基于双LPFG解调的高灵敏度振动检测系统

基于边缘滤波解调原理,提出了一种利用双长周期光纤光栅（LPFG）解调光纤布拉格光栅（FBG）振动传感信号的新方法。利用传输光谱叠加后的双LPFG作为边缘滤波器,增大了FBG传感信号解调灵敏度。静态实验结果表明,利用单、双LPFG作为滤波器解调的灵敏度分别为-1．1965dB／nm和-2．4836dB／nm,双LPFG解...     

基于镀铜长周期FBG的波长可调谐环形光纤激光器

将采用化学镀铜膜技术封装的长周期光纤光栅（LPFG）串人环形腔中,设计了一种新颖的波长可调谐掺Er3＋光纤激光器（EDFL）。铜镀膜（化学涂镀）的LPFG在激光器环腔中用作带阻滤波器,利用恒电流源调节LPFG所处温度场,影响LPFG透射谱,改变激光器环形腔增益最高点,实现输出激光波长的可调谐。在LPFG环境温度调谐20...     

一种多模式合成孔径雷达数字接收机

针对一种多模式极化合成孔径雷达（SAR），给出了中频数字接收机工作参数选择，混频滤波方法，实现了三种带宽信号的数字正交解调。通过分析同相、正交通道误差对正交解调性能的影响，确定了滤波器最佳设计准则。最后给出了基于FPGA的实现结构，仿真试验结果表明中频数字接收机性能比一般模拟接收机有显著提高。     

基于长周期光纤光栅线性边缘滤波的地震波解调系统

设计一种针对地震波信号的解调系统,讨论了长周期光纤光栅（LPFG）制作时参数的控制方法,选用边缘特性良好的LPFG做线性边缘滤波器,在1 550.35~1 553.14 nm间具有0.998 96的线性拟合度,功率灵敏度达1.692 dBm/nm。在信号处理中,采用参考光路与滤波光路比较,消除本底信号的影响;利用Lab...     

太赫兹波导多通道滤波器的研究

研究了一种基于多模共振的多通道太赫兹波导滤波器。在太赫兹周期结构波导中引入缺陷,可以在禁带范围内形成通带,从而实现窄带滤波。通过数值模拟对多通道滤波器的特性进行了研究。结果表明,通过改变缺陷长度可以实现通道数可调的多通道滤波功能,通道数可达10~12个,透过率均在98%以上。此外,改变波导结构的周期个数,还可实现对通带带宽的调控,最窄带宽可达0.01 GHz。该波导滤波器性能优良,具有结构紧凑、易于集成、透过率高、通道多、带宽窄等优点,为太赫兹波段功能器件的研制提供重要的技术参考。     

集成光学型快速可调谐滤波器的研究

本文提出并设计了一种新的基于LiNbO3衬底的非对称马赫－曾德（Mach-Zehnder,M-Z)结构集成光学型电光可调制谐滤波器,并利用耦合模方程和光束传播法（BPM）对单个滤波器的电压响应特性和频率响应特性进行了分析模拟。文中还利用多个滤波器级联实现多个波长的动态滤波和路由,所得各种特性满足全光网（AON）的要求。     

变采样多相滤波器组信道化接收机的实现

针对多相滤波器组信道化接收机的通道采样率在数值上等于通道带宽,因此无法兼顾最优信道带宽和最优采样率的问题,提出一种基于嵌入式变采样多相滤波器组的信道化接收机。该信道化接收机根据要求的变采样率改变数据的输入速率,并依据数学推导对原有系统的结构进行变形,可有效解决多相滤波器组通道采样率和通道带宽的耦合问题,从而实现嵌入式变采样的目的。本接收机设计方法在兼顾系统最优采样和最小信道带宽要求的前提下,能有效避免频道浪费或复杂的插值算法。仿真结果表明,该接收机在不增加计算量的基础上能有效改变采样率,提高系统实时处理能力。     

机械微弯长周期光纤光栅的制备及其光学特性研究

利用两个交替放置的周期性刻槽板对单模光纤（SMF）施力,形成了机械微弯长周期光纤光栅（LPFG）。实验研究了LPFG的偏振相关损耗（PDL）、刻槽板空间周期和压力等参数对透射谱的影响。结果表明,压力可改变LPFG的透射谱特性,最大损耗峰值可达24．6dB;在1551．9nm处,LP13包层模的最大PDL约为7．42dB...     

