The Deutsche Bundespost was a German state-run postal service and telecommunications business founded in 1947. It was the second largest federal employer during its time. After staff reductions in the 1980s, the staff was reduced to 543,200 employees in 1985; the corporation was dissolved in 1995 under the first and second postal reforms that took place in the German Post Office. Following the reforms, the former Deutsche Bundespost was broken into three publicly traded corporations: Deutsche Post AG, Deutsche Telekom, Deutsche Postbank AG, it was created in 1947 in the Trizone as a successor to the Reichspost. Between 1947 and 1950 the enterprise was called Deutsche Post; until 1989 the Deutsche Bundespost was a state-owned operation. The Bundespost was developed according to a three-tier principle common in public administration in the Federal Republic of Germany; the upper stage consisted of the federal ministry for the post telecommunication system. The middle stage consisted of regional directorates and the state post office management under western Allied authority in West Berlin as of 1949/1955).
The post office technical central office, telecommunication engineering central office, postal administration social office, post offices) were on an equal level with the directorates. The lower stage consisted of post office branches, postal giro savings bank offices and telecommunications office branches; the legal basis for the administrative activity of the Bundespost was the postal administration act. A central goal of public administrative policy after 1924 was financial self-sufficiency. Political goals, however superseded this goal. According to the PostVwG, the federal postal system was to be administered "according to the principles of the policy of the FRG, in particular trade, economic and social policies" and "the interests of the German national economy." The Deutsche Bundespost was the largest employer in the Federal Republic. In 1985 it employed 543,200 people. In the first post office reform, the Bundespost was divided into three divisions: Deutsche Bundespost Postdienst - postal service Deutsche Bundespost Telekom - communications service Deutsche Bundespost Postbank - postal bankThe central authorities remained as described above.
The divisions were privatized in the second post office reform, resulting in: Deutsche Post AG from the postal service Deutsche Telekom AG from the communications service Deutsche Postbank AG from the postal bankThe federal ministry for post office and telecommunications retained oversight responsibility for postal services and telecommunications. After the dissolution of that ministry on 1 January 1998, those tasks were taken over by a new federal network regulatory agency under the federal ministry for economics and technology. Other functions were taken over by the federal ministry of finance; some telecommunications functions were turned over to the federal ministry of the interior. For certain official and legal purposes, a "federal institution for post and telecommunication" was created. Postage stamps and postal history of Germany Deutsche Bundespost Berlin Deutsche Post of the GDR
Oakland is the largest city and the county seat of Alameda County, United States. A major West Coast port city, Oakland is the largest city in the East Bay region of the San Francisco Bay Area, the third largest city overall in the San Francisco Bay Area, the eighth most populated city in California, the 45th largest city in the United States. With a population of 425,195 as of 2017, it serves as a trade center for the San Francisco Bay Area. An act to incorporate the city was passed on May 4, 1852, incorporation was approved on March 25, 1854, which made Oakland a city. Oakland is a charter city. Oakland's territory covers what was once a mosaic of California coastal terrace prairie, oak woodland, north coastal scrub, its land served as a rich resource when its hillside oak and redwood timber were logged to build San Francisco. Oakland's fertile flatland soils helped. In the late 1860s, Oakland was selected as the western terminal of the Transcontinental Railroad. Following the 1906 San Francisco earthquake, many San Francisco citizens moved to Oakland, enlarging the city's population, increasing its housing stock and improving its infrastructure.
