Abstract
The vulnerable sensitivity to laser linewidth induced inter-carrier
interference (ICI) has long been recognized as a major problem to coherent
optical orthogonal frequency-division multiplexing (CO-OFDM) systems. Among
the existing phase noise compensation algorithms, the RF-pilot aided phase
recovery (RAPR) method shows a better compensation capability to laser linewidth.
However, RAPR may fail to extract the pre-inserted RF-pilot at the receiver
due to the influence of carrier frequency offset (CFO). An effective frequency
offset estimation (FOE) is thus required to implement before performing RAPR.
In consideration of the fact that the conventional FOE algorithm not only
has high computational complexity, but more importantly cannot work in coordination
with RAPR, a new RF-pilot aided frequency offset estimation (RAFOE) algorithm
is proposed, in which CFO can be easily estimated by searching the peak of
spectral samples. Furthermore, in order to obtain the optimum compensation
performance with lower computing cost at combining RAFOE and RAPR, a joint
frequency offset and phase noise compensation scheme is also proposed, and
its performance is numerically verified in a 475 Gbit/s polarization multiplexed
16-ary quadrature amplitude modulation coherent optical orthogonal frequency-division
multiplexing (PM-16QAM- CO-OFDM) system.
© 2013 IEEE
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