Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.

Observation of squeezed states generated by four-wave mixing in an optical cavity

Today’s telecommunication networks have become sources of enormous amounts of widely heterogeneous data. This information can be retrieved from network traffic traces, network alarms, signal quality indicators, users’ behavioral data, etc. Advanced mathematical tools are required to extract meaningful information from these data and take decisions pertaining to the proper functioning of the networks from the network-generated data. Among these mathematical tools, machine learning (ML) is regarded as one of the most promising methodological approaches to perform network-data analysis and enable automated network self-configuration and fault management. The adoption of ML techniques in the field of optical communication networks is motivated by the unprecedented growth of network complexity faced by optical networks in the last few years. Such complexity increase is due to the introduction of a huge number of adjustable and interdependent system parameters (e.g., routing configurations, modulation format, symbol rate, coding schemes, etc.) that are enabled by the usage of coherent transmission/reception technologies, advanced digital signal processing, and compensation of nonlinear effects in optical fiber propagation. In this paper we provide an overview of the application of ML to optical communications and networking. We classify and survey relevant literature dealing with the topic, and we also provide an introductory tutorial on ML for researchers and practitioners interested in this field. Although a good number of research papers have recently appeared, the application of ML to optical networks is still in its infancy: to stimulate further work in this area, we conclude this paper proposing new possible research directions.

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An Overview on Application of Machine Learning Techniques in Optical Networks

This book, published in 2007, provides comprehensive coverage of the theory and practice of OPAs and related devices, including fiber optical parametric oscillators (OPOs). After introducing the field, the theory and techniques behind all types of fiber OPAs are covered starting from first principles - topics include the scalar and vector OPA theory; the nonlinear Schrodinger equation; OPO theory; and quantum noise figure of fiber OPAs. Challenges of making fiber OPAs practical for a number of applications are discussed, and a survey of the state-of-the-art in feasibility demonstrations and performance evaluations is provided. The capabilities and limitations of OPAs; the potential applications for OPAs and OPOs, and prospects for future developments in the field are discussed. Theoretical tools developed in this text can also be applied to other areas of nonlinear optics. This is a valuable resource for researchers, advanced practitioners, and graduate students in optoelectronics.

Fiber Optical Parametric Amplifiers, Oscillators and Related Devices: The nonlinear Schrödinger equation

The theoretical fundamentals of fiber-based optical parametric amplifiers(OPA) are reviewed,and their applications are discussed in this paper.In the end the future research aspects are expected.

Fiber-based Optical Parametric Amplifiers and Their Applications

1. Introduction 2. Properties of single-mode optical fibers 3. Scalar OPA theory 4. Vector OPA theory 5. The optical gain spectrum 6. The nonlinear Schrodinger equation (NLSE) 7. Pulsed-pump OPAs 8. OPO theory 9. Quantum noise figure of fiber OPAs 10. Pump requirements 11. Performance results 12. Potential applications of fiber OPAs and OPOs 13. Nonlinear crosstalk in fiber OPAs 14. Distributed parametric amplification 15. Prospects for future developments Appendices: A.1 General theorems for solving typical OPA equations A.2 The WKB approximation A.3 Jacobian elliptic function solutions A.4 Solution of four coupled equations for the six-wave model A.5 Summary of useful equations.

Fiber Optical Parametric Amplifiers, Oscillators and Related Devices

In the paper, a novel three-port channel drop filter in two dimensional photonic crystals (2D PCs) with a wavelength-selective reflection micro-cavity is proposed. In the structure, two micro-cavities are used. One is used for a resonant tunneling-based channel drop filter. The other is used to realize wavelength-selective reflection feedback in the bus wave-guide, which consists of a point defect micro-cavity side-coupled to a line defect waveguide based on photonic crystals. Using coupled mode theory in time, the conditions to achieve 100% drop efficiency are derived thoroughly. The simulation results by using the finite-difference time-domain (FDTD) method imply that the design is feasible.

Photonic crystal channel drop filter with a wavelength-selective reflection micro-cavity

In this work, we proposed two k-means-clustering-based algorithms to mitigate the fiber nonlinearity for 64-quadrature amplitude modulation (64-QAM) signal, the training-sequence assisted k-means algorithm and the blind k-means algorithm. We experimentally demonstrated the proposed k-means-clustering-based fiber nonlinearity mitigation techniques in 75-Gb/s 64-QAM coherent optical communication system. The proposed algorithms have reduced clustering complexity and low data redundancy and they are able to quickly find appropriate initial centroids and select correctly the centroids of the clusters to obtain the global optimal solutions for large k value. We measured the bit-error-ratio (BER) performance of 64-QAM signal with different launched powers into the 50-km single mode fiber and the proposed techniques can greatly mitigate the signal impairments caused by the amplified spontaneous emission noise and the fiber Kerr nonlinearity and improve the BER performance.

K-means-clustering-based fiber nonlinearity equalization techniques for 64-QAM coherent optical communication system.

We present a modified method to design photonic crystal fibers with flattened dispersion characteristics. By replacing the circular air-holes of the first central ring with elliptic air-holes, we observe a more flattened dispersion curve. Plane-wave expansion (PWE) method is used to analyze the dispersion property in a high-index core PCF. The simulation results are presented, and ultra-low and ultra-flattened dispersion curves over wide wavelength range are demonstrated.

Modified design of photonic crystal fibers with flattened dispersion

In the paper, index-guided triangular PCF with air-core is introduced which guides light by total internal reflection (TIR) when the air-core is smaller than the air holes in cladding. Properties of dispersion and leakage loss are investigated using finite-element method. The total dispersion curve gets more flattened and leakage loss increases significantly as the air-core diameter increases. High birefringence PCF with elliptical air-core is put forward and the birefringence increases with the ellipticity of the air-core.

Properties of index-guided PCF with air-core

A new two-pump fiber optical parametric amplifier (FOPA) is presented, which is composed of two-section high nonlinear fibers (HNLFs). Genetic algorithm (GA), a multivariate stochastic optimization algorithm is applied to optimize parameters of two fiber segments, such as the length and dispersion coefficient of fiber. A broadband FOPA with twosection HNLFs is obtained using optimum design parameters, which theoretically provides a uniform gain of 20.3 dB with 0.2-dB uniformity over a 346-nm bandwidth.

Mingyi Gao

Papers

Photonic crystal channel drop filter with a wavelength-selective reflection micro-cavity

K-means-clustering-based fiber nonlinearity equalization techniques for 64-QAM coherent optical communication system.

Modified design of photonic crystal fibers with flattened dispersion

Properties of index-guided PCF with air-core

Optimized design of two-pump fiber optical parametric amplifier with two-section nonlinear fibers using genetic algorithm.