It continued to grow in the 20th century with its busy port, a thriving automobile manufacturing industry. The earliest known inhabitants were the Huchiun Indians; the Huchiun belonged to a linguistic grouping called the Ohlone. In Oakland, they were concentrated around Lake Merritt and Temescal Creek, a stream that enters the San Francisco Bay at Emeryville. In 1772, the area that became Oakland was colonized, with the rest of California, by Spanish settlers for the King of Spain. In the early 19th century, the Spanish crown granted the East Bay area to Luis María Peralta for his Rancho San Antonio; the grant was confirmed by the successor Mexican republic upon its independence from Spain. Upon his death in 1842, Peralta divided his land among his four sons. Most of Oakland fell within the shares given to Antonio Vicente; the portion of the parcel, now Oakland was called Encinal—Spanish for "oak grove"—due to the large oak forest that covered the area, which led to the city's name. During the 1850s—just as gold was discovered in California—Oakland started growing and developing because land was becoming too expensive in San Francisco.
The Chinese were struggling financially, as a result of the First Opium War, the Second Opium War, the Taiping Rebellion, so they began migrating to Oakland in an effort to provide for their families in China. However, the Chinese struggled to settle because they were discriminated against by the white community and their living quarters were burned down on several occasions; the majority of the Chinese migrants lived in unhealthy conditions in China and they had diseases, so plague spread into San Francisco though the Chinese were inspected for diseases upon their arrival to San Francisco. In 1851, three men—Horace Carpentier, Edson Adams, Andrew Moon—began developing what is now downtown Oakland. In 1852, the Town of Oakland became incorporated by the state legislature. During this time, Oakland had 75-100 inhabitants, two hotels, a wharf, two warehouses, only cattle trails. Two years on March 25, 1854, Oakland re-incorporated as the City of Oakland, with Horace Carpentier elected the first mayor, though a scandal ended his mayorship in less than a year.
The city and its environs grew with the railroads, becoming a major rail terminal in the late 1860s and 1870s. In 1868, the Central Pacific constructed the Oakland Long Wharf at Oakland Point, the site of today's Port of Oakland. A number of horsecar and cable car lines were constructed in Oakland during the latter half of the 19th century; the first electric streetcar set out from Oakland to Berkeley in 1891, other lines were converted and added over the course of the 1890s. The various streetcar companies operating in Oakland were acquired by Francis "Borax" Smith and consolidated into what became known as the Key System, the predecessor of today's publicly owned AC Transit. Oakland was one of the worst affected cities in California, impacted by the plague epidemic. Quarantine measures were set in place at the Oakland ports requiring the authorities at the port to inspect the arriving vessels for the presence of infected rats. Quarantine authorities at these ports inspected over a thousand vessels per year for plague and yellow fever.
By 1908, over 5,000 people were detained in quarantine. Hunters were sent to poison the affected areas in Oakland and shoot the squirrels, but the eradication work was limited in its range because the State Board of Health and the United States Public Health Service were only allotted about $60,000 a year to eradicate the disease. During this period Oakland did not have sufficient health facilities, so some of the infected patients were treated at home; the State Board of Health along with Oakland advised physicians to promptly report any cases of infected patients. Yet, in 1919 it still resulted in a small epidemic of Pneumonic plague which killed a dozen people in Oakland; this started when a man killed a squirrel. After eating the squirrel, he fell ill four days and another household member contracted the plague; this in turn was passed on either indirectly to about a dozen others. The officials in Oakland acted by issuing death certificates to monitor the spread of plague. At the time of incorporation in 1852, Oaklan
In telecommunications, a point-to-point connection refers to a communications connection between two communication endpoints or nodes. An example is a telephone call, in which one telephone is connected with one other, what is said by one caller can only be heard by the other; this is contrasted with a point-to-multipoint or broadcast connection, in which many nodes can receive information transmitted by one node. Other examples of point-to-point communications links are leased lines, microwave radio relay and two-way radio; the term is used in computer networking and computer architecture to refer to a wire or other connection that links only two computers or circuits, as opposed to other network topologies such as buses or crossbar switches which can connect many communications devices. Point-to-point is sometimes abbreviated as P2P; this usage of P2P is distinct from P2P meaning peer-to-peer in the context of file sharing networks. A traditional point-to-point data link is a communications medium with two endpoints and no data or packet formatting.
