Abstract
In coherent optical systems laser phase noise can interact with digital equalization to cause
equalization-enhanced impairments, which are a major obstacle for applying higher order modulation formats in coherent
optical systems with digital chromatic dispersion compensation. In this paper a code-aided expectation maximization
method to track phase noise in such systems is presented. A common measure of laser phase noise is the linewidth. It
is shown that with
$\sim 11\%$
redundancy, the laser linewidth
tolerance for 975 km transmission distance can be increased by
$50\%$
, or the system reach for a laser linewidth of 5 MHz can be doubled. A phase-noise-robust 16-point
4–4–4–4 ring constellation was found to have better performance compared to 16QAM and a
2–6–8 ring constellations. Performance can be further improved with a lower code rate and fewer pilot
symbols. It is also shown that algorithmic complexity can be reduced without significant reduction in the performance
by reducing iterations and using low complexity codes.
© 2013 IEEE
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription