Highly sensitive optical length measurement by using a microwave photonic filter with multi-passband

In this paper, a method for optical length measurement that employs a multi-passband microwave photonic filter (MPF) is analysed and demonstrated experimentally. The MPF consists of a sliced broadband light source, a phase modulator, a dual-parallel dispersion medium and a photodetector (PD). By cascading two Mach–Zehnder interferometers (MZIs) with different arm length difference, the MPF with eight passbands has been obtained. The variation of the length difference of MZI will lead the change of the free spectral range (FSR) of the interference spectrum, as well as the frequency of the passbands. By changing the arm length of the MZI, a high length measuring sensitivity of ?2.420?GHz/mm has been achieved. The MPF has broad application prospects in the field of multi-parameter sensing. Moreover, the sensor reveals the advantages of highly sensitive, easy to implement and is able to overcome the influence of the environmental perturbation, for example temperature.     

相位噪声标准的研制

为解决相位噪声测量系统校准无法溯源的问题,设计一套相位噪声标准系统,把相位噪声溯源到可调高斯白噪声源上.该系统可用来测试相位噪声测量系统的准确度及其本底噪声,解决传统比对方法各相位噪声测量系统之间精度较低的问题.利用不同频点的带通滤波器对相位噪声测试系统PN9000在5,10,100 MHz频点下的相位噪声测量结果进行校准,验证方案和整套系统的准确性.     

A high-quality 120 GHz millimeter-wave generation without laser phase noise

A 120-GHz millimeter-wave system using two lasers and two Mach–Zehnder modulation (MZM) with frequency 8-tupling of the radio frequency local oscillator’s signal frequency is proposed and demonstrated. The first MZM is the even-order harmonic modulations output and then optical filter filters the 0-order wave. The second MZM is the single sideband suppression output. In the system, two light components with the same phase noise are generated. The millimeter wave can avoid the laser phase noise. It has simplified the system, so the fibre dispersion is reduced.     

基于声子晶体的车内噪声研究

声子晶体是近年来提出的一种新型功能材料,是一种由两种或多种材料组成的具有周期性结构和弹性波带隙的声学功能材料或结构,并且振动频率在声子晶体带隙范围内的振动会被抑制或禁止传播,它所具有的这种弹性波带隙特性为汽车车内噪声控制,特别是车内低频噪声控制提供了一种新的研究方法.在介绍了声子晶体的概念、基本特征及能带结构的基础上,阐述了声子晶体在振动与噪声控制领域的研究现状,同时对车内噪声的产生机理进行了分析,最后对声子晶体在应用于汽车车内降噪方面的研究做了展望.     

Effect of modulation amplitude on low-field microwave absorption in hafnium-doped Y-Ba-Cu-O

Low-field differential microwave absorption has been studied for hafnium-doped Y-Ba-Cu-O at the first harmonic of modulation field. The effect of modulation amplitude on peak height, peak position and the area under hysteresis curve has been discussed.     

IFOG中相位调制器的残余强度调制及其测量

利用开环正弦波调制解调方法,推导了铌酸锂相位调制器的残余强度调制(简称RIM)对干涉型光纤陀螺(简称IFOG)信号的影响,指出在调制频率漂移或光纤环渡越时间变化时RIM可导致陀螺的零偏和噪声增大.对典型条件的计算表明,0.01°/h的IFOG容许的最大RIM为13ppm,0.1°/h的中低精度IFOG则为81ppm.提出利用锁相放大器精确测量相位调制器RIM的方法,并对国产器件进行测量,结果表明,器件RIM指标可在中低精度IFOG中应用.     

Temperature dependent study on the microwave noise performance of metamorphic InP/InGaAs heterojunction bipolar transistors

In this study, a detailed characterization on the microwave noise performance of high gain metamorphic heterojunction bipolar transistor (MHBT) in the temperature range of 300 K to 380 K is performed. The results are compared between the MHBT and the referenced lattice-matched InP HBT (LHBT) devices. The minimum noise figure (NF_min) versus frequency in the range of 2 to 20 GHz at different temperatures for a 1.6 × 20 μm² HBTs are measured. The experimental results show that the MHBT exhibits a slightly larger variation in NF_min compared to lattice-matched HBTs. Even though the MHBTs may have much higher thermal resistance, this may not significantly affect the device microwave noise performance.     

Infinite impulse response microwave photonic filter using a dual drive modulator with an optoelectronic feedback loop

A novel design of a microwave photonic filter with infinite impulse response is demonstrated. The design is based on a dual drive modulator with an optoelectronic feedback loop. The stopband of the filter can be switched to passband and vice versa by switching the bias point of the dual drive modulator. Measured results confirm the theoretical expressions and demonstrate a rejection ratio and frequency selectivity which is greater than 30 dB.     

A simplified filterless photonic frequency octupling scheme based on cascaded modulators

A simplified filterless frequency octupling scheme by connecting an intensity modulator (IM) with a dual-parallel Mach–Zehnder (DPMZM) in series is proposed in this paper. The LO signal is distributed into two parts, and one part is used to drive the IM and the other part is applied to drive the DPMZM’s upper sub-modulator, both at the peak point. The lower sub-modulator is only driven by dc bias, and the parent modulator works at null point. By properly adjusting dc bias of the lower sub-modulator, only ±4th-order optical sidebands dominate at the output of the DPMZM. The approach is verified by experiments, and 32-GHz and 40-GHz millimetre waves (mm-waves) are generated using 4-GHz and 5-GHz LO signals, respectively. We acquire a 15-dB electrical spurious suppression ratio (ESSR) and a relatively good phase noise of the signal. Compared with other schemes, the scheme is simple in configuration because only an IM and a DPMZM are needed. What’s more, the scheme is tunable in frequency as no filter is used.     

