基于受激布里渊散射的30GHz毫米波单边带调制生成技术

本文提出了一种基于受激布里渊散射原理的单边带调制产生30GHz毫米波的新方法,可应用于光载射频系统。该方法利用一个双布里渊散射移频结构生成泵浦光,并将其反向注入到传输信号光的25 km单模光纤;通过受激布里渊散射,直接放大受调制信号光的正三阶边带,实现光载波的单边带调制,有效改善由色散效应引入的功率涨落问题,保证了毫米波功率稳定。此外,信号光和泵浦光由同一个激光器产生,有效消除两者间的相对频率漂移,从而大大提升了毫米波生成系统的频率稳定性。通过我们的方法,实验系统所生成的毫米波功率增益了21dB,其3dB线宽为10kHz。     

基于强度调制和布里渊效应的六倍频可调毫米波信号产生

提出了一种新型的基于马赫-曾德尔调制器(MZM)和布里渊效应实现六倍频可调毫米波信号输出的方法。在本方案中,先调节MZM的直流偏置,抑制偶数边带,留下奇数边带;经过大功率掺Er3+光纤放大器(EDFA)放大之后,使两个一阶边带的功率达到布里渊阈值之上,然后采用了25km的单模光纤(SMF)作为布里渊介质,滤除一阶边带,留下三阶边带;最后经过EDFA放大和光电探测器(PD)光电转换得到六倍频的毫米波信号。因为布里渊边带滤波是窄带滤波,与波长无关,故本系统可以实现波长无关的微波信号产生。     

Dual-band bandpass tunable microwave photonic filter based on stimulated Brillouin scattering

A dual-band bandpass microwave photonic filter(MPF) based on stimulated Brillouin scattering(SBS) is theoretically analyzed and experimentally demonstrated. Two separated tunable laser sources(TLSs) are employed to generate two passbands by implementing phase modulation to amplitude modulation conversion by using SBS induced sideband amplification. The center frequencies of both passbands can be independently tuned ranging from 1 GHz to 19 GHz. High resolution with 3 d B bandwidth less than 30 MHz and large out-of-band rejection about 40 d B under 25 m W optical pump power are achieved.     

一种新型瑞利BOTDA系统的研究

搭建了一种新型的基于瑞利散射的布里渊光时域分析（Rayleigh Brillouin optical time domain analysis, RBOTDA）传感系统。该系统工作在单端,能克服传统 BOTDA双端接入的缺点;采用两个EOM并联的结构产生含有连续基底光的脉冲光,探测光由基底连续光的瑞利散射提供,避免了多种受激布里渊散射（stimulated Brillouin scattering,SBS）作用带来的干扰,信噪比更高,传感距离更长;采用双边带探测方法,有效减少泵浦脉冲的损耗与非本地效应。建模解析了该系统中的SBS作用过程,并实验验证了系统的可行性。结果表明,布里渊增益谱完好地贴合洛伦兹曲线,非本地效应得到了有效的抑制;在2.4 km光纤上,室温25℃下泵浦脉宽50 ns时,布里渊频移为10.867 GHz,布里渊线宽约为40.21 MHz。     

New progress of mm-wave radio-over-fiber system based on OFM

This paper presents an overview on new progresses-of millimeter wave (mm-wave) radio-over-fiber (RoF) system based on mm-wave generation by optical frequency multiplication (OFM), including gen-eration of high-order optical side modes by optical modulation using dual-drive Mach-Zehnder modulator (DD-MZM) and enhancement of high-order optical side mode induced by selective amplification due to stimulated Brillouin scattering (SBS). The paper describes OFM by using DD-MZM in principle and verifies it in an experimental bidirectional 40GHz RoF system. SBS amplification enhances the generated information-bearing mm-wave in downlink and also helps in producing a pure reference mm-wave for radio frequency-intermediate frequency (RF-IF) down-conversion in uplink. These efforts pushed the OFM technology of mm-RoF systems to achieve more and more feasibility and cost-effectiveness.     

