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Overview of Modern Electronic Communication Systems

Overview of Modern Electronic Communication Systems. Presented By: Dr. (Mrs) Neena Gupta Asstt Professor, E&EC Deptt. PEC, Chandigarh. Today, almost all of the wired and wireless communication is digital.Digital Communication offers following advantages over analog High SNR

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Overview of Modern Electronic Communication Systems

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  1. Overview of Modern Electronic Communication Systems Presented By: Dr. (Mrs) Neena Gupta Asstt Professor, E&EC Deptt. PEC, Chandigarh

  2. Today, almost all of the wired and wireless communication is digital.Digital Communication offers following advantages over analog • High SNR • Easy Signal processing • Error detection and correction • Multiplexing • Cheaper circuitry • Easy detection of signal; we have to detect the presence(1) or absence of signal(0).

  3. Modern electronic communication systems can be broadly classified into following types: • Optical Communication • Mobile Communication • Satellite Communication

  4. Optical Communication AN OVERVIEW

  5. Electrical Communication Optical Communication Structure of Optical Fiber and Optical Fiber Cable

  6. The spread of the use of Optical Communication through-out the world

  7. Information Systems Evolution & What is it ? • Why there is Demand of Large bandwidth ? • Why Optical Fiber Technology ? • Optical Transmission fundamentals. • How to Explode the optical fiber bandwidth ? • Data rate requirements for high speed networks. • Optical Fiber Solutions for today’s Systems & Networks.

  8. An Information Model Definition: Delivering information to an authorized user when it is needed, wherever it is needed i.e, regardless of the physical location of the user or of the information, and whatever form it is needed in a secure way.

  9. Needs For Today’s Optical Systems  Increase capacity of transmission (bit/sec).  Minimize insertion loss (dB).  Minimize polarization dependent loss (PDL).  Minimize temperature dependence of the optical performance (a thermal solutions).  Minimize component packaging size (integrability).  Modularity of components is an advantage (versatility)

  10. Trends • Internet: A Deriving force SOME ACTUAL FACTS • 12 Million email messages in next minute • 0.5 Million voice mail messages in next minute • 3.7 Million people log on the net today • Next 100 days, Internet traffic doubles • 100 Million additional internet users every year Data based on the survey at Bell Laboratories, USA in Nov., 2000. DEMAND FOR MORE BANDWIDTH ONLY SOLUTION IS OPTICAL COMMUNICATION

  11. The Race for Bandwidth

  12. Exploding Demands for Bandwidth

  13. Facts Regarding Optical Transmission

  14. Capacity Growth of Optical Fiber Each Year Year Capacity (Gb/s) • 1980                0.1 • 1985                1  • 1990 3 • 1995                5 • 2000                100 (40 practically shown) • 2005                1,000 (If limitations due to Dispersion & Nonlinearities are overcome)

  15. The optical world is approaching towards • 1. 50 THzTransmission Window • 1000Channel WDM • 100 Gb/sTDM • 1000 kmRepeater less transmission • If Nonlinearities can be controlled, transmission window will be 300THz

  16. Optical Fiber Applications

  17. OFC Backbone Capacity

  18. Bandwidth-What is it ? • Bandwidth is the a measure of information carrying capacity of a medium. • To the digital word, it is translated into a maximum bit rate at which signals can be sent without significant signal degradation • Fiber bandwidth is typically quoted in frequency and normalized to fiber length (MHz-Km) - As length increases bandwidth decreases • A fiber bandwidth is determined by its pulse spreading properties

  19. Bandwidth-What is it ? • The difference between the highest and lowest frequencies of a band that can be passed by a transmission medium without undue distortion. • A term used to indicate the amount of transmission or processing capacity possessed by a system or specific location in a system (Usually a network system)

  20. Copper Versus Fiber: Repeaters

  21. Eliminate the dangers found in areas of high lightning-strike

  22. Fiber links offer over 1,000 times as much bandwidth and distances over 100 times

  23. Introduction • The first practical scheme of optical communication, was invented by Alexander Grahm Bell, in 1880, the Photophone. • Photophone: Device in which speech can be transmitted on a beam of light, using mirrors & selenium detectors. • Present optical communication systems use Laser & Optical Fiber technologies. • Optical frequency is typically 1014 Hz, which can support wideband modulation. Compared to microwave frequencies 109 Hz, the optical career can offer 105 times more bandwidth.

