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| Digital India with Optical fibre technology | | | Nikhil Gupta | 7/21/2015 9:50:19 PM |
| Fibre optic communication has revolutionised the in
dustry nowadays . It has also made its presence widely
felt within the data networking community as well . Using fibre optic cable, optical communications have enabled telecommunications links to be made over much greater distances and with much lower levels of loss in the transmission medium and possibly most important of all, fibre optical communications has enabled much higher data rates to be accommodated. As a result of these advantages, fibre optic communications systems are widely employed for applications ranging from major telecommunications backbone infrastructure to Ethernet systems, broadband distribution, and general data networking.
Since the earliest days of telecommunications there has been an ever increasing need to transmit more data even faster. Initially single line wires were used.
These gave way to coaxial cables that enabled several channels to be transmitted over the same cable. However these systems were limited in bandwidth and optical systems were investigated. There are a number of compelling reasons that lead to the widespread adoption of fibre optic cabling for telecommunications applications There is much lower levels of signal attenuation in optical communication . Fibre optic cabling provides a much higher bandwidth allowing more data to be delivered . Fibre optic cables are much lighter than the coaxial cables that might otherwise be used. Fibre optics do not suffer from stray interference pickup that occurs with coaxial cabling or twisted pair cables . Any fibre optic data transmission system will comprise a number of different elements.
There are four major elements vital for practical systems and these are Transmitter or light source , Fibre optic cable , Optical repeater and Receiver or Detector . The different elements of the system will vary according to the application. Systems used for lower capacity links, possibly for local area networks will employ somewhat different techniques and components to those used by network providers that provide extremely high data rates over long distances. Nevertheless the basic principles are the same whatever the system.
In the optical communication system the transmitter or light source generates a light stream modulated to enable it to carry the data. Conventionally a pulse of light indicates a "1" and the absence of light indicates "0". This light is transmitted down a very thin fibre of glass or other suitable material to be presented at the receiver or detector. The detector converts the pulses of light into equivalent electrical pulses. In this way the data can be transmitted as light over great distances. A fibre optic cable consists of core, around which is another layer referred to as the cladding. Outside of this there is a protective outer coating. The fibre optic cables operate because their cladding has a refractive index that is slightly lower than that of the core. This means that light passing down the core undergoes total internal reflection when it reaches the core / cladding boundary, and it is thereby contained within the core of the optical fibre.
There is a maximum distance over which signals may be transmitted over fibre optic cabling. This is limited not only by the attenuation of the cable, but also the distortion of the light signal along the cable. In order to overcome these effects and transmit the signals over longer distances, repeaters and amplifiers are used. Opto-electric repeaters may be used.
These devices convert the optical signal into an electrical format where it can be processed to ensure that the signal is not distorted and then converted back into the optical format. It may then be transmitted along the next state of the fibre optic cable. An alternative approach is to use an optical amplifier. These amplifiers directly amplify the optical signal without the need to convert the signal back into an electrical format. In view of the much reduced cost of fibre optic amplifiers over repeaters, amplifiers are far more widely used. Light travelling along a fibre optic cable needs to be converted into an electrical signal so that it can be processed and the data that is carried can be extracted. The component that is at the heart of the receiver is a photo-detector. This is normally a semiconductor device and may be a p-n junction, a p-i-n photo-diode or an avalanche photo-diode. Photo-transistors are not used because they do not have sufficient speed. Once the optical signal from the fibre optic cable has been applied to the photo-detector and converted into an electrical format it can be processed to recover the data which can then be passed to its final destination. Fibre optic transmission of data is generally used for long distance telecommunications network links and for high speed local area networks. The choice between optical fiber and electrical or copper based transmission for a particular system is made based on a number of trade-offs. Optical fibre is generally chosen for systems requiring higher bandwidth or spanning longer distances than electrical cabling can accommodate.
The main benefits of fibre are its exceptionally low loss (allowing long distances between amplifiers/repeaters), its absence of ground currents and other parasite signal and power issues common to long parallel electric conductor runs (due to its reliance on light rather than electricity for transmission, and the dielectric nature of fibre optic), and its inherently high data-carrying capacity. Thousands of electrical links would be required to replace a single high bandwidth fibre cable. Another benefit of fibre is that even when run alongside each other for long distances, fibre cables experience effectively no crosstalk in contrast to some types of electrical transmission lines . Fibre can be installed in areas with high electromagnetic interference (EMI), such as alongside utility lines, power lines, and railroad tracks. Nonmetallic all-dielectric cables are also ideal for areas of high lightning-strike incidence.
Nowadays FILL or fibre in the local loop is in vogue . Generally, fibre is used in either all or part of the local loop distribution network of the telecom service providers . FILL can be implemented with architectures such as fibre to the cabinet (FTTC), fiber to the node (FTTN), and fibre to the premises (FTTP). Residential areas already served by balanced pair distribution plant call for a trade-off between cost and capacity. The closer the fiber head, the higher the cost of construction and the higher the channel capacity. In places not served by metallic facilities, little cost is saved by not running fibre to the home. A similar network called a Hybrid fibre Coaxial(HFC) network is used by cable TV operators but is usually not synonymous with "fibre In the local loop", although similar advanced services are provided by the HFC networks.
In India at present OFC (Optical Fibre Cable) connectivity is available in all State Capitals, Districts, HQs and upto the Block Level. There is a plan to connect all the 2,50,000 Gram panchayats in the country.
This will be done by utilizing existing fibre of PSUs (BSNL, Railtel and Power Grid) and laying incremental fibre to connect to Gram Panchayats wherever necessary. Dark fibre network thus created will be lit by appropriate technology thus creating sufficient bandwidth at the Gram Panchayats. This will be called the National Optical Fibre Network (NOFN). Thus connectivity gap between Gram Panchayats and Blocks will be filled. Non-discriminatory access to the NOFN will be provided to all the Service Providers.
These service providers like Telecom Service Providers(TSPs), ISPs, Cable TV operators and Content providers can launch various services in rural areas. Various categories of applications like e-health, e-education and e-governance etc. can be provided by these operators.
This is a part of Digital India which is an initiative of the Government of India to integrate the government departments and the people of India to ensure effective governance. It also aims at ensuring that the government services are made available to citizens electronically by reducing paperwork.
This initiative also includes a plan to connect rural areas under high speed internet networks. The programme also aims at providing digital infrastructure as a utility to every citizen as well as high-speed internet as a core utility in all Gram Panchayats . This is expected to facilitate broadband connectivity to over 600 million rural citizens of the country.
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