gzmuxa - I1070/T2000 Intro to Telecom Multiplexing Dr...

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I1070/T2000 Intro to Telecom Multiplexing Dr. Richard A. Thompson Telecommunications Program University of Pittsburgh
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Three Telecom “Divisions” Separating channels Space (most common) – pairs in a cable Time & frequency (wavelength) Others: direction(?), polarization Sharing (multiplexing) a super-channel Time multiplexing Frequency (& wavelength) multiplexing Space(?) multiplexing (“frequency sharing”) Need “shifters” for interface & switching
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Multiplexing “Super-channel ”: Cable of wire pairs of fibers CATV co-ax which is FDM-ed Digital carrier system (T1 or SONET) which is TDM-ed One fiber which is WDM-ed
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Frequency Division Multiplexing Space
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Frequency Division Multiplexing Useful bandwidth of medium exceeds required bandwidth of channel Each signal is modulated to a different carrier frequency Carrier frequencies separated so signals do not overlap (guard bands) e.g. broadcast radio Channel allocated even if no data
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FDM System
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FDM of Three Voiceband Signals Not at all what the voice spectrum looks like But, it’s what the Codec sees Cross-channel Interference. Need a guard-band
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Analog Carrier Systems AT&T (USA) - obsolete Hierarchy of FDM schemes Group 12 voice channels (4kHz each) = 48kHz Range 60kHz to 108kHz Supergroup FDM of 5 group signals on carriers: 420kHz - 612 kHz 60 voice channels Mastergroup 10 supergroups 600 voice channels
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Wavelength Division Multiplexing Multiple beams of light at different frequency Carried by optical fiber A form of FDM Each color (wavelength) carries separate data channel 1997 Bell Labs 100 beams, each at 10 Gbps Giving 1 Terabit per second (Tbps) total Commercial systems of 160 channels of 10 Gbps Fiber nonlinearities cross channel interference short lengths Trades off against dispersion in an odd way Lab systems (Alcatel) 256 channels at 39.8 Gbps each 10 x 1 Tbps Over 100km (special fiber) WDM = FDM? Wavelength and frequency Related by v = λ f 1 dimensions, v=(2/3)c
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WDM Operation Same general architecture as (other) FDM Number of sources generating laser beams at different frequencies - $$ Multiplexer consolidates sources for transmission over single fiber
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  • Fall '09
  • Menon
  • Synchronous optical networking, T-carrier, Time-division multiplexing, Multiplexing, Wavelength-division multiplexing, data rate

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