10 Gb/s optical carrier distributed network with W-band (0.1 THz) short-reach wireless communication system

Millimeter-wave (mm-wave) operated in W-band (75 GHz–0.11 THz) is of particular interests, since this frequency band can carry signals at much higher data rates. We demonstrate a 10 Gb/s optical carrier-distributed network with the wireless communication system. The mm-wave signal at carrier frequency of 0.1 THz is generated by a high speed near-ballistic uni-traveling carrier photodiode (NBUTC-PD) based transmitter (Tx), which is optically excited by optical short pulses. The optical pulse source is produced from a self-developed photonic mm-wave waveform generator (PMWG), which allows spectral line-by-line pulse shaping. Hence these optical pulses have high tolerance to fiber chromatic dispersion. The W-band 10 Gb/s wireless data is transmitted and received via a pair of horn antennas. The received 10 Gb/s data is envelope-detected and then used to drive an optical modulator at the remote antenna unit (RAU) to produce the upstream signal sending back to the central office (CO). 20 km single mode fiber (SMF) error free transmission is achieved. Analysis about the optimum repetition rate of the optical pulse source and the transmission performance of the upstream signal are also performed and discussed.     

Novel 60 GHz RoF system with optical single sideband mm-wave signal generation and wavelength reuse for uplink connection

In order to improve RF frequency to achieve higher bandwidth and larger capacity, we propose a novel scheme to generate optical single sideband (SSB) millimeter-wave, in which frequency doubling of local radio frequency (RF) is obtained by using one integrated Mach–Zehnder modulator (MZM), and we theoretically investigate the generating principle of SSB. The optical SSB modulation scheme is employed to generate 60 GHz optical mm-wave and the 2.5 Gb/s baseband signal is simultaneously up-converted at the central station (CS) for downlink transmission, and the optical carrier is reused for uplink connection at the base station (BS). The full-duplex 2.5 Gb/s data are successfully transmitted over 40 km standard single-mode fiber (SMF-28) for both uplink connection and downlink connection with less than 2-dB power penalty. Results show the novel 60 GHz RoF system with optical SSB mm-wave signal generation using optical frequency doubling is feasible and we can obtain simple cost-efficient configuration and good performance over long-distance transmission.     

Generation of pure electrical quadrature amplitude modulation with photonic vector modulator

A photonic vector modulator architecture for generating pure quadrature amplitude modulation (QAM) signals is presented. An electrical quadrature-modulated signal at microwave-millimeter-wave frequencies is generated from its corresponding baseband in-phase (I) and quadrature (Q) components. In the proposed scheme, no electrical devices apart from the electrical tone oscillator are needed in the generation process. In addition, the purity of the generated signal is increased, and the hardware requirements are reduced when compared with previously proposed architectures so a highly compact low-cost architecture can be implemented. A pure 1.25 Gbit/s 4-QAM signal has been experimentally generated at a 42 GHz carrier frequency.     

A full-duplex radio-over-fiber system using direct modulation laser to generate optical millimeter-wave and wavelength reuse for uplink connection

In this paper, we present a full-duplex radio-over-fiber system incorporating both optical millimeter-wave (mm-wave) generation and wavelength reuse for uplink connection. The optical double sidebands (DSB) signal is generated by using only one inexpensive broadband direct modulation laser (DML), to which a mixing RF signal is applied. An optical interleaver is then used to separate the first-order optical sidebands from the optical carrier of optical DSB signal. The separated first-order optical sidebands are beat to generate mm-wave signal that has double the frequency of the RF drive signal, while the separated optical carrier is reused as light source to remodulate uplink signal. Both detailed theoretical analysis and experiments to demonstrate the feasibility of the proposed system are presented. Experiment result shows that the bidirectional 2.5 Gb/s data can be successfully transmitted over 40 km standard single-mode fiber (SSMF) with less than 2 dB power penalty.     

A Photonic mm-Wave Frequency Sextupler Using an Integrated Mach–Zehnder Modulator with Three Arms

Abstract

A novel photonic mm-wave frequency sextupling scheme based on an integrated Mach–Zehnder modulator with three arms is proposed in this article. Without any optical filter, a high-quality frequency sextupling mm-wave signal can be generated. Compared with mm-wave generation schemes based on traditional two-arm Mach–Zehnder modulators, the proposed scheme does not need DC bias and a complex electrical bias control circuit. Some non-ideal factors are taken into consideration to verify its performance, which proves that a slight deviation of the ideal values does not cause great degradation of the performance of the mm-wave generation scheme.     

