声光多频衍射的三阶互调现象研究

基于布喇格衍射,讨论了多频声光衍射时三阶互调现象与频率之间的关系.以两个不同频率信号同时加载到声光偏转器的情况为例,具体分析了三阶互调产物的产生过程、光束衍射方式和频谱结构分布.针对三阶互调产物对系统准确探测信号的影响,介绍了几种减小三阶互调的方法.     

基于声光偏转的载频相干探测研究

基于声光偏转和相干光探测原理,构建了频率测量系统.从改善空间光相干探测效率出发,提出一种将空间光经声光偏转后注入保偏光纤的信号处理方法,并具体讨论了如何利用准直-聚焦透镜的注入系统保证带宽内信号光的注入效率.实验结果表明,此测频系统能准确、实时测量信号的频率,在测频带宽内其截获率达到100%.     

级联布喇格声光互作用的频移与光束偏转分析

声光器件在设计和制作中,由于器件结构和功能上的需要,常采用级联形式的声光互作用。根据声光互作用的一般理论,对不同的声光互作用条件下,级联布喇格声光互作用的频移和光束偏转进行了分析。当组合两次不同的声光互作用,可以得到不同的频移和光束偏转。并指出,通过调节两声波的频率,可以使输出光波的传播方向不随声波频率的改变而变化。     

电力光纤通信系统中信号组播的仿真研究

理论分析了基于光纤四波混频(FWM)的信号组播方案,并在此基础上搭建了Optisystem仿真平台,对方案可行性进行了验证.分析了多频信号作用下非线性系统可能产生的非线性失真,且对系统的互调失真情况进行了仿真分析.     

声光与光纤技术

２声光与光纤技术９５１３８实用声光偏转器的角频关系──ＧａｓｓＰＡＯｐｔＬｅｔｔ（ＵＳＡ），１９９３；１８（６）：１３７６～１３７８提出多种ＴｅＯ＿２各向异性声光衍射的声光偏转器设计方案。通常的声光互作用配置方式中，要求光束入射角固定，从而获得满足性...     

基于相干光探测的声光测频接收机

提出了一种采用声光信号处理的相干光探测方法,分析了声光测频原理,研究了采用相干光探测实现电磁频谱信号的前端截获,给出了提高系统瞬时测频精度和分辨率的基本措施.通过声光互作用建立衍射光栅,抑制不确定噪声和干扰信号对信号检测和频率测量带来的影响.实验证明,基于声光效应的相干光探测系统对带内随机噪声具有一定的选择和滤波作用,...     

驱动信号占空比对声光调Q脉冲光纤激光器输出脉冲重频的影响

搭建了声光调Q脉冲光纤激光器实验 系统,通过调节声光调制器(AOM)驱动信号的占空比,研 究了驱动信号占空比对声光调Q脉冲光纤激光器输出脉冲重频的影响。结果显 示,当AOM驱动信号频率 固定时,随着占空比的减小,输出脉冲重频依次为AOM驱动信号频率、AOM驱动信号频率的1/ 2、1/3。 实验结果表明,在声光调Q脉冲光纤激光器中,输出脉冲重频受A OM驱动信号频率和占空比的共同影响。     

第五讲 基础声光器件

在前面四讲里,我们较详细地讲述了声光互作用的基本理论和选择声光材料的基本原则,这是声光应用技术的基础.利用声光互作用效应可研制出各种声光器件,其中最基本的是声光调制器、声光偏转器和声光可调滤光器等.利用这些器件可构成各种时间和空间信号处理系统,因此,我们把这些器件称为基础声光器件.因篇幅所限,在这一讲     

基于Bragg衍射的多频声光衍射效应研究

文章首先介绍多频声光衍射的原理,然后推导Bragg声光介质的声光衍射耦合波方程,并结合该声光波矢量的分析,定量和定性地讨论了衍射效率、波矢量失配和三阶互调等多频衍射效应.实验表明,各种效应都能很好地与Bragg理论极限相吻合.     

基于多频布拉格声光衍射的多通道光学双稳态

本文分析了单频喇曼-奈斯型和布拉格型声光光学双稳态的多通道运用特性,进而提出基于多频声光衍射的多通道光学双稳态。作者推导出多频反常声光互作用耦合波方程,得出布拉格状态下的解。从理论上研究了多频反常布拉格声光衍射的各种线     

减小声光频谱仪频率测量方差算法研究

声光器件衍射光峰值偏转位置与输入信号频率成正比是声光频谱仪测频的基本原理,但实际中衍射的非线形效应会引起衍射光峰值偏转误差较大。为减小频率测量方差,需对衍射光强数据做相应处理。对CCD背景噪声的数字特征分析,以背景噪声数学平均值为阈值做去噪处理。根据最小二乘法原理,对衍射光强数据做一次高斯函数拟合,拟合数据与光强数据相关系数为0.997 6。在现有测试光学平台下,根据衍射光强峰值位置估计的频率测量方差为542.5 kHz2,利用拟合高斯函数中心值估计的频率测量方差为31.8 kHz2。为减小声光频谱仪频率测量方差提供了理论支持。     

Numerical analysis of intermodulation interference in an optical coherent multichannel system

Coherent optical transmission techniques have a potential for use in ultra-wide-band coherent optical lans (UCOL's) in addition to long distance applications. They offer the possibility of extremely high total bandwidth by making simultaneous transmission of multiple wide-band signals possible. This paper reports on the numerical simulation of the performance of a heterodyne optical FDM system as a function of channel spacing. The channel interference due to intermodulation noise is discussed. A possible channeling arrangement with a spectral efficiency of 45 percent is described.     

