Accurate Performance Estimation for Nonlinear System

Su, Xiaofei; Ye, Tong; Yang, Chengwu; Tao, Zhenning; Nakashima, Hideharu; Hoshida, Takeshi

doi:10.1364/oecc.2021.w2a.3

Cited by 9 publications

(4 citation statements)

References 1 publication

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“…10(a) and (b), the black lines denote the spectrum of the orthogonal component of PAM8 without a notch, and the other colors denote the spectra of PAM8 with a notch when the RMS of the digital signal was 54.5. The orthogonal component can be considered equivalent to the actual nonlinear noise [8]. The nonlinear noises measured by notch clearly agreed with the orthogonal component, and the nonlinear distortions caused by different nonlinear mechanisms had significant spectral differences.…”

Section: B Resultsmentioning

confidence: 56%

“…This is the standard measurement method for the NPR, and the result is denoted as NPRNotch. Because the orthogonal component can be considered actual equivalent nonlinear noise [8], we can define the power ratio of the spectrum of the orthogonal component (i.e., red curve) at the notch region to the output spectrum as NPROrth.…”

Section: B Noise-to-power Ratio Measurement By Notchmentioning

confidence: 99%

“…Orthogonal component analysis, which uses a finite impulse response (FIR) filter to separate the optimal linear approximation (i.e., correlated component) and residual nonlinear distortion (i.e., orthogonal component) from the nonlinear device output, has been applied to accurately estimate the nonlinear distortion of devices in optical communication systems [8]. However, this approach has many issues [9].…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Nonlinear Distortion in Intensity Modulation and Direct Detection Systems

et al. 2023

J. Lightwave Technol.

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Intensity modulation and direct detection (IM-DD) systems are widely used in short-reach optical networks. Thus, developing a practical and accurate method to characterize nonlinear distortion and to estimate system performance is essential, as this is the foundation of IM-DD system design. The amount of nonlinear distortion can be characterized using the noise-to-power ratio (NPR). Although measuring the NPR using a notch requires only a spectrum analyzer, this method cannot be applied to a nonlinear system with non-Gaussian stimuli in general. We employ the method of measuring the NPR using a notch to characterize the nonlinear distortion in directly modulated distributed feedback (DM-DFB) laser-based IM-DD systems. Nonlinear distortion in these IM-DD systems can be attributed to two specific mechanisms: the imperfect power-current characteristic of the DM-DFB laser and the interaction among the modulation, chromatic dispersion (CD), and detection. Experimental results demonstrated that the nonlinear distortion can be accurately characterized with a mean absolute error of 0.47 dB, even when the stimuli are pulse amplitude modulation. The system performance subjected to nonlinearity could be estimated by the equivalent additive noise model. Besides, the method of measuring the NPR using a notch is also effective when the Mach-Zehnder modulator-based IM-DD system has nonnegligible CD. However, it failed in the case of negligible CD. Considering that this method is not always effective, we analyzed the attributes of various nonlinear systems and found that the above method is applicable only to systems dominated by second-order nonlinearity.

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Section: B Resultsmentioning

confidence: 56%

Section: B Noise-to-power Ratio Measurement By Notchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of Nonlinear Distortion in Intensity Modulation and Direct Detection Systems

et al. 2023

J. Lightwave Technol.

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“…One choice on equivalent additive noise is the time-domain orthogonal item 32,34 , for instance, the orthogonal signal of another input bit pattern or the orthogonal item with sample shifting (Fig. 4aiii).…”

Section: Resultsmentioning

confidence: 99%

Nonlinear noise spectrum measurement using a probability-maintained noise power ratio method

Zhang

et al. 2022

Commun Eng

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Nonlinear distortion (noise) limits many communication systems, demanding a means of estimating system performance via device nonlinear characteristics. The noise power ratio (NPR) method which was proposed in 1971 solves this problem for systems with Gaussian stimuli or with special nonlinearity, but practical and accurate methods for many communication systems with non-Gaussian stimuli are rare. Here we propose a probability-maintained (PM) NPR method to accurately measure the spectrum of nonlinear noise via a spectrum analyzer in non-specific systems, including systems with non-Gaussian stimuli. Using an equivalent additive noise model in which the spectrum of equivalent nonlinear noise is the measurement result of PM NPRs, nonlinear system performance could be estimated with an error of 0.5 dB. Further, we find that zero-mean Chi-square noise, instead of Gaussian noise, should be selected for large memory and low-order nonlinear systems. Our method is verified in seven different scenarios with various nonlinear mechanisms and communication applications.

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Accurate Nonlinearity Characterization of Dual-Polarization 16QAM Transmitter Using Four-Level Probability-Maintained Notch Signal

Ye,

Su,

Zhang

et al. 2023

2023 Asia Communications and Photonics Conference/2023 International Photonics and Optoelectronics Meetings (ACP/POEM)

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Accurate Performance Estimation for Nonlinear System

Abstract: The nonlinear term cannot be considered as the equivalent nonlinear noise in general because the odd order term contains the signal information. The orthogonal component is the correct noise and the estimation error is 0.2dB.

Cited by 9 publications

References 1 publication

Characterization of Nonlinear Distortion in Intensity Modulation and Direct Detection Systems

Characterization of Nonlinear Distortion in Intensity Modulation and Direct Detection Systems

Nonlinear noise spectrum measurement using a probability-maintained noise power ratio method

Accurate Nonlinearity Characterization of Dual-Polarization 16QAM Transmitter Using Four-Level Probability-Maintained Notch Signal

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