基于幅度相位联合校正算法的8-QAM自由空间相干光通信

提出了基于幅度相位联合校正算法的8阶正交幅度调制(8-QAM)自由空间相干光通信方案。与传统的自由空间光通信方案相比,本文提出的方案不仅无需信道状态信息(CSI)就可以实现对原信号的高精度还原,同时还具有较高的光谱效率。仿真实验表明,当接收端与发射端的频偏f 0=20 MHz、激光器联合线宽Δf=10 kHz、信噪比为20 dB时,该方案在归一化大气闪烁标准差σ=0.25、归一化相位噪声方差σΦ^2=0.07的对数正态湍流信道条件下,其误码率(BER)与未采用联合校正算法的8-QAM系统相比低4个量级。     

Simultaneous multichannel NRZ-to-RZ format conversion of 4-ASK signal based on phase-intensity hybrid modulation and dispersion compensation fiber

We propose and investigate a novel technique to realize non-return-to-zero （NRZ） to return-to-zero （RZ） format conversion of a multichannel 4-ary amplitude shift keying （4-ASK） signal. The proposed format converter composed of two modulators and a dispersion compensating fiber （DCF） is theoretically inves-tigated using numerical simulation as basis. Research shows that a 4-channel 20-Gb/s NRZ-4-ASK signal can be converted to a RZ-4-ASK signal simultaneously without wavelength shifting and signal quality degradation, with the converted signal multiplexed to 40 Gb/s.     

Reduction of frequency fading and imperfect frequency response with pre-emphasis technique in OFDM-ROF systems

In this paper, a novel technique is proposed and experimentally demonstrated to reduce the effect of frequency fading (FF) and imperfect frequency response in direct-detection (DD) optical orthogonal frequency division multiplexing-radio-over-fiber (OFD-MROF) systems. To overcome FF effect in the optical fiber and imperfect frequency response in the optical and electrical devices at the high frequency, we pre-emphasize the power of the millimeter wave (mm-wave) OFDM sub-carriers appropriately in the center station. Experimental result of the proposed system shows the received sensitivity has been improved about 2 dB at the BER of 1 × 10^− 4 after 50 km SSMF transmission for 2.5 Gb/s OFDM signal carried on 60 GHz optical mm-wave compared to the original system without pre-emphasis technique.     

Analysis of 160 Gb/s all-optical NRZ-to-RZ data format conversion using quantum-dot semiconductor optical amplifiers assisted Mach-Zehnder interferometer

A scheme of all-optical data format conversion from nonreturn-to-zero to return-to-zero is proposed using quantum-dot semiconductor optical amplifiers (QD SOAs) assisted Mach-Zehnder interferometer (MZI). The proposed scheme has the potential to operate at much larger bit rate ∼160 Gb/s, and the converted signal has a lower frequency chirp. 160 Gb/s all-optical format conversion is verified through numerical simulations, and the output contrast ratio and Q-factor are analyzed to evaluate the system performance. With properly selected parameters, the converted signal with a contrast ratio over 8 dB and a Q-factor over 8 can be achieved.     

相干光正交频分复用传输系统中的 无导频相位纠偏方法

提出了一种适用于16-QAM的新型相位纠偏方法,克服了基于M次方算法的传统相位纠错方法不适用于高阶正交振幅调制的缺点.该方法结合正交频分复用调制方式,无需导频即可完成相位盲估计,且计算量较少.本文基于112 Gb/s 1 040 km的相干光正交频分复用传输系统进行了算法验证,并与传统的4次方纠偏方法进行了比较,实验证明该算法适用于正交频分复用和16-QAM调制平台,相位纠偏结果显著优于基于导频的4次方算法.     

