OPM产生四倍频光载毫米波的双向ROF系统

提出一种采用单个光相位调制器(OPM)和光纤布拉格光栅(FBG)滤波器产生四倍频光载毫米波的双向光纤无线通信(ROF)系统。在中心站(CS),系统采用基带信号与射频(RF)信号混频后去驱动OPM,以产生抑制一阶边带的多边带光信号。在基站(BS),利用FBG滤波器将信号的重复频率增至4倍。实验结果显示,经过40km光纤传输后,下行链路信号的眼图清晰可见,功率代价小于1.6dB。本文方案中,由于没有额外增加激光源使得基站结构进一步简化,同时四倍频技术降低了RF信号的频率,系统成本大大降低。     

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。     

Adaptive narrow-band interference rejection in a DS spread-spectrumintercept receiver using transform domain signal processing techniques

An intercept receiver which uses a transform-domain-processing filter is described. This receiver detects direct-sequence binary-phase-shift-keyed (DS-BPSK) spread-spectrum signals in the presence of narrowband interference by employing adaptive narrowband interference rejection techniques. The improvement in the system performance over that of conventional detection techniques is shown by presenting the results of experimental measurements of probability of detection versus false alarm for an enhanced total power detector. Also presented are certain results corresponding to detection of the spectral lines generated at twice the carrier frequency, wherein the goal is often not just signal detection, but also carrier frequency estimation. The receiver uses one of two transform-domain-processing techniques for adaptive narrowband interference rejection. In the first technique, the narrowband interference is detected and excised in the transform domain by using an adaptive notch filter. In the second technique, the interference is suppressed using soft-limiting in the transform domain     

LMS coefficient filtering for Time-varying chirped signals

This paper presents coefficient filtering techniques in the least mean squares (LMS) algorithm to improve adaptive predictor tracking performance for time-varying chirped signals. The example application used in this paper is an electronic support measure (ESM) receiver for detecting radar chirped pulses. The leakage LMS, momentum LMS, and the proposed future-state coefficient (FC-LMS) filtering algorithms have been studied. The leakage LMS algorithm has the ability to remove the memory effect of the initial converged time-varying frequency of the chirped signal, thus improving the radar pulse detection performance. The momentum LMS is able to search for the time-varying optimum weight solution more efficiently, and the FC-LMS uses a parallel technique to retain the LMS throughput while being able to show a better tracking performance for chirped signals compared with the standard LMS algorithm.     

Dispersion effects of FBG filter and optical SSB filtering in DWDM millimeter-wave fiber-radio systems

We study the optical filtering technique for dense wavelength division multiplexing (DWDM) channel allocation of millimeter-wave fiber-radio signals in the optical double-sideband (DSB) format. First, we investigate both theoretically and experimentally the dispersion effect of fiber Bragg grating (FBG) used as the filter on DWDM millimeter-wave optical signal transmissions. This result suggests that the dispersion effect has to be considered in the DWDM channel allocation for millimeter-wave fiber-radio access systems. Next, we propose a DWDM allocation for millimeter-wave fiber-radio systems, which adopts the optical single-sideband (SSB) filtering technique at the receiver side by using a square response of FBG filter. It can realize the minimum WDM channel interval for optical DSB signals, while it enables the optical frequency interleave between the neighboring channels without any serious signal degradation due to the interchannel interference. Then, we experimentally demonstrate the error-free DWDM transmission of two 60-GHz-band, 155.52-Mb/s differential phase-shift keying (DPSK) fiber-radio signals over 25-km-long single-mode fiber (SMF) with the minimum channel interval of 83.6 GHz (=0.68 nm) by using the test-square response FBGs. Finally, we show that based upon the experimental results, in the micro- or pico-cellular DWDM broad-band millimeter-wave fiber-radio access network 1000 antenna base stations (BSs) under the coverage of the single central office (CO) would be feasible by sectorizing the zone.     

基于实时校准技术的光纤光栅传感解调系统

报道了一种采用实时校准技术的数字化光纤光栅传感解调方案。解调系统利用锯齿波电压信号和数字相位同步信号控制可调谐光纤法布里一珀罗(TFFP)滤波器，对光纤光栅传感器阵列进行扫描式寻址，同时采用非测量环境中的参考光栅和数字温度计提供精确的参考波长，并由高速数字信号处理器(DSP)实时校准滤波器的波长读取值，很好地消除了滤波器渊谐的温度漂移、非线性和蠕动性引起的测量误差。结果表明，实验系统的波长寻址范围为1520～1570nm，扫描频率为100Hz，波长测量分辨率为5pm，应变测量分辨率为4．13με。     

Optical Generation of Binary Phase-Coded Direct-Sequence UWB Signals Using a Multichannel Chirped Fiber Bragg Grating

