1.
Single-mode optical fiber
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In fiber-optic communication, a single-mode optical fiber is an optical fiber designed to carry light only directly down the fiber - the transverse mode. Modes are the solutions of the Helmholtz equation for waves, which is obtained by combining Maxwells equations. These modes define the way the wave travels through space, i. e. how the wave is distributed in space, waves can have the same mode but have different frequencies. Although the ray travels parallel to the length of the fiber, the 2009 Nobel Prize in Physics was awarded to Charles K. Kao for his theoretical work on the single-mode optical fiber. In September 1970, they announced they had made single-mode fibers with attenuation at the 633-nanometer helium-neon line below 20 dB/km, professor Huang Hongjia of the Chinese Academy of Sciences, developed coupling wave theory in the field of microwave theory. He led a team that successfully developed Single-mode optical fiber in 1980. Like multi-mode optical fibers, single mode fibers do exhibit modal dispersion resulting from multiple spatial modes, Single mode fibers are therefore better at retaining the fidelity of each light pulse over longer distances than multi-mode fibers. For these reasons, single-mode fibers can have a higher bandwidth than multi-mode fibers, equipment for single mode fiber is more expensive than equipment for multi-mode optical fiber, but the single mode fiber itself is usually cheaper in bulk. A typical single mode optical fiber has a diameter between 8 and 10.5 µm and a cladding diameter of 125 µm. Data rates are limited by polarization mode dispersion and chromatic dispersion, as of 2005, data rates of up to 10 gigabits per second were possible at distances of over 80 km with commercially available transceivers. By using optical amplifiers and dispersion-compensating devices, state-of-the-art DWDM optical systems can span thousands of kilometers at 10 Gbit/s, and several hundred kilometers at 40 Gbit/s. The solution of Maxwells equations for the lowest order bound mode will permit a pair of orthogonally polarized fields in the fiber, in step-index guides, single-mode operation occurs when the normalized frequency, V, is less than or equal to 2.405. For power-law profiles, single-mode operation occurs for a frequency, V, less than approximately 2.405 g +2 g. In practice, the orthogonal polarizations may not be associated with degenerate modes, oS1 and OS2 are standard single-mode optical fiber used with wavelengths 1310 nm and 1550 nm with a maximum attenuation of 1 dB/km and 0.4 dB/km. OS1 is defined in ISO/IEC11801, and OS2 is defined in ISO/IEC24702, Optical fiber connectors are used to join optical fibers where a connect/disconnect capability is required. The basic connector unit is a connector assembly, a connector assembly consists of an adapter and two connector plugs. However, the assembly and polishing operations involved can be performed in the field, Optical fiber connectors are used in telephone company central offices, at installations on customer premises, and in outside plant applications. Outside plant applications may involve locating connectors underground in subsurface enclosures that may be subject to flooding, on outdoor walls, or on utility poles
2.
Fiber-optic communication
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Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms a carrier wave that is modulated to carry information. Fiber is preferred over electrical cabling when high bandwidth, long distance, optical fiber is used by many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals. Researchers at Bell Labs have reached speeds of over 100 petabit×kilometer per second using fiber-optic communication. First developed in the 1970s, fiber-optics have revolutionized the industry and have played a major role in the advent of the Information Age. Because of its advantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networks in the developed world, due to much lower attenuation and interference, optical fiber has large advantages over existing copper wire in long-distance and high-demand applications. However, infrastructure development within cities was difficult and time-consuming. Since 2000, the prices for fiber-optic communications have dropped considerably, the price for rolling out fiber to the home has currently become more cost-effective than that of rolling out a copper based network. Prices have dropped to $850 per subscriber in the US and lower in countries like The Netherlands, since 1990, when optical-amplification systems became commercially available, the telecommunications industry has laid a vast network of intercity and transoceanic fiber communication lines. Bell considered it his most important invention, the device allowed for the transmission of sound on a beam of light. On June 3,1880, Bell conducted the worlds first wireless transmission between two buildings, some 213 meters apart. Due to its use of a transmission medium, the Photophone would not prove practical until advances in laser. The Photophones first practical use came in military communication systems many decades later, in 1954 Harold Hopkins and Narinder Singh Kapany showed that rolled fiber glass allowed light to be transmitted. Initially it was considered that the light can traverse in only straight medium, after a period of research starting from 1975, the first commercial fiber-optic communications system was developed, which operated at a wavelength around 0.8 µm and used GaAs semiconductor lasers. This first-generation system operated at a bit rate of 45 Mbit/s with repeater spacing of up to 10 km, soon on 22 April 1977, General Telephone and Electronics sent the first live telephone traffic through fiber optics at a 6 Mbit/s throughput in Long Beach, California. The second generation of fiber-optic communication was developed for use in the early 1980s, operated at 1.3 µm. In 1984, they had developed a fiber optic cable that would help further their progress toward making fiber optic cables that would circle the globe. Canadian service provider SaskTel had completed construction of what was then the world’s longest commercial fiberoptic network, by 1987, these systems were operating at bit rates of up to 1.7 Gb/s with repeater spacing up to 50 km
3.
