Optical polarization

About: Optical polarization is a research topic. Over the lifetime, 13992 publications have been published within this topic receiving 244284 citations.

Multichannel frequency conversion experiment using fibre four-wave mixing

Abstract: Multichannel frequency conversion is demonstrated using fourwave mixing. A polarisation independent configuration is employed, by which polarisation control for each signal is not necessary. By setting the pump light frequency at the zero-dispersion wavelength of the fibre, three FSK modulated signals with a frequency spacing of 70 GHz are simultaneously converted with an equal efficiency of −27.5dB. Bit error rate measurements confirm the feasibility of this conversion scheme.

Machine Learning Techniques for Optical Performance Monitoring and Modulation Format Identification: A Survey

Abstract: The trade-off between more user bandwidth and quality of service requirements introduces unprecedented challenges to the next generation smart optical networks. In this regard, the use of optical performance monitoring (OPM) and modulation format identification (MFI) techniques becomes a common need to enable the development of next-generation autonomous optical networks, with ultra-low latency and self-adaptability. Recently, machine learning (ML)-based techniques have emerged as a vital solution to many challenging aspects of OPM and MFI in terms of reliability, quality, and implementation efficiency. This article surveys ML-based OPM and MFI techniques proposed in the literature. First, we address the key advantages of employing ML algorithms in optical networks. Then, we review the main optical impairments and modulation formats being monitored and classified, respectively, using ML algorithms. Additionally, we discuss the current status of optical networks in terms of MFI and OPM. This includes standards, monitoring parameters, and the available commercial products with their limitations. Second, we provide a comprehensive review of the available ML-based techniques for MFI, OPM, and joint MFI/OPM, describing their performance, advantages, and limitations. Third, we give an overview of the exiting ML-based OPM and MFI techniques for the emerging optical networks such as the new fiber-based networks that use future space division multiplexing techniques (e.g., few-mode fiber), the hybrid radio-over-fiber networks, and the free space optical networks. Finally, we discuss the open issues, potential future research directions, and recommendations for the potential implementation of ML-based OPM and MFI techniques. Some lessons learned are presented after each section throughout the paper to help the reader identifying the gaps, weaknesses, and strengths in this field.

Optical computing using hybrid encoded shadow casting

Abstract: The parallel processing property of optics has been recog­ nized as the main driving force behind digital optical computing. A parallel pattern logic operation, first proposed by Tanida and Ichioka, overlaps spatially coded 2-D bina­ ry pixel patterns situated in an optical input plane. These patterns, when illuminated by divergent light beams ema­ nating from a group of LEDs, form different interlaced pro­ jections (shadows) representing different parallel logic oper­ ations in the optical output plane. Since the pattern overlap corresponds to a spatial domain filtering process, it is also known as optical shadow casting (OSC). Using OSC, a large number of 2-D binary or multiple-valued logic inputs can be parallel processed. Another pattern logic method, proposed by Bartelt et al., uses theta modulation to encode the signal grey-level values into different grating orienta­ tions. The combination of these grey-level-dependent grat­ ings form the logic inputs that are to be manipulated by a coherent optical processor. Using spatial-frequency domain filtering, different optical logic functions can be generated. Recently, Yatagai described another pattern logic method in which the spatially encoded patterns are overlapped with an operational mask. Instead of using the OSC LED pat­ terns, this method switches an operational mask for the different logic operations. However, in all these pattern logic methods, either the spatial filtering or pixel casting process is performed by either a transparent or opaque screen. In this communication, the use of a polarization encoding and filtering method to perform lensless OSC logic operations is proposed. Both linear orthogonally polarized and hybrid form polarizations with transparent/opaque mask input, logic signals are used. Using this polarization or hybrid encoded OSC (POSC), doubleor triple-instruction logic operations can be performed. This technique can be extended to generate multivariate binary as well as twovariable multiple-valued logic functions and can also be used in conjunction with the Yatagai's pattern logic method. Pertinent examples such as the design of a binary fulland a ternary half-adder are presented.

Complex amplitude reflectance of the liquid crystal light valve.

Abstract: The complex amplitude reflectance of the liquid crystal light valve (LCLV) is determined as a function of the writing intensity and applied voltage using an approximate model. The input and output polarizers are assumed to have arbitrary directions. The theoretical results based on this model match our experimental measurements. This theory allows us to optimize the operation of the LCLV as an intensity or phase-only spatial light modulator. When the polarizers are orthogonal and the input polarizer is at -34 degrees with the front liquid crystal director, the intensity reflectance reaches 100% (compared to 81% for the conventional configuration). Phase-only modulation is realizable by use of appropriate applied voltage bias and configuration of polarizers.

Multi-photon, multi-mode polarization entanglement in parametric down-conversion

Abstract: The paper addresses the problem as to whether the microscopic photon polarization entanglement leaves any trace in the regime of high parametric down-conversion efficiency, where the number of down-converted photons can be rather large, and in which form. A local version of Stokes operators is defined and quantum correlation between operators measured from symmetric portions of the far field beam cross-section is studied.