A novel technique to generate binary phase-coded, direct-sequence ultra-wideband (DS-UWB) signals in the optical domain is proposed and demonstrated. In the proposed system, the wavelengths from a laser array are modulated by a Gaussian pulse, which is sent to a multichannel optical frequency discriminator, to generate a UWB monocycle or doublet pulse sequence with a predetermined phase-code pattern. By tuning the wavelengths of the laser array, or by tuning the states of polarization of the wavelengths, the generated pulse shape and code pattern can be changed. The key device in the system is the multichannel dispersive chirped fiber Bragg grating (FBG), which functions, in combination with a dispersive fiber, as a multichannel frequency discriminator with a step-increased group-delay response, to ensure the generated UWB sequence to have uniform time spacing among the chips and to compensate for the fiber-induced chromatic dispersion. The proposed scheme is experimentally demonstrated. A multichannel chirped FBG is designed and fabricated. Binary phase-coded DS-UWB signals with different code patterns are experimentally generated.      

从混合有色噪声背景中提取正弦随相调频信号的方法

提出了从混合有色背景噪声中提取正弦随机调频信号方法－－基于高阶累积量FIR自适应滤波方法。其主要特点是：FIR自适应滤波系数是用输入信号的四阶以上累积量进行更新的；FIR自适应滤波器是收敛于与有用信号类型匹配的滤波器。因此，它既能有效地提取有用信号（匹配信号），又能有效地抑制混合有色噪声（非匹配信号）。仿真结果表明，与短时相关方法相比，该方法是很有效的。     

基于啁啾FBG的三角形光脉冲发生器的优化设计

提出了利用啁啾光纤布拉格光栅(FBG)和马赫增德尔调制器产生三角形光脉冲的优化方案.方案采用FBG模拟单模光纤的色散特性,结合光载波抑制调制产生了三角形光脉冲, 并通过仿真分析,选择FBG的长度、调制深度、适当的折射率切趾函数对三角形光脉冲的线性特征进行了优化.仿真结果表明,在同一啁啾系数下,产生的三角形光脉冲的失真程度随啁啾光纤光栅的调制深度增大而增大,光栅长度、折射率切趾函数对三角形光脉冲的影响也比较明显.与现有系统相比,由于将FBG引入系统,省去长距离的光纤,优化方案系统结构更为简单,三角形光脉冲线性特征更好.     

利用线性啁啾光纤光栅补偿PMD的实验研究

对利用线性啁啾光纤光栅补偿偏振模色散(PMD)进行了实验研究.利用压电陶瓷的压电效应挤压线性啁啾光纤光栅使之产生双折射,用于补偿光通信系统中的偏振模色散.通过改变施加在压电陶瓷上的电压值,可实现对偏振模色散补偿量的线性调谐.实验结果与理论预期基本符合.     

A Carrier-Based Unipolar PWM Current Controller That Minimizes the PWM-Cycle Average Current-Error Using Internal Feedback of the PWM Signals

A carrier-based unipolar pulsewidth modulation (PWM) current controller is described using a one-phase PWM rectifier bridge as a test circuit. The controller PWM signal generator uses a sawtooth carrier signal to obtain both synchronized PWM waveforms and a constant switching frequency. A current-error signal and an amplitude modulation depth signal are used to create the input reference signal to the PWM signal generator. The amplitude modulation depth signal is obtained from the PWM-cycle average of the PWM signal generator output signals. This internal feedback is illustrated using a second-order low pass Butterworth filter. With an appropriately designed low-pass filter, the current-error signal is forced to be centered on zero over a PWM cycle. The maximum peak-peak magnitude of the current-error signal is used as a design guideline for deciding an appropriate gain constant in the controller current feedback loop. The low pass filter design is examined to determine a suitable gain and 20-dB attenuation frequency to minimize the current-error signal. The steady-state and transient operation of the proposed current controller is compared with a proportional-integral controller and an average current-error controller. SPICE simulations and experimental results are used to demonstrate the characteristics of the controller.     

Improved transmission of chirped signals from semiconductor opticaldevices by pulse reshaping using a fiber Bragg grating filter

Spectral filtering of chirped signals with an edge of a fiber grating filter improves propagation in nondispersion-shifted fiber. The improvement is due to a temporal shift of the frequency modulation with respect to the amplitude modulation. By filtering the chirped output of a semiconductor optical amplifier (SOA) wavelength converter with a fiber grating edge we obtain error-free transmission of converted data through 100 km of nondispersion-shifted fiber at 5 Gb/s     

A Delta Modulation Filter for Speech-Type Signals

This paper considers the realization of an all-digital system for direct filtering of a delta modulation (DM) encoded signal. We have shown [1] that this system can be realized fairly easily for any type of filter function when the signals are encoded with a linear DM. We now address the problem of digitally filtering an adaptive DM (ADM) encoded signal. We show that we can again realize any type of filter function and our system will operate directly on the ADM bit stream. In addition, we present a circuit realization that does not require complex digital hardware. Performance has been tested via simulation on a digital computer, using a variety of test signals; both temporal and spectral results are presented.     

