基于半导体光放大器交叉增益饱和的波长转换的理论分析

建立了基于半导体光放大器交叉增益饱和的波长转换的理论模型。分别讨论了小信号下波长转换特性和大信号下转换波形的畸变情况。结果表明,半导体光放大器的载流子寿命是导致输出波形畸变的主要因素。     

谐振式微光学陀螺中相位调制非线性研究

通过在相位调制器上施加线性变化的调制信号来实现对光波频率的方波调制是目前谐振式微光学陀螺(RMOG)中普遍采用的调制方法。而实现理想的方波频率调制要求完全线性的调制波形,极大地增加了系统实现难度。研究了调制曲线非线性对谐振腔输出的影响,仿真计算了具有二阶和三阶非线性误差的调制曲线引起的谐振曲线偏移和畸变。分析了解调输出误差与调制曲线非线性度的关系。通过搭建RMOG实验系统,测试了实际产生三角波调制信号的高阶非线性系数以及陀螺输出的标度因数。实验验证了理论分析计算方法的正确性以及采用模拟三角波产生方法改善微光学陀螺中相位调制非线性的可行性。     

塔康天线辐射场调制包络谐波测量方法

塔康天线辐射场调制包络是实现系统测位功能的重要技术参数,其波形质量直接影响测位精度,塔康系统采用谐波失真度指标描述调制包络的波形质量。本文提供了一种基于 USB 接口虚拟频谱仪、Excel 电子表格—傅立叶变换函数的简便方法来测量、计算塔康天线辐射场调制包络谐波失真度指标。     

Waveform distortion due to stimulated Raman scattering in wide-bandWDM transmission systems

The influence of stimulated Raman scattering (SRS) taking into account the random modulation and the walk-off effect on wide-band wavelength division multiplexing (WDM) transmission systems are studied theoretically. First, it is shown that power depletion due to SRS can be separated into average power loss and waveform distortion. The waveform distortion is evaluated for various types of pulse shapes and fibers, and simple equations for evaluating the waveform distortion due to SRS are derived. These equations can be easily applied for designing wide-band WDM transmission systems from the viewpoint of the SRS waveform distortion. We also compare results obtained from our method with those from the split-step Fourier method, and confirm validity of our method. Our method should be useful in the design of wide-band WDM transmission systems, in which SRS is expected to be a serious limitation     

谐振式集成光学陀螺三角波调制误差分析

在基于模拟三角波相位调制技术的谐振式集成光学陀螺(IORG)调制方案中,调制三角波参数受外界环境等变化而产生波动是陀螺输出误差的主要来源之一。给出了调制三角波参数与陀螺输出的特性关系;分析了调制三角波参数波动与陀螺标度因数的变化关系;仿真计算了调制三角波参数波动与陀螺输出非线性度的关系。搭建了IORG实验系统,通过采用精密高频波形产生器产生调制三角波,得到了1h零偏稳定性为0.69(°)/s,±500(°)/s动态范围内非线性度为0.96%的陀螺输出。实验验证了理论分析计算方法的正确性以及采用模拟三角波调制方法改善集成光学陀螺检测精度的可行性。     

Notes on the theory of modulation

The transmission system of "frequency modulation" (transmission by variation of the frequency of the radiated wave) is mathematically analyzed, and the width of the band of frequencies occupied by this method of transmission at a given speed is compared with the width of the corresponding band for transmission by amplitude variation. It is proved that the frequency modulation system using a spacing or compensating wave is inferior to the amplitude variation system both as to the width of the frequency band occupied and as to distortion of signal waveform.     

空地高速数据传输研究

针对高速空地数据传输时由于地面反射产生信号衰落、引起码间干扰的问题,阐述了空地数据传输的二径模型、信号衰落的模式及特点;在此基础上,对QPSK、QAM和OVTDM 3种调制体制进行了分析;使用MATLAB对3种调制方式在二径模型下信号的码间干扰进行了仿真、比较,并给出了一种2符号OVTDM的信号波形。仿真及分析结果表明,2符号OVTDM的码间干扰和波形畸变小,频谱利用率高,性能优于QPSK和16QAM。     

1.7 Tbit/s (85/spl times/22.8 Gbit/s) transmission over 9180 km using symmetrically collided transmission methodology

1.7 Tbit/s (85/spl times/22.8 Gbit/s) transmission over a transpacific distance of 9180 km using distributed Raman amplifiers followed by 35 nm C-band erbium-doped fibre amplifiers is demonstrated. A symmetrically collided transmission methodology mitigates unwanted waveform distortion caused by cross-phase modulation.     

