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Preview: Lightwave Technology, Journal of - new TOC

Journal of Lightwave Technology - new TOC

TOC Alert for Publication# 50


Physical-Layer Security in MCF-Based SDM-EONs: Would Crosstalk-Aware Service Provisioning be Good Enough?

Nov.15, 1 2017

In this paper, we consider a multicore fiber (MCF)-enabled elastic optical network, in which certain nodes have a lower trust level than the others, and study how to provision lightpaths with considerations of the impairments and security vulnerabilities caused by intercore crosstalk. We propose attack-aware routing, spectrum, and core assignment algorithms that give priority to avoiding physical-layer security threats and then try to reduce the crosstalk-induced impairments. Specifically, both static network planning and dynamic network provisioning are investigated. For static planning, we first formulate an integer linear programming (ILP) model to optimize the spectrum utilization and intercore crosstalk level jointly and then propose a time-efficient heuristic. Simulation results confirm that the proposed heuristic can approximate the ILP's performance with much higher time efficiency in a small-scale network and outperform an existing benchmark in large networks. For dynamic provisioning, we design a heuristic to balance the tradeoff between blocking probability and crosstalk and conduct extensive simulations to verify its effectiveness.

High-Resolution Simultaneous Measurement of Strain and Temperature Using $pi$-Phase-Shifted FBG in Polarization Maintaining Fiber

Nov.15, 1 2017

We present a high-resolution simultaneous strain and temperature measurement scheme using ${pi }$-phase-shifted fiber Bragg grating written in PANDA-type polarization maintaining fiber. Two optical parameters, the Bragg frequency and the birefringence-introduced frequency difference, are measured to perform the discrimination of strain and temperature. A double-sideband interrogation method together with a cross-feedback technique is introduced, which significantly reduces the measurement error in birefringence-introduced frequency difference, and hence improves the sensing resolution of strain and temperature. In the demonstration experiment, simultaneous measurement of strain and temperature with resolutions of 0.018 $mu$ ${epsilon }$ and 0.0014 $boldsymbol {^{circ }}$C respectively is realized.

Self-Seeded RSOA Fiber Cavity Laser and the Role of Rayleigh Backscattering—An Analytical Model

Nov.15, 1 2017

Reflective semiconductor optical amplifiers (RSOAs) in a fiber cavity are attractive self-seeding optical sources for wavelength division multiplexed (WDM) access networks. This paper presents an analytical model of this fiber cavity laser (FCL). The model accounts for the Rayleigh backscattering (RB) of the fiber cavity as a primary mechanism of optical feedback inside the FCL. Moreover, it also includes the reflectivity of the remote node mirror. The purpose of the model is to analytically estimate the threshold RSOA gain required for the FCL to lase, by taking into account the fiber cavity length, the related attenuation and the RB. The model is suitable to experimentally characterize the Rayleigh backscattering coefficient, once the threshold gain of RSOA-FCL is measured.

Label-Free Highly Sensitive Hybrid Plasmonic Biosensor for the Detection of DNA Hybridization

Nov.15, 1 2017

A highly sensitive hybrid plasmonic slot-waveguide (HPSW) biosensor based on silicon-on-insulator is proposed and analyzed for DNA hybridization detection. The reported design is based on increasing the light interaction with the sensing region by using slot waveguide with plasmonic material. Due to the high index contrast and plasmonic effect, an ultrahigh optical confinement is achieved in the low-index regions, which enables the detection of the smallest change in the analyte refractive index with high sensitivity. The normalized power confinement, power density, and effective index of the supported modes by the HPSW are analyzed to achieve high-power confinement through the suggested biosensor and hence high sensitivity can be obtained. The HPSW is also incorporated with straight slotted resonator to calculate the sensitivity of the proposed design. The simulation results are calculated using full vectorial finite element method. The reported biosensor has high sensitivity of 1890.4 nm/RIU (refractive index unit), which is the highest in the literature to the best of our knowledge with a detection limit of 2.65 × 10 –6 RIU.

Investigation of LP- and Vector-Modes for the Analysis of Space-Division Multiplexed Systems in the Nonlinear Regime

Nov.15, 1 2017

Space-division multiplexing in multimode fibers is a very promising approach to overcome the shortcoming of capacity in long-haul optical transmission systems. In this paper, we present an analysis of different mode representations in multimode fibers. We resume the properties and the interrelations of linearly polarized and vectorial modes. We take a look at the coupled nonlinear Schrödinger equation and Manakov equations for strongly coupled mode groups. The nonlinear coupling coefficient of the Manakov equation is investigated for both mode bases, in order to verify if the approximated linearly polarized modes are a valid representation for the analysis of nonlinearities in space-division multiplexed systems. Even though the effective mode areas differ considerably between LP- and vector modes, the simulated coupling coefficient shows a good agreement between both models. The results indicate that the mode basis does not affect the nonlinear parameter. For the analysis the field distributions of the modes are numerically calculated with a vector finite difference modesolver. Finally the simulated results are verified analytically.

