On the Nonlinear Shaping Gain With Probabilistic Shaping and Carrier Phase Recovery

Civelli, Stella; Forestieri, E.; Secondini, Marco

doi:10.1109/jlt.2023.3241449

Cited by 8 publications

(9 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the performance improvement obtained by em- ploying short-block-length DMs becomes nearly irrelevant when carrier phase recovery (CPR) is included in the system, as in all practical systems. Indeed, we have shown that also CPR mitigates some nonlinear interference-in fact, the same nonlinear interference that is avoided by reducing the PAS blocklength-improving the performance of all DMs and hiding the nonlinear shaping gain provided by short block length PAS in many practical scenarios [20]. This behaviour is predicted by the nonlinear phase noise (NPN) metric, which, differently from EDI, Kurtosis, and LSAS, allows to account also for the impact of CPR [20].…”

Section: A Nonlinear Performance Of Conventional Dmmentioning

confidence: 97%

“…The modulation format is dual polarization 64-QAM with probabilistic shaping and root-raised-cosine supporting pulse with rolloff 0.05. As a benchmark, and as a starting point (referred to as unbiased source) for sequence selection, we consider probabilistic amplitude shaping (PAS) with rate R 4D = 9.2 bit/4D (equivalent to R DM = 1.3 bit/amplitude), implemented with the serial mapping for quadratures and polarizations [20]. The signal is sent into a link composed of 30 × 100 km spans of single mode fiber (SMF) with erbiumdoped fiber amplifiers (EDFAs) with noise figure 5 dB.…”

Section: System Descriptionmentioning

confidence: 99%

“…Finding a good trade-off between rate loss and implementation complexity is a key aspect in the design of DMs.Different techniques for the implementation of DMs have been proposed in the past years, including the enumerative sphere shaping (ESS) and its variations [24]- [26]; the constant composition distribution matcher (CCDM) and its variations [10], [22]; and the hierarchical DM (HiDM), which, using multiple DM layers (each based, for instance, on ESS, CCDM, or even LUTs), achieves a lower rate loss compared to the equivalent-complexity single-layer DM [12], [13], [27]. We refer to [20] and references therein for more details about DM implementations.…”

Section: Probabilistic Constellation Shapingmentioning

confidence: 99%

“…The optimal block length and performance are obtained as a trade-off between these two effects and depend not only on the considered scenario, but also on the specific DM implementation. SpSh has better linear performance with respect to CCDM, band-limited ESS [31], Kurtosis limited ESS [32], and single-shell mapping [20], but has more energy variations and a larger Kurtosis, which are responsible to generate part of the nonlinear interference. Despite this, it was shown that SpSh is able to achieve the largest nonlinear shaping gain, because its lower rate loss allows to improve the linear performance and to use a shorter block length [20].…”

Section: A Nonlinear Performance Of Conventional Dmmentioning

confidence: 99%

“…SpSh has better linear performance with respect to CCDM, band-limited ESS [31], Kurtosis limited ESS [32], and single-shell mapping [20], but has more energy variations and a larger Kurtosis, which are responsible to generate part of the nonlinear interference. Despite this, it was shown that SpSh is able to achieve the largest nonlinear shaping gain, because its lower rate loss allows to improve the linear performance and to use a shorter block length [20]. In the past years, some metrics have been introduced to understand and predict the performance of PAS in the nonlinear regime.…”

Section: A Nonlinear Performance Of Conventional Dmmentioning

confidence: 99%

See 4 more Smart Citations

Sequence-Selection-Based Constellation Shaping for Nonlinear Channels

Civelli,

Forestieri,

Secondini

2024

J. Lightwave Technol.

Self Cite

View full text Add to dashboard Cite

Probabilistic shaping is, nowadays, a pragmatic and popular approach to improve the performance of coherent optical fiber communication systems. In the linear regime, the potential of probabilistic shaping in terms of shaping gain and rate granularity is well known, and its practical implementation has been mostly mastered. In the nonlinear regime, the advantages offered by probabilistic shaping remain not only valid, but might also increase thanks to the appealing opportunity to use the same technique to mitigate nonlinear effects and obtain an additional nonlinear shaping gain. Unfortunately, despite the recent research efforts, the optimization of conventional shaping techniques, such as probabilistic amplitude shaping (PAS), yields a relevant nonlinear shaping gain only in particular scenarios of limited practical interest, e.g., in the absence of carrier phase recovery. Recently, a more theoretical approach, referred to as sequence selection, has been proposed to understand the performance and limitation of nonlinear constellation shaping. Sequence selection shapes the distribution of the transmitted symbols by selecting or discarding the sequences generated by a certain source according to a metric that measures their quality. In this manuscript, after a brief review of conventional probabilistic shaping, we use sequence selection to investigate through simulations the potential, opportunities, and challenges offered by probabilistic shaping for nonlinear channels. First, we show that ideal sequence selection is able to provide up to 0.13 bit/s/Hz additional gain with respect to PAS with an optimized blocklength. However, this additional gain is obtained only if the selection metric accounts for the signs of the symbols, ruling out the possibility of using one of the simple recently proposed sign-independent metrics. We also show that, while the signs must be known to compute the selection metric, there is no need to shape them, since nearly the same gain can be obtained by properly selecting the amplitudes (with a sign-dependent metric) and leaving the signs uniform i.i.d. Furthermore, we show that the selection depends in a noncritical way on the symbol rate and link length: the sequences selected for a certain scenario still provide a relevant gain if the link length or baud rate are modified (within a reasonable range). Then, we analyze and compare several practical implementations of sequence selection by taking into account interaction with forward error correction (FEC), information loss due to selection, and complexity. Overall, we conclude that the single block and the multi block FEC-independent bit scrambling are the best options for the practical implementation of sequence selection, with a gain up to 0.08 bit/s/Hz. The main challenge and limitation to their practical implementation remains the evaluation of the metric, whose complexity is currently too high. Finally, we show that the nonlinear shaping gain provided by sequence selection persists when carrier phase recovery is included, in contr...

show abstract

Section: A Nonlinear Performance Of Conventional Dmmentioning

confidence: 97%

Section: System Descriptionmentioning

confidence: 99%