基于光纤光栅的微波扫描单边带调制法测量光纤布里渊散射特性

利用光纤布拉格光栅(FBG)和马赫-曾德尔电光调制器实现了单边带光调制输出。基于微波扫描的单边带调制技术提出了一种测量光纤受激布里渊散射(SBS)特性的方法,可有效地将布里渊频移与布里渊增益谱的测量统一起来。对一段50m长的光子晶体光纤(PCF)的SBS特性进行了测量,得到了PCF的SBS谱的布里渊频移为9.7443GHz,布里渊增益谱线宽为22.472MHz,布里渊增益系数为7.874×10-12 m/W。     

Experimental Demonstration of 1.25-Gb/s Radio-Over-Fiber Downlink Using SBS-Based Photonic Upconversion

We experimentally demonstrate a radio-over-fiber downlink system using a stimulated Brillouin scattering (SBS)-based photonic upconversion technique. The Brillouin selective amplification characteristic of SBS is incorporated to generate the 11-GHz band radio-frequency (RF) carrier. The dual-electrode Mach-Zehnder optical modulator, which is used to carry the broadband data in the optical carrier instead of the optical sideband, is adopted along with the SBS-based carrier generation setup. To vindicate the broadband capabilities of the proposed scheme, 1.25-Gb/s pseudorandom bit sequence data is carried in the optical carrier. Error-free operation of the 1.25-Gb/s downlink is achieved without critical power penalties after the 13-km fiber transmission.     

An Optical Millimeter-Wave Generation Technique Based on Phase Modulation and Brillouin-Assisted Notch-Filtering

A novel approach to generate continuously tunable microwave and millimeter-wave (mm-wave) signals is proposed and experimentally demonstrated based on an optical phase modulator and a Brillouin-assisted notch-filtering technique. The strong optical carrier of the phase modulated signal is deeply suppressed by using stimulated Brillouin scattering (SBS) in a dispersion-shifted-fiber ring while the sidebands keep unchanged. Therefore, only even-order electrical harmonics exist at the output of a photodetector. As this SBS-assisted carrier-filter is narrow bandwidth and wavelength-independent, a wavelength-flexible way of optical generation mm-wave signals can be successfully realized.      

Bandwidth-reduced Brillouin optical time-domain analysis based on a quarter of the frequency of modulation

Aiming at the problem of high requirement for the signal generator in the Brillouin optical time-domain analysis (BOTDA) system, a quarter of the Brillouin frequency shift (BFS) of modulation is proposed to reduce the required bandwidth of the sensing system. A functional model for solving the intensity of each-order sideband of the output light of electro-optic modulator (EOM) is proposed and applied, so the spectrum with suppressed the carrier and the first-order sidebands while maximizing the second-order sidebands is obtained. Compared with the latest scheme, the intensity of the second-order sidebands is increased by 21.1% based on this functional model. In the experiment, the second-order upper sideband and the second-order lower sideband are used as continuous wave (CW) probe light and pump pulse light, respectively, which ultimately reduces the required bandwidth of radio frequency (RF) signal sources to a quarter of the BFS (reduced from ~11 GHz to ~2.75 GHz), and the frequency sweep range is also reduced to a quarter of the original.     

采用单个相位调制器产生毫米波

实验研究了采用单个相位调制器(PM)产生毫米波的方案。该方案采用电混频器将射频(RF)信号与基带信号混频后再利用相位调制器产生双边带调制(DSB)信号,经光纤传输到基站后用一个光交叉复用器(IL)分离一阶边带和中心载波,一阶边带经过光电(O/E)检测器拍频产生两倍频于射频频率的毫米波,而中心载波可以作为上行链路载波重新利用。理论分析了该毫米波的传输性能,研究发现由于色散导致两个一阶边带时延不同,码元的占空比会随着传输距离的增加而减小,将限制毫米波的最大传输距离;实验中采用频率为20 GHz射频信号产生频率为40 GHz的毫米波,速率为2.5 Gbit/s的非归零(NRZ)码作为下行链路数据,经过20 km色散光纤传输后下行链路的功率代价为0.2 dBm。     