  24. Basics of Fiber Optic Communication • Fiber Optics is a revolutionary development that has changed the face of telecommunications around the world • Transmission of data as a light pulses through optical fiber (first converting electronic binary signals to light and then finally converting back to electronic signals) • Elements of Fiber Optics • Transmission • Light Source (such as Infrared LED converts pulses and sends into optical fiber) • 850 nm, 1300 nm • Low cost, easy to use • Used for multi mode fiber • Special edge emitting LEDs for single mode fiber

  25. Basics of Fiber Optic Communication (Contd..) • Laser Source having properties • Coherence • Monochromaticity • Directionality • High Specific Intensity • 850 nm, 1300 nm, 1550 nm • Very high power output • Very high speed operation • Very expensive • Need specialized power supply & circuitry Reception • Photo detector converts back to electrical pulses • PIN DIODES • 850, 1300, 1550 nm • Low cost • APDs (Avalanche Photodiodes) • 850, 1300, 1500 nm • High sensitivity, can operate at very low power levels • expensive

  26. Basics of Fiber Optic Communication (Contd..) • Propagation in Fiber • Light propagates by mans of total internal reflection. • Optical Fiber consists of two concentric layers • Core – inner layer • Cladding – outer layer • Refractive index of core is greater than cladding, necessary for total internal reflection • Light entering with acceptance angle propagates through fiber • Strikes core cladding interface > critical angle and gets reflected completely. • Zig-zags down lengthof core through repeated reflections. • Fairly lossless propagation through bends also. • Optical fiber • Multimode (Graded Index 50/125 & 62.5/125  ) • Single mode (8.7 /125  )

  27. Basics of Fiber Optic Communication (Contd..) • Major Advantages of FOC • Large Bandwidth (Extremely high information carrying capacity) • Carrier frequency – Light – 1014 Hz • Makes possible widespread long distance communication of high bandwidth signals • Color video • High speed network • High degree of Multiplexing, without much interference among them. • Low Loss (Long repeaterless link length/repeater spacing) • Loss as low as 0.1 dB/Km • Repeater spacing of over 100 Km possible over land & under sea. • EMI immunity (Even in noisy or harsh environments-Lightning, factory floor, high voltage lines, broadcast towers)

  28. Basics of Fiber Optic Communication (Contd..) • Major Advantages of FOC (Contd..) • Compact and light weight • Single fiber can easily replace 1000 pair copper cable of 10 cm dia. • Security (impossible to tap) • Safety (insulator & no sparks – ideal for hazardous environment) • Can be used in • Oil exploration • Oil refineries • Mines • Explosives • Petrochemical • Other hazardous chemical

  29. Basics of Fiber Optic Communication (Contd..) • Some practical disadvantages of FOC • Fiber is expensive • Connectors very expensive (due to degree of precision involved) • Connector installation time consuming & highly skilled operation • Joining (splicing) of fibers requires expensive equipment & skilled operators • Connections & joints are relatively lossy • Difficult to tap in & out (for bus architectures) need expensive couplers • Relatively careful handling required

  30. Advances in Optical Communication • First Generation Support: • Operating at: 850 nm • Bit Rates: 50 -100 Mbps • Repeater Spans: 10 Kms • Sources & Detectors made of InGaAsP compound semiconductor • Second Generation Support: • Operating at: 1300 nm • Bit Rates: 1-2 Gbps • Repeater Spans: 40 -50 Kms • Sources & Detectors made of InGaAsP compound semiconductor • Third Generation Support: • Operating at: 1550 nm • Bit Rates: 2.4 Gbps • Repeater Spans: 100 Kms

  31. First Generation, ~1975, 0.8 mm MM-fibre, GaAs-laser or LED Second Generation, ~1980, 1.3 mm, MM & SM-fibre InGaAsP FP-laser or LED Third Generation, ~1985, 1.55 mm, SM-fibre InGaAsP DFB-laser, ~ 1990 Optical amplifiers Fourth Generation, 1996, 1.55 mm WDM-systems Wavelength (mm) 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Optical Communication Systems Attenuation

  32. Information Transmission Sequence

  33. Fiber Structure • A Core Carries most of the light, surrounded by • A Cladding, Which bends the light and confines it to the core, covered by • A primary buffer coating which provides mechanical protection, covered by • A secondary buffer coating, which protects primary coating and the underlying fiber.

  34. Fiber Structure Cont…

  35. Types Of Optical Fibre Light ray n1 core n2 cladding Single-mode step-index fibre no air n1 core n2 cladding Multimode step-index fibre no air Variable n Multimode graded-index fibre Index porfile

  36. Multimode Step Index Fiber • Core diameter range from 50-1000mm • Light propagate in many different ray paths, or modes, hence the name multimode • Index of refraction is same all across the core of the fiber • Bandwidth range 20-30 MHz

  37. Multimode Graded Index Fiber • The index of refraction across the core is gradually changed from a maximum at the center to a minimum near the edges, hence the name “Graded Index” • Bandwidth ranges from 100MHz-Km to 1GHz-Km

  38. Pulse Spreading T Pulse from zero-order mode T T Pulses from other modes T Pulse from highest-order mode T Resulting pulse time

  39. Single-Mode Graded Index Fiber • The Core diameter is 8 to 9mm • All the multiple-mode or multimode effects are eliminated • However, pulse spreading remains • Bandwidth range 100GHz-Km

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