01-Overview of Optical Fiber Communication.pptx

optical fiber

1. Chapter One Overview of Optical Fiber Communication Systems Addis Ababa Science and Technology University College of Electrical and Mechanical Engineering Electrical and Computer Engineering Department Optics and Optical Communication (EEEg-4302)

2. Overview of Optical Fiber Communication Systems Outline : Introduction Historical Perspective Basic Elements of a Fiber Optic Link Transmission Media Alternatives to Fiber Optic Advantages of Optical Fiber Communication 2 Chapter 1- Overview of Optical Fiber Comm.

3. Introduction Optical Communication is the most modern mode of wired communication.   Optical communication is also the youngest mode of communication. Its capabilities supersede all other modes of communication.   Before optical communication most of the communication was in radio and microwave domain which has frequency range orders of magnitude lower than the optical. 3 Chapter 1- Overview of Optical Fiber Comm.

4. Introduction …. Optical fiber is the backbone of the modern communication networks The Optical Fiber Carries: Almost all long distance phone calls Most Internet traffic (Dial-up, DSL or Cable) Most Television channels (Cable or DSL) Most LAN, WAN and much more One fiber can carry up to 6.4 Tb/s (10 12 b/s) or 100 million conversations simultaneously. 4 Chapter 1- Overview of Optical Fiber Comm.

5. Introduction …. 5 Chapter 1- Overview of Optical Fiber Comm. Fig. International Submarine Optical Fiber Map

6. Introduction …. 6 Chapter 1- Overview of Optical Fiber Comm. Fig1. Electromagnetic spectrum of different guided medias

7. Historical Perspective The use of visible optical carrier waves or light for communication has been common for many years. Simple systems such as signal fires, reflecting mirrors and, more recently, signaling lamps have provided successful, if limited, information transfer. Moreover, as early as 1880 Alexander Graham Bell reported the transmission of speech using a light beam. The photophone proposed by Bell just four years after the invention of the telephone modulated sunlight with a diaphragm giving speech transmission over a distance of 200 m. 7 Chapter 1- Overview of Optical Fiber Comm.

8. General Vs Optical Communication Systems An optical fiber communication system is similar in basic concept to any type of communication system. In electrical communications the information source provides an electrical signal to a transmitter comprising electrical and electronic components which converts the signal into a suitable form for propagation over the transmission medium. The transmission medium can consist of a pair of wires, a coaxial cable or a radio link through free space down which the signal is transmitted to the receiver. 8 Chapter 1- Overview of Optical Fiber Comm.

9. General Vs Optical Communication Systems…….. For optical fiber communication system, the information source provides an electrical signal to a transmitter comprising an electrical stage which drives an optical source to give modulation of the light wave carrier. The optical source which provides the electrical/optical conversion may be either a semiconductor laser or light-emitting diode (LED). The transmission medium consists of an optical fiber cable and the receiver consists of an optical detector. 9 Chapter 1- Overview of Optical Fiber Comm.

10. General Vs Optical Communication Systems…….. 10 Chapter 1- Overview of Optical Fiber Comm. Fig . Comparison of General and Optical Communication Systems

11. Basic Elements of a Fiber Optic Link 11 Chapter 1- Overview of Optical Fiber Comm.

12. Basic Elements of a Fiber Optic Link…….. The Fiber – that carries the light Single Mode Fiber (only one EM mode exists), offers the highest bit rate, most widely used Multi Mode Fiber (multiple EM modes exist), hence higher dispersion (due to multiple modes) cheaper than SMF, used in local area networks Step Index Fiber – two distinct refractive indices Graded Index Fiber – gradual change in refractive index 12 Chapter 1- Overview of Optical Fiber Comm.

13. Basic Elements of a Fiber Optic Link…….. Optical Transmitter converts the electrical information to optical format (E/O) Light Emitting Diode (LED): cheap, robust and used with MMF in short range applications Surface emitting and edge emitting LED LASER Diode: high performance and more power, used with SMF in high speed links Distributed Feedback (DFB) Laser – high performance single mode laser Fabry-Perrot (FP) lasers – low performance multimode laser 13 Chapter 1- Overview of Optical Fiber Comm.

14. Basic Elements of a Fiber Optic Link…….. Optical Receiver - converts the optical signal into appropriate electrical format (E/O) PIN Photo Diode: Low performance, no internal gain, low cost, widely used Avalanche Photo Diode (APD): High performance with internal (avalanche) gain Repeater: receives weak light signal, cleans-up, amplifies and retransmits (O/E/O) Optical Amplifier: Amplifies light in fiber without O/E/O 14 Chapter 1- Overview of Optical Fiber Comm.

15. Transmission Media Alternatives to Fiber Optic There are various wired and wireless media used for long and short distance communication. Their broad characteristics are summarized as follows. 15 Chapter 1- Overview of Optical Fiber Comm.

16. Transmission Media Alternatives to Fiber Optic……. 16 Chapter 1- Overview of Optical Fiber Comm.

17. Transmission Media Alternatives to Fiber Optic……. The first two media have a very limited bandwidth. Microwave links and satellite communication have comparable bandwidths as in principle their mode of operation is same but the spatial reach of satellite is far greater. 17 Chapter 1- Overview of Optical Fiber Comm.

