基于光学倍频技术的WDM-ROF-PON系统设计

设计了一种将光载无线技术融合于波分复用无源光网络结构的系统。在发射端,系统采用光学倍频技术生成40GHz光毫米波载波,加载2.5Gbit/s的基带数据信号,下行链路传输性能良好且受色散影响小;在接收端,利用光波重用技术从下行信号中提取上行光载波,加载2.5Gbit/s上行基带数据信号。采用光学倍频技术降低了毫米波生成成本,提高了系统的实用性。     

单信道多业务光载无线系统研究

设计和仿真实现了在单信道中同时传输多种无线业务的光载无线系统,使用外调制器获得双边带调制方式的光毫米波信号,利用光纤布拉格光栅进行左右边带和载波的分离,通过选择边带和载波进行强度调制不同速率业务的信号来获得不同的系统方案。仿真结果显示,各个信号在光纤中传输50 km后,最大功率代价小于1 dB。证明了单信道多业务光载无线系统可以提高单一信道带宽的利用率,增加系统的灵活性。     

采用两个级联外部调制器产生四倍频光载毫米波的光纤无线通信系统

研究了一种采用两个级联外部调制器基于光载波抑制原理产生四倍频毫米波的光纤无线通信(ROF)系统.在中心站利用电混频器产生副载波复用信号,通过第一个外部调制器产生两倍射频(RF)信号的光载毫米波信号,再通过第二个外部调制器产生四倍射频信号的光载毫米波.实验显示采用频率为10 GHz的射频信号源和2.5 Gbit/s的数据基带信号混频通过两个级联外部凋制器后产生毫米波的频率为40 GHz,并且在单模光纤中传输距离达20 km,功率代价小于2 dB.     

A Novel Scheme to Generate Single-Sideband Millimeter-Wave Signals by Using Low-Frequency Local Oscillator Signal

We have proposed and experimentally demonstrated a novel scheme to generate optical millimeter-wave (mm-wave) signals by using single-sideband modulation with low-frequency local oscillator (LO) signals. In this architecture, by incorporating the proper dc bias of the modulator in central office, the optical mm-wave carriers are generated with two times frequency of the LO signal while largely reducing the bandwidth requirement of the modulator. We quantify the optical carrier-to-sideband ratio (CSR) of downstream transmission in this radio-over-fiber (ROF) link and establish that the performance of the ROF system can be significantly improved when the optical signals are transmitted at CSR equal to 0 dB.     

一种改进的光载波抑制产生光毫米波的方法

为了延长光毫米波的传输距离,提出了一种改进的光载波抑制产生光毫米波的方法。在中心站采用马赫-曾德尔调制器将射频信号调制到光载波上产生光载波抑制调制光信号,再将产生光信号的2个边带分离,将2.5Gbit/s数据信号调制到其中1个边带上,再与未调信号耦合后产生光毫米波并通过光纤传送至基站。在基站中通过光电转换器产生电毫米波。从理论上分析了这种光毫米波的传输特性并通过实验验证了光毫米波在光纤中可以传输40km。仿真和实验结果表明,这种方式产生的光毫米波具有很好的抗色散能力,延长了传输距离。     

基于波分复用的光纤多防区周界传感系统

提出了一种新的光纤多防区周界传感系统,采用波分复用技术实现了监控防区和通道的扩展。该系统对传统采用单根传感光纤和反射镜的结构作了改进,并扩展了传感光纤的数量,将多根传感光纤分别置于监控领域内的不同防区,每个防区分别用不同中心波长的光纤布拉格光栅作为反射装置,使每根传感光纤工作在不同的波长。利用波分复用器件与技术,多根传感光纤共用一套干涉系统,实现了多个干涉子系统同时、独立的监测。实验结果表明,该系统可以实现多个分散防区同时、独立的入侵检测和定位,信号响应时间小于1ms,不同防区间信号的串扰小于-20dB。     

Medium-density WDM system with Fabry-Perot laser diodes for subscriber loop applications

Medium-density wavelength division multiplexing (WDM) systems with approximately four to eight wavelengths can provide an evolution path from near-term fiber-to-the-curb systems to a broadband passive optical network. The authors demonstrate that multilongitudinal-mode Fabry-Perot laser diodes can be used in such a system, with four 622 Mb/s channels in the 1.3- mu m window. This may provide a lower-cost alternative to the use of DFB lasers for such applications. Despite a channel spacing of only 15 nm, significant wavelength misalignments of the laser diodes relative to the WDM passbands can be tolerated before filter-induced mode-partition-noise penalties are observed. The potential for extending the data rate to 1.25 Gb/s is demonstrated.<>     

