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7. Optical Fiber Communication Systems

7. Optical Fiber Communication Systems. Inter-Continental Optical Fiber Communications. Optical Fiber Communication Systems and Fiber Sensors ( Example of Measuring the Gap of Bridge ). Attenuation and Dispersion in Silica Fiber. Erbium Doped Fiber Amplifier (EDFA).

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7. Optical Fiber Communication Systems

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  1. 7. Optical Fiber Communication Systems

  2. Inter-Continental Optical Fiber Communications

  3. Optical Fiber Communication Systems and Fiber Sensors (Example of Measuring the Gap of Bridge)

  4. Attenuation and Dispersion in Silica Fiber

  5. Erbium Doped Fiber Amplifier (EDFA) • Er3+ ions doped into the core region of an optical fiber to achieve light amplification need (stimulated emission > absorption) population inversion required (N2> N1) • Optical gain, Gop=K(N2 –N1), where K is a constant depends on pumping intensity • Er3+-doped fiber is usually inserted into the fiber communication line by splicing • Gain efficiency : 8-10 dB/mW

  6. Classification of Optical Fibers

  7. Theory of Step-index Fiber

  8. Theory of Step-index Fiber (Cont’)

  9. Single-mode Operation of Step-index Fiber

  10. Coupling from LD to Fiber

  11. Fiber Lens to Improve Coupling Efficiency

  12. Optical Fiber Splice and Mismatches in a Fiber-to-fiber Connection

  13. Digital Signals—RZ and NRZ Formats • A return-to-zero (RZ) format is the signal returns to zero between each pulse. The signal is self-clocking. • A non-return-to-zero (NRZ) format does not have a rest state. NRZ is not inherently a self-synchronizing code, thus some additional synchronization technique must be used for avoiding bit slip.

  14. Some Digital Modulations in Communication • Amplitude Shift Keying (ASK) • Frequency Shift Keying (FSK) • Phase Shift Keying (PSK) • Quadrature Amplitude Modulation (QAM)

  15. Amplitude Shift Keying (ASK)

  16. Frequency Shift Keying (FSK)

  17. Phase Shift Keying (PSK)

  18. Quadrature PSK (QPSK) • In the example shown in the right figure, 00 is represented by sin(2πf0t), 10 is represented by sin(2πf0t+π), 01 is represented by sin(2πf0t+π/2), and 11 is represented by sin(2πf0t+3π/2).

  19. Analog Quadrature Amplitude Modulation (AQAM) A low-pass filter removes the high frequency terms containing cos(4πf0t), leaving only the I(t) term.

  20. Example of Digital 8-QAM • In this 8-QAM example, eight different modulation states using 4 phase angles and 2 amplitudes: one at 50% modulation; the other at 100%. (4 phases X 2 amplitudes = 8 modulation states). • In QAM, the constellation diagram is a useful representation. The constellation points are usually arranged in a square grid.

  21. Example of Constellation Diagramin16-QAM

  22. Examples of Constellation Diagrams in QAMs

  23. Example of 8-QAM Optical Fiber Communication System

  24. Eye Diagram

  25. Eye Diagram (Cont’)

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