Fig. 6. (a) Performance (QdB) of
14 GBaud DP-16QAM transmissions using LDC, CSS DBP, LSS DBP, and BLSS
DBP techniques over varying signal launch powers (dBm); (b) Performance
(QdB) of CSS DBP, LSS DBP, and BLSS against the number of calculation
steps/span at 13 dBm launch power.
The overall performance benefit of the BLSS DBP over other compensation
techniques as a function of signal launch power is analyzed, as shown in
Fig. 6(a). Observing the optimum launch power, indicating the NLT, the
logarithmic step size-based DBP techniques demonstrate superior
performance compared to the constant step size and linear dispersion
compensation only. Using the BLSS DBP technique, performance benefits
(∆Q) of 1.19 dB and 0.71 dB are obtained over CSS DBP and LSS DBP
techniques, respectively. The results indicate that the BLSS DBP
produces optimum step sizes for efficient DBP calculation. At higher
powers above the NLT, the performance of DBP is degraded by accumulated
stochastic ASE noise.
It is known that the effective implementation of DBP is significantly
dependent on the number of calculation steps/span, . However, a high
number of steps/spans comes at a high computational cost and are
undesirable. Fig. 6(b) shows the accuracy of DBP calculation (in
Q-factor) as a function of steps/span for different DBP implementations.
It is observed that for N ≤ 10, BLSS DBP cancels dispersion and
nonlinearity with higher accuracy than LSS DBP and CSS DBP.
Specifically, the BLSS DBP reaches optimum performance with N = 10. In
contrast, CSS DBP achieves optimum performance with N = 16, reducing the
number of calculation steps by 6, corresponding to a reduction in
complexity of 38% compared to the conventional CSS DBP. The
constellation diagrams for N = 1, 2, 6, and 10 with BLSS DBP are shown
in Fig. 7. At a high number of steps (N > 15), optimizing
the step sizes becomes less important as the conventional DBP algorithm
becomes equally accurate.