  The so-called improved soft-aided bit-marking algorithm was recently proposed
for staircase codes (SCCs) in the context of fiber optical communications. This
algorithm is known as iSABM-SCC. With the help of channel soft information, the
iSABM-SCC decoder marks bits via thresholds to deal with both miscorrections
and failures of hard-decision (HD) decoding. In this paper, we study iSABM-SCC
focusing on the parameter optimization of the algorithm and its performance
analysis, in terms of the gap to the achievable information rates (AIRs) of HD
codes and the fiber reach enhancement. We show in this paper that the marking
thresholds and the number of modified component decodings heavily affect the
performance of iSABM-SCC, and thus, they need to be carefully optimized. By
replacing standard decoding with the optimized iSABM-SCC decoding, the gap to
the AIRs of HD codes can be reduced to 0.26-1.02 dB for code rates of 0.74-0.87
in the additive white Gaussian noise channel with 8-ary pulse amplitude
modulation. The obtained reach increase is up to 22% for data rates between 401
Gbps and 468 Gbps in an optical fiber channel.
