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Optical fiber based communication systems

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  1. Introduction
    1. Optical fibre communication and data system
    2. Fibre material
    3. Optical communication link
    4. Types of light wave communication
    5. Basic elements of optical fibre system
  2. Propogation in optical fibres
    1. Principle
    2. Attenuation
    3. Advantages of optical fibre
  3. Construction
    1. Component used
    2. Basic principle
    3. Block diagram
    4. The circuit
    5. Component list
    6. Circuit diagram
  4. Working
    1. Transmitter section
    2. Receiver section
  5. Limitations and future expectations
  6. References

For years, fiber optics has been merely a system for piping light around corners and into the inaccessible places to allow the hidden to be lighted. But now, fiber optics has evolved into a system of significantly greater importance and use. Throughout the world, it is now being used to transmit voice, television and data signals as light waves over flexible hair-thin threads of glass or plastic. Its advantages as compared with conventional coaxial cable or twisted wire pairs are manifold. As a result, millions of dollars are being spent to put these light wave communication systems into operation.

Interest in fiber as a medium began in 1966 when C. Kao and G.A. Hockham at Standard Telecommunications Laboratory predicated that by removing the impurities in the glass, 20 dB/km attenuations would be achievable. At this level, fiber became a practical communication medium. Most of the optical fibers, in use today, are made of either silica glass (SiO2) or plastic. The change in refractive index, between the core and cladding is achieved by the addition of certain dopants to the glass; all-plastic fibers use different plastics for the core and cladding. In order to increase the reflective index, oxides of germanium (GeO2) or phosphorus, (P2¬O¬5) are commonly used. A decrease results from doping with Boron Oxide, (B2O3) or fluorine, (F).

[...] positive terminal of B2 to type collector. When the base emitter bias is about + 0.6 electrons (the majority carriers in the heavily doped n type emitter) cross the junction (as they would in any junction diode) into the base. Their loss is made good by electrons entering the emitter from the external circuit to form the emitter current. At the same time holes from the base to the emitter but, since the type base is lightly doped, this is small compared with the electron flow in the opposite direction, i.e. [...]

[...] The LEDs are made in the form of flat tiny P-N junction enclosed in a semi-spherical dome made up of clear coloured epoxy resin. The dome of a LED acts as a lens and diffuser of light. The diameter of the base is less than a quarter of an inch. The actual diameter varies somewhat with different makes. The common circuit symbols for the LED are shown in fig It is similar to the conventional rectifier diode symbol with two arrows pointing out. [...]

[...] Photo Transistor MISCELLANEOUS Speaker 8 ohms Optical Fiber General purpose 3.6 CIRCUIT DIAGRAM RECEIVER 4.WORKING 4.1 TRANSMITTER SECTION In this circuit we use two circuits one is DTMF generator and second is operational amplifier. In the DTMF generator circuit we use IC UM91214 as a DTMF generator. Working voltage of this IC is 3.3 volt dc. So that we use one 3.3 volt zener diode as a regulator and provide a regulated power supply to this circuit. Output signal is available on the pin no 7. [...]

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