FIBER OPTICS. Increase in Bitrate-Distance Product Agrawal-Fiber Optic Communications.
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Transcript of FIBER OPTICS. Increase in Bitrate-Distance Product Agrawal-Fiber Optic Communications.
FIBER OPTICS
Increase in Bitrate-Distance Product
Agrawal-Fiber Optic Communications
Progress In Lightwave Communication Technology
Agrawal-Fiber Optic Communications
Waveguide Basics• Light is guided by a medium with a higher refractive index (Core) surrounded by
that with a lower one (Cladding)• Step-index• Numeric aperture (NA) = sine of the largest acceptance angle
• Typically, NA=0.15 for single mode fiber (SMF) and 0.3 for multimode fiber (MMF).
' 2 21 2 1sin( ) 2mNA n n n
1
21
n
nn
Optical Fiber
• Some Typical Dimension :– Single Mode Fiber (SMF): 8 μm core– MultiMode Fiber (MMF) : 50, 62.5, 85, 100, 200
μm core• Index profile:
– Step vs. Graded vs. multi-step…
Graded index
8 8
Optical Loss
Agrawal-Fiber Optic Communications
Dispersion• Different components of transmitted signal travel at different
velocities in the fiber and arrive at different times at the receiver– Modal dispersion: different modal components of a pulse travel
at different velocities– Chromatic dispersion: different spectral components of a pulse
travel at different velocities• Material dispersion: due to -dependence in doped silica (or
any other core material)• Waveguide dispersion: due to waveguide design
– Polarization dispersion: different polarization components of a pulse travel at different velocities
Multimode Fiber Limitation: Modal Dispersion
Multimode Fiber Limitation: Modal Dispersion
Modal Dispersion is critical in MMF.