Wuliang Fang

Generation of 16-QAM-OFDM Signals Using Selected Mapping Method and Its Application in Optical Millimeter-Wave Access System

A simplified full-duplex 60-GHz optical millimeter-wave access system is proposed and experimentally demonstrated with a 16-QAM-OFDM downlink generated by selected mapping (SLM). The system receiver is realized with optical heterodyne detection and electrical self-mixing down-conversion. In the experiment, 5-Gb/s 16-QAM-OFDM signals are transmitted over 42-km SMF-28 and a 0.4-m wireless channel. The experimental results show that SLM can effectively reduce the peak-to-average power ratio and improve the receiver sensitivity. In addition, the proposed self-mixing down-conversion can simplify the transmitter and receiver configuration, since it eliminates the need for high-frequency microwave source at the central station and local oscillator at the base station.

A Novel Return-to-Zero FSK Format for 40-Gb/s Transmission System Applications

In this paper, we present the generation, the detection and the performance evaluation of a novel return-to-zero frequency shift keying (RZ-FSK) format for 40 Gb/s transmission. Non-return-to-zero (NRZ) FSK signal is generated by using two continues-wave (CW) lasers, one Mach-Zehnder modulator (MZM) and one Mach-Zehnder delay interferometer (MZDI). A RZ-FSK signal is successfully generated by cascading a dual-arm MZM, which is driven by a sinusoidal voltage at half of the bit rate. The demodulation can be simply achieved on 1 bit rate through one MZDI or an array waveguide grating (AWG) demultiplexer with balanced detection. By numerical simulation, two types of frequency modulation schemes using MZM or PM, and impact of the frequency tone spacing (FTS) of the generated FSK signal are discussed. The proposed scheme shows that the novel frequency modulation format offers a few transmission advantages comparing with than that of the other traditional modulation formats, such as RZ and differential phase-shift keying (DPSK), under varying dispersion management. The performance analysis of RZ-FSK signal in a 4 × 40 Gb/s WDM transmission system is introduced. We experimentally demonstrate, transparent wavelength conversion based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) and in a highly nonlinear dispersion shifted fiber (HNDSF) for a 40 Gb/s RZ-FSK signal, clearly validating the feasibility of all optical signal processing of high-speed RZ-FSK signal. Moreover, we investigate the receiver power penalty for the RZ-FSK signal after a 100 km standard single-mode fiber (SMF) transmission link with matching dispersion compensating fiber (DCF), under the post-compensation management scheme. Since the frequency modulation format is orthogonal to intensity modulation and vector modulation (polarization shift keying), it can be employed in the context of the combined modulation format to decrease the data rate or enhance the symbol rate. It can also be utilized in the orthogonal label-switching as the modulation format for the payload or the label.

A novel OFDM-CPM modulation scheme and its application in WDM-PON

A novel scheme to generate, transmit, and receive an optical orthogonal frequency division multiplexing (OFDM) continuous phase modulation (CPM) signal, which is combining minimum shift keying (MSK) coding with OFDM optical modulation, for downlink application in a 4×2.5-Gb/s wavelength division multiplexing (WDM) passive optical access network, is proposed and experimentally validated. We also realize wavelength remodulation for carrying upstream on-off keying (OOK) data to reduce the cost budget at the optical network unit. The experimental results show that the power penalties for the downlink and the uplink data after transmission over 25-km SMF-28 fiber are 0.1 dB and smaller than 0.4 dB, respectively.

A novel scheme for seamless integration of ROF system with OFDM-CPM WDM passive optical network

A novel scheme to generate, transmit and receive an optical OFDM-CPM signal in the architecture for seamless integration of ROF system with 4 × 2.5Gb/s WDM-PON is proposed and experimentally validated.

Experimental demonstration of visible light communication based on sub-carrier multiplexing of multiple-input-single-output OFDM

In this paper, a novel configuration of VLC system based on sub-carrier multiplexing of MISO OFDM is proposed. The system consists of a 2×1 MISO array of white LEDs to transmit and receive data. The data is respectively modulated by two sub-carriers at 6.25MHz and 12.5MHz. An overview of the system configuration is described, and the transmission experiment is setup. The experimental results and the relationship between the system BER and transmission range are also investigated.

DRZ, DQPSK, and PoISK orthogonal modulations for 100Gbit/s transmission system applications

In this paper, we propose and demonstrate a novel 4-bit/symbol optical data format based on modulating dark return-to-zero (DRZ), differential quadrature phase-shift keying (DQPSK) and polarization-shift-keying (PoISK) for 100Gbit/s transmission system applications, and the transmission performance is investigated.

Study of IQ imbalance effect in direct-detection optical OFDM systems

In-phase/quadrature-phase (IQ) imbalance can result in severe performance degradation in optical direct-detection orthogonal-frequency-division-multiplexing (DD-OFDM) systems. We build two optical back-to-back DD-OFDM systems, which implement double-sideband (DSB) and single-sideband (SSB) modulation, respectively. The tolerance to IQ imbalance of these two systems is analyzed and compared using error vector magnitude (EVM) and symbol error rate (SER). We find that, in the back-to-back case, the DSB system has stronger robustness to IQ imbalance than the SSB System. We further build two optical DD-OFDM systems each with 40-km transmission, which respectively implement DSB and SSB transmission. Similarly, we analyze and compare the tolerance to IQ imbalance of these two systems in terms of EVM and SER. We find that, however, in the case of 40-km transmission, the SSB system has stronger robustness to IQ imbalance than the DSB system. As a result, we conclude that, in the case of transmission, SSB modulation can enhance the tolerance to IQ imbalance of DD-OFDM systems.

Theoretical and simulation analysis of a novel multiple-input multiple-output scheme over multimode fiber links with dual restricted launch techniques

Different launching methods over multimode fiber (MMF) are reviewed and compared under various aspects such as coupling coefficient, mode power distribution, and bit error rate performance. Among these, center launch and ring launch are elaborated and chosen as the inputs of multiple-input multiple-output (MIMO) scheme for center launch exciting limited lower-order modes while ring launch exciting limited higher ones. Furthermore, we discuss the theoretical background and give a new wide-band MMF MIMO mathematical model. This paper also proposes a novel MMF MIMO system combining the dual restricted launches together with multi-segments receiving. The simulated results indicate that an aggregate data rate of 20  Gb/s over 800-m graded index-multimode fiber can be achieved by using this newly established MIMO scheme.

Frequency estimation for optical coherent MSK system

We propose algorithm to compensate frequency offset in optical coherent MSK system with little computation requirement. Simulations are performed to demonstrate the algorithm and its performance is excellent.

An optical MIMO transmission system over 80km of two-mode fiber using DSP

Simulations confirm stable MIMO transport of two channels over a two-mode fiber. Successful reception is achieved over 80km two-mode fiber at a bit error rate of 10−6- enabled by a new signal recovery algorithm we proposed.