Fig. 5. (a) Comparison of the
performance (Q) of transmissions at different symbol rates implementing
the BLSS DBP technique; (b) Performance benefits (Q) of LDC, CSS DBP,
LSS DBP, and BLSS at NLT for 12.5 GBaud, 14 GBaud, 21 GBaud, and 28
GBaud over 2400 km
As demonstrated by Fig. 5, the performance benefit of the logarithmic
step size distribution is dependent on the signal bandwidth, which is
indicated by the transmission symbol rate, also known as the Baud rate.
Fig. 5(a) shows that by increasing the symbol rate, the effectiveness of
the optimized BLSS techniques declines for the same number of
calculation steps/span. The best performance is demonstrated at a 14
GBaud symbol rate with a Q-factor of 10.9 dB (BER ~
2.25×10-4) using 10 calculation steps/span. The
observation can explain this trend that at small steps/span, the signal
waveform changes substantially over one step as the symbol rate is
increased due to the impact of increased dispersion. It is inferred that
more calculation steps are required for large data rates for optimum
performance of the logarithmic step size, indicating a trade-off between
data rate and complexity. The performance of different compensation
techniques as a function of symbol rate is shown in Fig. 5(b).