Optical fiber
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An optical fiber or optical fibre is a flexible, transparent fiber made by drawing glass or plastic to a diameter slightly thicker than that of a human hair. Fibers are also used for illumination, and are wrapped in bundles so that they may be used to carry images, thus allowing viewing in confined spaces, as in the case of a fiberscope. Specially designed fibers are used for a variety of other applications, some of them being fiber optic sensors. Optical fibers typically include a transparent core surrounded by a transparent cladding material with an index of refraction. Light is kept in the core by the phenomenon of internal reflection which causes the fiber to act as a waveguide. Fibers that support many propagation paths or transverse modes are called multi-mode fibers, multi-mode fibers generally have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted. Single-mode fibers are used for most communication links longer than 1,000 meters, being able to join optical fibers with low loss is important in fiber optic communication. This is more complex than joining electrical wire or cable and involves careful cleaving of the fibers, precise alignment of the cores. For applications that demand a permanent connection a fusion splice is common, in this technique, an electric arc is used to melt the ends of the fibers together. Another common technique is a splice, where the ends of the fibers are held in contact by mechanical force. Temporary or semi-permanent connections are made by means of specialized optical fiber connectors, the field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics. The term was coined by Indian physicist Narinder Singh Kapany who is acknowledged as the father of fiber optics. Guiding of light by refraction, the principle that makes fiber optics possible, was first demonstrated by Daniel Colladon, John Tyndall included a demonstration of it in his public lectures in London,12 years later. When the ray passes from water to air it is bent from the perpendicular. If the angle which the ray in water encloses with the perpendicular to the surface be greater than 48 degrees, the angle which marks the limit where total reflection begins is called the limiting angle of the medium. For water this angle is 48°27′, for flint glass it is 38°41′, unpigmented human hairs have also been shown to act as an optical fiber. Practical applications, such as close internal illumination during dentistry, appeared early in the twentieth century, image transmission through tubes was demonstrated independently by the radio experimenter Clarence Hansell and the television pioneer John Logie Baird in the 1920s. The principle was first used for medical examinations by Heinrich Lamm in the following decade
4.
