ee 230: optical fiber communication lecture 14 from the movie warriors of the net optical time...
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EE 230: Optical Fiber Communication Lecture 14
From the movieWarriors of the Net
Optical Time Division Multiplexing
OTDM Routing Network
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
Modulation
• Amplitude modulation
• Frequency modulation
• Phase modulation
Simple to implement
• amplitude modulation
• pulse amplitude modulation
• amplitude shift keying
Economize bandwidth
• quadrature amplitude modulation
• single sideband modulation
• vestigial sideband modulation
Economize power
• double sideband modulation
• double sideband carrier-suppressed modulation
These are easy to modulate but difficult to demodulate
Noise resistant
• phase modulation
• frequency modulation
• pulse position modulation
• pulse code modulation (widely used)
• amplitude shift keying
• frequency shift keying
Pulse Formats
Optical Bit and Packet Interleaving
OTDM Bit Interleaved Multiplexer
Packet Interleaved Multiplexer
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
Synchronizer
OTDM Bit Interleaved Demultiplexer
Packet Interleaved Demultiplexer
Nonlinear Optical Loop Mirror-NOLM
Solitons
Comparison of Soliton Transmission to other Technologies
Effective area of single-mode fiber
for 1.2<V<2.405,
otherwise
Aeff=w2
62/3
879.2619.165.0
VVa
w
Va
w
ln
1
Peak power for a soliton
where is the pulse width in time and n2 is the nonlinear index of refraction
22
2
3775.0
cn
ADP eff
Example: Corning SMF-28 fiber
• nCO=1.4504, nCL=1.4447, a=4.1 m, =1550 nm. NA=?
• NA=0.13. k=?• k=2/=4.05x106 m-1. V=?• V=2.16. w/a=?• w/a=1.19. w=?
• w=4.87 m. Aeff=?
• Aeff=7.46x10-11 m2
Example, continued
• D=19 ps/km-nm, n2=3.18x10-20 m2/W, =20 ps. P=?
• D=1.9x10-5 s/m2
3=3.72x10-18 m3
2=4x10-22 s2=9.87
• P=0.108W=108 mW—pretty high!
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