Chenglin Bai

Development of discrete Fourier transform-based channel estimation algorithms for a coherent optical orthogonal frequency division multiplexing transmission system

In this study, the authors presented discrete Fourier transform (DFT)-based channel estimation algorithms for a coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission system. Influence of the proposed algorithms to the performance and computational complexity of the CO-OFDM system was analysed and compared with other published algorithms. Their simulation results demonstrated that the improved DFT-based channel estimation algorithms are significantly efficient in our experimental conditions. Those algorithms can be considered as efficiently compromised systems in balance out the outcome of performance and the requirement on computational complexity. Such relatively economic and practical approaches have provided an optimistic prospect in studies of transmission systems for future optical communications.

Intelligent Bandwidth-Estimation Technique for Orthogonal Frequency Division Multiplexing-Based Elastic Optical Networking

Abstract—In orthogonal frequency division multiplexing (OFDM)-based elastic optical networking (EON), it is imperative to identify the parameters of the unknown OFDM signal intelligently, quickly, and robustly. Among these parameters, the bandwidth should be the first to be identified for the reason that other useful parameters such as number of subcarriers, baud rate, and frequency spacing can be obtained subsequently. In this paper we propose, for the first time to our knowledge, an intelligent bandwidth-identification technique for OFDM-based EON. The proposed technique can be divided into three sub-stages: estimation of power spectrum density, noise filtering based on empirical mode decomposition, and bandwidth identification based on a sliding window. When the number of samples is fixed at 215 and the optical signal-to-noise rate varies from 15 to 25 dB, the simulation results demonstrate that a bandwidth range from 2 to 40 GHz can all be successfully recognized with a minimum resolution of 39.1 MHz, and the average estimation absolute accuracies (EAAs) exceed 95%. Moreover, the technique has a good tolerance to chromatic dispersion and is independent of the number of subcarriers and frequency offsets. Finally, we verify the effectiveness of this technique by an experiment involving a 7.04 Gbps OFDMbased EON with minimum EAA of 94.12%, in which its bandwidth can be successfully recognized.

Interactions among Peakons, Dromions, and Compactons in (2+1)-Dimensional System

Starting from a quite universal formula, which is valid for some quite universal (2+1)-dimensional physical models, the interactions among different types of solitary waves like peakons, dromions, and compactons are investigated both analytically and graphically. Some novel and interesting features are revealed. The results show that the interactions for peakon-dromion, compacton-dromion, and peakon-compacton may be completely inelastic, not-completely elastic or completely elastic. - PACS numbers: 05.45.Yv, 02.30.Jr.

Joint tracking and mitigation of linear dynamic impairments using a 3-stage extended Kalman filter in fiber channel

We propose a novel joint tracking and mitigation scheme for linear dynamic impairments using a 3-stage extended Kalman filter. Simulation results show that it can quickly track and compensate the impairments including multi-polarization effects, frequency offset and phase noise.

Performance analysis of 4λ×20-Gb/s TWDM PON using an OFDM-OQAM modulated downstream

In this study, we investigated the performance of a 4λ×20-Gb/s time- and wavelength-division multiplexed passive optical network (TWDM PON) architecture with an orthogonal frequency division multiplexing offset quadrature amplitude modulation (OFDM-OQAM). At each optical network unit (ONU), the optical OFDM-OQAM signal with direct detection was demodulated, and the performance comparisons for different modulation schemes were done. We can achieve 80-Gb/s transmission using OFDM-OQAM scheme with 3dB sensitivity improvement as compared with OFDM.

Polarization I nsensitive B eam S plitter W ith F ocusing A bility U sing 2D H igh I ndex C ontrast G ratings

A polarization-insensitive 2D high index contrast gratings (HCGs) beam splitter based on silicon-on-insulator(SOI) is proposed and demonstrated, which performs two independent functions: transmission focusing and power equalization at the wavelength of 1550 nm.

Low-density parity-check code-based WDM-OFDM-PON

In this letter, a WDM-OFDM-PON architecture using LDPC code is brought up to increase transmission range and system performance. In optical line terminal (OLT), LDPC-coded OFDM signal at 10-Gb/s is transmitted as downstream. At each optical network unit (ONU), the optical OFDM signal is demodulated with direct detection, and on-off keying date at 2.5-Gb/s is returned as upstream. Simulation results show that the transmission distance could exceed 20-km with negligible penalty.

Multi-level phase-amplitude hybrid modulation and its transmission performance analysis+

The paper proposed a novel hybrid modulation format −16-level differential phase shift keying with binary amplitude shift keying(16DPSK-ASK), which carries 5 bits per symbol. With analyzing the characteristics of optical 16-level differential phase shift keying (16DPSK), the study analyzed 16DPSK-ASK modem methods theoretically and presented the methods in their achieving processes specifically. Based on RZ-16DPSK-ASK and CSRZ-16DPSK-ASK modulation methods, spectra and their eye diagrams following demodulator of Matlab simulation were obtained. The optimal back to back extinction ratio was derived, so that the equivalent eye opening was obtained for the amplitude tributary and phase tributary. The results showed that the 16DPSK-ASK hybrid modulation methods, as a possible new modulation format, not only have much narrower spectra with higher spectrum efficiency but also simplify the transmitter and receiver comparing with the same level modulation format. The satisfactory performance of the eye diagrams obtained after demodulation suggested that it was one of the dominant candidate modulation formats high-speed optical transmission system.

Influence of molecular composition on H-aggregation in hemicyanine Langmuir-Blodgett multilayers

Influence of molecular composition in hemicyanine Langmuir-Blodgett (LB) films, on the aggregation features was investigated by using steady state and time-resolved photoluminescence spectroscopy. It was found that a lower degree of H-aggregation (smaller aggregate size) could be realized in hemicyanine LB films with larger donor groups, leading to a smaller photoluminescence peak blue shift with respect to their solution spectra and longer aggregate lifetime.