Merits and Demerits of Fiber Optic Communication System

Merits and Demerits of Fiber Optic Communication System Points : merits and demerits of fiber optic communication system Merits 1. Very low attenuation: When high frequency signals are propagated through conventional coaxial cables, it loses half of its power only after few hundred meters where as the fiber optics loses the same amounts of power in 15 Km or more. Thus repeaters will be required at very large distances.

2. Large bandwidth: The transmission rate exceeding 10 G-bits/s are possible as compared to 1 G-bits/s for coaxial cables. This capacity can be further increased by using carrier waves of different wavelengths.

Uses of Fiber Optics in Telecommunication System

Uses of Fiber Optics in Telecommunication System Points : uses of fiber optics in telecommunication system The fiber optics is superior to metallic conductors as transmission medium for signals because of its high bandwidth, low attenuation, interference immunity, low cost, and light weight.

Due to these advantages the fiber optics is extensively used in the field of telecommunication. Some of the applications of fiber optics in the telecommunication system are:

Because of its very low attenuation, the fiber optics is used as junction cables between exchanges. where channel capacity is in excess of 240 channels.

LASER (Light Amplification by Stimulated Emission of Radiation)

LASER (Light Amplification by Stimulated Emission of Radiation) Points : laser (light amplification by stimulated emission of radiation) The Laser is like the LED but emit light in a different way, resulting in a higher output powers and more directional beams. The beam is produced by a cavity resonator that reflects light again and again through the excited medium. The cavity consists of a pair of mirrors, one at each end of the region occupied by excited atoms. The light emitted toward one mirror is reflected again and again between the two mirrors thus stimulating emission from electrons.

Light Emitting Diode (LED)

Light Emitting Diode (LED) Points : light emitting diode (led), Definition The basic operation of the LED is shown in the figure. The LED is a PN-junction diode and work when forward biased. When a small forward biased voltage is applied, it causes a current to flow across the junction. Electrons in the N-region and holes in the P-region flow toward the junction where they recombine and release some energy. The recombination continues as long as the voltage is applied. In Silicon and Germanium semiconductors, the released energy is dissipated as heat. While in the LEDs, the released energy appears as photon of light. The semiconductor materials used for LEDs in fiber optic systems arc gallium aluminum arsenide or gallium arsenide. Other semiconductor compound used to make LEDs is gallium-arsenide-phosphide and indium-gallium-arsenide- phosphide. GaAs LEDs emit near 930 nm. While GaAIAs emit light at wavelengths of 750 to 900 nm. GaAsP emits visible red light at 665 nm.

Physics of Optical Fibers

Physics of Optical Fibers Points : Physics of Optical Fibers, Electromagnetic Spectrum, Reflection of Light, Refraction of Light, Total Internal Reflection, Numerical Aperture, The working of optical fibers depends on the basic principles of optics and the interaction of light with matter. From physical point of view, light can be considered either electromagnetic waves or as photons, quanta of electromagnetic energy. Both points of views are valid and valuable. But the most useful point of view is that light is rays and travel in straight lines, between or within optical elements, which can reflect or refract (bend) light rays at their surfaces.

Block Diagram of Fax-Machine

Block Diagram of Fax-Machine Points : block diagram of fax-machine, components of fax-machine, Central Microprocessor, Fax-Modem, Control Panel, Image Buffer and Control, CCD (Charge Coupled Device) Image Sensor, Thermal Printer, Power Supply In spite of the fact, that Fax-machine is small in appearance yet it incorporates a large amount of electronics and mechanical components into its operation. A simplified block diagram of the Fax-machine is shown in the figure. Central Microprocessor It is the heart of all Fax-Machines. The microprocessor manages all the operations of the machine and coordinates the flow of data into and out of the system. The microprocessor consists of the following memories:
a. ROM: It stores the program used to run the machine.
b. RAM: It stores results of calculations, variables, system status flags, or any other information that will change regularly during normal operations.

Facsimile or Fax Machine

Facsimile or Fax Machine Points : facsimile or fax machine, Definition The Fax Machine digitizes printed images and transmits the corresponding, Data over the telephone network. Similarly, it receives digital image information from the telephone network and reproduces an exact copy of the image on the paper.

To transmit a document through Fax machine, the document is positioned in the machine. Then a telephone call is made by dialling the number of the person who is to receive this document. By doing so, an electrical connection is established between the calling and called machines. The “Send” key is then pressed at the transmitting end, which switches the telephone circuits to the Fax machine. When the circuit between the two machines is complete, a process called handshaking takes place which means that both machines are in synchronization.

Application of Computer in Digital Exchange

Application of Computer in Digital Exchange Points : application of computer in digital exchange A computer is programmable electronic device that can store, retrieve, and process data. The use of computer and, more recently, microprocessor has brought a revolution in the design and operation of switching systems. In modern exchanges, particularly those using S.P.C., the use of a powerful and highly reliable computer control all the functions of an exchange.

All the information used in the translation processes are stored in the computer, thus it is easier to update the system when required. The computer has a complete overview of the system, so is able to analyse traffic patterns and diagnose faults more easily. Details of traffic and faults along with information for the preparation of user’s bills can also be recorded in the computer.