The host computers at either end take full responsibility for formatting the data transmitted between them. The connection between the computer and the communications medium was implemented through an RS-232 or similar interface. Computers in close proximity may be connected by wires directly between their interface cards; when connected at a distance, each endpoint would be fitted with a modem to convert analog telecommunications signals into a digital data stream. When the connection uses a telecommunications provider, the connection is called a dedicated, leased, or private line; the ARPANET used leased lines to provide point-to-point data links between its packet-switching nodes, which were called Interface Message Processors. In modern computer networking, the term point-to-point telecommunications means a wireless data link between two fixed points; the telecommunications signal is bi-directional and either time division multiple access or channelized. This can be a microwave relay link consisting of a transmitter which transmits a narrow beam of microwaves with a parabolic dish antenna to a second parabolic dish at the receiver.
It includes technologies such as lasers which transmit data modulated on a light beam. These technologies require an unobstructed line of sight between the two points and thus are limited by the visual horizon to distances of about 40 miles. In a local network, repeater hubs or switches provide basic connectivity. A hub provides a point-to-multipoint circuit in which all connected client nodes share the network bandwidth. A switch on the other hand provides a series of point-to-point circuits, via microsegmentation, which allows each client node to have a dedicated circuit and the added advantage of having full-duplex connections. From the OSI model's layer perspective, both switches and repeater hubs provide point-to-point connections on the physical layer. However, on the data link layer, a repeater hub provides point-to-multipoint connectivity – each frame is forwarded to all nodes – while a switch provides virtual point-to-point connections – each unicast frame is only forwarded to the destination node.
Within many switched telecommunications systems, it is possible to establish a permanent circuit. One example might be a telephone in the lobby of a public building, programmed to ring only the number of a telephone dispatcher. "Nailing down" a switched connection saves the cost of running a physical circuit between the two points. The resources in such a connection can be released when no longer needed, for example, a television circuit from a parade route back to the studio
Redwood City, California
Redwood City is a city on the San Francisco Peninsula in Northern California's Bay Area 27 miles south of San Francisco, 24 miles northwest of San Jose. Redwood City's history spans its earliest inhabitation by the Ohlone people to being a port for lumber and other goods; the county seat of San Mateo County in the heart of Silicon Valley, Redwood City is home to several global technology companies including Oracle, Electronic Arts, Evernote and Informatica. The city had an estimated population of 86,685 in 2017; the Port of Redwood City is the only deepwater port on San Francisco Bay south of San Francisco. Redwood City is the location of the San Mateo County Jail, for both men; the Hetch Hetchy water pipeline runs through Redwood City and supplies a vast majority of the surrounding area with low grain rated water. According to the United States Census Bureau, the city has an area of 34.7 square miles, of which 19.4 square miles is land and 15.2 square miles is water. A major watercourse draining much of Redwood City is Redwood Creek, to which several significant river deltas connect, the largest of, Westpoint Slough.
Redwood City stretches from the San Francisco Bay towards the Santa Cruz Mountains between San Carlos to the northwest and Atherton to the southeast with Woodside to the southwest. It is divided by Highway 101 and further inland El Camino Real on the northwest/southeast axis and Woodside Road on the north-northeast/south-southwest axis. Locally, the former two are regarded as north/south and the latter east/west, as 101 and El Camino connects Redwood City to San Francisco and San Jose and Woodside Road runs from San Francisco Bay to the Santa Cruz Mountains. Neighborhoods include Bair Island to the northeast of Highway 101; the northern neighborhood of Redwood Shores to the northeast of Highway 101 is part of Redwood City, although it is not possible to travel by road from one to the other without passing through the neighboring city of San Carlos, or through Belmont via unincorporated San Mateo County. Stretching along Highway 101 to the southeast of Woodside Road is Friendly Acres, further inland and still to the southeast of Woodside Road are Redwood Village and Redwood Oaks.
