Nonlinear Compensation Assessment in Few-Mode Fibers via Phase-Conjugated Twin Waves (original) (raw)
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Analytical formula of nonlinear interference in few-mode fibers in strong coupling regime
2015 17th International Conference on Transparent Optical Networks (ICTON), 2015
We derive a closed-form formula for the nonlinear interference in few-mode fibers (FMFs) in strong coupling regime. We also formulate an expression for the nonlinear FMFs capacity. This is carried out by extending the Gaussian noise model (GN-model), that has been used with single-mode fibers (SMFs), to FMFs. We inspect the derived formulas over a mode-division multiplexing (MDM) system that carries wavelength-division multiplexed (WDM) signals on each polarization of every spatial mode. The nonlinear coupling among three co-propagated modes reduces the average optical signal-to-noise ratio (OSNR) by about 11.5 dB when compared to single-mode propagation. Also, a differential mode group delay (DMGD) of 300 ps/km between the fundamental mode LP 01 and the other two modes Lp 11a(b) reduces the nonlinearity penalty by about 10%.
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2016 21st European Conference on Networks and Optical Communications (NOC), 2016
In this paper, we investigate the impact of linear mode coupling on the efficiency of intermodal four-wave mixing and on the group delay statistics in few-mode fibres. The investigation will include not only the weak or strong linear coupling regimes, but also the transition region between them, the intermediate coupling regime. This analysis will allow to assess the level of coupling strength require to suppress the nonlinear distortion in a few-mode fibre below the level of distortion for single-mode propagation without mode coupling.
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IEEE Photonics Technology Letters, 2000
In this letter, a nonlinear semi-analytical model (NSAM) for simulation of few-mode fiber transmission is proposed. The NSAM considers the mode mixing arising from the Kerr effect and waveguide imperfections. An analytical explanation of the model is presented, as well as simulation results for the transmission over a two mode fiber (TMF) of 112 Gb/s using coherently detected polarization multiplexed quadrature phase-shift-keying modulation. The simulations show that by transmitting over only one of the two modes on TMFs, longhaul transmission can be realized without increase of receiver complexity. For a 6000-km transmission link, a small modal dispersion penalty is observed in the linear domain, while a significant increase of the nonlinear threshold is observed due to the large core of TMF.
Interplay of Modal Dispersion and Nonlinear Interference in Fiber Optic Systems
Masters Thesis, 2021
Network traffic increases by 30% percent each year and is even expected to increase by a greater margin as more people and devices are getting connected to the internet. During this COVID-19 period, optical networking vendors have reported experiencing an unpredictable surge in data demands that are stressing the existing optical networks. Studies have shown that we are almost approaching the capacity crunch of single-mode fibers, and since the current optical networks are mainly made of single-mode fibers, we need new technologies to meet these increasing demands. Space division multiplexing, elastic optical networks, high order modulation formats are some of the technologies being proposed with each technology having its pros and cons. Space division multiplexing (SDM) has received a lot of attention as an alternative solution and it involves exploiting the spatial diversity of optical fibers in the form of polarization, the number of modes, number of cores or fibers working as bundles. Although SDM fibers represents a promising solution compared to the current single-mode fibers, such fibers introduce new challenges due to the interactions among the propagating modes. In ideal optical fibers, birefringence does not exist, and thus optical modes propagate inside the fiber without coupling. In practical cases, birefringence manifests itself due to imperfections, such as imperfect circular symmetry during the fiber manufacture, or due to external stresses, such as mechanical pressure exerted after manufacturing. This asymmetry results in random perturbation causing the two field polarizations to have different group delays, hence polarization mode dispersion (PMD) arises. In a multi-mode fiber, random birefringence leads to spatial mode dispersion (MD) among the different spatial models, in addition to the PMD among the polarizations of each mode. This thesis investigated the impact of PMD and SMD on optical fiber transmissions, especially focusing on its interaction with the nonlinear interference (NLI) arising during the signal propagation along the optical fiber. With this aim, we exploited the Gaussian noise (GN) model extended to include PMD and SMD to estimate the cross-channel nonlinear interaction. Such a closed-form expression allows to quickly estimate the impact of SMD on non-linearities for several transmissions and links configurations. We also performed numerical simulations by means of the Split Step Fourier method (SSFM) to confirm the model prediction. The obtained results showed that modal dispersion can be very beneficial in reducing the NLI in various scenarios. In particular, we tested different optical systems in terms of: dispersion, attenuation, channel spacing, symbol rate, and number of modes.
