Morse Code

    Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment.Morse code speed is specified in words per minute (WPM) and associated with an "element time" equal to 1.2 seconds divided by the speed in WPM. A dot consists of an "on" element followed by an "off" element, and a dash is three "on" elements and one "off" element.Beginning in 1836, Samuel F. B. Morse and Alfred Vail developed an electric telegraph, which sent pulses of electrical current to control an electromagnet that was located at the receiving end of the telegraph wire.The technology available at the time made it impossible to print characters in a readable form, so the inventors had to devise an alternate means of communication.

    In contrast, Morse's and Vail's initial telegraph, which first went into operation in 1844, made indentations on a paper tape when an electrical current was transmitted. Morse's original telegraph receiver used a mechanical clockwork to move a paper tape. When an electrical current was received, an electromagnet engaged an armature that pushed a stylus onto the moving paper tape, making an indentation on the tape. When the current was interrupted, the electromagnet retracted the stylus, and that portion of the moving tape remained unmarked.

Pair Gain system

Pair gain is a method of  transmitting multiple telephone signals over the twisted pair used for telecommunication, This system has the advantage of including more number of subscriber lines. Thus it helps a lot in the shortage of copper pair in some remote areas. The pair gain system consist of multiplexers which combine seperate signals and at the receiver side it will be decombined into

FSL III

In FTTB up to the subscribers building or appartment the medium used is OF and after that connections to the subscriber will be given through existing copper cable or Cat5 cable.In FTTC up to the curb the transmission medium used is fiber and after that the connections to individual susbcribers will be given through copper cable.

Advantages  of Implementing FTT-x Technology

1. People can enjoy enormous amount of bandwidth.
2. In the operator side also if people are enjoying variety of services means the bandwidth will be increased there by the ARPU(Average Revenue Per User) is increased .
3. Operators can provide its subscribers the new technologies thus they can compete with their competitors.
4. Enormous amount of bandwidth is available so it can be upgraded to incorporate future technologies.

FSL- II

FSL can be implemented in three ways.Fiber from the operator end to the subscribers home  FTTH(Fiber To The Home),Fiber from the operator end to subscribers building in which many subscribers are residing FTTB(Fiber To The Building).Fiber to operator end to a nearby place in which subscriber is residing FTTC(Fiber To The Curb).These are generally termed as FTT-X where x denotes the termination point.

FSL-Fiber in the Subscriber Loop-I

All the telephone exchanges,local exchanges will be connected or interconnected through optical fiber .Thus it enables to enjoy enormous amount of  bandwidth to the suscriber.But there is a limitation.ie  from the exchange to the subscribers home we are connecting with ordinary copper cable,which will have limited bandwidth.If we use ADSL2+ technology we could achieve a bandwidth of  24 Mbps for a distance of 5 km.or less.But if we use VDSL techonology the bandwidth we can achieve is about 52 Mbps.but the distance is limited to 1 Km.So all the subscribers should reside within the 1 km radius,which is not possible.Also at each and every 1Km we should place exchanges,which is also not possible.So we will lay optical cable from the exchange to the subscribers home or a very near point.This is called Fiber in Subscriber Loop.FSL.

Blue Tooth

This is a wireless technology for exchanging data using short length radio waves.Invented by Erisscon.We can create personal network also using Bluetooth.Blutooth uses a radio technology called frequency hopping spread spectrum.The band used is 2.4 Ghz  short range frequney band which is globally unlicenced.In basic bluetooth the modulation used is GPSK.As this use radio broadcast communication system,they donot have to be in line of sight.

Optical Fiber Cable types

Pigtail/Patch Cord: These cables are tight buffered cables used for indoor purposes.There will be only one fiber in a single cable.The fiber will be coated with kevlar/aramid material..These are sometimes used for desktop connectivity also.

Loose tube Fibers: These are mainly used for outdoor purposes and contains large number of buffer tubes and inside the buffer tubes large number of fibers depending upon the number of fibers.These fibers will be mostly filled with  jelly to prevent harm to the fibers from water.

Armoured cable: These cables are extensevely used in places where rodents is a problem.There will be metal armouring to prevent rodent penetering. Since there is a  metal part  these should be earthed properly.

xDSL Tester

   xDSL line tester is used for testing the line conditions of various lines like ADSL,ADSL2,ADSL2+.This tester evaluates the line quality,Aprrox SNR,Attenuation,BER etc.There are two types of measurements ,the first one is automatic and second one is manual.In automatic measurement it will give the aprrox value of snr and from that we can conclude whether the line is suitable for providing ADSL connections.By the manual testing we can find the exact attenuation,bandwidth configuration.etc. There is an LED indicator in the meter .At first it will blinks and will be steady afterwareds.Itwill shows whether theDSL line  is enabled.The meter runs on battery.
   The other tests include upstream and downstream statistics,noise margin etc.Various tests can be performed for other layers like ATM Layer,PPP Layer,IP Layer can also be done using the meter.The main benift is that the meter can be configured as a pc as well as a modem.And with out the help of a pc we can test the line parameters .Also from the Pillar/DP we can connect to this meter,.There is a Port called CPE Jack .In that we can connect the ADSL Line .