双环推挽型高线性M-Z光强调制器特性研究

对损耗影响下的双环推挽（TRAPP）型马赫一曾德（M-Z）光调制器的线性特性进行了研究。分析表明,存在损耗时,设计特定的光微环与M-Z干涉臂间的耦合大小,并控制偏置点,总可以获得2次与3次高阶项为零的调制曲线;当微环1周损耗小于5dB时,线性范围总是可以达到90％以上;当损耗过大时,导致基于微环的全通滤波器的相位响应受限,虽然调制曲线在自身范围内依然保持高的线性度,但调制曲线固有的调制深度将限制整体线性范围。     

全光纤平顶梳状滤波器技术综述

对全光纤平顶梳状滤波器的发展现状进行了详细介绍,并利用琼斯矩阵分析方法对利用三个级联M-Z干涉仪结构设计的光学梳状滤波器进行了详细的理论分析和数值模拟。在系统输出端3处获得一平顶的梳状滤波谱,同时在输出端4获得一个消光比约为M-Z干涉仪消光比两倍的梳状滤波谱。该系统滤波谱由M-Z干涉仪的臂长差决定,与臂长以及输入光的偏振态都无关。     

On the design of a multiplexer with a common junction

Two sets of formulas for scattering parameters are presented for multiplexers having parallel and series configurations with a common junction. A new general design approach is developed for multiplexers having any response types and any number of channel filters of arbitrary degree, bandwidth, and interchannel spacing. By using these formulas and computer optimization techniques for all the element values in the channel filters, the design process results in a good match at the common input port over the transmission frequency band. Several examples including a contiguous multiplexer are given to demonstrate the design procedure.This work was supported by Air Force Systems Command under Contract F33615-84-K-1556.     

Optimization of Single-Sideband DCS-RZ Format for Long-Haul 43-Gb/s/channel Ultradense WDM Systems

The optimization of the single-sideband (SSB) duobinary carrier-suppressed (DCS) return-to-zero (RZ) format for long-haul ultradense wavelength-division multiplexing (UDWDM) systems with a 43-Gb/s/channel and a channel spacing of 50 GHz is investigated numerically. It is shown that the optimized SSB-DCS-RZ format with an electrical transmitter bandwidth of 0.35 of the bit rate has about 1 dB of Q-factor improvement relative to the conventional SSB-DCS-RZ format (an electrical transmitter bandwidth of 0.25 of the bit rate) due to the reduction of noise bandwidth, smaller linear crosstalk, and better tolerance to the intra-channel fiber nonlinear effects. No substantially different UDWDM system performance is observed when varying the duty cycle of the DCS-RZ signal with optimized SSB filters settings. The UDWDM transmission performance of SSB-DCS-RZ formats is compared with the bandwidth-limited (BL)-duobinary formats. It is shown that generally, the SSB-DCS-RZ formats have poorer Q-factor and tolerance to the total residual dispersion but much higher tolerance to the in-line dispersion compensation and intra-channel nonlinear effects than the BL-duobinary formats     

采用半导体光放大器的多波长光纤环形激光器

报道了一种插入马赫-曾德尔(M-Z)光纤干涉仪的半导体光放大器(SOA)多波长光纤环形激光器,实现了信道间隔为100 GHz的稳定的多波长连续光激射,其输出光谱3 dB带宽为19.5 nm,消光比大于30 dB.其中在17.9 nm范围内获得了22个波长的连续光,功率不平坦度为1.2 dB,总输出功率为5.1 dBm.对该结构的多波长激光器输出光谱宽,不同波长间功率波动小的特性进行了分析,提出在较低环腔损耗下,半导体光放大器的增益饱和及四波混频(FWM)效应的共同作用使环腔内多波长光功率获得自动均衡;并对实验观测到的激光器输出光谱带宽及中心波长随半导体光放大器驱动电流降低或环腔损耗增大而减小的现象进行了讨论.     

The effect of pulse shaping and transmitter filter on theperformance of FSK-DPD and CPM-DPD in satellite mobile channel

This paper investigates how a bandlimiting transmitter filter and the shape of the frequency pulse effect the bit-error probability of frequency shift keying with differential phase detection in satellite mobile channel. Numerical results are presented for the case when the transmitter and receiver filters are Butterworth filters of order N_T=4 and N_R=3, respectively, and the frequency shaping pulse is rectangular or raised cosine. It is shown that in all cases of practical interest, continuous phase modulation (with raised cosine pulse shaping) gives a lower bit-error probability and requires less bandwidth than frequency-shift keying (with rectangular pulse shaping) when all other parameters (number of symbols, Rician factor of the channel, order of filters, etc.) are the same     

Hybrid Genetic Algorithm for the Design of Modified Frequency-Response Masking Filters in a Discrete Space

This paper presents the design of high-speed, arbitrary bandwidth sharp finite impulse response filters with signed powers-of-two coefficients based on a modified frequency-response masking (FRM) structure. A novel hybrid genetic algorithm (HGA) is proposed to jointly optimize all subfilters in a discrete space. The proposed HGA introduces the simulated annealing technique into the genetic algorithm (GA) optimization process and effectively prevents the GA from prematurely converging. It is shown, by means of examples, that FRM filters designed by the HGA achieve a significant reduction in the number of bits.     