Full-Duplex Radio-over-Fiber System Based on a Novel Octupling mm-Wave Generation Scheme

Abstract

A novel mm-wave generation scheme based on two phase modulators and two unbalanced Mach-Zehnder interferometers is proposed. Compared with the conventional Mach-Zehnder modulator-based scheme, the phase-modulator-based scheme can work steadily without an electrical control circuit for the DC bias, and it has smaller insertion loss. A full-duplex radio-over-fiber system was investigated by simulation, and its performance is not affected by chromatic dispersion for both downstream and upstream transmission. A 40-GHz mm-wave is generated from a 5-GHz driving signal. The system performance is analyzed by using eye diagrams and bit error rate. Results demonstrate that the performance is still very good, even after a 50-km transmission.     

Photonic generation of 60 GHz-band vector signals for RoF systems based on optical vector signal down-conversion

A novel photonic method of 60 GHz-band vector signal generation for RoF systems based on optical vector signal down-conversion is proposed and experimentally demonstrated in this paper. In the proposed method, the target vector signals are first generated in the optical domain with the help of mature commercial optical devices and then directly distributed to the base stations (BSs) through the fiber link. The generated vector signals can be automatically down-converted to the 60 GHz band in the BSs after O/E conversion, and then directly transmitted to the users without any further processing. With the proposed method, higher spectrum efficiency and system capacity will be obtained compared with the traditional OOK RoF systems while almost no extra system complexity and cost is brought in. According to the characteristics of different types of vector signals, two particular modulation schemes are provided, which are then verified by corresponding simulations and experiments. In the experimental 60 GHz RoF system, the 622 MSym/s 60 GHz-band 8-QAM and 4-QAM signals generated with two different schemes respectively are successfully transmitted over 50 km SMF and 5 m wireless channel without any compensation, and the power penalty are both about 1.7 dB at the BER of 10^− 9.     

Using dual-mode self-locked semiconductor laser for optical millimeter-wave application

In this study, an optical millimeter-wave (mm-wave) generator is proposed and experimentally demonstrated by using a self-injected Fabry-Perot laser diode (FP-LD), having mode spacing of 1.11 nm, for dual-mode beating in 140 GHz band (terahertz band). The created dual-wavelength also can be also modulated at 1.25, 2.5, and 10 Gb/s with on-off keying (OOK) modulation format by external optical modulator, respectively, in 20 km fiber transmission. Moreover, the dual-mode laser can be selected in difference wave-lengths by tuning the optical filter inside cavity for the future WDM applications.     

Full-Duplex Link Providing Alternative Wired and Wireless Broadband Access for the Wavelength-Division Multiplexing Passive Optical Network with a Uniform Converged Signal Format

Abstract

A full-duplex link implementing alternative wired and wireless access for wavelength-division multiplexing passive optical network is proposed with the uniformed three-tone converged optical signal, which provides a wired or wireless downlink access signal alternatively and an uplink optical carrier. The uplink optical carrier reversed by the converged optical signal makes the hybrid optical node unit free from the optical source. The simulation results show that the full-duplex link with a 10-Gb/s 16-quadrature amplitude modulation (16-QAM) downstream and 5 Gb/s binary upstream can provide both wired access with a bit-error rate below 10^?9 and radio-over-fiber-based wireless access with a bit-error rate below 10^?7 over 40 km of fiber without an optical source and optical amplifier in the hybrid optical node unit.     

Investigation of a high-speed optical FSK scheme for WDM-PON applications with centralized lightwave source

This paper proposes and numerically investigates a novel high-speed wavelength-division-multiplexed passive optical network (WDM-PON) architecture with colorless user terminals based on the use of orthogonal modulation scheme for downstream and upstream transmission. The 40 Gb/s optical frequency shift keyed (FSK) downstream data is generated based on carrier-suppressed modulation. At optical network unit, the downstream signal is directly re-modulated by the 2.5 Gb/s up-stream data and sent back with the same fiber. Error free transmission over 20 km single mode fiber can be observed for both downstream and upstream signals in our simulation. Power budget, tolerance of channel spacing, FSK tone spacing and dispersion are all investigated. Factors that might influence the stability of the system are analyzed and an extended hybrid wired/wireless version of the scheme is also given.     

