一种新的微波/毫米波产生方法

提出一种新的微波/毫米波光产生方法,将激光脉冲入射到单模光纤FP腔中,激发腔中的两个本征模,利用两本征模相位失谐与光外差方法得到微波/毫米波信号,得出单模光纤FP腔结构参数与微波/毫米波信号频率间的关系表达式。数值计算表明：调制频率为25 MHz的脉冲激光入射到单模光纤FP腔时,可得到频率为2.083 GHz的微波信号。通过调节FP腔内的双折射强度,可得到从微波到毫米波的信号。该方案只需一个激光光源,成本低、可靠性高、稳定性好。     

复合滤波结构的窄线宽高频微波信号产生装置

为了在较低泵浦功率下实现单纵模双波长激光信号的输出,进而获得窄线宽的高频微波信号,设计并实验了一种基于复合滤波结构的窄线宽高频微波信号产生装置。通过8字腔结构布里渊增益腔和反射式光纤光栅构成的波长选择滤波器实现了4倍布里渊频移间隔的双波长斯托克斯光信号输出,采用200 m长单模光纤作为增益介质,同时与50 m长单模光纤构成级联光纤环结构,采用三端口耦合器与2 m长未泵浦的保偏掺铒光纤构成萨格纳克环结构,利用级联光纤环结构和萨格纳克环结构的复合滤波作用实现了斯托克斯光信号模式的选择,使输出的斯托克斯光信号由多纵模运行状态变为单纵模运行状态。实验证明:通过对输出的单纵模双波长斯托克斯光信号进行拍频检测可得42.85 GHz的高频微波信号产生,线宽为38 kHz;通过改变可调谐泵浦激光器的输出波长,可实现42.25~43.51 GHz范围内的频率调谐;通过稳定性测试,产生的42.85 GHz高频微波信号的频率变化在0.83 MHz内,峰值功率变化在±0.8 dB内,稳定性良好,满足实际应用需求。     

All-optical generation of microwave and Millimeter wave using a two-frequency Bragg grating-based Brillouin fiber laser

A novel all-optical technique for microwave/millimeter-wave generation using two-frequency fiber Bragg grating (FBG)-based Brillouin fiber laser is presented. The mechanism for the microwave and millimeter-wave generation is theoretically analyzed. An approximately 33-GHz millimeter wave can be achieved through mixing the pump wave with the third Stokes' wave. In the experiment, an 11-GHz microwave signal is attained. The microwave frequency can be tuned by varying temperature of the fiber Fabry-Pe/spl acute/rot cavity of the Brillouin fiber laser. A more than 100-MHz tuning range around a frequency of 11 GHz is experimentally achieved.     

一种频率可调的光学生成微波毫米波源

实现了一种频率可调的光纤微波毫米波信号源.利用掺饵光纤(EDF)环形腔中的偏振烧孔(PHB)效应和激光反向传播的特点,在室温下得到了波长间隔可调的稳定的单频单纵模双波长激光器,将两束激光在PIN光电二极管中拍频得到了频率在472.5MHz~26.5GHz间变化的毫米波信号,输出功率不小于0.015mW,3dB带宽约为3...     

一种12倍频全双工RoF系统

为提高光载无线(RoF)通信系统倍频系数,提出了一种基于集成双平行马赫曾德尔调制器(MZM)和抑制载波光双边带调制的12倍频光生毫米波方案。理论分析了光生毫米波信号产生机理,讨论了相关参数对光生毫米波信号的影响,理论分析与仿真结果基本吻合。在此基础上设计了一种基于该方案的全双工RoF系统,通过调整基站(BS)线偏振器(Pol)偏振角度即可恢复出下行数据和上行载波。仿真结果表明,在误码率(BER)为10-9时,传输90km后上行链路功率代价为0.86dB,相同条件下下行链路功率代价仅为0.47dB。     

Pulse-train uniformity in optical fiber lasers passivelymode-locked by nonlinear polarization rotation

