Generation and distribution of a wide-band continuously tunable millimeter-wave signal with an optical external modulation technique

A new technique to generate and distribute a wide-band continuously tunable millimeter-wave signal using an optical external modulator and a wavelength-fixed optical notch filter is proposed. The optical intensity modulator is biased to suppress the odd-order optical sidebands. The wavelength-fixed optical notch filter is then used to filter out the optical carrier. Two second-order optical sidebands are obtained at the output of the notch filter. A millimeter-wave signal that has four times the frequency of the microwave drive signal is generated by beating the two second-order optical sidebands at a photodetector. Since no tunable optical filter is used, the system is easy to implement. A system using an LiNbO/sub 3/ intensity modulator and a fiber Bragg grating filter is built. A stable and high spectral purity millimeter-wave signal tunable from 32 to 50 GHz is obtained by tuning the microwave drive signal from 8 to 12.5 GHz. The integrity of the generated millimeter-wave signal is maintained after transmission over a 25-km standard single-mode fiber. Theoretical analysis on the harmonic suppression with different modulation depths and filter attenuations is also discussed.     

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.      

基于相位调制器的宽带窄线宽的线性调频激光源的产生

提出了一种基于相位调制器(PM)和可调谐光滤波器产生线性调频激光信号的方法。该方法利用带有基频的微波线性调频信号作为相位调制器的驱动信号,窄线宽的激光种子源经相位调制器调制后产生一系列的宽带线性调频激光信号。通过可调谐光滤波器抑制其他边带保留所需阶次的线性调频激光信号。实验结果表明:当光滤波器保留正二阶调频激光信号时,获得了调频带宽为2 GHz、调频速率为6 THz/s的线性调频激光信号。在观测时间为1 ms时,测得的线性调频激光信号的瞬时线宽为3.2 kHz。该方法结构简单,易于实现,并且对调频连续波激光雷达、相干光谱分析等测量应用有重要意义。     

基于分布反馈注入锁定的连续可调光子微波倍频实验研究

提出了一种基于注入锁定分布反馈式(DFB)激光器的双波长差频微波/毫米波信号产生方案。方案利用正弦波光信号通过半导体光放大器(SOA)进行非线性展宽,产生高阶分量,然后注入到两个DFB激光器后进行锁定放大,产生频率连续可调的倍频信号。在实验中,注入的正弦波光信号频率为1.25GHz,得到20～40GHz频率范围内1.25GHz的任意自然数倍的连续可调微波信号,其最高倍频数为32。     

Optical generation and distribution of continuously tunable millimeter-wave signals using an optical phase modulator

In this paper, we propose an approach to generate and distribute two wide bands of continuously tunable millimeter-wave (mm-wave) signals using an optical phase modulator and a fixed optical notch filter. We demonstrate theoretically that the odd-order electrical harmonics are cancelled and even-order electrical harmonics are generated at the output of a photodetector when the optical carrier is filtered out from the phase-modulated optical spectrum. Analysis shows that dispersion compensation is required in order to maintain the suppression of the odd-order electrical harmonics, in order to eliminate signal fading of the generated electrical signal when the optical signal is distributed using conventional single-mode optical fiber. It is experimentally demonstrated that, when the electrical drive signal is tuned from 18.8-25 GHz, two bands of mm-wave signals from 37.6 to 50 GHz and from 75.2 to 100 GHz with high signal quality are generated locally and remotely. This approach does not suffer from the direct current (dc) bias-drifting problem observed when an optical intensity modulator is used.     

Tunable Photonic Microwave Bandpass Filter With Negative Coefficients Implemented Using an Optical Phase Modulator and Chirped Fiber Bragg Gratings

A continuously tunable photonic microwave bandpass filter with positive and negative coefficients implemented using an optical phase modulator and chirped fiber Bragg gratings (FBGs) is proposed and experimentally demonstrated. The positive and negative coefficients are generated through optical phase-modulation to intensity-modulation conversion by reflecting the phase-modulated optical carrier from linearly chirped FBGs (LCFBGs) with positive and negative dispersions. The tunability of the filter is realized by changing the wavelength of the optical carrier such that it is reflected at different physical locations in the LCFBGs. A two-tap microwave bandpass filter with a free spectral range tunable from 1.14 to 4.55 GHz is experimentally demonstrated.     

Negative Tap Photonic Microwave Filter Based on a Mach–Zehnder Modulator and a Tunable Optical Polarizer

A negative tap photonic microwave filter based on a Mach-Zehnder modulator (MZM) and a tunable optical polarizer is proposed. In the proposed filter, the output light from the MZM, after experiencing a time delay difference between the two orthogonal modes in a polarization-maintaining fiber, is sent to the tunable optical polarizer. By adjusting the dc bias of the MZM and the polarization angle of the tunable polarizer with respect to the two orthogonal modes, two positive or one positive and one negative coefficient are generated. A theoretical analysis is presented which is verified by experiments. A two-tap microwave filter with two positive or one positive and one negative coefficient is demonstrated.     

