Degree of polarization degradation due to cross-phase modulation and its impact on polarization-mode dispersion compensators

A novel analytical model is proposed to predict the cross-phase modulation (XPM)-induced depolarization in a two-channel transmission system, in which the Stokes' vector of each channel rotates around a space-invariant pivot by a time-varying angle which depends on the total instantaneous optical power in the fiber, on the angle between pump and probe input Stokes' vectors, and on the walk-off between channels. The model leads to a simple formula of the probe degree of polarization (DOP) which is validated both by simulation and experiment. The model helps identify the key physical factors that determine the XPM-induced performance degradation of DOP-based first-order polarization-mode dispersion compensators, and experiments that quantify such degradation are presented.     

Context‐aware Android applications through transportation mode detection techniques

In this paper, we study the problem of how to detect the current transportation mode of the user from the smartphone sensors data, because this issue is considered crucial for the deployment of a multitude of mobility‐aware systems, ranging from trace collectors to health monitoring and urban sensing systems. Although some feasibility studies have been performed in the literature, most of the proposed systems rely on the utilization of the GPS and on computational expensive algorithms that do not take into account the limited resources of mobile phones. On the opposite, this paper focuses on the design and implementation of a feasible and efficient detection system that takes into account both the issues of accuracy of classification and of energy consumption. To this purpose, we propose the utilization of embedded sensor data (accelerometer/gyroscope) with a novel meta‐classifier based on a cascading technique, and we show that our combined approach can provide similar performance than a GPS‐based classifier, but introducing also the possibility to control the computational load based on requested confidence. We describe the implementation of the proposed system into an Android framework that can be leveraged by third‐part mobile applications to access context‐aware information in a transparent way. Copyright © 2016 John Wiley & Sons, Ltd.     

Intensity distortion induced by cross-phase modulation andchromatic dispersion in optical-fiber transmissions with dispersioncompensation

In dispersion compensated systems, the intensity distortion induced by the interplay between cross-phase modulation and fiber chromatic dispersion can be a primary cause of transmission degradation. This interplay is mostly studied by time-consuming computer simulations. This letter introduces a new model of this interplay in fiber transmissions with dispersion compensation, leading to a linear filter that, applied to the input intensity of a modulated interfering channel, gives the intensity distortion of a continuous-wave probe signal at the receiver. The model can be of significant value in the search for optimized dispersion maps     

Analysis of the automatic frequency control in heterodyne opticalreceivers

A theoretical analysis of the automatic frequency control (AFC) in binary DPSK and FSK heterodyne optical receivers is presented, and its impact on the system performance is evaluated. The effects of the shot-noise AM/FM conversion in the frequency discriminator are analyzed. It is shown that with commercial DFB lasers a common analysis of the frequency control loop can be done for the three modulations considered. Design guidelines are given that account for the presence of the AFC loop by properly using some performance results derived in the assumption of perfect frequency tracking     

Analytical evaluation of improved access techniques in deflectionrouting networks

This paper presents an extension of a known analytical model for the performance evaluation of nonpriority deflection routing networks in uniform traffic. The extension allows the analysis of improved access techniques. The key features of the analytical technique are described by casting it in a very simple setting: nonpriority hot-potato in a two-connected slotted shufflenet (SN) network. Results are presented for three access techniques: transmit-no-hold (TXNH), transmit-hold (TXH), and bypass queuing (BQ)     

Parametric-gain approach to the analysis of single-channel DPSK/DQPSK systems with nonlinear phase noise

This paper presents a novel method based on a parametric gain (PG) approach to study the impact of nonlinear phase noise in single-channel dispersion-managed differentially phase-modulated systems. This paper first shows through Monte Carlo simulations that the received amplified spontaneous emission (ASE) noise statistics, before photodetection, can be reasonably assumed to be Gaussian, provided a sufficiently large chromatic dispersion is present in the transmission fiber. This paper then evaluates in a closed form the ASE power spectral density by linearizing the interaction between a signal and a noise in the limit of a distributed system. Even if the received ASE is nonstationary in time due to pulse shape and modulation, this paper shows that it can be approximated by an equivalent stationary process, as if the signal were continuous wave (CW). This paper then applies the CW-equivalent ASE model to bit-error-rate evaluation by using an extension of a known Karhunen-Loe/spl acute/ve method for quadratic detectors in colored Gaussian noise. Such a method avoids calculation of the nonlinear phase statistics and accounts for intersymbol interference due to a nonlinear waveform distortion and optical and electrical postdetection filtering. This paper compares binary and quaternary schemes with both nonreturn- and return-to-zero (RZ) pulses for various values of nonlinear phases and bit rates. The results confirm that PG deeply affects the system performance, especially with RZ pulses and with quaternary schemes. This paper also compares ON-OFF keying (OOK) differential phase-shifted keying (DPSK) systems, showing that the initial 3-dB advantage of DPSK is lost for increasing nonlinear phases because DPSK is less robust to PG than OOK.     