18. Transmission Media Alternatives to Fiber Optic……. Satellite Communication Systems Cover very large areas (global coverage) Very useful in sparsely populated areas: rural areas, sea, mountains, etc. Different orbit heights GEOs (39000 Km) versus LEOs (2000 Km) Limited-quality voice/data transmission Iridium , Globalstar , Teledesic and Inmarsat are some example of communication satellites 18 Chapter 1- Overview of Optical Fiber Comm.

19. Transmission Media Alternatives to Fiber Optic……. Classification of Satellites: There are three basic categories of satellites based on their location of their orbits. Low Earth Orbit (LEO) Medium Earth Orbit (MEO) Geosynchronous Orbit (GEO) 19 Chapter 1- Overview of Optical Fiber Comm.

20. Transmission Media Alternatives to Fiber Optic……. 20 Chapter 1- Overview of Optical Fiber Comm.

21. Transmission Media Alternatives to Fiber Optic……. Applications of satellite communication: Traditional Applications (GEO and MEO satellites) Weather satellite Radio and TV broadcasting Military satellites GPS Telecommunication Applications (LEO satellites) Global telephone connections Backbone for global network 21 Chapter 1- Overview of Optical Fiber Comm.

22. Comparison of Satellite and Optical communication Before fiber optic communication became viable, satellite communication was the only choice for long distance communication. 22 Chapter 1- Overview of Optical Fiber Comm.

23. Comparison of Satellite and Optical communication…. The two modes of transmission have their own merits and limitations. The two can in fact play a complementary role. We therefore conclude that Satellite and Optical communication will co-exist due their complementary nature. 23 Chapter 1- Overview of Optical Fiber Comm.

24. Advantages of Optical Fiber Communication Enormous potential bandwidth: The optical carrier frequency in the range 10 13 to 10 16 Hz (generally in the near infrared around 10 14 Hz or 10 5 GHz) yields a far greater potential transmission bandwidth than metallic cable systems. Indeed, by the year 2000 the typical bandwidth multiplied by length product for an optical fiber link incorporating fiber amplifiers was 5000 GHz km in comparison with the typical bandwidth–length product for coaxial cable of around 100 MHz km. 24 Chapter 1- Overview of Optical Fiber Comm.

25. Advantages of Optical Fiber Communication……… Small size and weight: Optical fibers have very small diameters which are often no greater than the diameter of a human hair . Hence, even when such fibers are covered with protective coatings they are far smaller and much lighter than corresponding copper cables. This is a tremendous boon towards the alleviation of duct congestion in cities, as well as allowing for an expansion of signal transmission within mobiles such as aircraft, satellites and even ships. 25 Chapter 1- Overview of Optical Fiber Comm.

26. Advantages of Optical Fiber Communication……… Electrical isolation: Optical fibers which are fabricated from glass, or sometimes a plastic polymer, are electrical insulators and therefore, unlike their metallic counterparts, they do not exhibit earth loop and interface problems. Furthermore, this property makes optical fiber transmission ideally suited for communication in electrically hazardous environments as the fibers create no arcing or spark hazard at abrasions or short circuits. 26 Chapter 1- Overview of Optical Fiber Comm.

27. Advantages of Optical Fiber Communication……… Immunity to interference and crosstalk: Optical fibers form a dielectric waveguide and are therefore free from electromagnetic interference (EMI), radio-frequency interference (RFI), or switching transients giving electromagnetic pulses (EMPs). Hence the operation of an optical fiber communication system is unaffected by transmission through an electrically noisy environment and the fiber cable requires no shielding from EMI. 27 Chapter 1- Overview of Optical Fiber Comm.

28. Advantages of Optical Fiber Communication……… Immunity to interference and crosstalk: The fiber cable is also not susceptible to lightning strikes if used overhead rather than underground. Moreover, it is fairly easy to ensure that there is no optical interference between fibers and hence, unlike communication using electrical conductors, crosstalk is negligible, even when many fibers are cabled together. 28 Chapter 1- Overview of Optical Fiber Comm.

29. Advantages of Optical Fiber Communication……… Signal security: The light from optical fibers does not radiate significantly and therefore they provide a high degree of signal security. Unlike the situation with copper cables, a transmitted optical signal cannot be obtained from a fiber in a noninvasive manner. This feature is obviously attractive for military, banking and general data transmission (i.e. computer network) applications. 29 Chapter 1- Overview of Optical Fiber Comm.

30. Advantages of Optical Fiber Communication……… Low transmission loss: The development of optical fibers over the last 20 years has resulted in the production of optical fiber cables which exhibit very low attenuation or transmission loss in comparison with the best copper conductors. Fibers have been fabricated with losses as low as 0.15 dB/km and this feature has become a major advantage of optical fiber communications. 30 Chapter 1- Overview of Optical Fiber Comm.

31. Advantages of Optical Fiber Communication……… Potential low cost: The glass which generally provides the optical fiber transmission medium is made from sand – not a scarce resource. So, in comparison with copper conductors, optical fibers offer the potential for low-cost line communication. This low cost potential in optical fibers has not yet been achieved in all the other component areas associated with optical fiber communications. 31 Chapter 1- Overview of Optical Fiber Comm.

32. 32 Chapter 1- Overview of Optical Fiber Comm. The End! Any Question?