Helmholtz equation
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In mathematics, the Helmholtz equation, named for Hermann von Helmholtz, is the partial differential equation ∇2 A + k 2 A =0 where ∇2 is the Laplacian, k is the wavenumber, and A is the amplitude. The Helmholtz equation often arises in the study of problems involving partial differential equations in both space and time. The Helmholtz equation, which represents a time-independent form of the wave equation, for example, consider the wave equation u =0. Separation of variables begins by assuming that the function u is in fact separable. Substituting this form into the equation, and then simplifying, we obtain the following equation. Notice the expression on the left-hand side depends only on r, as a result, this equation is valid in the general case if and only if both sides of the equation are equal to a constant value. Rearranging the first equation, we obtain the Helmholtz equation, ∇2 A + k 2 A = A =0 and we now have Helmholtzs equation for the spatial variable r and a second-order ordinary differential equation in time. The solution in time will be a combination of sine and cosine functions, with angular frequency of ω. Alternatively, integral transforms, such as the Laplace or Fourier transform, are used to transform a hyperbolic PDE into a form of the Helmholtz equation. Because of its relationship to the equation, the Helmholtz equation arises in problems in such areas of physics as the study of electromagnetic radiation, seismology. The solution to the spatial Helmholtz equation A =0 can be obtained for simple geometries using separation of variables, the two-dimensional analogue of the vibrating string is the vibrating membrane, with the edges clamped to be motionless. The elliptical drumhead was studied by Émile Mathieu, leading to Mathieus differential equation, the solvable shapes all correspond to shapes whose dynamical billiard table is integrable, that is, not chaotic. When the motion on a billiard table is chaotic, then no closed form solutions to the Helmholtz equation are known. The study of systems is known as quantum chaos, as the Helmholtz equation. An interesting situation happens with a shape where about half of the solutions are integrable, a simple shape where this happens is with the regular hexagon. Another simple shape where this happens is with an L shape made by reflecting a square down, if the domain is a circle of radius a, then it is appropriate to introduce polar coordinates r and θ. The Helmholtz equation takes the form A r r +1 r A r +1 r 2 A θ θ + k 2 A =0 and we may impose the boundary condition that A vanish if r = a, thus A =0. The method of separation of variables leads to solutions of the form A = R Θ
5.
Maxwell's equations
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Maxwells equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electromagnetism, classical optics, and electric circuits. They underpin all electric, optical and radio such as power generation, electric motors, wireless communication, cameras, televisions. Maxwells equations describe how electric and magnetic fields are generated by charges, currents, one important consequence of the equations is the demonstration of how fluctuating electric and magnetic fields can propagate at the speed of light. This electromagnetic radiation manifests itself in ways from radio waves to light. The equations have two major variants, the microscopic Maxwell equations have universal applicability but are unwieldy for common calculations. They relate the electric and magnetic fields to total charge and total current, including the complicated charges, the macroscopic Maxwell equations define two new auxiliary fields that describe the large-scale behaviour of matter without having to consider atomic scale details. However, their use requires experimentally determining parameters for a description of the electromagnetic response of materials. The term Maxwells equations is used for equivalent alternative formulations. The space-time formulations, are used in high energy and gravitational physics because they make the compatibility of the equations with special and general relativity manifest. In many situations, though, deviations from Maxwells equations are immeasurably small, exceptions include nonclassical light, photon-photon scattering, quantum optics, and many other phenomena related to photons or virtual photons. In the electric and magnetic field there are four equations. The two inhomogeneous equations describe how the fields vary in space due to sources, Gausss law describes how electric fields emanate from electric charges. Gausss law for magnetism describes magnetic fields as closed field lines not due to magnetic monopoles, the two homogeneous equations describe how the fields circulate around their respective sources. A separate law of nature, the Lorentz force law, describes how the electric and magnetic field act on charged particles, a version of this law was included in the original equations by Maxwell but, by convention, is no longer. The precise formulation of Maxwells equations depends on the definition of the quantities involved. Conventions differ with the systems, because various definitions and dimensions are changed by absorbing dimensionful factors like the speed of light c. This makes constants come out differently, the vector calculus formulation below has become standard. For formulations using tensor calculus or differential forms, see alternative formulations, for relativistically invariant formulations, see relativistic formulations
6.
