assistant transmitted a wireless voice telephone message of considerable distance, from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters (about 700 ft) away.Carson 2007, pg. 76-78Groth, Mike
Photophones Revisted
'Amateur Radio' magazine,
Wireless Institute of Australia The Wireless Institute of Australia (WIA) was formed in 1910, and is the first and oldest national amateur radio society in the world. It represents the amateur radio operators of Australia as the AR "peak body" in dealings with the Australia ...
, Melbourne, April 1987 pp. 12–17 and May 1987 pp. 13–17.
Mims 1982, p. 11. Bell believed the photophone was his most important
invention An invention is a unique or novel device, method, composition, idea or process. An invention may be an improvement upon a machine, product, or process for increasing efficiency or lowering cost. It may also be an entirely new concept. If an ...
. Of the 18
patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...
s granted in Bell's name alone, and the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his'' 'greatest achievement, telling a reporter shortly before his death that the photophone was ''"the greatest invention haveever made, greater than the telephone"''.Mims 1982, p. 14. The photophone was a precursor to the
fiber-optic communication Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared light through an optical fiber. The light is a form of carrier wave that is modulated to carry information. Fiber is pr ...
systems which achieved popular worldwide usage starting in the 1980s.Morgan, Tim J. "The Fiber Optic Backbone", University of North Texas, 2011.Miller, Stewart E. "Lightwaves and Telecommunication", '' American Scientist'', Sigma Xi, The Scientific Research Society, January–February 1984, Vol. 72, No. 1, pp. 66-71
Issue Stable URL
Gallardo, Arturo; Mims III, Forrest M.br>Fiber-optic Communication Began 130 Years Ago
''
San Antonio Express-News The ''San Antonio Express-News'' is a daily newspaper in San Antonio, Texas. It is owned by the Hearst Corporation and has offices in San Antonio and Austin, Texas. The ''Express-News'' is the third largest newspaper in the state of Texas, with ...
'', June 21, 2010. Accessed January 1, 2013.
The master patent for the photophone ( ''Apparatus for Signalling and Communicating, called Photophone''), was issued in December 1880, many decades before its principles came to have practical applications.


Free-space optical communication

Free-space optics (FSO) systems are employed for ' last mile'
telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that ...
s and can function over distances of several kilometers as long as there is a clear line of sight between the source and the destination, and the optical receiver can reliably decode the transmitted information. Other free-space systems can provide high-data-rate, long-range links using small, low-mass, low-power-consumption subsystems which make them suitable for communications in space. Various planned
satellite constellation A satellite constellation is a group of artificial satellites working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global coverage, such that at any time everywhere on Earth at least one s ...
s intended to provide global broadband coverage take advantage of these benefits and employ
laser communication Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking. "Free space" means air, outer space, vacuum, or ...
for inter-satellite links between the several hundred to thousand satellites effectively creating a space-based optical mesh network. More generally, transmission of unguided optical signals is known as
optical wireless communications Optical wireless communications (OWC) is a form of optical communication in which unguided visible, infrared (IR), or ultraviolet (UV) light is used to carry a signal. It is generally used in short-range communication. OWC systems operating in th ...
(OWC). Examples include medium-range visible light communication and short-distance
IrDA The Infrared Data Association (IrDA) is an industry-driven interest group that was founded in 1994 by around 50 companies. IrDA provides specifications for a complete set of protocols for wireless infrared communications, and the name "IrDA" also ...
, using infrared LEDs.


See also

* Fiber tapping *
Interconnect bottleneck The interconnect bottleneck comprises limits on integrated circuit (IC) performance due to connections between components instead of their internal speed. In 2006 it was predicted to be a "looming crisis" by 2010. Improved performance of computer ...
* Jun-Ichi Nishizawa an inventor of optical communication. * Modulating retro-reflector *
OECC The OECC, established in 1996, is an annual conference which publishes proceedings and scientific research articles as a result of its conferences. ''OECC'' stands for the OptoElectronics and Communications Conference, which has conducted annual mee ...
(OptoElectronics and Communications Conference) *
Optical interconnect In integrated circuits, optical interconnects refers to any system of transmitting signals from one part of an integrated circuit to another using light. Optical interconnects have been the topic of study due to the high latency and power consumpt ...
*
Opto-isolator An opto-isolator (also called an optocoupler, photocoupler, or optical isolator) is an electronic component that transfers electrical signals between two isolated circuits by using light. Opto-isolators prevent high voltages from affecting the ...
*
Parallel optical interface A parallel optical interface is a form of fiber optic technology aimed primarily at communications and networking over relatively short distances (less than 300 meters), and at high bandwidths. Parallel optic interfaces differ from traditional fi ...


References


Citations


Bibliography

* Alwayn, Vivek
Fiber-Optic Technologies
Cisco Press, Apr 23, 2004. * Bruce, Robert V ''Bell: Alexander Bell and the Conquest of Solitude'', Ithaca, New York:
Cornell University Press The Cornell University Press is the university press of Cornell University; currently housed in Sage House, the former residence of Henry William Sage. It was first established in 1869, making it the first university publishing enterprise in ...
, 1990. . * * Mims III, Forest M
The First Century of Lightwave Communications
''Fiber Optics Weekly Update'', Information Gatekeepers, February 10–26, 1982, pp. 6–23. * Paschotta, Rüdiger

RP-Photonics.com website, 2012.


Further reading

* Bayvel, Polinabr>Future High-Capacity Optical Telecommunication Networks
''Philosophical Transactions: Mathematical, Physical and Engineering Sciences'', Vol. 358, No. 1765, January 2000, Science into the Next Millennium: Young Scientists Give Their Visions of the Future: II. Mathematics, Physics and Engineering, pp. 303–329, stable article URL: https://www.jstor.org/stable/2666790, published by The Royal Society. * Dilhac, J-M
The Telegraph of Claude Chappe -An Optical Telecommunication Network For The XVIII Century
Toulouse: Institut National des Sciences Appliquées de Toulouse. Retrieved from IEEE Global History Network. {{Authority control Telecommunications