基于DSP的超磁致伸缩换能器驱动电源设计

为了提高稀土超磁致伸缩换能器驱动电源的效率以及实用性,采用DSP器件TMS320F2812作为主控芯片,结合混合脉宽调制方法实现SPWM波形。采用半桥型逆变电路实现SPWM的功率放大,并对隔离驱动电路、反馈电路和滤波匹配电路进行合理而有效的设计,保证了换能器的输出效能。同时使用电流控制频率的方法实现谐振频率的自动跟踪。实验证明,该驱动电路输出频率稳定,波形失真度低,且能量转换效率较高。     

Transmission performance of chirp-controlled signal by usingsemiconductor optical amplifier

We examine the fiber transmission performance of the optical signal whose chirp is controlled by utilizing phase modulation in semiconductor optical amplifier (SOA) with both simulations and experiments. This chirp control technique converts a positive chirp created by electroabsorption (EA) modulator into negative chirp, which reduces the waveform degradation due to the chromatic dispersion in transmission over standard single-mode fiber (SMF). It also provides an optical gain that is sufficient to compensate the insertion loss of the EA modulator. We investigate how the chirp control is affected by the input power to the SOA and the carrier lifetime of the SOA. As the SOA input power increases, the negative chirp becomes large, while the waveform is largely distorted due to gain saturation. However, the waveform distortion at high SOA input powers can be shaped by using a frequency discriminator. The acceleration of the carrier lifetime also reduces the waveform distortion due to gain saturation. We demonstrate that the chirp control technique is effective even for a high bit rate optical signal up to 10 Gb/s, when the carrier lifetime is expedited by optical pumping     

抛弃式海水温度测量仪数据传输系统设计

提出一种抛弃式海水温度测量仪数据传输系统的设计方案。针对传输信道距离长,波形畸变大的特点,采用频率调制的方法克服传输信道自身和海洋环境的不利条件。系统选用单片调制解调芯片MSM7512B对信号进行FSK调制和解调,实现了水下探头和水面控制单元的通信。采用低功耗的MSP430单片机作为运算处理器,软件设计上充分利用其多种低功耗工作模式,降低了系统的功耗。     

All-Optical 40-GHz Time-Domain Fourier Transformation Using XPM With a Dark Parabolic Pulse

We demonstrate a 40-GHz all-optical time-domain Fourier transformation, in which an ideal parabolic phase modulation is applied to a signal by cross-phase modulation (XPM) with a dark parabolic pulse. The dark optical parabolic pulse is generated by the line-by-line spectral manipulation of a 40-GHz picosecond optical pulse source using an arrayed waveguide grating pulse shaper. By applying the parabolic XPM, the time interval for eliminating linear waveform distortions is expanded to a full bit slot. Dispersion slope-induced distortion is successfully eliminated with this scheme.      

Analysis of distortion in a PAM-FM television transmission andapplication to the MUSE signal

From the viewpoint of signal format, the MUSE signal for HDTV-DBS transmission is a kind of pulse amplitude modulation (PAM) signal. Since PAM signals have never been used for TV signal transmission, the author investigated the relationship between distortion due to FM transmission and picture quality. The relationship is made clear by the following two steps. First, a rating function, by which the degree of picture quality impairment due to baseband distortion can be described, is developed by applying the variable frequency electric circuit theory due to J.R. Carson and T.C. Fry (1937). The degree of picture quality impairment due to FM transmission of the MUSE signal can be obtained by the rating function with calculated waveform distortion. This approach can be used for other PAM television signals such as the HD-MAC system     

Dispersion of microwave-modulated optical signals

Experimental and analytical evaluation of dispersion effects that control intersymbol interference in gigabit, single-mode-fiber, digital systems is described. Both direct modulation of distributed-feedback (DFB) lasers and external modulation by Mach-Zehnder modulators are studied. The experiment uses sinusoidal modulation of the light at a microwave frequency, e.g. 5 GHz, and the subsequent measurement of signal gain or loss in a dispersive fiber. For DFB lasers, the transmission measurements are used to derive the transient and adiabatic components of chirp. It is shown that, for external modulation at 5 GHz, the 1.55- mu m optical signals suffer relatively little dispersion loss for transmission distances up to 60 km. Analytical solutions for waveform distortion are given for external modulation and show good agreement with measurements.<>     