The generation of uniform soliton pulse trains by additive pulse mode locking has been experimentally demonstrated in a birefringent fiber laser with a passive polarizer. Numerical simulations of pulse propagation around such a fiber loop are presented which reveal that this mode-locking scheme does not result in strictly uniform pulse trains. Rather, the train of output pulses exhibits periodic fluctuations in intensity and polarization. A model for the pulse dynamics is developed which shows that these fluctuations depend on the strength of the fiber birefringence and the alignment of the polarizer with the fast- and slow-polarization axes of the fiber. It is also shown that increased uniformity of pulse trains is achieved with near alignment of the polarizer with the slow axis of the birefringence     

Multitap Photonic Microwave Filters With Arbitrary Positive and Negative Coefficients Using a Polarization Modulator and an Optical Polarizer

A novel multitap photonic microwave filter with arbitrary positive and negative coefficients implemented using an electrooptic polarization modulator (PolM) and an optical polarizer is proposed and experimentally demonstrated. In the proposed filter, the optical polarizer is connected at the output of the PolM with its transmission axis aligned at an angle of 45 to one principal axis of the PolM. By adjusting the polarization direction of the input lightwave to be 45 or 135 to one principal axis of the PolM, an inverted or noninverted intensity-modulated optical microwave signal is obtained at the output of the optical polarizer, which leads to the generation of a negative or positive coefficient. A time delay difference between adjacent taps is generated by using a wavelength-dependent delay line. A five-tap photonic microwave filter with arbitrary positive and negative coefficients is demonstrated. The reconfigurability of the filter is also investigated.     

基于并联调制器的高倍频毫米波信号生成

为了获得更高频率的信号，采用了一种基于并联马赫-曾德尔调制器（MZM）和半导体光纤四波混频效应的二十四倍频光生毫米波方案。本振信号被并联MZM调制后可以获得高纯度的±4阶边带，在四波混频效应下，又可以生成±12阶边带，用级联的布喇格光栅滤波器滤除±4阶边带，经光电探测器拍频便可生成二十四倍频信号。结果表明，当输入本振信号为5GHz时，生成的120GHz高频微波毫米波信号射频杂散抑制比为22dB，频谱纯度很高，且具有很好的可调谐性。该研究为高频微波毫米波信号的生成提供了更高的倍频方法。     

单偏振双波长非保偏有源掺杂光纤激光器

利用宽带保偏光纤光栅(PFBG)、普通有源光纤和窄带普通光纤光栅构成独立的谐振腔,且窄带普通光纤光栅的中心波长分别与保偏光纤光栅的一个反射峰波长对准,可以输出稳定的双波长/单波长的单偏振激光.利用这一思想,制成了基于非保偏有源掺杂光纤的单偏振双波长光纤激光器.实验结果表明,双波长同时激射时的激光消光比为46.7 dB,单波长激光的消光比为59.6 dB,滤波出单波长测量其偏振度为98.5%.这种激光器在微波光子领域可用于在光域产生微波.     

A coupled optoelectronic oscillator with three resonant cavities

A new single-mode optoelectronic oscillator (OEO) with three coupled cavities is proposed and demonstrated. A Fabry-Perot (F-P) cavity fiber laser and an optical-electrical feedback branch are coupled together to construct an optoelectronic oscillator, where the F-P cavity fiber laser serves as a light source, and a modulator is placed in the laser cavity to implement reciprocating modulation, which simultaneously splits the laser cavity into two parts and forms a dual-loop configuration. To complete an optoelectronic oscillator, part of optical signal is output from the F-P cavity to implement the feedback modulation, which constructs the third cavity. Since only the oscillation signal satisfies the requirements of all the three cavities, a single-mode oscillation can be finally achieved. Three resonant cavities are successfully designed without adding more optoelectronic devices, and the side-modes can be well suppressed with low cost. The oscillation condition is theoretically analyzed. In the experimental demonstration, a 20 GHz single longitudinal mode microwave signal is successfully obtained.     