Statistical characterization of the Jones matrix of long fibers affected by polarization mode dispersion (PMD)

The unitary transfer matrix of a fiber affected by polarization mode dispersion (PMD) is analyzed using the Stokes representation of its eigenmodes and its retardation angle, or equivalently through its Pauli coordinates. We develop a statistical theory applied to these parameters and relate it to the extensive existing literature on the statistics of the PMD vector Dynamical equations are established for the Pauli coordinates. Assuming a standard "white Gaussian" model for the local birefringence, and using the tools of stochastic calculus, we derive the distributions of the eigenmodes, the retardation angle, the Pauli coordinates, and of the frequency derivatives of all these parameters. The evolution in space of the Pauli coordinates is also characterized as a standard Brownian motion on the unit sphere in /spl Rfr//sup 4/. An expression for the frequency autocorrelation function of the Pauli coordinates, the eigenmodes and the retardation angle is derived and their coherence bandwidth is compared to that of the PMD vector. All theoretical results are supported by simulation over an ensemble of 10000 fibers, using the standard retarder plate model.     

Improving vehicular safety message delivery through the implementation of a cognitive vehicular network

The Wireless Access in Vehicular Environments (WAVE) protocol stack has been recently defined to enable vehicular communication on the Dedicated Short Range Communication (DSRC) frequencies. Some recent studies have demonstrated that the WAVE technology might not provide sufficient spectrum for reliable exchange of safety information over congested urban scenarios. In this paper, we address this issue, and present a novel cognitive network architecture in order to dynamically extend the Control Channel (CCH) used by vehicles to transmit safety-related information. To this aim, we propose a cooperative spectrum sensing scheme, through which vehicles can detect available spectrum resources on the 5.8 GHz ISM band along their path, and forward the data to a fixed infrastructure known as Road Side Units (RSUs). We design a novel Fuzzy-Logic based spectrum allocation algorithm, through which the RSUs infer the actual CCH contention conditions, and dynamically extend the CCH bandwidth in network congestion scenarios, by using the vacant frequencies detected by the sensing module. The simulation results reveal the effectiveness of our architecture in providing dynamic and scalable allocation of spectrum resources, and in increasing the performance of safety-related applications.     

Neuroendocrine tumors of the gastroenteric canal. Anatomopathological and diagnostic-therapeutic definition. Description of a case with a rare cecal localisation

The E1 and E2 reading frames of 158 cervical carcinoma samples containing human papillomavirus (HPV) 16 were mapped using polymerase chain reaction (PCR). The reading frames were amplified using primers spanning the entire genes. Of the analyzed samples, 23% showed no amplification with the E1 primers and 29% showed no amplification with the E2 primers. There was an overlap, but not complete identity, between the E1- and E2-disrupted groups. All E1- and E2-negative samples were further analyzed with primers spanning subsections of the E1 and E2 reading frames, which together covered the entire genes. Of the 35 samples negative for E1, 11 were positive in specific amplification of the 3' end of the E1 gene. Several different subsections of E2 could be amplified from most samples negative for the entire gene (37/46). Five classes of patterns were found, in which either all subsections of the E2 gene or subsections in the 5', middle, or 3' end were disrupted. Although a variable pattern of disruption/deletion in the E1-E2 area of the HPV 16 genome was found in cervical carcinoma, the 5' end disruption was the most common one in both E1 and E2. Patients with carcinomas showing disruptions in E1/E2 had a poorer survival than those without such changes, and E1 disruptions were the most important prognostically.