浅海中舰船辐射噪声非均匀调制特征分析

真实海洋环境下,信道复杂的畸变作用使目标分类识别特征的实际应用效果并不理想,因此寻找能够在信道中稳定传播的目标分类识别特征显得尤为必要。文章提取出平均窄带包络相关和最佳窄带包络相关两个非均匀调制特征来衡量舰船噪声在频带上的调制分布差异,并构建浅海相干多途信道的射线模型,通过仿真实验分析非均匀调制特征的传播变化。结果表明,舰船噪声的这种非均匀调制特征在相干多途信道的传播过程中具有良好的稳定性,是目标分类识别的一种稳定特征。     

Sensitive photonic crystal phase logic gates

Total optical phase logic gates are reported in this paper. They are constructed by coupled-defect photonic crystal after two problems are overcome by a heterostructure or an asymmetric structure. Both half and all-phase logic gates are discussed. The sensitivity of these total optical phase logic gates not only are two orders sensitive than those using amplitude-signal, but also have many other advantages: such as very low energy cost. By using such phase logic gates, only a continued wave laser with one frequency is sufficient to operate the phase logic gate or the whole optical integrated circuit.     

A microwave photonic generator of chaotic and noise signals

The transition to chaos in a microwave photonic generator has been experimentally studied for the first time, and the generated broadband chaotic microwave signal has been analyzed. The generator represented a ring circuit with the microwave tract containing a low-pass filter and a microwave amplifier. The optical tract comprised a fiber delay line. The possibility of generating chaotic oscillations with uniform spectral power density in a 3–8 GHz range is demonstrated.     

Photonic microwave frequency conversion scheme with flexible phase shift

In this paper, a single, flexible and stable optical frequency conversion scheme with tunable phase shift is proposed. It mainly consists of a dual-parallel binary phase shift keying (DP-BPSK) modulator and a polarization modulator (PolM). Properly setting the values of two DC bias points in the DP-BPSK modulator, the frequency conversion ability can be achieved. Meanwhile, the phase shift can also be realized by controlling the DC voltage that drives the PolM or tuning the polarization controller (PC3). The simulation results show that a 20?GHz RF signal can be converted into a 10?GHz IF signal with the conversion efficiency of ?4.45?dB and a full 0° to 360° phase shift. It should be noted that the system performs well against different non-ideal factors such as extinction ratio, DC drifting or different LO and RF amplitudes. In addition, spurious free dynamic range of 82.14 dB·Hz^2/3 is achieved and it can be greatly improved if a better extinction ratio is available.     

Multimode analysis of relative intensity noise associated with intensity modulation of semiconductor lasers

This paper analyzes the relative intensity noise (RIN) associated with intensity modulation (IM) of multilongitudinal mode semiconductor lasers. We considered two states of operation; namely, stable single-mode and multimode hopping that correspond to weak and strong asymmetric gain suppression. The former is typically considered by AlGaAs lasers, whereas the latter is considered by InGaAsP lasers. We introduce comparison of the influence of the modulation parameters on both the total and modal RIN between both lasers. We show that the IM response and 2HD display a peak at the relaxation frequency. The multimode hopping in the InGaAsP laser induces levels of signal distortion much higher than those in the AlGaAs laser in the regime of low modulation frequencies. Under weak modulation, the total and modal RINs of both the lasers vary little from those of the non-modulated lasers. The deep modulation releases the multimode hopping phenomenon in the InGaAsP laser and suppresses the mode-hopping peak in the RIN spectrum.     

一种用于MPLS光波长路由器的自适应路由策略

针对现有MPIS光波长路由器存在IP层和光层分别路由的不足,提出了一种使用了联合路由算法的自适应路由策略,该路由策略可以适应流量疏导端口资源的变化,合理利用波长和流量疏导端口,提高网络性能和资源利用率。同时为了支持该路由策略,还提出了一种辅助拓扑的构造方法。仿真结果显示,该自适应路由策略具有更好的性能,可以承载更多的业务。     

Measurement of radio-frequency temporal phase modulation using spectral interferometry

We present an optical method to measure radio-frequency electro-optic phase modulation profiles by employing spectrum-to-time mapping realized by highly chirped optical pulses. We directly characterize temporal phase modulation profiles of up to 12.5 GHz bandwidth, with temporal resolution comparable to high-end electronic oscilloscopes. The presented optical set-up is a valuable tool for direct characterization of complex temporal electro-optic phase modulation profiles, which is indispensable for practical realization of deterministic spectral-temporal reshaping of quantum light pulses     

轿车风噪声及其测量

本文介绍了轿车风噪声的形成及其重要的影响因素,以及轿车风噪声的测量方法。     

Failure analysis of the adhesive joint of microwave ferrite phase shifter

Failure investigation is carried out on the adhesive joint of microwave ferrite phase shifter. Though, practically, the failure mode of microwave ferrite phase shifter can be described as the fracture of adhesive joint between ferrite and microwave dielectric ceramic, the failures of adhesive layer could be found in various ways and at various stages of manufacture, assembly and service. They may be due to the strength degradation caused by moisture environment, or the voids defects originated from dehydration effect of the adhesive as well as the contamination during manufacturing. With the help of SEM, FTIR and TGA, both the normal and failed samples of microwave ferrite phase shifter were selected, compared and analyzed. Recommendations for the structural design and the adhesive process are presented, and the responsibility of the failures was charged to the negligence of the manufacturer of the microwave ferrite phase shifters.