External cavity controlled operation of a semiconductor diode gain element in series with an optical fiber

The series combination of a semiconductor diode gain element (a diode laser whose end facets have been antireflection coated) and an optical fiber has been placed inside an external cavity and the combined system has lased in a single spectral line whose width was less than the1.7 times 10^{-5}-nm (7.5-MHz) resolution of the scanning Fabry-Perot interferometer used in the measurement. This result has been achieved with either a single-mode or a multimode optical fiber in series with the diode gain element and for experiments in which a polarizer, oriented so its polarization is parallel to the diode gain element polarization, was placed at the other end of either fiber. The output of the external cavity is temporally stable as measured both by a 225-MHz-bandwidth detector system and a spectrum analyzer. Over a one minute interval the maximum fluctuation in the output frequency of the external cavity was found to be 2 MHz. Analysis of the threshold behavior of the external cavity for the cases where the multimode or single-mode fiber are in the cavity indicates that the coupling coefficients for either fiber are nearly the same. Without an external cavity, the coupling coefficient from the diode gain element (or from a similar, not anti-reflection-coated, laser) to the multimode fiber is over five times larger than that to the single-mode fiber. These coupling results are explained by postulating that for the multimode fiber, only one or a selected number of the many modes of the fiber can participate in the laser action of the external cavity. It is believed that only these mode(s) are reflected back into the fiber by the spherical mirror in appropriate phase and angle to participate in the laser emission.     

星上光电振荡器的微波信号产生与转发研究

为了降低星上通信系统的质量和体积、增强系统的温度稳定性和抗电磁干扰能力,采用了一个新方法,将光电振荡器用作星上微波本振源,产生微波信号,利用光纤转发,将微波信号的产生、分配、传输与变频处理融为一个系统,并进行了理论分析和实验验证。结果表明,基于光电振荡器产生了11.5GHz的微波本振信号,通过光纤进行多路转发,其中第1路信号频率与本振源相同,相位噪声为-100.5dBc/Hz@10kHz,第2路信号频率为本振信号的2倍,相位噪声为-86.6dBc/Hz@10kHz。与传统电学方法相比,该方法有显著成效,可提高转发效率,减小系统体积和重量,增强系统抗干扰性和温度稳定性,提高系统的带宽和微波信号质量、降低卫星通信成本。     

In-House Networks Using Multimode Polymer Optical Fiber for Broadband Wireless Services

A novel system concept is presented to transport microwave signals over an in-house multimode graded-index polymer optical fiber network, in order to feed the radio access points in high-capacity wireless LANs. By employing optical frequency multiplying, the network's intrinsically limited bandwidth is overcome. The feasibility of this concept to carry data at several hundreds of Mbit/s speed for various microwave signal formats at carrier frequencies in the tens of GHz range is shown. The concept enables cost-effective system implementation, and easy upgrading by offering data signal transparency. It can readily be integrated with other system technologies such as wired Gigabit Ethernet in a single multi-service in-house polymer optical fiber network.     

基于可调谐真相移的可调谐光电振荡器

提出一种基于真相移(TPS)实现可调谐光电振荡器( OEO)的方案。只需通过调谐Mach-Zehnder 调制器(MZM)的偏置电压,就可以实现可谐滤波器的频谱响应的改变,即可实现TPS滤波器。 其中,两个抽头的可调谐滤波器是由双光源、双调制器以及叠印光栅来实现。OEO的输出频 率由二抽头可调 谐滤波器的峰值频率决定,而滤波器可调谐,这样就可以实现输出OEO的输出频率可调。 仿真结果表明,输出频率可以实现5～10GHz宽带宽可调谐。     

光纤干涉系统光学湍流测量原理及其偏振噪声问题的分析

光纤干涉仪具有测量精度高、探测灵敏度大等优点,可用于直接测量大气湍流折射率起伏.首先简要介绍了光纤Mach-Zehnder干涉仪的光学湍流测量原理,描述了低双折射单模光纤中光束偏振态变化诱导的偏振信号衰落现象,并通过偏振态的邦加球分析和详细的公式推导,得出了干涉仪可见度和相移噪声的关系式.结果表明:控制输入光偏振态与干涉仪本征向量之间的夹角在零度左右,可有效地抑制偏振噪声,最后给出了偏振控制器实现偏振控制的原理,为构建稳定的光学湍流测量光纤干涉系统提供了科学依据.     