基于1 bit时间调制技术的功率控制方法

针对传统数控衰减器结构复杂、控制信号路数多的问题,提出了一种基于1 bit时间调制技术的功率控制方法. 通过对1 bit移相器0°和180°两种状态占空比的调节,该方法可以有效实现对输入信号基波功率的动态控制,利用带通滤波器抑制多余谐波后其可具备数控衰减器的功能. 还进一步讨论了调制信号时间精度对不同衰减量和不同调制频率的约束. 仿真和实验结果验证了所提功率控制方法的有效性. 相比于传统数字控制衰减器级联网络和多路控制信号的结构,本文方法只需一个调制模块和两路控制信号即可实现多种衰减状态可调的功能,因此具备结构简单的优势.     

Novel FBG triangular filter for interrogating a FBG sensor in dynamic strain measurement

In recent years ,fiber Bragg gratings (FBGs) have at-tracted great considerationsinsensor applications .Inad-dition to the advantages of optical fiber sensors ,e.g.small size and i mmune to electromagnetic interference,FBGs possess flexible multiplexing c…     

Performance evaluation of prechirped RZ and CS-RZ formats inhigh-speed transmission systems with dispersion management

This paper describes the transmission performance of prechirped return-to-zero (RZ) and prechirped carrier-suppressed return-to-zero (CS-RZ) signals over a periodically dispersion-compensated transmission line. We analyze the transmission characteristics of both formats, taking account the transmitter configuration expected, in which pulse chirping is generated by using both a phase modulator and a linear dispersion compensating device. We also discuss the dependence of the transmission characteristics on phase modulation, pre- and postcompensating dispersion, and receiver optical and electrical filter widths. We show that, in single-channel transmission, phase modulation effectively reduces the intrachannel nonlinear interaction and improves the transmission performance. Next, we discuss the transmission characteristics of chirped RZ and chirped CS-RZ signals in dense wavelength division multiplexed (DWDM) signal transmission. In 100-GHz spaced 40-Gb/s-per-channel systems, it is shown that the phase modulation must be carefully optimized in order to minimize the linear crosstalk and waveform distortion induced by the intra- and interchannel nonlinear interaction in the transmission fiber     

Design of High-Channel-Count Multichannel Fiber Bragg Gratings Based on a Largely Chirped Structure

We propose a novel technique to design a high-channel-count, multichannel fiber Bragg grating (FBG) based on a largely chirped structure. The minimization of refractive-index modulation has been widely discussed in the previously demonstrated multichannel grating designs. The complexity of the grating structure, however, is also important from the point of view of practical fabrication. In this paper, the degree of grating complexity (DGC) is defined. We show that the DGC of a multichannel grating can be significantly reduced by designing a grating with a largely chirped structure. A detailed grating design process based on this technique is discussed, by which four multichannel gratings are designed and numerically studied, for applications such as periodic and nonperiodic spectral filtering, chromatic dispersion compensation and dispersion slope compensation. The proposed theory and examples show that different gratings with high-channel-count and multichannel responses can be designed and fabricated using a single commercially available phase mask, and all the gratings can be realized by a conventional FBG fabrication facility since the gratings have a low DGC with low index modulation.      

一种新型FBG动态应变解调系统

提出并演示了一种基于光纤布拉格光栅(FBG)三角形滤波器的动态应变解调系统.通过周期啁啾和折射率调制变迹,制作了FBG三角形滤波器,并利用该滤波器实现了一种新型的FBG动态应变解调方案.通过与传统应变片测量结果进行比较,结果表明,该系统能够准确地实现动态应变测量.由于系统紧凑、无源,因此可被制成便携式的解调模块.     

基于卡尔曼滤波的IFM系统测量LFM信号载频方法

现代雷达广泛使用线性调频(LFM)信号,而雷达对抗侦察中传统的瞬时测频(IFM)系统却无法分析测量LFM信号的脉内频率信息,限制了IFM系统的使用.采用在IFM系统中微波鉴相器输出I、Q正交信号后加入模数转换器(ADC)和卡尔曼滤波器的方法,对传统1FM系统进行了优化改进,不但实现了对LFM信号脉内频率和调频系数的测量...     

单通带微波光子滤波器泵浦响应性能研究

基于受激布里渊散射效应和相位调制技术,实现了可调谐单通带微波光子滤波.单泵浦信号时,滤波器的频率调谐范围为0.5GHz~18.3GHz.采用一个激光器,通过外加在强度调制器上的微波信号强度调制得到泵浦信号时,滤波系统的稳定性优于两个激光器分别作光载波和泵浦信号的系统.当采用频率间隔为布里渊频移两倍的双泵浦信号时,滤波器的频率调谐范围为0.9GHz~31.3GHz.