Most neighborhoods are to the northwest of Woodside Ride and southwest of Highway 101. Centennial and Stambaugh Heller are adjacent to 101. Next inland are Edgewood, Mt. Carmel and Palm Canyon, Eagle Hill and Woodside Plaza. Furthest inland is Farm Hills. Neighborhoods associated with Redwood City but not part of the incorporated city include Emerald Lake Hills and Kensington Square inland and to the north and North Fair Oaks to the southeast. Palomar Park, just north of Emerald Hills and east of San Carlos' Crestview area, is another Redwood City neighborhood, formally part of unincorporated San Mateo County. Although Redwood City has a large middle class, the south eastern section of Redwood City resembles working class North Fair Oaks in demographic make-up and income level. Redwood City, along with most of the Bay Area, enjoys a mild Mediterranean climate, with warm, dry summers and cool wet winters; the National Weather Service, which maintains both a forecast center and a cooperative office in Redwood City, reports that December is the coolest month and July is the warmest month.
The record highest temperature of 110 °F was recorded on both July 14 and 15, 1972. The record lowest temperature of 16 °F was recorded on January 11, 1949. Annually, there are an average of 21.6 days with highs of 90 °F or higher and 2.8 days with highs of 100 °F or higher. The normal annual precipitation is 20.56 inches. The most rainfall in one month was 12.42 inches in February 1998. The record 24-hour rainfall of 4.88 inches was on October 13, 1962. There are an average of 62.1 days with measurable precipitation. Snow flurries have been observed on rare occasions. Redwood City incorporated in 1867, the first city to do so in San Mateo County, it has been the county seat since the county was formed in 1856; the land had been part of the Rancho de las Pulgas granted to the Arguello family in 1835 by the Mexican government. Their control was challenged after the Mexican–American War when California became part of the United States; the family lawyer, Simon M. Mezes, in 1854 defended the claim somewhat and was allowed to buy the part of the estate, now Redwood City.
Mezes sold some of the land to people squatting on it along the banks of Redwood Creek and named the settlement, Mezesville. Though the city did not keep that name, Mezes Park still exists on land Mezes had given for open space. In 1907 Eikichi and Sadakusi Enomoto, Japanese immigrant brothers, grew the first chrysanthemums commercially in the United States in Redwood City. In 1926 the chamber of commerce proclaimed the city the "Chrysanthemum Center of the World" though the internment of Japanese Americans in 1941 and other factors removed flower growing as a major industry in the city; the 2010 United States Census reported that Redwood City had a population of 76,815. The population density was 3,955.5 people per square mile. The racial makeup of Redwood City was 46,255 White, 1,881 African American, 511 Native American, 8,216 Asian, 795 Pacific Islander, 14,967 from other races, 4,190 from two or more races. Hispanic or Latino of any race were 29,810 persons. Non-Hispanic Whites n
San Francisco the City and County of San Francisco, is the cultural and financial center of Northern California. San Francisco is the 13th-most populous city in the United States, the fourth-most populous in California, with 884,363 residents as of 2017, it covers an area of about 46.89 square miles at the north end of the San Francisco Peninsula in the San Francisco Bay Area, making it the second-most densely populated large US city, the fifth-most densely populated U. S. county, behind only four of the five New York City boroughs. San Francisco is part of the fifth-most populous primary statistical area in the United States, the San Jose–San Francisco–Oakland, CA Combined Statistical Area; as of 2017, it was the seventh-highest income county in the United States, with a per capita personal income of $119,868. As of 2015, San Francisco proper had a GDP of $154.2 billion, a GDP per capita of $177,968. The San Francisco CSA was the country's third-largest urban economy as of 2017, with a GDP of $907 billion.