40 Gb/s, secure optical communication based upon fast reconfigurable time domain spectral phase en/decoding with 40 Gchip/s optical code and symbol overlapping

We propose and experimentally demonstrate a 40 Gb/s secure optical communication system with on-off-keying (OOK) modulation format by using a time domain spectral phase en/decoding scheme, which employs a highly dispersive element and high-speed phase modulator for introducing significant symbol overlapping for both the encoded and incorrectly decoded noiselike signals to enhance the information security against eavesdropping using a power detector. The influence of dispersion and chip modulation rate on the symbol overlapping of the incorrectly decoded signal has been analytically investigated and experimentally verified. Security enhancement for 40 Gb/s OOK data using fast reconfigurable 40 Gchip/s optical codes with code lengths of up to 1024 has been demonstrated and compared with a 10 Gb/s system.     

Generation of optical carrier suppression millimeter-wave signal using one dual-parallel MZM to overcome chromatic dispersion

In this paper, we have proposed a novel approach to generate optical carrier suppression (OCS) mm-wave with signal only carried by one first-order sideband using a dual-parallel MZM in radio-over-fiber (RoF) system, and the transmission performance was also investigated. As the optical mm-wave signal is transmitted along the fiber, there is no time shift of the data symbols resulting from the group velocity dispersion in the fiber because the signal is only modulated on one sideband. The simulation results showed that the eye diagram keeps open and clear even when the optical mm-wave signals are transmitted over 96-km and the power penalty is about 1-dB after fiber transmission distance of 60-km, which is quite consistent with our theoretical analysis. Furthermore, the proposed OCS optical mm-wave generation approach is also used in a full-duplex RoF link based on wavelength reuse at the base station for the uplink due to another pure sideband without carrying data. The bidirectional 2.5-Gbit/s data is successfully transmitted over 40-km standard single mode fiber with less than 0.5-dB power penalty in the simulation. Both the unidirectional RoF downlink and the full-duplex RoF system have good performance.     

Millimetre-wave fibre–wireless transmission systems with reduced effects of fibre chromatic dispersion

This paper describes two techniques for the implementation of millimetre-wave (mm-wave) wireless communication systems incorporating optical fibre distribution networks. Fibre chromatic dispersion can exhibit severe effects on the transportation of mm-wave frequencies over fibre, resulting in greatly reduced post-detection rf powers. Each mm-wave fibre–wireless system demonstrated here incorporates a method for the generation and modulation of an optical mm-wave carrier, which enables the effect of fibre dispersion to be significantly reduced. One set-up is a direct-detection scheme where optical single-sideband (SSB) with carrier modulation is used to overcome fibre dispersion effects. The other system employs a self-heterodyne arrangement in which a dual-frequency optical source generates a low phase-noise mm-wave beat signal. Data transmission is achieved by externally modulating the dual-mode signal and reduced effects of fibre dispersion are observed.     

Optical signal processing using nonlinear fibers

Ultra-fast optical signal processing is a promising technology for future photonic networks. This paper describes possible applications of nonlinear fibers to optical signal processing. The third-order optical nonlinearities in a fiber are discussed by analyzing the interaction of co-propagating optical waves. The properties of a nonlinear fiber are then considered in terms of optimizing the dispersion for achieving phase matching and decreasing walk-off. A highly nonlinear fiber (HNLF) is a practical candidate for an ultra-high-speed signal processor. Using HNLF, the following experiments are successfully demonstated: ultra-broadband wavelength conversion/optical phase conjugation by four-wave mixing, 160 Gb/s optical 3R-regeneration, and optical switching up to 640 Gb/s using a parametric amplified fiber switch. Steps for further improvements are also discussed.     

高速多量子阱激光器混沌保密通信系统研究

研究了外部光注入高速多量子阱激光器激光混沌全光保密通信系统,导出系统同步方程,理论证明并数值实现了系统的同步,分析了增加反馈系数以缩短同步时间且增强系统同步稳定性的方法。研究分析了多量子阱激光器混沌隐藏和混沌键控保密通信全光调制解调系统模型,数值模拟了具有正弦调制信号的调制频率0．2GHz混沌模拟保密通信和数字信号调制速率20Gb／s的混沌数字保密通信以及调制速率0．05Gb／s混沌键控保密通信的应用,系统确实具有较高的保密性能和反破译能力;分析了混沌数字信号保密通信调制带宽20Gb／s调制解调时的同步误差以及混沌键控调制速率,系统都具有非常好的调制解调特性,且在高速混沌通信中,系统解调具有相对较小的同步误差,而1Gb／s是混沌键控通信的速率上限。