Interplay of Modal Dispersion with Nonlinear Interference in Fiber Optic Systems
Masters Thesis, 2021
Network traffic increases by 30% percent each year and is even expected to increase by a greater margin as more people and devices are getting connected to the internet. During this COVID-19 period, optical networking vendors have reported experiencing an unpredictable surge in data demands that are stressing the existing optical networks. Studies have shown that we are almost approaching the capacity crunch of single-mode fibers, and since the current optical networks are mainly made of single-mode fibers, we need new technologies to meet these increasing demands. Space division multiplexing, elastic optical networks, high order modulation formats are some of the technologies being proposed with each technology having its pros and cons. Space division multiplexing (SDM) has received a lot of attention as an alternative solution and it involves exploiting the spatial diversity of optical fibers in the form of polarization, the number of modes, number of cores or fibers working as bundles. Although SDM fibers represents a promising solution compared to the current single-mode fibers, such fibers introduce new challenges due to the interactions among the propagating modes. In ideal optical fibers, birefringence does not exist, and thus optical modes propagate inside the fiber without coupling. In practical cases, birefringence manifests itself due to imperfections, such as imperfect circular symmetry during the fiber manufacture, or due to external stresses, such as mechanical pressure exerted after manufacturing. This asymmetry results in random perturbation causing the two field polarizations to have different group delays, hence polarization mode dispersion (PMD) arises. In a multi-mode fiber, random birefringence leads to spatial mode dispersion (MD) among the different spatial models, in addition to the PMD among the polarizations of each mode. This thesis investigated the impact of PMD and SMD on optical fiber transmissions, especially focusing on its interaction with the nonlinear interference (NLI) arising during the signal propagation along the optical fiber. With this aim, we exploited the Gaussian noise (GN) model extended to include PMD and SMD to estimate the cross-channel nonlinear interaction. Such a closed-form expression allows to quickly estimate the impact of SMD on non-linearities for several transmissions and links configurations. We also performed numerical simulations by means of the Split Step Fourier method (SSFM) to confirm the model prediction. The obtained results showed that modal dispersion can be very beneficial in reducing the NLI in various scenarios. In particular, we tested different optical systems in terms of: dispersion, attenuation, channel spacing, symbol rate, and number of modes.
Compensation of Mode Crosstalk in MDM System Using Digital Optical Phase Conjugation
IEEE Photonics Technology Letters, 2019
We propose to utilize the digital optical phase conjugation (D-OPC) technique for the compensation of mode crosstalk in the mode-division-multiplexed (MDM) transmission system. To realize the D-OPC technique, we send the CW light from the receiver side, measure its wavefront at the transmitter side, and then transmit the phase-conjugated signal to the receiver. By using this technique, we demonstrate the transmission of four LP modes, each carrying 10-Gb/s on-off keying signals, over a 100-m long few-mode fiber link. These signals are detected by using direct-detection receivers with no electrical equalizer. The results show that, by applying the proposed D-OPC technique, we can achieve the bit-error rate of <10-3 for all four modes.
IEEE Photonics Journal, 2012
In this paper, we first measure fiber nonlinear Kerr coefficient of a two-mode fiber (TMF) by characterizing the four-wave mixing (FWM) components. Based on the measured nonlinear coefficient, we present an analysis of the link capacity for a two-mode fiber. It is shown that despite strong spatial overlapping of the three modes, the overall capacity approaches three times of that of a single-mode fiber.