Of the 500+ primary statistical areas in the US, the San Francisco CSA had among the highest GDP per capita in 2017, at $93,938. San Francisco was ranked 14th in the world and third in the United States on the Global Financial Centres Index as of September 2018. San Francisco was founded on June 29, 1776, when colonists from Spain established Presidio of San Francisco at the Golden Gate and Mission San Francisco de Asís a few miles away, all named for St. Francis of Assisi; the California Gold Rush of 1849 brought rapid growth, making it the largest city on the West Coast at the time. San Francisco became a consolidated city-county in 1856. San Francisco's status as the West Coast's largest city peaked between 1870 and 1900, when around 25% of California's population resided in the city proper. After three-quarters of the city was destroyed by the 1906 earthquake and fire, San Francisco was rebuilt, hosting the Panama-Pacific International Exposition nine years later. In World War II, San Francisco was a major port of embarkation for service members shipping out to the Pacific Theater.
It became the birthplace of the United Nations in 1945. After the war, the confluence of returning servicemen, significant immigration, liberalizing attitudes, along with the rise of the "hippie" counterculture, the Sexual Revolution, the Peace Movement growing from opposition to United States involvement in the Vietnam War, other factors led to the Summer of Love and the gay rights movement, cementing San Francisco as a center of liberal activism in the United States. Politically, the city votes along liberal Democratic Party lines. A popular tourist destination, San Francisco is known for its cool summers, steep rolling hills, eclectic mix of architecture, landmarks, including the Golden Gate Bridge, cable cars, the former Alcatraz Federal Penitentiary, Fisherman's Wharf, its Chinatown district. San Francisco is the headquarters of five major banking institutions and various other companies such as Levi Strauss & Co. Gap Inc. Fitbit, Salesforce.com, Reddit, Inc. Dolby, Weebly, Pacific Gas and Electric Company, Pinterest, Uber, Mozilla, Wikimedia Foundation and Weather Underground.
It is home to a number of educational and cultural institutions, such as the University of San Francisco, University of California, San Francisco, San Francisco State University, the De Young Museum, the San Francisco Museum of Modern Art, the California Academy of Sciences. As of 2019, San Francisco is the highest rated American city on world liveability rankings; the earliest archaeological evidence of human habitation of the territory of the city of San Francisco dates to 3000 BC. The Yelamu group of the Ohlone people resided in a few small villages when an overland Spanish exploration party, led by Don Gaspar de Portolà, arrived on November 2, 1769, the first documented European visit to San Francisco Bay. Seven years on March 28, 1776, the Spanish established the Presidio of San Francisco, followed by a mission, Mission San Francisco de Asís, established by the Spanish explorer Juan Bautista de Anza. Upon independence from Spain in 1821, the area became part of Mexico. Under Mexican rule, the mission system ended, its lands became privatized.
In 1835, Englishman William Richardson erected the first independent homestead, near a boat anchorage around what is today Portsmouth Square. Together with Alcalde Francisco de Haro, he laid out a street plan for the expanded settlement, the town, named Yerba Buena, began to attract American settlers. Commodore John D. Sloat claimed California for the United States on July 7, 1846, during the Mexican–American War, Captain John B. Montgomery arrived to claim Yerba Buena two days later. Yerba Buena was renamed San Francisco on January 30 of the next year, Mexico ceded the territory to the United States at the end of the war. Despite its attractive location as a port and naval base, San Francisco was still a small settlement with inhospitable geography; the California Gold Rush brought a flood of treasure seekers. With their sourdough bread in tow, prospectors accumulated in San Francisco over rival Benicia, raising the population from 1,000 in 1848 to 25,000 by December 1849; the promise of great wealth was so strong that crews on arriving vessels deserted and rushed off to the gold fields, leaving behind a forest of masts in San Francisco harbor.
Some of these 500 abandoned ships were used at times as storeships and hotels.
