Abstract
We propose an accurate and low-complexity blind adaptive
algorithm for chromatic dispersion (CD) compensation and estimation in coherent
optical systems. The method is based on a Frequency Domain Equalizer (FDE),
a low complexity Time Domain Equalizer arranged in a butterfly structure (B-TDE)
and an Optical Performance Monitoring (OPM) block in a loop configuration.
The loop is such that, at each iteration, the CD value compensated by the
B-TDE and estimated by the OPM is given to the FDE; according to this estimation,
in the subsequent iteration, the FDE compensates also this quantity. The procedure
is repeated until the majority of CD is compensated by the FDE and a small
residual quantity is compensated by a low complexity B-TDE with a small number
of taps. The method is extended to long haul uncompensated links exploiting
the information on the mean square error (MSE) provided by the B-TDE. The
proposed algorithm is then experimentally validated for a polarization multiplexed
quadrature phase shift keying (PM-QPSK) signal at 112 Gbit/s propagating along
1000 km of uncompensated Z PLUS® optical fiber. A statistical analysis
of the performance of the proposed solution, in terms of mean value and standard
deviation of the CD estimation error, is carried out, running a set of simulations
including different impairments, such as noise, polarization dependent loss,
polarization mode dispersion and self-phase modulation in a line of 1000 km
of uncompensated G.652 optical fiber. Our method could be used to compensate
and estimate any CD quantity without increasing the number of taps in the
B-TDE and exploiting devices already included in the system (TDE, FDE and
OPM) arranged in a loop.
© 2013 IEEE
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