Transverse mode
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A transverse mode of electromagnetic radiation is a particular electromagnetic field pattern of radiation measured in a plane perpendicular to the propagation direction of the beam. Transverse modes occur in waves and microwaves confined to a waveguide. Transverse modes occur because of conditions imposed on the wave by the waveguide. For this reason, the supported by a waveguide are quantized. The allowed modes can be found by solving Maxwells equations for the conditions of a given waveguide. Unguided electromagnetic waves in space, or in a bulk isotropic dielectric, can be described as a superposition of plane waves. However in any sort of waveguide where boundary conditions are imposed by a physical structure and these modes generally follow different propagation constants. When two or more modes have a propagation constant along the waveguide, then there is more than one modal decomposition possible in order to describe a wave with that propagation constant. Modes in waveguides can be classified as follows, Transverse electromagnetic modes. Transverse electric modes, no field in the direction of propagation. These are sometimes called H modes because there is only a field along the direction of propagation. Transverse magnetic modes, no field in the direction of propagation. These are sometimes called E modes because there is only a field along the direction of propagation. Hybrid modes, non-zero electric and magnetic fields in the direction of propagation, hollow metallic waveguides filled with a homogeneous, isotropic material support TE and TM modes but not the TEM mode. In coaxial cable energy is transported in the fundamental TEM mode. The TEM mode is usually assumed for most other electrical conductor line formats as well. In an optical fiber or other dielectric waveguide, modes are generally of the hybrid type, in circular waveguides, circular modes exist and here m is the number of full-wave patterns along the circumference and n is the number of half-wave patterns along the diameter. In a laser with cylindrical symmetry, the transverse mode patterns are described by a combination of a Gaussian beam profile with a Laguerre polynomial, the modes are denoted TEMpl where p and l are integers labeling the radial and angular mode orders, respectively
7.
Electromagnetic radiation
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In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, light, ultraviolet, X-, classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum. The oscillations of the two fields are perpendicular to other and perpendicular to the direction of energy and wave propagation. The wavefront of electromagnetic waves emitted from a point source is a sphere, the position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves are produced whenever charged particles are accelerated, and these waves can interact with other charged particles. EM waves carry energy, momentum and angular momentum away from their source particle, quanta of EM waves are called photons, whose rest mass is zero, but whose energy, or equivalent total mass, is not zero so they are still affected by gravity. Thus, EMR is sometimes referred to as the far field, in this language, the near field refers to EM fields near the charges and current that directly produced them, specifically, electromagnetic induction and electrostatic induction phenomena. In the quantum theory of electromagnetism, EMR consists of photons, quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation. The energy of a photon is quantized and is greater for photons of higher frequency. This relationship is given by Plancks equation E = hν, where E is the energy per photon, ν is the frequency of the photon, a single gamma ray photon, for example, might carry ~100,000 times the energy of a single photon of visible light. The effects of EMR upon chemical compounds and biological organisms depend both upon the power and its frequency. EMR of visible or lower frequencies is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules, the effects of these radiations on chemical systems and living tissue are caused primarily by heating effects from the combined energy transfer of many photons. In contrast, high ultraviolet, X-rays and gamma rays are called ionizing radiation since individual photons of high frequency have enough energy to ionize molecules or break chemical bonds. These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating, Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the speed of light. Maxwell’s equations were confirmed by Heinrich Hertz through experiments with radio waves, according to Maxwells equations, a spatially varying electric field is always associated with a magnetic field that changes over time. Likewise, a varying magnetic field is associated with specific changes over time in the electric field. In an electromagnetic wave, the changes in the field are always accompanied by a wave in the magnetic field in one direction
8.
