A

PRESENTATION

ON

NORTH WESTERN RAILWAYS

BY: KAVITA KHANDEKAR

08ERWEC038

Optical fiber can be used as a medium for telecommunication and networking because it is flexible and can be bundled as cables.

Optical fiber can be used to supply a low level of power (around one watt) to electronics situated in a difficult electrical environment.

This method is most commonly used in front sights.

An optical fiber doped with certain rare earth elements such as erbium can be used as the gain medium of a laser of optical amplifier.

Both wavelengths of light are transmitted through the doped fiber, which transfers energy from the second pump wavelength to the signal wave.

Principle of operation  An optical fiber is a cylindrical dielectric waveguide

(nonconducting waveguide) that transmits lights along its axis, by the process of total internal reflection.

The fiber consists of a core surrounded by a cladding layer, both of which are made of dielectric material.

To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding.

The boundary between the core and cladding may either be abrupt, in step-index fiber, or gradual, in graded-index fiber.

Total internal reflection  When light traveling in a dense medium hits a boundary

at a steep angle (lager than the “critical angle” for the boundary), the light will be completely reflected.

In simpler terms, there is a maximum angle form the fiber axis at which light may enter the fiber so that I tit will propagate, or travel, in the core of the fire, the since of this maximum angle is the numerical aperture (NA) of the fiber.

Optical fiber types. Single-mode fiber Special-purpose fiber

In 1933 a French scientist established communication across the English Channel with an I Watt transmitter operating on 170 um wavelength.

This he called " It is multi channel directional narrow band radio relay system. Microwave MICRO" .

The Microwave frequency spectrum is usually taken to extend from 1 GHz to 1000 GHz. The electromagnetic wave spectrum of interest is

Ultra high frequency (UHF) from 300 to 3000 MHz Super high frequency (SHF) 3 to 30 GHz Externally high frequency (EHF) 30 to 300 GHz Microwave communication is known as a form of "line of

sight" communication, because there must be nothing obstructing the transmission of data between these towers for signals to be properly sent and received.

FEATURES OF DIGITAL MICROWAVE

It is having 100% hot stand by system with space diversity provision.

The modulation is QPSK (quadrature phase shift keying).

Independent switching for TX and Rx direction. To avoid overreach interference 4 or 6 frequency plan is

used.

The reliability of circuit is very high i.e. efficiency is 99.999%.

Computerized passenger reservation system is the most useful facility, which enhances the image of Indian railways in public.

Initially it was installed in Delhi by Criss and for western and central railways a common super computer is installed CSTN and the trains of both railways are programmed on this computer.

When more than one terminal is required at a place then another 8 terminal modem Mux called CODEC is used.

In PRS there is only one set of computer in which all the information regarding the main coaches, reservation fare, status are available.

Modulation :- Process of superimposing original signal on carrier signal is b/a modulation.

Multiplexing :- Converting multi input signal into one output signal is known as multiplexing.

MODEM :- It is the combination of modulator and demodulator. Actually multiplexer is also a device which itself also as multiplexing and demultiplexing.

It is analogous to modem the help of modulation analog data is converted into is converted into analog data.

PGM:- Pluse code modulation. It is the process of tranferring the digital data through the fiber. The analog data is first converted into digital data. (sampling, Filtering , Quantization)

In early days the officials works in railway was done on the paper like information to department or any other instruction for the employee was given only in the written way on the paper.

The networks used in railway are

1) Railnet 2) FOIS : Freight operation and information system

 Indian railways have decided to setup their own Corporate Wide Information system called Railnet to provide computer connectivity between Zonal railways, production units.

Composition of Railnet

Intranet Intra-net is an internal network of Indian railway

allowing the railway officer and staff to communicate on this digitzed network.

Internet Internet allows users to get into a global communication

and global pool of knowledge advertisement and entertainment through www ( World Wide Web) in a secured manner. It is operated by railway board.

The main server is attached to all station and exchanges with help of interface protocol & MUX.

The railway department has taken 2 MB stream of MTNL.