全新布里渊散射可切换微波光子滤波器

提出了一个新的基于布里渊散射效应的微波光子滤波器。该滤波器可通过调谐系统中光滤波器的中心波长,实现高解析度带通滤波器与陷波滤波器之间的灵活切换,并且通过调谐产生受激布里渊散射的泵浦光的波长可实现滤波器通带或阻带的中心频率在很大频率范围内连续调谐。该滤波器为全光结构,因此具有非常大的调谐范围（调谐上限仅受限于试验中使用的矢量网络分析仪的显示频率上限）。系统中采用相位调制器,因此没有偏置电压漂移问题。实验结果展示了一个带通与陷波滤可灵活切换的高解析度微波光子滤波器,并且通带和阻带的中心频率在9～26.5 GHz范围内连续可调谐,其中带通滤波器的通带具有极窄3 dB带宽,约28 MHz（由光纤本身布里渊增益区线宽所决定）。     

基于双平行PM调制的60GHz光毫米波RoF系统研究

提出了一种采用相位调制器产生六倍频光载毫米波的RoF系统。该系统使用一个双平行相位调制器实现六倍频的调制,通过调节相位调制器的相位偏移量,产生出抑制一阶边带的光谱,耦合相减后得到三阶边带信号,在光电检测器中拍频,产生六倍于射频信号的光载毫米波。仿真结果表明,10GHz射频信号可以产生60GHz光载毫米波信号,5Gb/s的数据信号可在单模光纤中传输10km以上。     

基于微波光子的24倍频毫米波信号生成

提出了一种基于级联双电极马赫-曾德尔调制器、光延迟线和半导体光放大器的24倍频毫米波信号生成方案。将两个双电极马赫-曾德尔调制器通过一个光延迟线级联,获得高纯度±4阶边带,进而利用半导体光放大器的四波混频效应,得到±4阶和±12阶边带,通过波分解复用器选出±12阶边带,经光电探测器拍频即可得到24倍频毫米波信号。理论分析和仿真验证结果表明,当输入信号频率为4~10GHz时,可以生成射频杂散抑制比不低于26dB的24倍频毫米波信号,且其频谱纯度高,可调谐性好。     

Photonic Microwave Bandpass Filter With Negative Coefficients Using a Polarization Modulator

A novel photonic microwave bandpass filter with negative coefficients implemented using a polarization modulator (PolM) is proposed and experimentally demonstrated. In the proposed filter, a lightwave from a tunable laser source (TLS) is sent to a PolM, with the incident lightwave adjusted to have its polarization direction aligned at an angle of plusmn45deg to the principal axes of the PolM. A microwave signal is applied to the PolM through its RF port. Thanks to the polarization modulation in the PolM, two complementary microwave signals with identical amplitudes carried by two optical carriers with orthogonal polarizations are generated. The two complementary optical microwave signals are then sent to an optical delay line consisting of one section or two sections of polarization-maintaining fiber (PMF), with the polarization directions aligned with the fast and slow axes of the PMF. A photonic microwave bandpass filter with two or four taps is obtained     

Optical Millimeter-Wave Signal Generation Using Frequency Quadrupling Technique and No Optical Filtering

This letter demonstrates a novel method to generate high-purity optical millimeter-wave signals with carrier suppression by using a frequency quadrupling technique. To the authors' knowledge, this is the first time that a frequency quadrupling system requires only a single integrated Mach-Zehnder modulator without a narrowband optical filter to remove undesired optical sidebands. Since no optical filter is needed, fast frequency tuning is straightforward and this approach will be particularly attractive for optical up-conversion in wavelength-division-multiplexing radio-over-fiber systems. This letter provides both theoretical analysis and experimental demonstration. The generated optical millimeter-wave signals have very high quality with an optical carrier and harmonic distortion suppression ratio of more than 38 and 36 dB at 40 and 72 GHz, respectively.     

采用PM调制实现光生毫米波的RoF系统

提出有效产生四倍频光载毫米波的RoF系统.系统在中心站配置一个PM调制器和光滤波器,产生抑制一阶边带和中心载波的信号,发送至基站.基站侧两个二阶边带在光电检测器中拍频,产生四倍于射频信号的光载毫米波.仿真结果显示,12GHz射频频率可产生48GHz光载毫米波,2.5Gb/s的数据可在下行链路的光纤中传输35km以上,功...     

A tunable optoelectronic oscillator based on a tunable microwave attenuator

A novel realization of a wideband tunable optoelectronic oscillator (OEO) based on dual-port electrode Mach–Zehnder modulator (DMZM), a tunable microwave attenuator (TMA), and a chirped fiber Bragg grating (CFBG) is proposed and demonstrated. By simply adjusting the power ratio between the two arms of DMZM, the chirp of the DMZM will be tuned, and the center frequency of the microwave photonic filter will be tuned. When the OEO loop in the proposed system is closed, the output frequency of OEO is determined by the microwave photonic filter, and a high spectral purity microwave signal with a tunable frequency from 5.8 to 11 GHz is generated. The single sideband (SSB) phase noise of the generated signal could reach −107.4 dBc/Hz at an offset frequency of 10 kHz.     