Nobel Prize in Physics
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The Nobel Prize in Physics is a yearly award given by the Royal Swedish Academy of Sciences for those who conferred the most outstanding contributions for mankind in the field of physics. The first Nobel Prize in Physics was awarded to German/Dutch physicist Wilhelm Röntgen in recognition of the services he has rendered by the discovery of the remarkable rays. This award is administered by the Nobel Foundation and widely regarded as the most prestigious award that a scientist can receive in physics and it is presented in Stockholm at an annual ceremony on December 10, the anniversary of Nobels death. Through 2016, a total of 203 individuals have been awarded the prize, only two women have won the Nobel Prize in Physics, Marie Curie in 1903, and Maria Goeppert Mayer in 1963. Though Nobel wrote several wills during his lifetime, the last one was written a year before he died and was signed at the Swedish-Norwegian Club in Paris on 27 November 1895. Nobel bequeathed 94% of his assets,31 million Swedish kronor, to establish. Due to the level of surrounding the will, it was not until April 26,1897 that it was approved by the Storting. The executors of his will were Ragnar Sohlman and Rudolf Lilljequist, the members of the Norwegian Nobel Committee who were to award the Peace Prize were appointed shortly after the will was approved. The prize-awarding organisations followed, the Karolinska Institutet on June 7, the Swedish Academy on June 9, the Nobel Foundation then reached an agreement on guidelines for how the Nobel Prize should be awarded. In 1900, the Nobel Foundations newly created statutes were promulgated by King Oscar II, according to Nobels will, The Royal Swedish Academy of sciences were to award the Prize in Physics. A maximum of three Nobel laureates and two different works may be selected for the Nobel Prize in Physics, compared with other Nobel Prizes, the nomination and selection process for the prize in Physics is long and rigorous. This is a key reason why it has grown in importance over the years to become the most important prize in Physics, the Nobel laureates are selected by the Nobel Committee for Physics, a Nobel Committee that consists of five members elected by The Royal Swedish Academy of Sciences. In the first stage begins in September, around 3,000 people – selected university professors, Nobel Laureates in Physics and Chemistry. The completed nomination forms arrive at the Nobel Committee no later than 31 January of the following year and these nominees are scrutinized and discussed by experts who narrow it to approximately fifteen names. The committee submits a report with recommendations on the candidates into the Academy. The Academy then makes the selection of the Laureates in Physics through a majority vote. The names of the nominees are never announced, and neither are they told that they have been considered for the prize. Nomination records are sealed for fifty years, while posthumous nominations are not permitted, awards can be made if the individual died in the months between the decision of the prize committee and the ceremony in December
9.
Charles K. Kao
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Kao holds multiple citizenship of Hong Kong, the United Kingdom and the United States. Charles Kao was born in Shanghai in 1933, and his home is in nearby Jinshan. He studied Chinese classics at home with his brother, under a tutor and he also studied English and French at an international school in Shanghai which was founded by a number of progressive Chinese educators including Cai Yuanpei. Kaos family moved to Hong Kong in 1948 where he completed his education at St. Josephs College in 1952. He did his studies in electrical engineering at Woolwich Polytechnic. It is there that Kao did his first groundbreaking work as an engineer and researcher working alongside George Hockham under the supervision of Alec Reeves. Kao joined The Chinese University of Hong Kong in 1970, to found the Department of Electronics, under his leadership, the School of Education and other new research institutes were established. He then went back to ITT Corporation in 1974 in the United States and worked in Roanoke, Virginia, first as Chief Scientist, in 1982, he became the first ITT Executive Scientist and was stationed mainly at the Advanced Technology Center in Connecticut. While there, he served as a professor and Fellow of Trumbull College at Yale University. In 1985, Kao spent one year in West Germany, at the SEL Research Centre, in 1986, Kao was the Corporate Director of Research at ITT. Kao was the Vice-Chancellor of the Chinese University of Hong Kong from 1987 to 1996, from 1993 to 1994, he was the President of ASAIHL. Kao then worked as the Chairman and CEO of Transtech Services Ltd. a telecommunication consultancy company in Hong Kong and he was the founder, Chairman and CEO of ITX Services Limited. From 2003 to January 30,2009, Kao was an Independent Non-executive Director, since 1991, Kao has been an Independent Non-Executive Director and a member of the Audit Committee of the Varitronix International Limited in Hong Kong. In 2000, Kao founded the Independent Schools Foundation Academy, which is located in Cyberport and he was its founding Chairman in 2000, and stepped down from the Board of the ISF in December 2008. Kao was the speaker at IEEE GLOBECOM2002 in Taipei. In 2003 Kao was named a Chair Professor by special appointment at the Electronics Institute of the College of Electrical Engineering and Computer Science, National Taiwan University. In 1996, Kao donated to Yale University, and the Charles Kao Fund Research Grants was established to support Yales studies, research, the fund currently is managed by Yale University Councils on East Asian and Southeast Asian Studies. Kao has been suffering from Alzheimers disease since early 2004 and has speech difficulty, Kaos father also suffered from the same disease
This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C".
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