Presence Of Polarization Dependent Loss Research Articles

Analytical Formulation of Fiber Nonlinear Noise Statistics in the Presence of Polarization Dependent Loss

Analytical Formulation of Fiber Nonlinear Noise Statistics in the Presence of Polarization Dependent Loss

Exact Noise Statistics in Equalized Polarization Multiplexing Systems in the Presence of Polarization Dependent Loss

In polarization multiplexing systems, signal and noise have different correlation matrices in the presence of polarization dependent loss (PDL). Therefore, the noise will be correlated after the signal equalization process, and the statistical characteristics of the noise correlation matrix is vital for the system capacity evaluation. In this paper, a stochastic differential equation (SDE) for the evolution of the noise correlation matrix after equalization is derived and the statistics of the correlation matrix elements are obtained by the related ordinary differential equations (ODEs). A threshold of the link gain, which equals half of the local PDL vector variance, exists. If the gain is above the threshold, one may ensure the average accumulated noise power not to grow exponentially. Monte Carlo simulations are conducted to verify the proposed theory and an excellent agreement is observed.

Erratum to “Inter-Channel Nonlinear Interference Noise in the Presence of PDL” [Jan 23 547-557

We presented analytical model which predicts the statistical properties of nonlinear interference noise (NLIN) in fiber links which are affected by polarization dependent loss (PDL) [1]. Although the model and results shown in [1] are correct, we found several typos and omissions in the analytical derivation. While the final results presented in the paper are correct, these errors may hinder anyone trying to reproduce the mathematical steps of the derivation. Hence, we correct them here.

Inter-Channel Nonlinear Interference Noise in the Presence of PDL

We present an analytical model which predicts the statistical properties of nonlinear interference noise (NLIN) in fiber links which are affected by polarization dependent loss (PDL). The model enables to investigate many PDL scenarios in a computationally efficient way, reducing the need to run costly split-step Fourier simulations. Using this model, we show that many features of NLIN, such as its phase and polarization rotation noise and time-varying intersymbol interference, may be significantly modified by PDL components present in the link.

Experimental secure quantum key distribution in the presence of polarization-dependent loss

Quantum key distribution (QKD) is theoretically secure using the principle of quantum mechanics; therefore, QKD is a promising solution for the future of secure communication. Although several experimental demonstrations of QKD have been reported, they have not considered the polarization-dependent loss in state preparation in the key-rate estimation. In this study, we experimentally characterized polarization-dependent loss in realistic state-preparation devices and verified that a considerable polarization-dependent loss exists in fiber- and silicon-based polarization modulators. Hence, the security of such QKD systems is compromised because of the secure key rate overestimation. Furthermore, we report a decoy-state BB84 QKD experiment considering polarization-dependent loss. Finally, we achieved rigorous finite-key security bound over up to 75 km fiber links by applying a recently proposed security proof. This study considers more realistic source flaws than most previous experiments; thus, it is crucial toward a secure QKD with imperfect practical devices.

Polarization Tracking in the Presence of PDL and Fast Temporal Drift

In this paper, we analyze the effectiveness of polarization tracking algorithms in optical transmission systems suffering from fast state of polarization (SOP) rotations and polarization-dependent loss (PDL). While most of the gradient descent (GD)-based algorithms in the literature may require step size adjustment when the channel condition changes, we propose tracking algorithms that can perform similarly or better without parameter tuning. Numerical simulation results show higher robustness of the proposed algorithms to SOP and PDL drift compared to GD-based algorithms, making them promising candidates to be used in aerial fiber links where the SOP can potentially drift rapidly, and therefore becomes challenging to track.

Polarization-induced distortion effects on the information rate in single-mode fibers

In this paper, we examine information theoretical properties of single-mode fibers in the presence of polarization-induced distortion effects. We derive some capacity results and further obtain several nonergodic achievable rates. In this work, however, mostly linear distortions are considered. Since polarization-dependent loss (PDL) is a nonunitary phenomenon, information rate loss caused by PDL is fundamentally inevitable. Interestingly, it is shown that in the presence of channel state information at the transmitter, PDL can increase the capacity in some scenarios. We analytically found also that the highest average capacity improvement from the knowledge of PDL at the transmitter is equal to the mean PDL of the link, and this benefit vanishes at high signal-to-noise ratio. In order to achieve the ergodic capacity, it is established that sending uncorrelated Gaussian signals with equal power via both polarizations is the optimum transmit strategy. As it turns out from the results, perhaps counterintuitively, in the presence of PDL, polarization mode dispersion (PMD) always improves the maximum outage rate; however, the PMD impact on the maximum throughput and the maximum two-layer expected rate is trivial. Finally, an extension to the simple Gaussian noise model of fiber nonlinearity is explored. All theoretical results are illustrated by numerical simulations.

PMD-Induced Crosstalk in Ultrahigh-Speed Polarization-Multiplexed Optical Transmission in the Presence of PDL

We present a new type of crosstalk in a polarization-multiplexed ultrahigh-speed transmission caused by polarization-mode dispersion (PMD) in the presence of polarization-dependent loss (PDL). When PMD and PDL are both present, the orthogonality between two principal states of polarization (PSP) is reduced. As a result, crosstalk inevitably occurs between two polarizations and prevents the two channels from being separated completely during polarization demultiplexing. The system impact of these effects in a polarization-multiplexed terabit/s transmission is also demonstrated experimentally.

The dynamics of state of polarization in the presence of conventional polarization effects in optical fibers

The presence of polarization mode dispersion (PMD) vector in an optical fiber leads to rotating the input state of polarization (SOP) vector with an angle determined by both the value of PMD vector and the frequency. Also, the PMD leads to differential group delay (DGD) among the polarization components. The presence of polarization dependent loss (PDL) vector leads to attenuating one of the components and increases the other by a magnitude determined by the value of PDL vector. The study of each phenomenon individually does not give a proper description of the physical nature of the optical fiber system, because these two phenomena arise together at the same time. In this paper, a new theoretical model is introduced to determine the output SOP as a function of PMD, PDL, and input SOP. On the other hand, a new expression was formulated to the dynamical equation and proved that the principal state of polarization (PSP) vector is a complex, where real and imaginary parts of PSP vector represent the PMD and PDL vectors, respectively. Using these vectors, a new value of DGD and PDL may be found.

Disjoint detection in polarization multiplexed communication systems affected by polarization dependent loss

We study the performance of a simple optical receiver for use with polarization multiplexed transmission in the presence of polarization dependent loss (PDL). The receiver is based upon filtering of each of the channels with a polarizer that is orthogonal to the other channel, such that interference due to loss of orthogonality is avoided at the expense of a reduction in the detected signal to noise ratio. In spite of its simplicity, this receiver is shown to perform almost as well as the optimal maximum likelihood receiver, and much better than receivers that are based on conventional polarization splitting.

Effect of PDL-induced coherent crosstalk on polarization-division-multiplexed direct-detection systems

We analyze the effect of polarization-dependent loss (PDL) on the performance of the polarization-division-multiplexed (PDM) signals in direct-detection systems. We present the theoretical analysis of the sensitivity penalty caused by PDL-induced coherent crosstalk and compare the results with experimental data obtained by using a simple variable PDL emulator based on a LiNbO3 Mach-Zehnder modulator. Also presented is the performance degradation caused by the polarization misalignment between the received signals and the polarization beam splitter at the receiver in the presence of PDL.

Estimation of polarization mode dispersion and polarization dependent loss in a cascade of optical components

A general vector approach to the polarization mode dispersion (PMD) and polarization dependent loss (PDL) calculation in a cascade of optical components with each component having both PMD and PDL is presented. By using the formalism, the PMD-PDL coupling effect is quantitatively described and its implications are discussed. In particular, it is shown that the presence of PDL in the components is a second-order effect in the PMD of the cascade. As an illustration of the formalism, a statistical estimation of PMD and PDL in a practical optical device is performed. The accuracy and the computational advantage of the vector approach are demonstrated.

Study of PMD and PDL Equalization Via a Nonunitary FIR Lattice Filter

We study a novel configuration and synthesis algorithm for equalization of polarization-mode dispersion (PMD) alone and combined with polarization-dependent loss (PDL) using a nonunitary optical lattice filter (NU-OLF). The NU-OLF is a generalization of a previously studied unitary lattice filter (U-OLF) for PMD equalization. Comparison of the improvement in the noise loaded PMD/PDL-induced eye closure, for typical optical signal-to-noise ratio values, shows that a NU-OLF is always superior to a U-OLF of the same order and it offers a significant advantage over a U-OLF with the same number of degrees of freedom in the equalization of PMD in the presence of PDL.

Polarization-mode dispersion influenced by polarization-dependent loss and chirp for a Gaussian pulse

A combination of polarization-mode dispersion (PMD) and polarization-dependent loss (PDL) in optical fibers may lead to anomalous pulse broadening. It raises the issue for more complete assessments when studying pulse propagation in the presence of polarization-dependent loss. A mathematical description is put forward in this work, where PMD is evaluated in the presence of XPM, PDL, and chirp. Simulation shows that the delay of a chirped Gaussian pulse depends not only on PDL, but also on the chirp of the pulse itself. To some degree, effective PMD can be controlled by PDL and chirp. The results give guidance for PMD compensation.

Higher Order Polarization-Mode Dispersion in the Presence of Polarization-Dependent Loss in Optical Fiber Systems

The statistics of first- and second-order polarization-mode dispersion and statistical dependencies between corresponding quantities are investigated with regard to fiber-optic links with polarization-dependent loss (PDL). We show the occurrence of an infinite depolarization rate of the principal states of polarization (PSPs) caused by an abrupt interchange of the two PSPs with a probability that grows with the global PDL. We finally discuss the influence of the frequency resolution of measurement and simulation methods on the depolarization results

Demonstration of broad-band PMD mitigation in the presence of PDL through distributed fast polarization scrambling and forward-error correction

We experimentally demonstrate broad-band mitigation of polarization-mode dispersion (PMD) in the presence of polarization-dependent loss (PDL) by using distributed fast polarization scramblers in systems adopting forward-error correction. The combined penalty of PMD and PDL is smaller than the sum of the individual penalties, which shows the robustness of the PMD mitigation scheme against PDL and the enhancement of PMD tolerance improvement in the presence of PDL. The desired number of scramblers and their distribution are also discussed.

Robustness of polarization-mode-dispersion compensation in the presence of polarization-dependent loss

The robustness of polarization-mode dispersion (PMD) compensation utilizing radio-frequency feedback in the presence of polarization-dependent loss (PDL) is investigated using a closed-loop dynamic model. Simulations using mean PMD of 30% of the bit period show that mean PDL of up to 2 dB increases the Q-penalty after PMD compensation by less than 0.1 dB. We find that the compensator can become trapped in secondary optima at high PDL, incurring significant additional penalty.

Polarization-dependent loss-induced pulse narrowing in birefringent optical fiber with finite differential group delay

A combination of polarization-mode dispersion (PMD) and polarization-dependent losses in optical fiber may lead to anomalous pulse narrowing despite the existence of finite differential group delay. It raises the issue for more complete assessments when studying the pulse propagation in single-mode fiber (SMF) in the presence of polarization-dependent loss.