7. Optical Fiber Communication Systems. Inter-Continental Optical Fiber Communications

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Transcript of 7. Optical Fiber Communication Systems. Inter-Continental Optical Fiber Communications

  • 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)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 intensityEr3+-doped fiber is usually inserted into the fiber communication line by splicingGain efficiency : 8-10 dB/mW

  • Classification of Optical Fibers

  • Theory of Step-index Fiber

  • Theory of Step-index Fiber (Cont)

  • Single-mode Operation of Step-index Fiber

  • Coupling from LD to Fiber

  • Fiber Lens to Improve Coupling Efficiency

  • Optical Fiber Splice and Mismatches in a Fiber-to-fiber Connection

  • Digital SignalsRZ and NRZ FormatsA 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.

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

  • Amplitude Shift Keying (ASK)

  • Frequency Shift Keying (FSK)

  • Phase Shift Keying (PSK)

  • Quadrature PSK (QPSK) In the example shown in the right figure, 00 is represented by sin(2f0t), 10 is represented by sin(2f0t+), 01 is represented by sin(2f0t+/2), and 11 is represented by sin(2f0t+3/2).

  • Analog Quadrature Amplitude Modulation (AQAM) A low-pass filter removes the high frequency terms containing cos(4f0t), leaving only the I(t) term.

  • Example of Digital 8-QAMIn 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.

  • Example of Constellation Diagram in 16-QAM

  • Examples of Constellation Diagrams in QAMs

  • Example of 8-QAM Optical Fiber Communication System

  • Eye Diagram

  • Eye Diagram (Cont)