基于综合光学调制技术的光纤无线双向通信系统设计

提出并研究了一种使用单光源的光纤无线双向传输系统.该系统只需在中心站配置一个可调谐激光器,以产生频率恒定的激光光源,通过综合光学调制(频率调制、强度调制)技术将基带信号调制到光载波上,最终形成60 GHz毫米波下行信号;同时,相同的光我波在基站被重用,作为上行链路传输光源.系统结合光载波重用技术和综合调制技术特点,合理...     

光相位调制器和光强度调制器产生40GHz光载OFDM毫米波信号的传输性能比较

实验研究了分别采用光相位调制器和光强度调制器产生40GHz光载正交频分复用(OFDM)信号的毫米波光纤无线通信(ROF)系统,并比较了二者的传输性能。在中心站,将20GHz的射频(RF)正弦波信号与2.5Gb/s的OFDM信号混频后驱动相位调制器或强度调制器进行双边带(DSB)调制,产生的光载OFDM信号的毫米波经标准单模光纤(SSMF)传输到基站。在基站,经光纤布拉格光栅(FBG)滤除中心载波后的光调制信号经光电检测器转换成电调制信号,再与射频信号混频,恢复出基带OFDM信号,而分离出来的中心载波信号可以用于实现波长重用。实验验证了OFDM信号峰值-平均(峰均)功率比大小对系统误码率的影响。实验结果显示,在大入纤功率情况下,相位调制和强度调制产生的毫米波光信号经过50kmSSMF传输后,其功率代价分别为小于0.5dB和大于1dB。说明光相位调制器产生光载毫米波加载OFDM信号在光纤中的传输性能优于光强度调制器。     

一种改进的双边带调制产生光毫米波的方案

提出了应用于光纤无线通信系统中一种改进的双边带调制产生光毫米波方案。在中心站采用强度调制将射频信号调制到光载波上产生一个双边带信号,滤掉中心载波后,利用光交叉复用器把双边带信号的上下边带模分开,将数据速率为2.5Gbit/s的基带信号调制到下边带模后,再与未调信号耦合后产生光毫米波,然后通过单模光纤传输至基站,在基站经过光电转换后产生电毫米波信号。从理论上对该毫米波的色散特性进行了分析,发现毫米波的接收功率不会周期的衰减。同时通过实验研究表明,下行链路信号通过光纤能传输50km而不需要色散补偿,功率代价小于1dBm。因此,该方法产生的光毫米波能有效克服光纤色散引起的信号时延而导致的基带信号退化,适合于远距离传输。     

一种基于相干检测的双向输出信号频率可选的光纤无线系统

提出了一种单光源、双向输出信号频率可选的光纤无线系统,该系统在单光源条件下,利用相干检测技术、数字信号处理技术,结合并行相位调制器以及波长选择开关结构,在上下行链路实现基带信号、多个毫米波信号输出.仿真验证表明,针对20Gbit/s 16-QAM调制信号,经30km光纤传输,系统下行输出信号频率实现0~60GHz可选,其传输最小矢量误差为6.53%(0GHz)~7.61%(60GHz);上行输出信号频率实现0~120GHz可选,其传输最小矢量误差为6.89%(0GHz)~8.30%(120GHz).理论分析和仿真结果表明,该系统双向链路均可实现频率可选的信号输出,且双向传输具有较好的性能表现.     

基于新型偏振稳定毫米波发生器的光载无线通信下行链路

为了降低ROF系统成本,增加传输距离,提高系统性能, 提出了一种基于新型偏振稳定毫米波发生器的光载无线通信下行链路传输系统.与传统ROF系统相比, 该系统利用保偏光纤光栅选频产生的两个偏振稳定激光信号拍频产生毫米波, 易于实现并降低了功率噪声对系统的影响.仿真分析了该系统中环形激光器强度、谱线宽度、保偏光纤光栅反射谱特性对毫米波性能的影响;分析了系统中保偏光纤光栅的群时延、长度、色散,双波长激光信号脉冲包络宽度、啁啾系数对毫米波频率的影响.优化保偏光纤参数, 差频产生60 GHz的毫米波信号,并分析该毫米波信号在ROF下行链路的传输性能,结果表明该毫米波 作为副载波调制到光波上从中心站传输80 km至基站后经天线发射至用户端,解调仍然得到很好的眼图, 充分证明了本方案的优越性能.     