Parallel and serial Transmission

Consider a case where  8 bits are to be transferred from sender end to receiver

Transmission of digital data

At the end of the session you will be able to

1. 
   
    understand the various types of data transmission
   
   
   
2. 
   
   Working of Modem and its interfaces
   
   
   
3. 
   
   Types of modems
   
   
   

First the information transmitted from a sender to receive is encoded in a method that can be transmitted.Then we will have to discuss the ways itcan be transmitted.ie Pc will sends and receives digital signal but we have to transmit analog signals ..so some sort of conversion is needed at both ends.that has to be considered.and some devices should be there to do this.Also these devices may be of different makers  and should be standardized for proper working,so there should be some rules or protocols  governing the devices sending and receiving.Then we can transmit the data in many ways...bit by bit we can transmit  or we can transmit the whole data simultaneously.

Splicing

Optical Fibres are layed over long distances.Mostly the optical fibre cables are available in drums of 2 km,4 km etc.So at each 4 km there will be a joint.This jointing method here used is called splicing.There are two types of splicing one is the mechanical splicing and the second one is the fusion splicing.The fig here shows mechanical splicing method.This is a quick method and the fibers won't be permanently joined,only precisely held together,so that light can pass through it very easily.The second method is fusion splicing ,here permanent joint is made between two fibers,Lot of patience and care is needed for this splicing.First we have to prepare the cable for splicing.The steps involved are

1. Remove the outer jacket of the cable using sheath remover to a required length.
2. Remove the inner jacket of the cable using sheath remove(both are similar)
3. Cutoff the strength member up to the required length.
4. Cut off the dummy buffers up to the required length.
5. Clean the jelly filled using Iso Propyl Alchol.
6. Remove the buffer tubes using Buffer tube remover.
7. Clean the jelly filled using Iso Propyl Alchol.
8. Remove the primary Coating using Primary Coating Stripper or Fiber optic stripper.
9. Clen the jelly filled using Iso Propyl Alchol until a knocking sound is heard.
10. Prepare the 2 ndcable also like this
11. Bring them near the Splicing machine.
12. Using the cleaver available in the machine do a perfect vertical cut in the two fibers
13. Place the fibers in the v-groove correctly
14. close the lids
15. Fuse the fibers
16. note the loss

Fiber optics Basics

Optical fiber communication is made successful with the invention of optical fiber cables,which is readly available as the raw material is sand or silica.The opticalfiber consist of a core and a cladding.Core have high refractive index than cladding,but the difference is only small. It works on the principle of total internal reflection .When the light travels from denser medium ,if the incident angle is greater than a particular values(it is called critical angle.) all the light will be reflected.This is called total internal reflection.Critical angle is the angle of incidence above which total internal reflection occuurs.There are two types of fibers single mode and multi mode,For carrying light over long distances we opt only single mode fibers . Also multimode fibers suffer losses like modal dispersion which affects the bandwidth carrying capacity.Multimode has large core diameter,also less precise.

Components

The Fiber optical cable comprises of an outer jacket(usually orange coloured),inside that there will be an inter coveringof black color.Inside that there will be binder which will be of plaster or yarn.Inside that the buffer tubes will be there.mostly all the buffer tubes wont be filled with fiber,some will be empty they are called fillers or dummy buffer tubes.Along with that there will be a srength member which will be made of glass reinforced plastic or fiber reienforced plastic.It will give the fiber proper strength from breaking while we bend the cable.Inside the buffer tubes there will be optical fibers.They will be coated with an acrylic coating called primary coating.when we remove that we get bare fiber.

Usually the optical fiber cables will be available in bundles of 2 km 4 km...For long distance cable laying we have to join the cables after 2 kms...This process we are using is called Fiber Splicing.

Magic of optical Fiber

Cost of almost Everything in the universe goes on increasing...but take the case of telecommunication,whether it is increasing or decreasing,yeh sure its decresing day by day.But the facilities are increasing.Also the users are also increasing day by day.Can any one say why the rate of communication or the tariff in coming down? People may say its competition,but thatis not true coz in almost fields there is competition and the price is going up.ITs the magic of optical fiber that helps this low cost communication possible with high quality and latest facilities.