分布式Alamouti空时码的信道容量及最优资源分配方案

该文针对基于译码转发协议的分布式Alamouti空时码(DF-DASTC)系统的信道容量以及最优资源分配策略问题.利用退化中继信道模型,推导得到了DF-DASTC系统在衰落信道下的信道容量闭式解.以DF-DASTC信道容量最大化为目标,对该系统在固定带宽分配时,中继及信源节点的最优功率分配方案进行了研究,推导得到了DF-DASTC系统的最优功率分配方案的闭式解.利用凸优化理论,将以DF-DASTC信道容量最大化为目标函数的多目标优化问题转换为非线性不等式约束的单目标凸优化问题,进一步得到了可变带宽分配时的DF-DASTC系统的最优带宽和功率分配策略.理论分析和系统仿真表明,该文所提出的资源分配策略,比平均分配的资源方案具有更大的信道容量.另外,该文的最优资源分配策略适用于具有多个中继节点的无线中继网络,具有普适性.     

Adjacent-Channel and Quadrature-Channel Interference in Minimum Shift Keying

In this paper we present formulas for the computation of error probability in the presence of quadrature-channel or adjacentchannel interference in addition to intersymbol interference in a minimum shift keying system. The filters in the receiver and transmitter are arbitrary but with a finite number of poles. The effect of phase jitter in the main channel, phase and symbol timing misalignment in the interfering channels, and sampling time jitter is taken into account. The probability of error is averaged over the phase and symbol timing misalignment. Numerical results are presented for Butterworth filters in the receiver and transmitter with two, three, and four poles. Curves of error probability as a function of various variables (signal-to-noise ratio, bandwidth of receiver and transmitter filters, number of poles, channel frequency separation, phase jitter, sampling time, and symbol timing and phase misalignment) are presented. The method of this paper can readily be applied to other filters; hence, it can be used in the design and prediction of the performance of digital communication systems.     

最佳小波调制

小波分析的理论正在逐步走向通信领域,小波调制因其频谱利用率的优势而受到重视。以往研究较多的是Daubechies和Battle-Lemarie小波系列,本文从频谱利用率的角度出发,讨论如何设计用FIR滤波器实现的最佳正交小波和尺度函数,给出了设计方法和结果。通过比较我们得出这样的结论:经过最优化设计,在同样的实现复杂性条件下,小波调制的频谱利用率有了明显的提高,因而可以用较简单的FIR滤波器获得较好的频谱性能。     

采用移频反馈的SOA多波长光纤环形激光器

文章报道了一种基于移频反馈的半导体光放大器(SOA)多波长光纤环形激光器,其环腔内插入声光调制器作为移频器,用自制的光纤马赫-曾德干涉仪进行梳状滤波,在输出光谱1.5 dB带宽为21.7 nm范围内,获得了间隔50 GHz的54个稳定的多波长连续光激射,消光比为28 dB.该激光器具有工作稳定性好、输出光谱宽和不同波长功率平坦度高的优点.实验证明,移频反馈技术能够实现激光器不同起振波长间的增益均衡,使输出光谱带宽增大21.7%.     

基于包络信息的BPSK 信号与侦收信道带宽定量关系分析

针对二相编码信号经过数字信道化接收机会产生包络缺口现象,通过改变了信号与接收机相关参数,发现对包络缺口个数正确估计的条件要强于对脉宽的估计,且位于信道边沿的信号不能保证包络缺口个数的正确估计。该研究以包络缺口个数与二相编码相位跳变点相等,脉宽估计相对误差小于10%作为正确接收的条件,得到了信号带宽与信道带宽之间的定量关系:当信号载频与信道中心的距离不大于信道带宽的44. 4% 时,可正确接收的信号带宽为信道带宽的0. 493;当距离不大于信道带宽的37. 2% 时,可正确接收的信号带宽增大至信道带宽的0. 704;该结果对不同的编码方式依然成立。