基于激光外调制的频率可调谐光电振荡器

为了实现光电振荡器(OEO)输出频率的可调谐,提出了一种基于外调制激光的频率可调谐光电振荡器。此方案在单环OEO的基础上增加一个由微波滤波器、电衰减器、电放大器和电移相器构成的电增益选频腔,通过调节电移相器的偏置电压可以等效改变电选频腔的腔长,从而改变其输出微波信号的频率;同时调节光延时线来改变光电振荡器的起振模式,通过电增益选频腔信号与光电振荡器自由振荡信号的电注入锁定,即可实现频率可调谐的光电振荡器,其输出信号的频率由锁定OEO模式的电增益选频腔决定。实验结果表明,本方案产生了频率调谐范围为10.05 GHz~10.09 GHz、调谐步长为400 kHz的输出信号,频率在40 MHz的范围内连续可调谐。在输出频率为10.0519 GHz时,其边模抑制比为60 dB,相位噪声为-115 dBc/Hz @10 kHz。该方案结构简单,既保留了单环OEO低相位噪声的优势,又能有效抑制边模,为实现频率可调谐OEO提供了一种新的方法。     

Bidirectional single-mode Er-doped fiber ring laser

Rare Er-doped fiber lasers have been studied for fibe sensor applications with the advantage of frequency readou [1,2]. Due to this advantage, gyroscope application for a bidi rectional Er-doped fiber-ring laser was also demonstrated They also have high s…     

利用高双折射光纤的色散效应产生微波脉冲

研究了一种基于啁啾高斯脉冲在高双折射光纤中的光学色散效应和干涉产生微波脉冲的新方法，推导了啁啾高斯光脉冲在经过色散延迟后产生的微波频率的解析表达式。输出的微波频率可以通过选择不同的光学系统参数和啁啾高斯脉冲参数实现控制。研究了不同啁啾参数对输出脉冲强度、脉冲持续时间和脉冲频率的影响，结果表明，输入脉冲啁啾参数的引入不仅可以提高输出脉冲的持续时间，还可以使所需脉冲频率实现约10％的可选范围。     

Transversal Loading Sensor Based on Tunable Beat Frequency of a Dual-Wavelength Fiber Laser

Microwave signal generation by using the photonic beating from a phase-shift fiber Bragg grating (PS-FBG)-based dual-wavelength laser is proposed and experimentally demonstrated. The dual-wavelength laser is formed by a linear cavity, in which a PS-FBG is used as a dual-wavelength selective component. Transversal loading on the PS-FBG enhances the birefringence of the optical fiber and consequently makes the transmission peak of the PS-FBG splitting into two sharp transmission peaks of orthogonal polarizations. The wavelength spacing between the two transmission peaks increases with the transversal loading on the PS-FBG, thus making the polarization beating frequency increase. This property is exploited in a transversal loading sensor.      

耦合式光电振荡器的理论与实验研究

为了研究耦合式光电振荡器,阐述了耦合式光电振荡器的模式选择理论,给出了维持最佳锁模状态的相位匹配条件,分析了影响射频信号相位噪声的因素,进行了基于保偏机制的耦合式光电振荡器的实验研究。采用分别调节光环形腔和光电微波振荡环路中的保偏可变光纤延迟线可改变腔长的方法,获得了腔长与振荡频率的关系。同时,采用鉴频法测量了不同条件下5GHz射频信号的相位噪声,研究了影响射频信号相位噪声的因素。结果表明,耦合式光电振荡器的振荡模式取决于光环形腔的腔长,射频信号相位噪声受到光信号偏振态、相位匹配、环路长度等因素的影响。实验中获得了偏移频率10kHz处相位噪声达到-136dBc/Hz的5GHz射频信号,是目前国内已知的相位噪声最低的耦合式光电振荡器。