Optical communication is any form of telecommunication that uses light as the transmission medium. Telecommunication is the transmission of signals over a distance for the purpose of communication. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength. ...

An optical communication system consists of a transmitter, 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. Antenna tower of Crystal Palace transmitter, London A transmitter (sometimes abbreviated XMTR) is an electronic device which with the aid of an antenna propagates an electromagnetic signal such as radio, television, or other telecommunications. ... In information theory, a signal is the sequence of states of a communications channel that encodes a message. ... Channel, in communications (sometimes called communications channel), refers to the medium through which information is transmitted from a sender (or transmitter) to a receiver. ...

Forms of optical communication

There are many forms of non-technological optical communication, including body language and sign language. This article is in need of attention from an expert on the subject. ... A sign language (also signed language) is a language which uses manual communication instead of sound to convey meaning - simultaneously combining handshapes, orientation and movement of the hands, arms or body, and facial expressions to fluidly express a speakers thoughts. ...

Techniques such as semaphore, ship flags, smoke signals, and beacons; fires were the earliest form of technological optical communication. A Chappe semaphore tower near Saverne, France // The semaphore or optical telegraph is an apparatus for conveying information by means of visual signals, with towers with pivoting blades or paddles, shutters, in a matrix, or hand-held flags etc. ... The system of international maritime signal flags is a way of representing individual letters of the alphabet on ships or in nautical situations. ... Smoke signals is an early form of the optical telegraph, developed by the Native Americans and in China. ... This page discusses Beacons, fires designed to attract attention. ...

The heliograph uses a mirror to reflect sunlight to a distant observer. By moving the mirror the distant observer sees flashes of light that can be used to send a prearranged signaling code. Navy ships often use a signal lamp to signal in Morse code in a similar way. Signaling with heliograph, 1910 A heliograph uses a mirror to reflect sunlight to a distant observer. ... A mirror is a surface with good specular reflection that is smooth enough to form an image. ... Spheres reflecting the floor and each other. ... The multinational Combined Task Force One Five Zero (CTF-150) The British Grand Fleet, the supreme naval force of WW1 A rare occurrence of a 5-country multinational fleet, during Operation Enduring Freedom in the Oman Sea. ... Italian ship-rigged vessel Amerigo Vespucci in New York Harbor, 1976 A ship is a large, sea-going watercraft, usually with multiple decks. ... Signal lamp, also called Aldis lamp, is a visual signaling device for optical communication (typically using Morse code) – essentially a focussed lamp which can produce a pulse of light. ... 1922 Chart of the Morse Code Letters and Numerals Morse code is a method for transmitting information, using standardized sequences of short and long marks or pulses — commonly known as dots and dashes — for the letters, numerals and special characters of a message. ...

Distress flares are used by mariners in emergencies, while lighthouses and navigation lights are used to communicate navigation hazards. An Orion-brand single shot, breech loaded, 12 gauge flare gun. ... Look up Emergency in Wiktionary, the free dictionary An emergency is a situation that poses an immediate threat to human life or serious damage to property. ... The Peggys Point lighthouse in Nova Scotia, Canada An aid for navigation and pilotage at sea, a lighthouse is a tower building or framework sending out light from a system of lamps and lenses or, in older times, from a fire. ... A Navigation Light is a colored source of specular illumination (a point source) on an aircraft, water-borne vessel, or land vehicle. ...

Aircraft use the landing lights at airports to land safely, especially at night. Aircraft landing on an aircraft carrier use a similar system to land correctly on the carrier deck. The light systems communicate the correct position of the aircraft relative to the best landing glideslope. Airbus A380 An aircraft is any machine capable of atmospheric flight. ... An aircraft carrier is a warship designed to deploy and recover aircraft—in effect acting as a sea-going airbase. ... Glideslope is the word used for the final approach segment of an Instrument Approach by an airpline, by means of ILS (Instrument Landing System) or MLS (Microwave Landing System). ...

Optical fiber is the most common medium for modern digital optical communication. Optical fibers An optical fiber or fibre is a thin, transparent fiber, usually made of glass or plastic, for transmitting light. ...

Free-space optical communication is also used today in a variety of applications. Free-space optical communication involves the use of optical links across the space between two points, either within the Earths atmosphere, or in outer space. ...

Optical fiber communication

Optical fiber is the most common type of channel for optical communications, however other types of optical waveguides are used within communications gear, and have even formed the channel of very short distance (e.g. chip-to-chip) links in laboratory trials. The transmitters in optical fiber links are generally light-emitting diodes (LEDs) or laser diodes. Infrared light, rather than visible light is used more commonly, because optical fibers transmit infrared wavelengths with less attenuation and dispersion. The signal encoding is typically simple intensity modulation, although historically optical phase and frequency modulation have been demonstrated in the lab. These coherent optical transmission schemes were largely superseded by the introduction of the erbium-doped fiber amplifier, which extended link distances at lower cost. Optical fibers An optical fiber or fibre is a thin, transparent fiber, usually made of glass or plastic, for transmitting light. ... Look up waveguide in Wiktionary, the free dictionary. ... Blue, green and red LEDs. ... A packaged laser diode with penny for scale. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... Attenuation is the decrease of the amount, force, magnitude, or value of something. ... Dispersion can mean any of several things: A phenomenon that causes the separation of a wave into components of varying frequency. ... Intensity modulation (IM): In optical communications, a form of modulation in which the optical power output of a source is varied in accordance with some characteristic of the modulating signal. ... In telecommunication, an optical amplifier is a device that amplifies an optical signal directly, without the need to convert it to an electrical signal, or amplify it electrically, and reconvert it to an optical signal. ...

