EE 230: Optical Fiber Communication Lecture 14

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EE 230 Optical Fiber Communication Lecture 14
Optical Time Division Multiplexing
From the movie Warriors of the Net
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OTDM Routing Network
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Multiplexing

• Frequency-division multiplexing (FDM) for
  electrical signals
• Code-division multiplexing (CDM) for electrical
  signals
• Wavelength-division multiplexing (WDM) for
  optical signals
• Time-division multiplexing (TDM) for both types

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Modulation

• Amplitude modulation
• Frequency modulation
• Phase modulation

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Simple to implement

• amplitude modulation
• pulse amplitude modulation
• amplitude shift keying

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Economize bandwidth

• quadrature amplitude modulation
• single sideband modulation
• vestigial sideband modulation

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Economize power

• double sideband modulation
• double sideband carrier-suppressed modulation
• These are easy to modulate but difficult to
  demodulate

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Noise resistant

• phase modulation
• frequency modulation
• pulse position modulation
• pulse code modulation (widely used)
• amplitude shift keying
• frequency shift keying

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Pulse Formats
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Optical Bit and Packet Interleaving
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OTDM Bit Interleaved Multiplexer
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Packet Interleaved Multiplexer
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Demultiplexing

• OTDM and soliton systems require RZ format
• Nonlinear devices required to demultiplex
• n EO modulators required for 2n channels
• Sagnac interferometer (NOLM) uses XPM
• FWM devices use clock signal as pump, generate
  new wavelength for 1 bits

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Synchronizer
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OTDM Bit Interleaved Demultiplexer
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Packet Interleaved Demultiplexer
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Nonlinear Optical Loop Mirror-NOLM
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Solitons
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Comparison of Soliton Transmission to other
Technologies
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Effective area of single-mode fiber

• for 1.2ltVlt2.405,
• otherwise
• Aeff?w2

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Peak power for a soliton

• where ? is the pulse width in time and n2 is the
  nonlinear index of refraction

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Example Corning SMF-28 fiber

• nCO1.4504, nCL1.4447, a4.1 ?m, ?1550 nm.
  NA?
• NA0.13. k?
• k2?/?4.05x106 m-1. V?
• V2.16. w/a?
• w/a1.19. w?
• w4.87 ?m. Aeff?
• Aeff7.46x10-11 m2

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Example, continued

• D19 ps/km-nm, n23.18x10-20 m2/W, ?20 ps. P?
• D1.9x10-5 s/m2
• ?33.72x10-18 m3
• ?24x10-22 s
• ?29.87
• P0.108W108 mWpretty high!