Design of all-optical multi-level regenerators based on Mach–Zehnder interferometer

et al. 2019

IEEE Access

Self Cite

We demonstrate a multilevel amplitude regeneration experiment for non-return-to-zero 4level pulse amplitude modulated (NRZ-PAM4) signals in the proposed polarization-orthogonal continuouswave-light-assisted nonlinear-optical loop mirror (PC-NOLM) subsystem. A uniform regenerative behavior including the same noise-suppression efficiency and the noise-handling capability is observed across multiple amplitude levels. The pre-phase modulation is carried out for the input signal enabling the multilevel amplitude regeneration directly on highly-spectral-efficient modulated formats. An overall improvement of 2.33 dB is achieved by optimizing the launched optical power and the distortion strength in the all-optical NRZ-PAM4 regeneration experiment. The uniform regenerative performance for the proposed PC-NOLM regenerator is also analyzed numerically to reveal the regenerative mechanism and the influence from the operational parameters.INDEX TERMS All-optical signal regeneration, optical fiber communication, optical signal processing, fiber nonlinear optics, nonlinear optical devices.

Section: Experimental Setup and Resultsmentioning

confidence: 99%

All-Optical Multilevel Amplitude Regeneration Based on Polarization-Orthogonal Continuous-Wave-Light-Assisted Nonlinear-Optical Loop Mirror (PC-NOLM) Subsystem

Guo

et al. 2019

IEEE Access

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“…From the above analysis, our method can be well applied to the QPSK signals with a single amplitude level. In fact, it can also be used to evaluate the output OSNR of multilevel signals only if each level of the multilevel signals have an identical linear gain at each operating point [5]. In principle, for the case with different gain at each operating point, a similar analysis process may also be used in spite of complexity.…”

Section: Resultsmentioning

confidence: 99%

“…It should be noted that the gain G 0 is dependent on the input signal power at the operating point. For this reason, Equation (2) is applied to the cases with the same gain for each regenerative level, that is, the operating points locate on a common linear gain curve [5].…”

Section: Gsmentioning

confidence: 99%

In-Band OSNR Measurement Method for All-Optical Regenerators in Optical Domain

Wan

et al. 2019

Applied Sciences

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We propose an in-band measurement method of optical signal-to-noise ratio (OSNR) output from an all-optical regeneration system with a nonlinear power transfer function (PTF) according to the fact that there are different average gains of signal and noise. For the all-optical quadrature phase-shift keying (QPSK) regenerator as an example, the output OSNR is derived from the input OSNR and the total gain of the degraded QPSK signal. Our simulation shows that the OSNR results obtained by this method are in agreement with those calculated from the error vector magnitude (EVM) formula. The method presented here has good applicability for different data rates but is also useful for analyzing the OSNR degradation of other nonlinear devices in optical communication links. IntroductionWith the exponential growth of data information, optical communication networks are becoming more and more intelligent and elastic [1]. Optical performance monitoring (OPM), especially in optical signal-to-noise ratio (OSNR), will play an important role in optical link diagnosis, flexible bandwidth allocation, and fast network service deployment [2]. In high-speed long-haul optical transmission systems, amplified spontaneous emission (ASE) noise from erbium-doped fiber amplifier (EDFA) is one of the main factors resulting in the degradation of the transmitted signals. Different from fiber dispersion and nonlinearity, it cannot be eliminated by some compensation methods. In this case, all-optical regeneration technology has attracted much attention [3], especially to high-order modulation signal regeneration, such as multi-level amplitude regeneration based on nonlinear interference structure [4,5], multi-stage phase regeneration based on phase-sensitive four-wave mixing (FWM) [6,7], and several regeneration schemes of quadrature amplitude modulation (QAM) signals [8,9].Just like in-line EDFAs, all-optical regenerators are usually integrated into the intermediate nodes of optical links. However, most of the previous studies paid more attention to the regeneration performance in the electrical domain, instead of the optical domain. In other words, the OSNR improvement for all-optical regenerators is seldom considered in experiments due to a lack of more accurate OSNR measurement methods in the optical domain. As is well-known, the traditional OSNR measurement method used in WDM systems is based on the spectral interpolation technique by optical spectrum analysis [10]. Unfortunately, the use of optical filters or all-optical regenerators can give rise to the out-band distortion of the optical spectrum distribution, and then the validation of the interpolation measurement. Secondly, the coherent receivers are extensively used in high-order modulation systems such as those of quadrature phase-shift keying (QPSK) or QAM signals, so the performance of all-optical regenerators is often evaluated in the electrical domain as well. In fact, there are

“…Secondly, the distorted QPSK signal is sent into a nonlinear MZI configuration which is used to adjust the distribution of amplitude and phase states of the distorted QPSK signal. A nonlinear MZI configuration has been used to finish the amplitude regeneration for the pulse amplitude modulation (PAM) signal and the amplitude difference erasure for the 8ary quadrature amplitude modulation (8QAM) signal [4], [21], [22]. It's formed by one HNLF and one VOA in the upper arm, one variable phase shifter (VPS) and one tunable optical delay line (TODL) in the lower arm.…”

mentioning

confidence: 99%

All-Optical Regeneration and Format Conversion for 4APSK Signals Based on Nonlinear Effects in HNLF

Yang

et al. 2023

IEEE Photonics J.

An all-optical format conversion and regeneration 1 scheme about 4-ary amplitude and phase shift keying (4APSK) 2 signals is proposed and numerically simulated based on nonlinear 3 effects in the high nonlinear fiber (HNLF). The input 4APSK 4 signal is firstly converted into a regular quadrature phase 5 shift keying (QPSK) signal by the nonlinear Mach-Zehnder 6 interferometer (MZI) based on the self-phase modulation (SPM).7 Secondly, a degenerate phase-sensitive amplification (PSA) based 8 on the four-wave mixing (FWM) is utilized to convert the 9 regular-QPSK into two binary phase shift keying (BPSK) signals. 10 The nonlinear MZI configuration is also used to compress the 11 amplitude noise of BPSK. Thirdly, one phase shifter and one 12 variable optical attenuator (VOA) are used to adjust the relative 13 phase and power relationships of the two amplitude-regenerated 14 BPSK signals. The regenerated 4APSK and converted QPSK 15 signals can be generated in one 3-dB optical coupler through 16 coherent addition of the two regenerated BPSK signals. The 17 error-vector-magnitude (EVM) and the bit-error-rate (BER) are 18 calculated and compared to evaluate the scheme performance. 19 The proposed scheme can be applied as an optical regenerator 20 or format convertor at the network gateway to increase the 21 transmission distance or connect optical networks with different 22 modulation formats. 23 Index Terms-quadrature phase shift keying, amplitude and 24 phase shift keying, self-phase modulation, four-wave mixing, 25 nonlinear Mach-Zehnder interferometer, phase-sensitive ampli-26 fication. 27 I. INTRODUCTION 28 W ITH the development of emerging technologies and 29 services, including the Internet of Energy (IoE), the 30 Internet of Things (IoT), the big data, the cloud comput-31 ing, the artificial intelligence (AI) and the fifth-generation 32