A multiwavelength source having precise channel spacing for WDMsystems

We report a wavelength-division-multiplexed (WDM) source in which a combination of a periodically driven Mach-Zehnder modulator and a nonlinear fiber are used to generate an optical spectrum that consists of several wavelength components precisely spaced by 64 GHz (>0.5 nm). The 13 strongest spectral components are within a 10-dB optical power range and their performance as channel sources in a WDM transmitter have been evaluated. We also propose and demonstrate a technique to generate an optical spectrum in which the separation between the major components is four times the modulator drive frequency     

All-Optical Subcarrier Demodulation in Up-Link of WDM mm-Wave Radio-Over-Fiber System

We have proposed and experimentally demonstrated a scheme of all-optical broadband subcarrier demodulation in the up-link of wavelength-division-multiplexing (WDM) millimeter-wave radio-over-fiber systems. In this scheme, the subcarriers of all the WDM channels can be demodulated by only one optical demodulation module, hence its cost can be reduced remarkably. Because of its all-optical implementation, it can offer more bandwidth. The radio-frequency power degradation introduced by the channel dispersion is also avoided in this scheme even when the conventional simple double-sideband modulation method is employed in the base stations.     

High-speed optical FSK modulator for optical packet labeling

We described a novel optical label swapping (OLS) technique for optical packet systems using frequency-shift-keying (FSK) optical labeling. High-speed optical FSK signal can be generated by using an external FSK modulator consisting of four optical phase modulators. The FSK modulator was based on optical single-sideband (SSB) modulation technique, and comprised of traveling-wave electrodes for high-speed frequency switching. We demonstrate 10 Gbps FSK transmission, and simultaneous modulation by FSK and intensity modulation (IM). OLS using double-sideband modulation was also demonstrated, where this technique can be used for a bundled wavelength-domain-multiplexing (WDM) channels without using an array of pumping light sources.     

Digital signal processing techniques in Nyquist-WDM transmission systems

In single-carrier wavelength-division multiplexing (WDM) systems, the spectral efficiency can be increased by reducing the channel spacing through digital signal processing (DSP). Two major issues with using tight filtering are cross talk between channels and inter-symbol interference (ISI) within a channel. By fulfilling the Nyquist criterion, Nyquist spectral-shaped WDM systems can achieve narrow channel spacings close to the symbol rate \((\hbox {R}_{\mathrm{S}})\) with negligible cross talk and ISI. In principle, DSP can generate any signals with arbitrary waveforms and spectrum shapes. However, the complexity of DSP is limited by its cost and power consumption. It is necessary to optimize the DSP to achieve the required performance at a minimum complexity. In this paper, we first introduced the background of digital signal processing for Nyquist spectral shaping in optical fiber WDM systems. Then, we investigated the use of digital finite impulse response (FIR) filters to generate Nyquist-WDM 16-ary quadrature amplitude modulation (16QAM) signals with the raised-cosine (RC) and root-raised-cosine (RRC) shape spectra. The system performance of both the RC and RRC spectra is also examined. Moreover, we explored the various methods to reduce digital-to-analog converter (DAC) sampling speed, such as using super-Gaussian electrical filters (E-filter) and spectral pre-emphasis. We also discussed receiver-side matched filter design for Nyquist-WDM receiver optimization.     

基于单边带调制的光毫米波产生及其传输特性研究

提出了一种新型单边带调制(SSB)产生光毫米波的全双工光纤无线通信(ROF)系统.利用射频(RF)信号驱动马赫-曾德尔调制器(MZM)产生偶数双边带信号,并通过技术基带信号调制到中心载波上,再与未被调制双边带的任一边带耦合产生光毫米波信号.理论分析发现,该毫米波的接收功率不会发生周期衰减.实验研究表明,经过50 km传...     

ROF中基于单个光波长与LiNdO3调制器的多频光毫米波

实验研究了一种采用单个光载波和一个单臂LiNdO3调制器同时产生多个不同频率光毫米波的光无线通信(ROF)系统。在中心站,多路不同频率的射频(RF)信号与相应的基带数据信号进行混频,再用功率耦合器将它们耦合成一路信号,输出信号用于驱动单臂LiNdO3调制器进行载波抑制调制去产生多频率的光毫米波信号。经过光纤传输后,在基站,利用光滤波器将载有不同频率光毫米波的光频成分进行分离,之后再分别进入光电检测器(O/E)进行检测。实验结果显示,采用频率为10 GHz与20 GHz的RF信号源可以产生频率为20GHz与40 GHz的光毫米波,20 GHz的毫米波携带2.5 Gb/s的下行基带数据信号在单模光纤中可以传输40km以上,因此这种方案是有效和可行的。     

A millimeter-wave WDM-ROF system based on supercon- tinuum technique

In this paper, a new millimeter-wave (mm-wave) wavelength division multiplexing (WDM) system based on radio-over-fiber (ROF) technology is proposed. In this approach a multi-wavelength light source is obtained by supercontinuum (SC) technique, and mm-wave signals are obtained by using optical heterodyning method. We experimentally demonstrate the generation of optical carriers for 6-WDM channels, obtain 40 GHz mm-wave signals by employing optical heterodyne technique, and successfully achieve low error rate transmission of 2.5 Gbit/s in WDM channels over a distance of 25 km in a G.652 fiber. The experimental results verify that the proposed solution is feasible and cost effective.     

