Abstract
The advent of digital signal processing (DSP) to optical coherent detection
means that more phase estimation options are available, compared to the earlier
generation where phase-locked loops (PLLs) were invariably deployed in synchronous
coherent receivers. Several phase estimation methods are numerically modeled:
the maximum a posteriori (MAP) phase estimate, decision
directed estimate, power law-Wiener filter estimate and power law-PLL estimate.
An asynchronous coherent detection case is also modeled. The phase estimates
are evaluated with respect to their tolerance of finite laser linewidth and
their suitability for implementation in a parallel digital processor. Laser
phase noise causes transmission system performance to be degraded by excess
bit errors and cycle slips. The optimal phase estimate is the MAP estimate,
and it is also included as a baseline. The power law-Wiener filter phase estimate
is found to perform only marginally worse than the MAP estimate. It must be
recast using a look-ahead computation to be implemented in a parallel digital
processor, and the impact is investigated of the increase in the number of
computations required. Differential logical detection is often used to reduce
the impact of cycle slip events, and the implications of this operation on
the bit error rate are studied. It is found that by choosing the correct FEC
scheme differential logical detection does not increase the Q-factor penalty.
© 2009 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