A novel scheme to implement duplex 60-GHz radio-over-fiber link with 20-GHz double-sideband optical millimeter-wave transmitted along the fiber

A duplex radio-over-fiber (RoF) link with a novel scheme to generate 60-GHz millimeter (mm)-wave using 20 GHz double sideband (DSB) optical mm-wave with signal carried only by its optical carrier is investigated. In the RoF downlink, the modulation frequency to generate the DSB optical mm-wave is reduced greatly. The theoretical analysis and numerical simulation show that this scheme cannot only eliminate the code form distortion caused by the time shifting of the sidebands, but also reduce the influence of the fading effect as the DSB optical mm-wave signal is transmitted along the fiber. Based on the scheme, the duplex RoF link with the frequency up- (down-) conversion of the down- (up-) link mm-wave signal is built and the uplink transmission performance is analyzed theoretically.     

Simple distributed optical fiber sensor based on Brillouin amplification of microwave photonic signals

A simple distributed fiber sensor is proposed by Brillouin amplification and depletion of microwave photonic signals. This technique utilizes optical carrier suppression (OCS) modulation to generate two sidebands acting as the pump waves. After Fresnel reflection at the cleaved end of the fiber under test (FUT), the pump waves are converted to probe waves. By sweeping the modulated microwave frequency, the stimulated Brillouin scattering (SBS) spectra and Brillouin frequency shift (BFS) can be precisely characterized. As a result, the accurate measurement of the Brillouin frequency shift makes good determination of the distributed temperature or stain along the FUT, and the position along the FUT can be resolved and controlled by the delay of the microwave pulses. Furthermore, our proposed sensing system is implemented with a single-ended configuration which has shown many advantages such as immunity of the laser frequency fluctuation and compact setup without additional pump laser source and filters.     

用IQ调制器产生载波抑制单边带信号的研究

载波抑制单边带调制是一种特殊的幅度调制形式,它将载波和另一个边带抑制,提高频带利用率,增加了光纤的传输容量。并可有效抑制色散,延长信号的传输距离。被广泛应用于长距离高频微波ROF系统中。文中详细分析了利用商用铌酸锂调制器产生载波抑制单边带信号的原理,并据此分析,搭建了试验系统,分别产生了±1阶(即长波方向和短波方向)的载波抑制单边带信号。     

Photonic Frequency Upconversion by SBS-Based Frequency Tripling

We describe a photonic frequency upconversion by the stimulated Brillouin scattering (SBS)-based frequency tripling method. The frequency tripling and the photonic frequency upconversion are simultaneously obtained by incorporating a dual-electrode electrooptic modulator (EOM) and a single optical source. Each electrode of the dual-electrode EOM is driven by both an intermediate frequency (IF) and a microwave radio frequency (RF) signal, respectively, along with the optical frequency tripling scheme. The dual-electrode EOM generates appropriate optical sidebands, while the IF signal is conveyed by the pump signal. After the successive SBS shifting process, one of the third optical sidebands is amplified by the narrow gain spectrum of SBS. The carrier signal at 32.493 GHz with narrow linewidth, which is amplified by 20 dB while the other signals are suppressed more than 20 dB, is obtained after photodetection. From the simultaneous frequency upconversion and tripling, an IF signal at 1 GHz is upconverted around the 32.493-GHz signal, which is tripled from the RF signal (10.831 GHz). To verify the ability of conveying broadband data that is limited in the previous method based on SBS, the upconversion of a pilot tone at 1 GHz is demonstrated, which means that the data rate exceeds 1 Gb/s. The proposed photonic frequency upconversion shows the spurious free dynamic range of 75.1 dBldrHz^2/3 , which is suitable for a wireless personal communication system adopting the analog fiber-optic link.     