Precise Measurement of Fiber Third-Order Dispersion Using Transfer Function of a Microwave Photonic Filter

Nov.15, 1 2017

Third-order dispersion (TOD) is a fundamental parameter to characterize optical fiber. In this paper, we propose a method to precisely measure TOD of an optical fiber by using the amplitude and phase transfer function of a microwave photonic filter (MPF). The fiber under test (FUT) plays an important role in the MPF, of which the transfer function has a quadratic phase distortion due to the TOD of the FUT. Through iteratively modifying the quadratic phase spectral coefficient of the optical signal in the MPF to counteract the TOD effect, the transfer function distortion can be almost compensated. According to the definite relationship between the TOD and the compensation coefficient, we can determine the TOD precisely. In the experiment, the measurement uncertainty of 0.2% is obtained of a dispersion compensating fiber, designed for the compensation of 80 km standard fiber.

Experimental Comparison of Probabilistic Shaping Methods for Unrepeated Fiber Transmission

Nov.15, 1 2017

This paper studies the impact of probabilistic shaping on effective signal-to-noise ratios (SNRs) and achievable information rates (AIRs) in a back-to-back configuration and in unrepeated nonlinear fiber transmissions. For the back-to-back setup, various shaped quadrature amplitude modulation (QAM) distributions are found to have the same implementation penalty as uniform input. By demonstrating in transmission experiments that shaped QAM input leads to lower effective SNR than uniform input at a fixed average launch power, we experimentally confirm that shaping enhances the fiber nonlinearities. However, shaping is ultimately found to increase the AIR, which is the most relevant figure of merit, as it is directly related to spectral efficiency. In a detailed study of these shaping gains for the nonlinear fiber channel, four strategies for optimizing QAM input distributions are evaluated and experimentally compared in wavelength division multiplexing (WDM) systems. The first shaping scheme generates a Maxwell–Boltzmann (MB) distribution based on a linear additive white Gaussian noise channel. The second strategy uses the Blahut–Arimoto algorithm to optimize an unconstrained QAM distribution for a split-step Fourier method based channel model. In the third and fourth approach, MB-shaped QAM and unconstrained QAM are optimized via the enhanced Gaussian noise (EGN) model. Although the absolute shaping gains are found to be relatively small, the relative improvements by EGN-optimized unconstrained distributions over linear AWGN optimized MB distributions are up to 59%. This general behavior is observed in 9-channel and fully loaded WDM experiments.

Maximum Likelihood Estimation of Optical Path Length in Spectral Interferometry

Nov.15, 1 2017

Optical path length demodulation is a subject of fundamental importance in spectral interferometry applications. We propose an algorithm based on maximum likelihood estimation to achieve absolute optical path length demodulation with high sensitivity and noise resistance and to elucidate the cause and behavior of undesirable demodulation discontinuity. From an interference spectrum model with additive Gaussian noise, a maximum likelihood estimator is derived in Fourier domain to determine the optical path length. To assess its sensitivity performance, the Cramer–Rao bound of sensitivity is derived from Fisher information matrix. By simulations and experimental validations, the proposed method demonstrates its capability of achieving the Cramer–Rao bound over a large dynamic range of optical path lengths, initial phases, and signal-to-noise ratios. When compared with some state-of-the-art demodulation methods, it also demonstrates improved resistance to demodulation jumps at low signal-to-noise ratios. Importantly, the mechanism of such jumps can be readily explained from a new, intuitive perspective, which may permit the quantification of jump occurrences in the future.

Leap-Frog Continuous–Discontinuous Galerkin Time Domain Method for Nanoarchitectures With the Drude Model

Nov.15, 1 2017

A continuous–discontinuous Gakerkin time domain method (CDGTD) with vector basis functions is proposed to analyze the wideband response of plasmonic structures with the Drude dispersive model. Compared to the conventional time domain approaches, such as FDTD and PSTD, the unstructured mesh can provide a better geometrical approximation of curved surfaces and fine features. An EB scheme Riemann solver is employed to calculate the flux between adjacent subdomains. The relationship between the electric field and the polarization currents is modeled by a first order auxiliary differential equation (ADE). A leap-frog scheme is proposed to update Maxwell's equations, the ADEs of the Drude medium and the perfectly matched layer (PML) in an efficient manner. This new approach is validated by virtue of simulating the ultra-wideband behavior of a gold nanoloop antenna with and without a substrate as well as the reflectivity of a dual-band infrared absorber. Its advantage in computational cost is demonstrated via comparison to a commercial software package. In this light, the CDGTD method represents a more efficient forward modeling tool, which has been successfully employed here to perform a parametric study of a dual-band infrared absorber.