Palo Alto, California
Palo Alto is a charter city located in the northwest corner of Santa Clara County, United States, in the San Francisco Bay Area. Palo Alto means tall stick in Spanish; the city was established by Leland Stanford Sr. when he founded Stanford University, following the death of his son, Leland Stanford Jr. Palo Alto includes portions of Stanford University and shares its borders with East Palo Alto, Mountain View, Los Altos, Los Altos Hills, Portola Valley, Menlo Park; as of the 2010 census, the city's total resident population is 64,403. Palo Alto is one of the five most expensive cities in the United States to live in and its residents are among the highest educated in the country. Palo Alto is headquarters to a number of high-technology companies, including Hewlett-Packard, Space Systems/Loral, VMware, Ford Research and Innovation Center, PARC, IDEO, Palantir Technologies and Lockheed Martin Advanced Technology Center. Palo Alto has served as an incubator and as headquarters to several other prominent high-technology companies such as Apple, Facebook, Intuit and PayPal.
Prior to the arrival of Europeans, the Ohlone lived on the San Francisco peninsula. The area of modern Palo Alto was first recorded by the 1769 party of Gaspar de Portolà, a 63-man, 200-horse expedition from San Diego to Monterey; the group overshot Monterey in the fog and when they reached modern-day Pacifica, ascended Sweeney Ridge and saw the San Francisco Bay. Portolà descended from Sweeney Ridge southeast down San Andreas Creek to Laguna Creek and the Filoli estate, thence to the San Francisquito Creek watershed camping from November 6–11, 1769 by a tall redwood to be known as El Palo Alto. Thinking the bay was too wide to cross, the group retraced their journey to Monterey, never became aware of the Golden Gate entrance to the Bay. In 1777, Father Junipero Serra established the Mission Santa Clara de Asis, whose northern boundary was San Francisquito Creek and whose lands included modern Palo Alto; the area was under the control of the viceroy of Mexico and under the control of Spain. On November 29, 1777, Pueblo de San Jose de Guadalupe was established by order of the viceroy despite the displeasure of the local mission.
The Mexican War of Independence ending in 1821 led to Mexico becoming an independent country, though San Jose did not recognize rule by the new Mexico until May 10, 1825. Mexico proceeded to grant much of the mission land. During the Mexican–American War, the United States seized Alta California in 1846. Mexican citizens in the area could choose to become United States citizens, their land grants were to be recognized if they chose to do so; the land grant, Rancho Rinconada del Arroyo de San Francisquito, of about 2,230-acre on the lower reaches of San Francisquito Creek was given to Maria Antonia Mesa in 1841. She and her husband Rafael Soto had settled in 1835 near present day Newell and Middlefield roads and sold supplies. In 1839, their daughter María Luisa Soto married John Coppinger, to be, in 1841, the grantee of Rancho Cañada de Raymundo. Upon Coppinger's death in 1847, Maria inherited it and married a visiting boat captain, John Greer. Greer owned a home on the site, now Town & Country Village on Embarcadero and El Camino Real.
Greer Avenue and Court are named for him. To the south of the Sotos, the brothers Secundino and Teodoro Robles in 1849 bought Rancho Rincon de San Francisquito from José Peña, the 1841 grantee; the grant covered the area south of Rancho Rinconada del Arroyo de San Francisquito to more or less present day Mountain View. The grant was bounded on the south by Mariano Castro's Rancho Pastoria de las Borregas grant across San Antonio Road; this became the Robles Rancho, which constitutes about 80% of Palo Alto and Stanford University today. In 1863, it was whittled down in the courts to 6,981 acres. Stories say the grand hacienda was built on the former meager adobe of José Peña near Ferne off San Antonio Road, midway between Middlefield and Alma Street, their hacienda hosted fiestas and bull fights. It was ruined in the 1906 earthquake and its lumber was used to build a large barn nearby, said to have lingered until the early 1950s. On April 10, 1853, 250 acres, comprising the present day Barron Park, Matadero Creek and Stanford Business Park, was sold for $2,000 to Elisha Oscar Crosby, who called his new property Mayfield Farm.