光纤混沌双芯双向保密通信系统研究

把量子阱激光混沌耦合反馈同步系统应用于光纤保密通信中,提出光纤混沌双芯双向保密通信设想.通过耦合外部光注入多量子阱激光混沌全光耦合反馈同步系统和光纤传输信道,建立了光纤混沌双芯双向通信系统物理模型.理论和数值证明了激光混沌同步,理论分析指出光纤中的自相位调制是限制激光混沌在光纤传输中同步的主要原因,并推导出混沌信号双芯双向传输中的非线性相移以及混沌激光功率限制和传输距离公式.数值实现了该系统在长距离二根光纤传输中的同步,详细地分析了系统同步时间随光纤传输长度的关系.模拟了调制频率06 GHz的混沌模拟通 关键词： 混沌 同步 光纤 保密通信     

基于光载波抑制调制的可调谐高倍频毫米波信号发生器

提出了一种基于改进的光载波抑制调制方式的光学生成高倍频可调谐毫米波的方案.该方案利用均匀光纤光栅型声光可调谐滤波器选取光载波抑制信号中的两个边带分量进行拍频,实现高倍频且倍频因子可调的毫米波信号的生成.为避免色散所致的码元时移效应,将基带数据信号仅调制到光载波抑制信号的一个边带分量上.仿真验证了倍频因子分别为2,6,10,14,18和22的毫米波信号的生成.另外,对22倍频下的光载无线电系统的链路性能进行了仿真分析,毫米波信号在调制2Gbit/s的非归零码型数据信号经50km的光纤传输后,系统的眼图仍保持良好的睁开度,链路的功率代价仅为0.4dB.系统具有良好的传输性能,可以满足通信系统的需求.     

面向Li原子D1线频率测量应用的掺铒飞秒光纤光梳系统

报道了自主研制的面向Li原子D1线频率测量应用的掺铒飞秒光纤光学频率梳,包括飞秒激光源,频率探测及控制单元,光谱展宽及拍频单元.光纤光梳系统中飞秒激光光源是一套基于非线性偏振旋转锁模机制的掺铒飞秒光纤激光器,重复频率为196.5MHz,中心波长为1 572nm.利用f-2f法探测载波包络相移频率,获得信噪比约为40dB的信号(分辨率带宽300kHz).改变飞秒激光光源泵浦控制载波包络相移频率、频率稳定度是3.74×10-18/τ1/2;通过电光晶体和压电陶瓷改变飞秒激光光源腔长来控制重复频率frep、频率稳定度是1.75×10-13/τ1/2.利用高非线性光纤和倍频晶体将光纤光梳直接输出光谱由1 520～1 607nm扩展到671nm,获得了单模功率为208nW的光信号.与671nm单频激光拍频产生约为60dB(分辨率带宽1Hz)信号,满足Li原子D1线频率测量实验的需求.     

承载正交频分复用信号的58GHz光载毫米波波分复用光纤无线通信系统

实验研究了一种采用马赫-曾德尔强度调制器和光交叉复用器(IL)产生58 GHz光载毫米波传输正交频分复用(OFDM)信号的波分复用光纤无线通信(WDM-ROF)系统。中心站的4路连续光波耦合后输入射频(RF)信号频率为29 GHz的强度调制器进行双边带(DSB)调制,再用另一个强度调制器将2.5 Gb/s的OFDM信号调制到DSB信号上。经20 km单模光纤(SMF)传输至基站,通过IL将中心载波和一阶边带分离。经可调谐光滤波器(TOF)滤取所需信道的一阶边带,由高速光电检测器产生58 GHz的电毫米波,利用相干解调恢复下行OFDM基带数据信号。实验结果表明,在无色散补偿和误码率为10-3的条件下,下行OFDM信号经光纤传输20 km后的功率代价小于0.5 dB,而且星座图依然清晰。     

包含掺铒光纤和微结构光纤的光纤环镜光开关

设计了一种低开关功率的全光开关.将掺铒光纤和微结构光纤引入Sagnac环镜中,信号光在泵浦光作用下经过掺铒光纤被放大,破坏了环镜的平衡,利用交叉相位调制效应使两束反向传输的信号光产生非线性相移,实现了光开关效应.理论分析表明:信号光经过掺铒光纤后,增益越大微结构光纤的非线性系数越高,开关功率越低,并且环镜信号光的透射率随两束反向传输信号光的相移差成余弦变化.仿真得到开关功率约为26.73 mW,与理论分析一致.     

A multi-channel full-duplex 60-GHz-band radio-over-fiber system

We propose and simulate a novel full-duplex radio-over-fiber system using a single light source at central station (CS). The scheme is employed to generate 60-GHz optical millimeter wave at CS for down-link transmission while the same optical carrier is reused at base station for up-link connection. There is no additional laser source for the upstream data generation in the base station. The bidirectional full-duplex 2.5 Gb/s data are successfully transmitted over 40 km standard single-mode fiber (SMF). The power penalty for the down-link data after transmission over 40 km SMF is less than 0.6 dB, while for the up-link data, the power penalty after transmission over 40 km SMF is neglected. This system shows good performance over long-distance delivery and has important applicable value in high radio frequency (RF) sector and multi-channel full-duplex system.     

