There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Lithium niobate on insulator (LNOI) technology is revolutionizing the lithium niobate industry, enabling higher performance, lower cost and entirely new devices and applications. The availability of LNOI wafers has sparked significant interest in the platform for integrated optical applications, as LNOI offers the attractive material properties of lithium niobate, while also offering the stronger optical confinement and a high optical element integration density that has driven the success of more mature silicon and silicon nitride (SiN) photonics platforms. Due to some similarities between LNOI and SiN, established techniques and standards can readily be adapted to the LNOI platform including a significant array of interface approaches, device designs and also heterogeneous integration techniques for laser sources and photodetectors. In this contribution, we review the latest developments in this platform, examine where further development is necessary to achieve more functionalities in LNOI integrated optical circuits and make a few suggestions of interesting applications that could be realized in this platform. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Status and Potential of Lithium Niobate on Insulator (LNOI) for Photonic Integrated Circuits

Data transmission rates in optical communication systems are approaching the limits of conventional multiplexing methods. Orbital angular momentum (OAM) in optical vortex beams offers a new degree of freedom and the potential to increase the capacity of free-space optical communication systems, with OAM beams acting as information carriers for OAM division multiplexing (OAM-DM). We demonstrate independent collinear OAM channel generation, transmission and simultaneous detection using Dammann optical vortex gratings (DOVGs). We achieve 80/160 Tbit s−1 capacity with uniform power distributions along all channels, with 1600 individually modulated quadrature phase-shift keying (QPSK)/16-QAM data channels multiplexed by 10 OAM states, 80 wavelengths and two polarizations. DOVG-enabled OAM multiplexing technology removes the bottleneck of massive OAM state parallel detection and offers an opportunity to raise optical communication systems capacity to Pbit s−1 level. Dammann gratings are used to realize multiplexing based on the generation, transmission and detection of optical angular momentum (OAM). The OAM of optical vortex beams offers a new degree of freedom for multiplexing and hence the promise of higher data communication rates, but massive parallel detection of OAM states has proved challenging. Now, researchers in China, Australia and Singapore have used Dammann optical vortex gratings (DOVGs) to realize multiplexing of massive OAM channels with individual modulation and simultaneous detection capabilities. They achieved a data capacity of 80 Tbit s−1 by multiplexing 1600 channels using ten OAM states, 80 wavelengths and two polarizations. This DOVG-enabled OAM multiplexing technology removes the bottleneck of massive parallel detection of OAM states and has the potential to increase optical communication capacities to the Pbit s−1 level.

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Massive individual orbital angular momentum channels for multiplexing enabled by Dammann gratings

In this paper, we propose a low-complexity and efficient carrier recovery algorithm for single carrier transmission systems that is capable of tracking frequency offset (FO) variations. Working as a FO tracking estimator, the algorithm demonstrates good accuracy in simulation and a FO drift of up to 200 MHz/μs can be compensated with minimal degradation in a QPSK system. In 112 Gb/s dual polarization (DP) QPSK experiments, the algorithm recovers a data sequence having >80 MHz of FO drift within 250 μs, providing better performance than a one-time estimator. In a regime that utilizes parallel processing of the data, we further demonstrate FO tracking and carrier phase recovery (CPR) using only one of the streams in a parallelized configuration, and we apply the carrier information to recover neighbouring streams directly. Consequently, the complexity of both the FO tracking and the CPR is further reduced.

Simple and efficient frequency offset tracking and carrier phase recovery algorithms in single carrier transmission systems.

Channel estimation for a reduced-guard-interval (RGI) CO-OFDM system shows a unique dependence on the training symbol design in the presence of intra-channel nonlinearities. Because smaller FFT sizes can be used, the RGI CO-OFDM system also demonstrates better nonlinearity tolerance than conventional CO-OFDM with larger FFT sizes.

Impact of intra-channel fiber nonlinearity on reduced-guard-interval CO-OFDM transmission

We propose and experimentally demonstrate polarization demultiplexing, frequency offset and phase noise compensation using an electrically inserted pilot for 28 Gbaud PDM-QPSK. We report excellent back-to-back and transmission performances, frequency offset and phase noise tolerances.

Experimental demonstration of pilot-aided polarization recovery, frequency offset and phase noise mitigation

With the advance of elastic optical networks, optical communication systems are becoming more flexible and dynamic. In this scenario, soft failures are more likely to occur due to various link impairments, of which the filter impairment caused by WSS is a major one. If these soft failures are not handled properly and timely, the quality-of-transmission (QoT) will degenerate, even leading to service disruption. During this process, it is important to know the accurate location and the magnitude of soft failure. However, it is difficult for traditional methods to accomplish this target. Fortunately, with the fast progress of the powerful machine learning (ML) algorithms, a new promising way is provided to address this problem. In this article, we propose to use artificial neural network (ANN) and Gaussian process regression (GPR) to localize the soft failure location and estimate anomaly value. The input of the ANN and GPR is extracted from the power spectrum density (PSD) and the equalizer taps, which can be easily obtained from a coherent receiver. We explore two types of soft failure caused by the WSS, including the offset of WSS's center frequency, i.e., frequency shift (FS), and the tightening of WSS's 3-dB bandwidth, i.e., frequency tightening (FT). To validate the proposed method, we perform extensive simulations. The localization accuracy of the ANN can reach 95%, and the mean-absolute-error (MAE) of the GPR can reach 0.1-GHz, demonstrating the effectiveness of the proposed method. Besides, we validate the generalization of the proposed method under different link conditions. Finally, the importance of each input feature is explored, showing the effectiveness of the selected features.

ROADM-Induced Anomaly Localization and Evaluation for Optical Links Based on Receiver DSP and ML

We experimentally demonstrate a 4-dimensional modulation direct detection system based on Stokes vector receiver and a novel reduced-complexity SSBI cancellation algorithm for signal linearization. A 480 Gb/s data rate over 80 km SSMF is achieved.

Qunbi Zhuge

Papers

Simple and efficient frequency offset tracking and carrier phase recovery algorithms in single carrier transmission systems.

Impact of intra-channel fiber nonlinearity on reduced-guard-interval CO-OFDM transmission

Experimental demonstration of pilot-aided polarization recovery, frequency offset and phase noise mitigation

ROADM-Induced Anomaly Localization and Evaluation for Optical Links Based on Receiver DSP and ML

Single Wavelength 480 Gb/s Direct Detection Transmission Over 80 km SSMF Enabled by Stokes Vector Receiver and Reduced-Complexity SSBI Cancellation