Document #: GP-UM-PMD-1000-21
Page 115 of 122
a PMD compensator is required. An EDFA may be used before the PMD source
to boost the signal level.
Figure 36 Polarization optimized PMD source in an in-service WDM link for the determination of its PMD
and diagnosis of performance issues.
6)
System impairment diagnosis. It can be difficult to identify the cause of
performance problems in a fiber link. Signal degradation can be caused by PMD,
chromatic-dispersion (CD), signal-to-noise ratio (SNR) issues, or other problems.
Performing PMD compensation can help determine whether the problem is
principally due to PMD: If PMD compensation substantially solves the
transmission problem, it can be deduced that PMD is the principal cause of the
problem. If not, it may be possible to rule out PMD. With such a diagnosis, it is
possible to decide whether PMD compensation is required for the fiber link.
7)
PMD emulation. The PMD generator can generate statistical PMD distributions to
emulate PMD variations in fiber systems.
8)
Polarization control functions. Using its built-in polarization controller and
polarimeters, this instrument can perform all polarization control functions,
including deterministic SOP generation, polarization scrambling, and polarization
trace generation. It can therefore be used as a general purpose polarization
synthesizer/controller for all polarization control needs.
Polarization optimization is used in the following three functions.
1)
DGD tolerance test: Optimize input SOP using the SOP information from the first
polarimeter as feedback to obtain the worst-case signal degradation caused by
DGD.
2)
PMD tolerance test: Optimize input SOP to minimize the DOP detected by the
second polarimeter to obtain the worst-case signal degradation caused by both
DGD and SOPMD.
3)
PMD compensation: Optimize input SOP by maximizing DOP detected by the
second polarimeter to minimize signal degradation caused by DGD and SOPMD.
TX
Link with PMD
WDM
MUX
WDM
DeMUX
RX
Polarization optimized PMD source
