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Masataka Nakazawa
Masataka Nakazawa (born 17 September 1952) is a Japanese researcher in optical communication engineering. He is a distinguished professor at Tohoku University in Japan. His pioneering work on erbium-doped fiber amplifier (EDFA) has made a significant contribution to the development of global long-distance, high-capacity optical fiber network. Biography Masataka Nakazawa received B.S. in Electronics from Kanazawa University in 1975, M.S. in Physical Electronics from Tokyo Institute of Technology in 1977, and Ph.D. in Applied Electronics from Tokyo Institute of Technology in 1980. After receiving a Ph. D. degree, he joined the Electrical Communication Laboratory of Nippon Telegraph & Telephone Public Corporation in 1980. He was a visiting scientist at Massachusetts Institute of Technology in 1984. In 1999, he became an NTT R&D Fellow. Then, in 2001, he moved to the Research Institute of Electrical Communication (RIEC) at Tohoku University. He became a distinguished professor (D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yamanashi Prefecture
is a prefecture of Japan located in the Chūbu region of Honshu. Yamanashi Prefecture has a population of 787,592 (1 February 2025) and has a geographic area of 4,465 km2 (1,724 sq mi). Yamanashi Prefecture borders Saitama Prefecture to the northeast, Nagano Prefecture to the northwest, Shizuoka Prefecture to the southwest, Kanagawa Prefecture to the southeast, and Tokyo to the east. Kōfu is the capital and largest city of Yamanashi Prefecture, with other major cities including Kai, Minamiarupusu, and Fuefuki. Yamanashi Prefecture is one of only eight landlocked prefectures, and the majority of the population lives in the central Kōfu Basin surrounded by the Akaishi Mountains, with 27% of its total land area being designated as Natural Parks. Yamanashi Prefecture is home to many of the highest mountains in Japan, and Mount Fuji, the tallest mountain in Japan and cultural icon of the country, is partially located in Yamanashi Prefecture on the border with Shizuoka Pref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Time Domain Reflectometer
An optical time-domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber. It is the optical equivalent of an electronic time domain reflectometer which measures the impedance of the cable or transmission line under test. An OTDR injects a series of optical pulses into the fiber under test and extracts, from the same end of the fiber, light that is scattered ( Rayleigh backscatter) or reflected back from points along the fiber. The scattered or reflected light that is gathered back is used to characterize the optical fiber. The strength of the return pulses is measured and integrated as a function of time, and plotted as a function of length of the fiber. Reliability and quality of OTDR equipment The reliability and quality of an OTDR is based on its accuracy, measurement range, ability to resolve and measure closely spaced events, measurement speed, and ability to perform satisfactorily under various environmental extremes and after v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mode Locking
Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). A laser operated in this way is sometimes referred to as a femtosecond laser, for example, in modern refractive surgery. The basis of the technique is to induce a fixed phase relationship between the longitudinal modes of the laser's resonant cavity. Constructive interference between these modes can cause the laser light to be produced as a train of pulses. The laser is then said to be "phase-locked" or "mode-locked". Laser cavity modes Although laser light is perhaps the purest form of light, it is not of a single, pure frequency or wavelength. All lasers produce light over some natural bandwidth or range of frequencies. A laser's bandwidth of operation is determined primarily by the gain medium from which the laser is constructed, and the range of frequencies over which a lase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherent Transmission
A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several ''senders'' to one or several '' receivers''. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second. Communicating an information signal across distance requires some form of pathway or medium. These pathways, called communication channels, use two types of media: Transmission line-based telecommunications cable (e.g. twisted-pair, coaxial, and fiber-optic cable) and broadcast (e.g. microwave, satellite, radio, and infrared). In information theory, a channel refers to a theoretical ''channel model'' with certain error characteristics. In this more general view, a storage device is al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quadrature Amplitude Modulation
Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signals, or two digital bit streams, by changing (''modulating'') the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation scheme. The two carrier waves are of the same frequency and are out of phase with each other by 90°, a condition known as orthogonality or Quadrature phase, quadrature. The transmitted signal is created by adding the two carrier waves together. At the receiver, the two waves can be coherently separated (demodulated) because of their orthogonality. Another key property is that the modulations are low-frequency/low-bandwidth waveforms compared to the carrier frequency, which is known as the In-phase and quadrature components#Narrowband ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harry Nyquist
Harry Nyquist (, ; February 7, 1889 – April 4, 1976) was a Swedish-American physicist and electronic engineer who made important contributions to communication theory. Personal life Nyquist was born in the village Nilsby of the parish Stora Kil, Värmland, Sweden. He was the son of Lars Jonsson Nyqvist (1847–1930) and Catarina (or Katrina) Eriksdotter (1857–1920). His parents had eight children: Elin Teresia, Astrid, Selma, Harry Theodor, Amelie, Olga Maria, Axel Martin and Herta Alfrida. He immigrated to the United States in 1907. Education He entered the University of North Dakota in 1912 and received B.S. and M.S. degrees in electrical engineering in 1914 and 1915, respectively. He received a Ph.D. in physics at Yale University in 1917. Career He worked at AT&T's Department of Development and Research from 1917 to 1934, and continued when it became Bell Telephone Laboratories that year, until his retirement in 1954. Nyquist received the IRE Medal of Honor in 1960 fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fourier Transformation