The name of Mayfield was attached to the community that started nearby. On September 23, 1856, the Crosby land was transferred to Sarah Wallis to satisfy a debt he owed her. In 1880, Secundino Robles, father to twenty-nine children, still lived just south of Palo Alto, near the location of the present-day San Antonio Shopping Center in Mountain View. Many of the Spanish names in the Palo Alto area represent the local heritage, descriptive terms and former residents. Pena Court, Miranda Avenue, Foothill Expwy, was the married name of Juana Briones and the name occurs in Courts and Avenues and other street names in Palo Alto and Mountain View in the quadrant where she owned vast areas between Stanford University, Grant Road in Mountain View and west of El Camino Real. Yerba Buena was to her credit. Rinconada wa
Single-mode optical fiber
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 possible solutions of the Helmholtz equation for waves, obtained by combining Maxwell's equations and the boundary conditions; these modes define the way the wave travels through space, i.e. how the wave is distributed in space. Waves have different frequencies; this is the case in single-mode fibers, where we can have waves with different frequencies, but of the same mode, which means that they are distributed in space in the same way, that gives us a single ray of light. Although the ray travels parallel to the length of the fiber, it is called transverse mode since its electromagnetic oscillations occur perpendicular 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 1961, Elias Snitzer while working at American Optical published a comprehensive theoretical description of single mode fibers in the Journal of the Optical Society of America.
At the Corning Glass Works, Robert Maurer, Donald Keck and Peter Schultz started with fused silica, a material that can be made pure, but has a high melting point and a low refractive index. They made cylindrical preforms by depositing purified materials from the vapor phase, adding controlled levels of dopants to make the refractive index of the core higher than that of the cladding, without raising attenuation dramatically. In September 1970, they announced they had made single-mode fibers with attenuation at the 633-nanometer helium-neon line below 20 dB/km. Like multi-mode optical fibers, single-mode fibers do exhibit modal dispersion resulting from multiple spatial modes but with narrower modal dispersion. 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 cheaper in bulk.
A typical single-mode optical fiber has a core diameter between 8 and 10.5 µm and a cladding diameter of 125 µm. There are a number of special types of single-mode optical fiber which have been chemically or physically altered to give special properties, such as dispersion-shifted fiber and nonzero dispersion-shifted fiber. Data rates are limited by 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, several hundred kilometers at 40 Gbit/s; the lowest-order bounds mode is ascertained for the wavelength of interest by solving Maxwell's equations for the boundary conditions imposed by the fiber, which are determined by the core diameter and the refractive indices of the core and cladding. The solution of Maxwell's equations for the lowest order bound mode will permit a pair of orthogonally polarized fields in the fiber, this is the usual case in a communication 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 normalized frequency, V, less than 2.405 g + 2 g,where g is the profile parameter. 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/IEC 11801, OS2 is defined in ISO/IEC 24702. 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 two connector plugs. Due to the sophisticated polishing and tuning procedures that may be incorporated into optical connector manufacturing, connectors are assembled onto optical fiber in a supplier’s manufacturing facility. However, the assembly and polishing operations involved can be performed in the field, for example to make cross-connect jumpers to size.
Optical fiber connectors are used in telephone company central offices, at installations on customer premises, in outside plant applications. Their uses include: Making the connection between equipment and the telephone plant in the central office Connecting fibers to remote and outside plant electronics such as Optical Network Units and Digital Loop Carrier systems Optical cross connects in the central office Patching panels in the outside plant to provide architectural flexibility and to interconnect fibers belonging to different service providers Connecting couplers and Wavelength Division Multiplexers to optical fibers Connecting optical test equipment to fibers for testing and maintenance. Outside plant applications may involve locating connectors underground in subsurface enclosures that may be subject to flooding, on outdoor walls, or on utility poles; the closures that enclose them may be hermetic, or may be “free-breathing.” Hermetic closures will prevent the connectors within being subjected to temperature swings unless they are breached.
Free-breathing enclosures will subject them to temperature