LEDs are generally restricted to low data rates, up to about 100 Megabits per second (Mb/s). Lasers are used for higher data rates. These devices are often directly modulated, that is the light output is controlled by a current applied directly to the device. For very high data rates or very long distance links, a laser source may be operated continuous wave, and the light modulated by an external device such as an electroabsorption modulator or Mach-Zehnder interferometer. External modulation increases the achievable link distance by eliminating laser chirp, which broadens the linewidth of directly-modulated lasers, increasing the chromatic dispersion in the fiber. Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information. ... A continuous wave (CW) is an electromagnetic wave of constant amplitude and frequency. ... The Mach-Zehnder interferometer is used to determine the phase shift caused by a small sample which is to be placed into one of the two beams D and U, respectively, from a coherent light source. ... A chirp is a signal in which the frequency increases (up-chirp) or decreases (down-chirp) with time. ... The Q factor or quality factor is a measure of the quality of a resonant system. ... The chromatic dispersion of an optical medium is basically the frequency dependence of the phase velocity and group velocity of light propagating in a medium. ...

Receivers used in fiber links use p-i-n diodes, avalanche photodiodes, or other semiconductor devices as the optical-electrical converter. The optical-electrical converters is typically coupled with a transimpedance amplifier and limiting amplifier to produce a digital signal in the electrical domain from the incoming optical signal, which may be attenuated and distorted by passing through the channel. Further signal processing such as clock recovery from data (CDR) by a phase-locked loop may also be applied before the data is passed on. A PIN diode (p-type, intrinsic, n-type diode) is a photodiode with a wide, undoped intrinsic semiconductor region between p-type semiconductor and n-type semiconductor regions. ... Avalanche photodiodes (APDs) are photodetectors that can be regarded as the semiconductor analog to photomultipliers. ... A transimpedance amplifier is a method used to speed up the response time of a current to voltage converter, while keeping the gain of the amplifier high. ... In electronics, a phase-locked loop (PLL) is a closed-loop feedback control system that maintains a generated signal in a fixed phase relationship to a reference signal. ...

To increase the link distance, early optical fiber links contained repeaters, which were essentially back-to-back receivers and transmitters that converted the signal from the optical to electrical domain and back to an optical signal again and essentially broke a long link into many short ones. Since its invention, however, the erbium-doped fiber amplifier (EDFA), has replaced the repeater in most telecommunication links.

By using different light wavelengths (or colors) multiple communications can be sent optically, in what is known as wavelength division multiplexing (WDM). This requires a wavelength division multiplexer in the transmitting equipment and a wavelength division demultiplexer (essentially a spectrometer) in the receiving equipment. Arrayed waveguide gratings are commonly used for multiplexing and demultiplexing in WDM. In telecommunications wavelength division multiplexing (WDM) is a technology which multiplexes several optical carrier signals on a single optical fibre by using different wavelengths (colours) of laser light to carry different signals. ... A multiplexer combines more than one input into a single output. ... // Headline text Bold text:For Acoustic uses in spectrographs of sound waves, see below. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ...

Free-space optical communication

IrDA is an example of low-data-rate, short distance free-space optical communications using LEDs. RONJA is an example of 10Mbit/s 1.4 km full-duplex optical point-to-point link. The Infrared Data Association (IrDA) defines physical specifications communications protocol standards for the short range exchange of data over infrared light, for uses such as personal area networks (PANs). ... RONJA (Reasonable Optical Near Joint Access) is an Free Technology (like Free Software) project of optical point-to-point data link (Free Space Optics). ... A megabit per second (mbps or mbit/s) is a unit of data transmission equal to 1,000 kilobits per second or 1,000,000 bits per second. ...

See also

• Laser
• Optical telegraph
• Telegraph
• Jun-Ichi Nishizawa an inventor of optical communication.

Lasers range in size from microscopic diode lasers (top) with numerous applications, to football field sized neodymium glass lasers (bottom) used for inertial confinement fusion, nuclear weapons research and other high energy density physics experiments. ... The optical telegraph preceded the electrical telegraph. ... Telegraphy (from the Greek words tele = far away and grapho = write) is the long distance transmission of written messages without physical transport of letters, originally over wire. ... Jun-Ichi Nishizawa(西澤潤一, born September 12, 1926 in Sendai, Japan) is a Japanese engineer known for his invention of optical communication systems (including optical fiber,laser diode etc. ...

References