Frequency response equalization in phase modulated RoF systems using optical carrier Brillouin processing

A novel method is demonstrated to tunably compensate dispersion effect in phase modulated radio over fiber (RoF) links using an optical carrier Brillouin processing technique,which is based on stimulated Brillouin scattering (SBS) to control the phase shift of optical carrier in the modulated iightwave signal.Since this phase shift can be dynamically tuned,frequency response can be tunably improved.Both simulation and experimental results show that a uniform frequency response ranging from 1-12 GHz with a fluctuation of less than --1 dB can be obtained by an optimal phase shift on the optical carrier.     

A 6-9 GHz 5-band CMOS synthesizer for MB-OFDM UWB

An ultra-wideband frequency synthesizer is designed to generate carrier frequencies for 5 bands distributed from 6 to 9 GHz with less than 3 ns switching time.It incorporates two phase-locked loops and one single-sideband (SSB) mixer.A 2-to-1 multiplexer with high linearity is proposed.A modified wideband SSB mixer,quadrature VCO, and layout techniques are also employed.The synthesizer is fabricated in a 0.18μm CMOS process and operates at 1.5-1.8 V while consuming 40 mA current.The measured phase noise ...     

基于双平行马赫曾德尔调制器和受激布里渊散射效应的十倍频毫米波信号生成

提出了一种基于双平行马赫-曾德尔调制器(DPMZ M)和受激布里渊散射(SBS)效应的10倍频mm 波信号生成方案,具有覆盖频段高和频谱纯度高等优点。在本文方案中,低频率的射频(RF )信号通过DPMZM 对激光器发出的光波进行调制,调节直流偏置电压,使DPMZM的主调制器和两个子调制器均 工作在最小传 输点(MITP),抑制光载波和偶数边带,进一步调节两个子调制器的调制深度和移相器的相 移,抑制一阶和 七阶边带,留下三阶和五阶边带,然后利用SBS效应进行布里渊边带滤波滤除三阶边带,仅 保留五阶边带, 再经光电探测器(PD)拍频即可获得10倍频mm波信号。通过仿真实验,以10 GHz的R F信号为驱 动信号,得到了100GHz的mm波信号,验证了方案的可行性。     

布里渊光子晶体光纤环形移频器

通过实验研究了一种光子晶体光纤环形移频器,该移频器基于布里渊频移原理,利用光子晶体光纤布里渊增益高、阈值低的特点,同时利用光纤环形腔选频放大技术获得窄线宽高增益激光输出。实验结果表明:在波长为1 548 nm单纵模光纤激光泵浦下,10 m长光子晶体光纤的受激布里渊散射阈值功率约为457mW,环形腔输出的受激布里渊散射Stokes光相对于入射光移频量为9.778GHz、线宽500 kHz,并且移频量可以通过温度进行微调。该移频器可以用于分布式光纤布里渊传感器和微波发生器。     

Enlargement of measurement range in a Brillouin optical correlation domain analysis system using double lock-in amplifiers and a single-sideband modulator

We demonstrate a novel technique to enlarge the measurement range of a correlation-based fiber Brillouin distributed sensing system using double lock-in amplifiers and a single-sideband (SSB) modulator. In our work, the lock-in detection is applied to both a probe and a pump waves at different frequencies to effectively remove the noise induced by the backward reflection of the pump waves, and the SSB modulator is used to purify the probe wave by suppressing the other first-order sideband component. A 300-m measurement range with a 20-cm spatial resolution is achieved successfully without any optical filter.     

着色丙酮中受激热散射和纯丙酮中受激布里渊散射的频率响应

受激布里渊散射(SBS)的频移量远大于受激热散射(STS),达到GHz的量级;而STS的频移量很小,一般只有几十M Hz;在以前的实验中,要区分这两种散射需要非常复杂的实验系统,或者高精度、大测量范围的光谱分析仪器,这在一般的实验室条件下是难于满足的。实验研究了掺杂Cu(NO3)2的丙酮溶液中产生的STS与纯丙酮中的SBS的频率响应。结果显示：随着泵浦能量的增加,SBS的线宽随机起伏,而STS的线宽有规律地变化。这可以替代高精度、大测量范围的光谱仪或者复杂系统而成为一种简便的区分STS和SBS的方法。据我们所知,目前文献中尚无相关报道。