基于级联双平行MZM的16倍频光生毫米波技术

为解决毫米波信号生成中存在的困难,提出了一 种基于级联双平行马赫-曾德尔调制器(DPMZM)的16倍频光生毫米波 系统。首先通过控制第1个DPMZM的直流偏压、驱动信号相位差和调制指数,完全抑制光载波 和±2阶边带,获得±4阶光边带;然后将该光波输入到另一个完全一样的DPMZM,获得±8阶光边 带和光载波输出;最后利用光滤波器(OF)滤除光载波,用光电探测器(PD)拍频得到 16倍频的毫米波输出。详细分析 了系统的工作原理,并通过仿真验证了方案的可行性。当输入射频(RF)驱动信号频率为2.5GHz时,可 得到40GHz毫米波输出,并且调制器的调制带宽仅需要 2.5GHz。本文方案具有倍频次数高、频谱纯度好等优点。     

60 GHz OCS mm-wave generation for ROF system based on saturated parametric amplification effect in HNLF

A novel approach to generate 60 GHz optical carrier suppression (OCS) millimeter-wave (mm-wave) signal based on the saturated optical parametric amplification (OPA) effect in high non-linear fiber (HNLF) is investigated. In the proposed system, the OPA effect occurs when the signal and pump with 30 GHz frequency interval are set into the high non-linear fiber. By controlling the length of HNLF, OPA effect saturates, and the pump power is delivered in a large extent to the signal and idler light, so a 60 GHz OCS mm-wave is generated. The system does not need high-speed external modulator, high-frequency vibration source or narrow-band filter, which greatly reduces the cost and improves the stability of the radio over fiber (ROF) system. Results show that the 10 Gb/s downstream signal can be transmitted with negligible power penalty.     

基于双平行MZM和HNLF四波混频效应的24倍频光生毫米波技术

提出了一种基于双平行马赫-曾德尔调制器(DPMZM ) 和高非线性光纤(HNLF)四波混频(FWM)效应的24倍频光生毫米波方案。首先 通过控制DPMZM的 直流偏压、驱动信号相位差和调制指数,完全抑制光载波和±2阶边带,获得±4阶光边 带;再将其放大后输入到HNLF,通过FWM效应生成±12阶光边带,最后由光 电控制器(PD)拍 频得到24倍 频的毫米波输出。通过仿真,验证了方案的可行性。本文方案具有倍频次数高、频谱纯度好 等优点。     

Microwave/millimeter-wave frequency subcarrier lightwavemodulations based on self-sustained pulsation of laser diode

A method of subcarrier lightwave modulation based on the self-sustained pulsation (SSP) of laser diodes is presented. The tunable microwave/millimeter-wave frequency subcarrier is generated by the laser diode itself under proper DC biases. The subcarrier is frequency-modulated when the DC bias is superimposed with a small AC signal. No external modulation is needed. A theoretical analysis based on a double-section laser diode reveals that Hopf bifurcation is the origin of SSP. Theoretical calculations also show that the modulator has the potential of generating subcarriers up to 100 GHz by proper control of the device parameters V-channeled substrate inner-stripe (VSIS) GaAlAs laser diodes were used to generate 1-7-GHz SSP subcarriers. A preliminary subcarrier multiplexing (SCM) experiment demonstrated the transmission of 1-GHz modulation and video signals on a readily FM-modulated 6.3-GHz SSP subcarrier     

采用电光调制器产生光毫米波的全双工通信光纤无线通信系统

实验研究了一种采用单个电光调制器产生光毫米波的方法和相应的全双工无线通信系统。在中心站采用电混频器产生电毫米波,然后再利用电光制器产生双边带信号。利用光交错复用器将中心载波和双频一阶边带信号分离。双频一阶边带用于产生2倍射频信号的光毫米波,而中心光载波用来作为上行链路的光载波。实验显示采用频率为20GHz射频信号产生光毫米波的频率为40GHz,而且将下行链路和上行链路中2.5Gbit/s的数据在单模光纤中传输距离达20km,而功率代价均小于0.5dB。     

Millimeter-wave generation and characterization of a GaAs FET byoptical mixing

Coherent mixing of optical radiation from a tunable continuous-wave dye laser and a stabilized He-Ne laser was used to generate millimeter-wave signals in GaAs FETs attached to printed-circuit millimeter-wave antennas. The generated signal was further down-converted to a 2-GHz IF by an antenna-coupled millimeter-wave local oscillator at 62 GHz. Detailed characterizations of power and S/N under different bias conditions have been performed. This technique is expected to allow signal generation and frequency-response evaluation of millimeter-wave devices at frequencies as high as 100 GHz