In mathematics, the Fourier transform (FT) is an integral transform that takes a function as input then outputs another function that describes the extent to which various frequencies are present in the original function. The output of the transform is a complex-valued function of frequency. The term ''Fourier transform'' refers to both this complex-valued function and the mathematical operation. When a distinction needs to be made, the output of the operation is sometimes called the frequency domain representation of the original function. The Fourier transform is analogous to decomposing the sound of a musical chord into the intensities of its constituent pitches. Functions that are localized in the time domain have Fourier transforms that are spread out across the frequency domain and vice versa, a phenomenon known as the uncertainty principle. The critical case for this principle is the Gaussian function, of substantial importance in probability theory and statistic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Solitons
In optics, the term soliton is used to refer to any optical field that does not change during propagation because of a delicate balance between nonlinearity, nonlinear and dispersion (optics), dispersive effects in the medium. There are two main kinds of solitons: * spatial solitons: the nonlinear effect can balance the dispersion (optics), dispersion. The electromagnetic field can change the refractive index of the medium while propagating, thus creating a structure similar to a graded-index fiber. If the field is also a propagating mode of the guide it has created, then it will remain confined and it will propagate without changing its shape * temporal solitons: if the electromagnetic field is already spatially confined, it is possible to send pulses that will not change their shape because the nonlinear effects will balance the dispersion (optics), dispersion. Those solitons were discovered first and they are often simply referred as "solitons" in optics. *Spatial solitons* In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gaussian Function
In mathematics, a Gaussian function, often simply referred to as a Gaussian, is a function (mathematics), function of the base form f(x) = \exp (-x^2) and with parametric extension f(x) = a \exp\left( -\frac \right) for arbitrary real number, real constants , and non-zero . It is named after the mathematician Carl Friedrich Gauss. The graph of a function, graph of a Gaussian is a characteristic symmetric "Normal distribution, bell curve" shape. The parameter is the height of the curve's peak, is the position of the center of the peak, and (the standard deviation, sometimes called the Gaussian Root mean square, RMS width) controls the width of the "bell". Gaussian functions are often used to represent the probability density function of a normal distribution, normally distributed random variable with expected value and variance . In this case, the Gaussian is of the form g(x) = \frac \exp\left( -\frac \frac \right). Gaussian functions are widely used in statistics to describ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser Diode
file:Laser diode chip.jpg, 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 semiconductor laser or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create active laser medium, lasing conditions at the diode's p–n junction, junction. Driven by voltage, the doped p–n-transition allows for carrier generation and recombination, recombination of an electron with a electron hole, hole. Due to the drop of the electron from a higher energy level to a lower one, radiation is generated in the form of an emitted photon. This is spontaneous emission. Stimulated emission can be produced when the process is continued and further generates light with the same phase, coherence, and wavelength. The choice of the semiconductor material determines the wavelength of the emitted beam, which in today's laser diodes range from the inf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
InGaAsP
Indium gallium arsenide phosphide () is a quaternary compound semiconductor material, an alloy of gallium arsenide, gallium phosphide, indium arsenide, or indium phosphide. This compound has applications in photonic devices, due to the ability to tailor its band gap via changes in the alloy mole ratios, ''x'' and ''y''. Indium phosphide-based photonic integrated circuits, or PICs, commonly use alloys of to construct quantum wells, waveguides and other photonic structures, lattice matched to an InP substrate, enabling single-crystal epitaxial growth onto InP. Many devices operating in the near-infrared 1.55 μm wavelength window utilize this alloy, and are employed as optical components (such as 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'' originated as an acronym for light amplification by stimulated emission of radi ... transmitters, p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David N
David (; , "beloved one") was a king of ancient Israel and Judah and the Kings of Israel and Judah, third king of the Kingdom of Israel (united monarchy), United Monarchy, according to the Hebrew Bible and Old Testament. The Tel Dan stele, an Canaanite and Aramaic inscriptions, Aramaic-inscribed stone erected by a king of Aram-Damascus in the late 9th/early 8th centuries BCE to commemorate a victory over two enemy kings, contains the phrase (), which is translated as "Davidic line, House of David" by most scholars. The Mesha Stele, erected by King Mesha of Moab in the 9th century BCE, may also refer to the "House of David", although this is disputed. According to Jewish works such as the ''Seder Olam Rabbah'', ''Seder Olam Zutta'', and ''Sefer ha-Qabbalah'' (all written over a thousand years later), David ascended the throne as the king of Judah in 885 BCE. Apart from this, all that is known of David comes from biblical literature, Historicity of the Bible, the historicit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