全双工光载无线隧道通信系统

鉴于长距离隧道内复杂的无线传输环境,传统通信技术不能满足旅客高质量的通信需求,提出了一种基于波分复用无源光网络的光载无线（RoF）分布式隧道通信系统。采用波分复用技术实现不同业务在光域的物理隔离,协同分布式天线技术,在隧道内部提供高频无线接入,提升系统带宽的同时解决了隧道内部信号急剧衰减的问题。通过实验搭建了全双工的光载无线试验平台,实现了用光学的方法产生和传输载频为24 GHz的16/64QAM矢量信号,并且通过测量上下行链路的EVM值验证了方案的可行性。     

A Novel Scheme for Seamless Integration of ROF With Centralized Lightwave OFDM-WDM-PON System

We have experimentally demonstrated a novel transmission system for seamless integration of ROF with centralized lightwave OFDM-WDM-PON based on an integrated external modulator. At the one of two arms of the integrated external modulator, the optical carrier suppression (OCS) is realized to generate 40–GHz optical millimeter-wave (mm-wave) and up-converted baseband data signal as wireless signal. In another arm of the integrated external modulator, 16 quadrature amplitude modulation intensity-modulated OFDM signals at 10 Gbit/s are used for downstream transmission as wired signal based on double sideband modulation. By using one intensity modulator (IM), the downstream RF OFDM signal is remodulated for upstream on–off keying (OOK) data at 2.5 Gbit/s because of its downstream RZ shape waveform. The 10-Gbit/s wired signal, 2.5-Gbit/s wireless signal, and 2.5-Gbit/s upstream signal have been transmitted over 20-km single mode fiber (SMF) successfully.      

Optical Tandem Single-Sideband-Based WDM Interface for Millimeter-Wave Fiber-Radio Multisector Antenna Base Station

We propose and demonstrate a spectrally efficient wavelength division multiplexed (WDM) optical interface for millimeter-wave radio access networks with the capability of being integrated within a standard 100-GHz WDM infrastructure. The proposed WDM optical interface is realized by the use of a multiport optical circulator in conjunction with fiber Bragg grating filters. The interface supports demultiplexing of wavelength-interleaved optical tandem single-sideband modulated signals for a millimeter-wave fiber radio backbone with a sectorized antenna interface at the remote base station. The functionality of the interface is verified experimentally for RF signals at 29 and 31.6 GHz with 155-Mb/s binary phase-shift keying data. The effects of optical impairments on the transmission performance of WDM channels are experimentally analyzed. The experimental results demonstrate that the WDM optical interface performs efficiently with very low channel impairments due to optical crosstalk.      

Optical signal processing for lightwave communications networks

A number of optical signal processing functions that might be potentially important for future lightwave communication networks are described. An optical network with a distribution capacity of 100 HDTV channels is considered along with how such a network can be implemented using the following functional subsystems: frequency converters; transmitter banks; modified (wavelength division multiplexing) WDM demultiplexers; and tunable optical receivers. Discussed are the key network-level issues: the power budget, the channel separation, and the overall rationale for selection of multiplexing techniques. A hardware implementation of the functional subsystems using three basic building blocks-tunable amplifiers/filters, phase locked loops, and comb generators-is discussed     

10频道无再生中继使用光纤放大器的波分复用光纤传输实验系统

在国内首次研制了１０频道、１０２ｋｍ无再生中继使用１个平坦增益光纤放大器的ＷＤＭ光纤传输实验系统。每频道传输码率为１４０Ｍｂ／ｓ（２＾２３－１ ＮＲＺ ＰＲＢＳ或ＣＭＩ ＰＲＢＳ）。系统全部采用国产ＤＦＢ激光器，它们的波长分别为１５３１ｎｍ、１５３５ｎｍ、１５３７ｎｍ、１５４５ｎｍ、１５４７ｎｍ、１５４９ｎｍ、１５５１ｎｍ、１５５９ｎｍ、１５６１ｎｍ，在波长为１５５１ｎｍ的频道内布置了２路频率间隔     

Simultaneous generation of 3G and millimeter-wave signals using a dual-electrode MZM in ROF systems

A novel radio-over-fiber (ROF) scheme to simultaneously generate and transmit the 3rd generation telecommunication (3G) and millimeter-wave (MMW) signals by using a single dual-electrode Mach-Zehnder modulator (MZM) is proposed. There is no apparent nonlinearity induced by the ROF system. By employing this analog ROF signal transmission technique, highly transparent fiber-wireless convergence networks can be realized, which are ideal for multi-standard wireless system operation.