Optical Fiber communication

ECE 7th sem

1. What is Communication Communication is the process of exchanging information. Sending and receiving of messages from one place to another is called communication. The basic elements involved in communication— Information Source Transmitter Communication Channel Receiver

2. Types of Electronic Communication Simplex This type of communication is one-way. Examples are: Radio TV broadcasting Beeper (personal receiver) Half Duplex The form of two-way communication in which only one party transmits at a time is known as half duplex . Examples are: Police, military, etc. radio transmissions Citizen band (CB) Family radio Amateur radio Full Duplex Most electronic communication is two-way and is referred to as Full-duplex. When people can talk and listen simultaneously, it is called full duplex . The telephone is an example of this type of communication.

3. Types of Communication Analog Communication AM, FM, PM etc. Digital Communication ASK, FSK, PSK, QPSK etc. Microwave Communication Communication through radio/microwaves/frequencies Optical Communication Communication through Light

4. Basic Block Diagram of Communication System Noise degrades or interferes with transmitted information Figure: General Model of All Communication Systems

5. Basic Concepts of Communication Analog Signals An analog signal is a smoothly and continuously varying voltage or current. Examples are: Sine wave Voice Video (TV) Analog and Digital Signals

6. Basic Concepts of Communication Digital Signals Digital signals change in steps or in discrete increments. Most digital signals use binary or two-state codes. Examples are: Telegraph (Morse code) Continuous wave (CW) code Serial binary code (used in computers) Analog and Digital Signals

7. Channel Multiplexing and Modulation Modulation and multiplexing are electronic techniques for transmitting information efficiently from one place to another. Modulation makes the information signal more compatible with the medium. Multiplexing allows more than one signal to be transmitted concurrently over a single medium.

8. Channel Multiplexing and Modulation Figure: Multiplexing and Modulation at The Transmitter

9. Channel Multiplexing and Modulation Frequency Division Multiplexing Each signal is modulated to a different carrier frequency Carrier frequencies separated so signals do not overlap (guard bands)

10. Channel Multiplexing and Modulation Time Division Multiplexing Multiple digital signals interleaved in time domain. Time slots preassigned to sources and fixed.

11. Modulation Formats NON-RETURN-TO-ZERO- In Communication, a non-return-to-zero ( NRZ ) line code is a binary code in which ones are represented by one significant condition, usually a positive voltage, while zeros are represented by some other significant condition, usually a negative voltage, with no other neutral or rest condition. RETURN-TO-ZERO- (RZ or RTZ) describes a line code used in communications signals in which the signal drops (returns) to zero between each pulse.

12. 12 Need of Fiber Optic Communications Fiber communication promised extremely high data rates, which allow high capacity transmission quickly. It also had the potential for transmission over long distances without the need to amplify and retransmit along the way. Speed limit of electronic processing, limited bandwidth of copper/coaxial cables. Optical fiber has very high-bandwidth (~30 THz) Optical fiber has very low loss (~0.25dB/km @ 1550nm ) suitable for long-distance transmission

13. Increase of the bit rate distance product BL for different communication Technologies over time. Evaluation of Lightwave Communication Systems A figure of merit of communication systems is the bit rate–distance product, BL, where B is the bit rate and L is the repeater spacing.

14. Frequency and Wavelength Graph

15. 15 Optical Communication amplitude wavelength position/distance electromagnetic wave carry energy from one point to another travel in straight line described in wavelength (usually in mm or nm ) speed of light in vacuum = 3  10 8 m/s

16. Block Diagram of Optical Fiber Communication System Figure: Basic Block Diagram of Optical Communication System

17. Block Diagram of Optical Fiber Communication System

18. Optical Transmitter

19. Optical Modulator

20. Optical Receiver

21. Advantages of optical fiber communication Increased Bandwidth and Channel Capacity Low Signal Attenuation Immune to Noise No Crosstalk Lower Bit Error Rates Signal Security Electrical Isolation Reduced Size and Weight of Cables Radiation Resistant and Environment Friendly Resistant to Temperature Variations etc.

22. Disadvantages of optical fiber communication Specialist skills needed Cost of installation Cost of transmission equipment from electrical to optical signals Optical fibers can not carry electrical power

23. Applications of optical fiber communication As fibers are very flexible, they are used in flexible digital cameras. Fibers are used in mechanical imaging i.e. for inspection of mechanical welds in pipes and engines of rockets, space shuttles, airplanes. Fibers are used in medical imaging such as endoscopes and laparoscopes. Fibers can be used under sea communication. Fibers are used in military applications such as aircrafts, ships, tanks etc. Nuclear testing applications use optical fiber phase sensors and transducers Fibers are used in public utility organizations like railways, TV transmission etc. Fibers are used in LAN systems of offices, industrial plants and colleges etc. Fibers are used in telecommunication such as voice telephones, video phones, telegraph services, message services and data networks.

24. Queries…….. ?