Effect of optical pulse shaping and adaptive equalization on the performance of 100G DP-QPSK WDM system

Dual polarization quadrature phase shifting keying (DP-QPSK) modulation format along with coherent receiver helps in increasing the data carrying capability of existing optical networks without any major change in existing transmission infrastructure. The various linear and nonlinear fiber effects, frequency and phase errors are corrected in electrical domain at the receiver end with digital back propagation algorithms (DBP) instead of in-line compensation. In such a case the selection of optimum values of system parameters make the task easier for DBP algorithms. This paper highlights the importance of finding optimum operating point of continuous modulus algorithm (CMA) for better adaptive equalization (AE). The paper also discusses the optical pulse shaping using Gaussian optical band-pass filter to improve the spectral characteristics of DP-QPSK signal.

Research of Fiber Optic Connector Ferrule End-Face Degradation Influence on Optical Pulse Distortion during Propagation over Indoor Multi-Gigabit Optical Network Link with Crypto-Fibers

This article presents results of approbation of developed model of piece-wise regular fiber optic link, operating in a few-mode regime, with series-connected couple of special multimode optical crypto-fibers “encryptor-decoder”. Unlike the previously developed solution, the model was modified with an ability to take into account influence of fiber optic connector end-face contamination on laser-excited optical signal launching conditions. We present comparison results of computed optical pulse response envelops, distorted during propagation over 10GBase-LX network fiber optic links, containing optical crypto-fibers, depending on various conditions of transceiver laser source connector ferrule end-face contamination.

Comparative Study on Characteristics of Partial Discharge Optical Pulse and UHF Pulse in Switch Equipment

The article explores the performance of the new silicon photoelectric sensor in partial discharge detection, and compares the measured optical pulse with the traditional UHF pulse. Through optical and electrical synchronous partial discharge experiments, the article analyzes and discusses the detection performance, working characteristics and statistical characteristics of various sensors, and explores the advantages and feasibility of silicon photoelectric partial discharge sensors in actual discharge monitoring; In addition, the statistical performance of the two physical phenomena of partial light radiation and electromagnetic radiation was obtained through the analysis of optical and electrical synchronous monitoring data. Compared with UHF sensor, silicon photoelectric sensor under the optimal working voltage has a higher signal-to-noise ratio (SNR); Under the electromagnetic interference of the high-frequency motor, silicon photoelectric sensor exhibits better anti-electromagnetic interference ability; Discharge phase interval and characteristics reflected by the PRPD obtained by two detection methods maintain good consistency; Pulse repetition rate has the same trend with applied voltage, but statistical frequency of optical pulses obtained is higher than that of electromagnetic pulses because silicon photoelectric sensor has a higher SNR and single-photon sensitivity.

A Numerical Study of Optimization Methods for Phase-Only Optical Pulse-Shaping

The field of optical pulse-shaping and its applications is introduced, with a focus on time-domain approaches. A numerical investigation of all-fiber, time-domain, phase-only filtering is conducted for arbitrary temporal pulse synthesis. The theoretical phase modulation function required for generating use- specific target-intensity profiles is calculated using different optimization methods including a Brute Force Monte Carlo search, the Simulated Annealing method and the Genetic Algorithm method. The convergence speed, computational complexity and accuracy of these methods is compared under binary phase-only modulation, where the Genetic algorithm was found to outperform other methods.

Mathematical Modeling of Soliton-Like Modes at Optical Rectification

We discuss the results of numerical modeling of forming optical-terahertz bullets at the process of optical rectification. Our calculations are based on a generalization of the well-known Yajima - Oikawa system, which describes the nonlinear interaction of short (optical) and long (terahertz) waves. The generalization relates to situations when the optical component is close to a few-cycle pulse. We study the influence of the number of optical pulse oscillations on the formation of an optical-terahertz bullet. We develop original nonlinear conservative pseudo-spectral difference scheme approximating the generalization of the Yajima-Oikawa system. It is realized with the help of FFT algorithm. Mathematical modeling demonstrates scheme efficiency.

Time-of-flight photoelectron momentum microscopy with 80–500 MHz photon sources: electron-optical pulse picker or bandpass pre-filter

The small time gaps of synchrotron radiation in conventional multi-bunch mode (100–500 MHz) or laser-based sources with high pulse rate (∼80 MHz) are prohibitive for time-of-flight (ToF) based photoelectron spectroscopy. Detectors with time resolution in the 100 ps range yield only 20–100 resolved time slices within the small time gap. Here we present two techniques of implementing efficient ToF recording at sources with high repetition rate. A fast electron-optical beam blanking unit with GHz bandwidth, integrated in a photoelectron momentum microscope, allows electron-optical `pulse-picking' with any desired repetition period. Aberration-free momentum distributions have been recorded at reduced pulse periods of 5 MHz (at MAX II) and 1.25 MHz (at BESSY II). The approach is compared with two alternative solutions: a bandpass pre-filter (here a hemispherical analyzer) or a parasitic four-bunch island-orbit pulse train, coexisting with the multi-bunch pattern on the main orbit. Chopping in the time domain or bandpass pre-selection in the energy domain can both enable efficient ToF spectroscopy and photoelectron momentum microscopy at 100–500 MHz synchrotrons, highly repetitive lasers or cavity-enhanced high-harmonic sources. The high photon flux of a UV-laser (80 MHz, <1 meV bandwidth) facilitates momentum microscopy with an energy resolution of 4.2 meV and an analyzed region-of-interest (ROI) down to <800 nm. In this novel approach to `sub-µm-ARPES' the ROI is defined by a small field aperture in an intermediate Gaussian image, regardless of the size of the photon spot.