CD / PMD Fundamentals
Jean-Sébastien Tassé
Product Line Manager
Contributions from Gwennael Amice
and Francis Audet
August 2014
•Dispersion = pulse broadening or pulse spreading as
light propagates in a fiber.
•In other words, dispersion increases pulse duration.
What is dispersion?
•Dispersion causes pulses to broaden which might lead
to pulses that overlap.
•In extreme cases, we get inter-symbol interference (ISI)
and higher Bit Error Rate.
Impact of dispersion
Inability to operate at high speed
(extreme)
SLA Penalties
Significant delays and expense in
installation and commissioning
Bit Errors and BERT issues
Pulse Broadening
Dispersion CD/PMD
Dispersion consequences
•Chromatic Dispersion (CD):
•Different wavelengths travel at different velocities
•Polarization Mode Dispersion (PMD):
•Two polarization modes travel at different velocities
Pulse Spreading
Pulse Spreading
Two main types of dispersion
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