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.     

A full-duplex radio-over-fiber system based on frequency decupling

A full-duplex radio-over-fiber system using frequency-decupling optical millimeter-wave based on external modulation via a Mach–Zehnder modulator is proposed and analyzed theoretically. The simulation results show that the power penalties for both the downstream and upstream signals are less than 0.5 dB. In this scheme, the configuration of a base station is simplified due to no laser at a base station, and the frequency of local oscillator signal is largely reduced due to the frequency-decupling millimeter-wave technique. The costs of central office and base station are largely reduced.     

Investigation on wavelength re-modulated bi-directional passive optical network for different modulation formats

In this paper, the cost effective bi-directional passive optical network architecture with wavelength remodulated scheme is investigated. To realize the cost-effective PON, remodulation scheme is used, in which the downstream optical signal is reused as a carrier for the upstream transmission as it eliminates the need for an extra laser source at optical network units. The performance of proposed passive optical network is analyzed and compared for various modulation formats such as Non Return to Zero (NRZ), Return to Zero (RZ) and On–Off Keying (OOK) with 64 optical networks units (ONUs) at different traffic speed for downlink and uplink, respectively. It has been observed that the most suitable data format for proposed PON network is NRZ. Further the proposed system performance is compared with the current state-of-the-art PON architectures.     

RoF downlink transmission system using FWM effect of SOA for generating MM-Wave

We propose a millimeter wave radio-over-fiber system to provide downlink service by using four-wave-mixing effect in semiconductor optical amplifier for millimeter-wave generation. At the central station, microwave source is 5.4-GHz. The optical carrier suppression modulation scheme and semiconductor optical amplifier are employed to simultaneously generate 32.4-GHz (sextuple fundamental) optical millimeter wave and up-convert data signal. At the base station, the downstream is received by a high-speed photodiode and base data are recovered by an electrical mixer. Theoretic analysis and experimental results show that the downlink 2.5-Gb/s data is successfully transmitted over 20-km single mode fiber with less than 0.15-dB power penalty.     

Photonic instantaneous microwave frequency measurement based on two different phase modulation to intensity modulation conversions

A novel photonic technique for instantaneous frequency measurement of microwave signal based on phase modulation to intensity modulation conversion is proposed and demonstrated. In the proposed system, an optical carrier is modulated by a microwave signal with its frequency to be measured through a phase modulator. The phase-modulated optical signal is then converted to intensity-modulated signals in two independent paths using a dispersive media and a frequency discriminator respectively. Since the dependence of the received microwave power on the input microwave frequency in the two paths differs, the microwave power ratio between the two paths can be used to uniquely determine the microwave frequency. The major advantages of the approach lie in that only one laser source and the bias-free phase modulator is employed in the system, which improves the stability of the system. Experimental demonstrations of the frequency measurement based on the proposed approach are presented.     

谐振式集成光学陀螺解调特性分析

基于激光器频率谱检测技术,沿着光的传输方向分析了光波在谐振式集成光学陀螺系统中的传播,结合输入信号特征,建立频域内的数学模型,通过数值仿真和实验得到了调频检测系统下的解调曲线。按照光的传输方向：激光器、声光晶体移频器、光波导环形谐振器、探测器,利用贝塞尔函数展开和光场耦合模理论分析了谐振式集成光学陀螺解调特性,及其调频调制检测系统解调输出信号与谐振频率偏差之间的关系。通过数值计算,分析了解调曲线的变化规律,得到了施加在激光器压电陶瓷驱动器上调制波形的最佳调制系数。在实验上搭建了激光器频率调制解调技术系统,得到了解调曲线。数值仿真和实验结果表明,当调制系数M=2时,线性工作区间斜率最大,解调曲线最好。实测形状与理论分析结果相符,从解调信号得到±2×10³ rad/s的陀螺动态范围。     

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.     

强度调制532 nm激光水下测距

激光水下探测在水下目标搜寻、资源勘探等领域具有重要的应用,而散射是激光水下探测面临的主要挑战.载波调制激光雷达具有抗散射、抗干扰的优点,本文利用自行研制的532 nm强度调制激光源,在3 m长的水箱中搭建激光水下探测系统. 532 nm激光源最大输出功率为2.56 W,强度调制范围为10.0 MHz—2.1 GHz,光束发散角约0.5 mrad.通过在水箱中添加氢氧化镁(Mg(OH)_2)粉末,测量了不同浑浊度下水的衰减系数.采用相位测距的方法,目标反射光的调制信号为探测信号,对激光源进行调制的电信号作为参考信号,利用相关运算获得激光的延时时间,进而可以获得水下目标的距离.最大调制频率为500 MHz时,实现了距离为4.3个衰减长度目标的探测,测距误差约12 cm.探测距离越远,测距误差越大,调制频率越高,测距精度越高.