An optical fiber (or fibre in British English) is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light[a] between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers.
Optical fibers typically include a core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total 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, while those that support a single mode are called single-mode fibers (SMF). 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 (3,300 ft).
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 fiber cores, and the coupling of these aligned 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 mechanical 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-American physicist Narinder Singh Kapany, who is widely acknowledged as the father of fiber optics.
Coventry (/ˈkɒvəntri/ (About this soundlisten) KOV-ən-tree or /ˈkʌv-/ KUV-) is a city, administrative centre and metropolitan borough in England and the United Kingdom. It is built on the River Sherbourne, which remains largely hidden by infrastructure, although it can be seen by the canal. Coventry has been a large settlement for centuries, although it was not founded and given its city status until the Middle Ages; since then it has been one of the most important and largest cities of the country. The conurbation consists of the Coventry and Bedworth Urban Area, being the 20th largest in the country; the city is governed by Coventry City Council.
Historically part of Warwickshire, at the 2011 census Coventry had a population of 316,915, making it the 9th largest city in England and the 11th largest in the United Kingdom. It is the second largest city in the West Midlands region, after Birmingham, and is separated from the West Midlands conurbation by the Meriden Gap.
Coventry is 19 miles (31 km) east-southeast of Birmingham, 25 miles (40 km) southwest of Leicester, 11 miles (18 km) north of Warwick and 94 miles (151 km) northwest of London. Coventry is also the most central city in England, being only 12 miles (18 km) south-southwest of the country's geographical centre in Leicestershire; it is located in the West Midlands.
The current Coventry Cathedral was built after most of the 14th century cathedral church of Saint Michael was destroyed by the Luftwaffe in the Coventry Blitz of 14 November 1940. Coventry motor companies have contributed significantly to the British motor industry. The city has three universities, Coventry University in the city centre, the University of Warwick on the southern outskirts and the smaller private Arden University, with its headquarters close to Coventry Airport.
On 7 December 2017, the city won the title of UK City of Culture 2021, after beating Paisley, Stoke-on-Trent, Swansea and Sunderland to the title. It will be the third title holder of the quadrennial award which began in 2013. In July 2020 it was announced that the City of Culture festivities would not commence until May 2021 and conclude in May 2022 due to preparational and infrastructural delays caused by the COVID-19 pandemic. Following this Coventry City of Culture Trust released a manifesto film, celebrating the city of Coventry and announcing the brand for Coventry UK City of Culture 2021, 'Coventry Moves'.