Multiple sets of solutions for harmonic elimination PWM bipolar waveforms: analysis and experimental verification

Multiple sets of solutions for the selective harmonic elimination pulse-width modulation method for inverter control exist. These sets present an independent solution to the same problem but further investigation reveals that certain sets may offer an improved overall harmonic performance. In this paper, a minimization method is discussed as a way to obtain these multiple sets of switching angles. A simple distortion harmonic factor that takes into account the first two most significant harmonics present in the generated waveform is considered in order to evaluate the performance of each set. The bipolar waveform is thoroughly analyzed and two cases are considered; single-phase patterns which eliminate all odd harmonics and three-phase counterparts which eliminate only the nontriplen odd harmonics from the line-to-neutral pattern but such harmonics are naturally eliminated from the line-to-line waveform. Experimental results support the theoretical considerations reported in the paper.     

Space Vector Sequence Investigation and Synchronization Methods for Active Front-End Rectifiers in High-Power Current-Source Drives

Space vector pulsewidth modulation (PWM) schemes for the active front end of a high-power drive normally produce low-order and suborder harmonics due to the low switching frequency and the drifting of synchronization between the PWM waveform and the rectifier input frequency. To provide a synchronized PWM and achieve the best harmonic performance, different space vector sequences suitable for a current-source converter are investigated in this paper. Details on how to achieve the waveform symmetries with a minimum switching frequency for each sequence are discussed. A thorough comparison of the harmonic performance of different space vector sequences is carried out. An optimum space vector modulation method by switching between two best sequences is proposed to achieve the best line-current total harmonic distortion with reduced switching losses. In addition, two synchronization methods, namely a PWM frame regulation method and a direct digital phase-locked loop synchronization method, are proposed. Both methods are equally effective in providing tight synchronization of the PWM waveform with the rectifier input frequency. The work has been verified in simulation and experiment.     

Long-span optical FSK heterodyne single-filter detection transmission experiment using a phase-tunable DFB laser diode

High receiver sensitivity (?51.9 dBm) and long span (243 km) transmission expriments have been achieved with a 140 Mbit/s optical FSK heterodyne single-filter detection system, using a phase-tunable DFB laser diode as a transmitter. This has enabled direct FSK modulation without waveform distortion. Also, a 280 Mbit/s 204 km transmission experiment has been carried out successfully.     

Exact compensation for both chromatic dispersion and Kerr effect ina transmission fiber using optical phase conjugation

We propose a new method to compensate exactly for both chromatic dispersion and self-phase modulation in a transmission fiber, where the light intensity changes due to fiber loss and amplifier gain. This method utilizes optical phase conjugation (OPC). The pulse shape is precompensated before OPC by transmission through a fiber with large dispersion. A computer simulation demonstrates effective compensation for waveform distortion in a 40 Gb/s NRZ intensity-modulated light transmission     

基于波形预先设计和相位对消技术的步进频信号ISAR成像研究

针对步进频雷达系统,分析了目标匀加速运动对回波相位的调制效应,提出基于波形预先设计和相位对消技术组合的ISAR成像方法,该方法通过对脉冲重复时间的设计消除目标速度带来的相位高次项,并通过相位对消技术消除由目标加速度带来的相位高次项.因此对于匀加速运动的目标,算法不需要估计速度和加速度,减少了计算量.仿真试验演示了算法的...     

A comparison of multipath distortion characteristics among digital modulation techniques

In a digital mobile radio transmission, long-delayed multi-path propagation causes frequency selective fading, resulting in signal waveform distortion and hence bit error rate (BER) degradation. Comparison of multipath distortion among various digital modulation techniques (binary, quaternary, offset quaternary, and minimum phase shift keying (BPSK, QPSK, OQPSK and MSK)) is made using a two-ray propagation model, which is a fundamental model to evaluate multipath tolerant capability. The analysis clarified the multipath conditions causing severe distortions and also the mechanisms of eye pattern degradation, showing the superiority of BPSK in multipath tolerance.