声光频谱仪频率分辨率判断方法研究

频率分辨率是声光频谱仪的一个重要指标。声 光布拉格器件实际衍射光宽度远大于 理论宽度,因 此对声光频谱仪频率分辨率的估计需根据实际衍射光的宽度来判断。本文在现有光学测试平 台下,对单频信号 产生的衍射光,通过高斯函数建立数学模型,利用二分迭代法得到两高斯函数在满足瑞利 判据条件下可 分辨的最小间距。根据光路系统衍射光偏转距离与对应频率带宽,估计系统频率分辨率与 实测系统频率分辨率基本一致。研究结果表明,本文方法能有效估计声光频谱仪的频率分辨 率。     

基于声光效应的声光器件特性研究

构建了声光效应实验装置,对Bragg衍射时声光器件的调制、偏转、带宽和中心频率特性进行实验研究,进一步利用Origin软件对实验中得到的关系曲线进行理论模拟。结果证明,入射激光穿过声波传播后的光学媒质时会产生多级衍射。在适当的设计条件下,一级衍射光会有最高的衍射效率。一级衍射光的偏射角与声波的频率成正比,衍射波强度随声波功率变化而变化。该研究不仅为声光效应实验提供更完备的理论参考,更为声光器件的实际应用研究提供了可靠依据。     

Long distance fiber-optic transmission of C-band microwave signals to and from a satellite antenna

We demonstrate here the use of high-speed semiconductor lasers and detectors with low loss optical fiber for the transmission of the 500-MHz C-band microwave signal spectrum to and from a satellite antenna. The optical system has low attenuation and large band, width, so the microwave signals can be transmitted directly at the microwave frequency (4 or 6 GHz) over 20 km of fiber without regeneration or qualization. The optical system introduces ≈ 1 dB or less of degradation for both low spectral density QPSK signals and high spectral density FM video signals present in typical satellite transmission systems. For the video signals, the signal to noise after AM conversion was reduced from 56 to 55 dB. The microwave drive level to the laser must be significantly larger (typically > -10 dBm) than the intensity noise of the laser, yet small enough (typically < 10 dBm) to reduce the intermodulation distortion signals to an acceptable level. The laser bias current must be several times threshold so that the resonance frequency is beyond the frequency band of interest (4-6 GHz in this case). A flat modulation response is then obtained, and the intensity noise and intermodulation levels are low.     

Optical-frequency encoder using polarization-maintaining fibre

A new method for monitoring the frequency modulation of coherent laser light is presented. The measurement system is an optical-frequency encoder which utilizes multireflection in a short polarization-maintaining fiber. The multireflection in each orthogonal polarization mode of the fiber produces beat signals by sweeping the optical frequency. The resultant two beat signals are monitored as an increase or decrease in optical frequency by holding the two signals in phase quadrature. The experimental setup, the principle for obtaining quadrature signals, and the results of monitoring distributed-feedback laser-diode frequency modulation are presented     

利用声光差频抑制集成光学陀螺背散噪声研究

研究了利用两个声光移频器间的差频抑制谐振式集成光学陀螺中的背向散射噪声.测试了声光移频器的输出特性,结果表明声光移频器输出功率随调制频率变化.测试并说明了两路声光移频器的功率不平衡会影响环形谐振器的谐振曲线深度和陀螺解调曲线的斜率,并最终导致陀螺的测量误差.实验中通过补偿声光移频器的输出功率,有效地克服了声光移频器功率带宽的影响,陀螺零漂从补偿前的0.28 mV降低为0.095 mV.     

Frequency division multiplexed microwave and baseband digitaloptical fiber link for phased array antennas

A frequency-division multiplexed optical fiber link is described in which microwave (1-8 GHz) and baseband digital (1-10 Mb/s) signals are combined electrically and transmitted through a direct-modulation microwave optical link. The microwave signal does not affect bit error rate (BER) performance of the Manchester-coded baseband digital data link. The baseband digital signal affects microwave signal quality by generating second-order intermodulation noise. The intermodulation noise power density is found to be proportional to both the microwave input power and the digital input power, enabling the system to be modeled as a mixer (AM modulator). The conversion loss for the digital signal is approximately 68 dB for a 1-GHz microwave signal and is highly dependent on the microwave frequency, reaching a minimum value of 41 dB at 4.5 GHz corresponding to the laser diode relaxation oscillation frequency. It is shown that Manchester coding on the digital link places the intermodulation noise peak away from microwave signal, preventing degradation of close-carrier phase noise (<1 kHz offset). A direct trade-off between intermodulation noise and digital link margin is developed to project system performance