Dirtortion AND Crosstalk Caused by Multipath Propagation in Frequency-Modulation Sound Broadcasting

The characteristics of multipath distortion in FM sound broadcasting were determined through computer analysis and subjective listening tests. Stereophonic multipath distortion is found to be far greater than monophonic multipath distortion, especially for long delay times. Crosstalk into stereophonic main-program reception due to multipath propagation from the SCA (Subsidiary Communications Authorization) using a 67-kHz subcarrier was also analyzed and multiplexing of the SCA is found to have a potential for causing severe crosstalk trouble. The DU ratios required to suppress the distortion and the crosstalk are provided.     

Elimination of signal distortion and crosstalk from carrier densitychanges in the shared semiconductor amplifier of multifrequency signalsources

The signals from multifrequency sources that utilize a shared semiconductor optical amplifier often exhibit distortion and crosstalk due to carrier density changes in the shared amplifier. We propose a technique that eliminates the signal distortion and crosstalk by keeping the carrier density in the shared amplifier constant via feedforward of the electrical drive signals. We demonstrate the technique using a waveguide grating router multifrequency laser     

Asymmetric, multi-conductor low-coupling structures for high-speed,high-density digital interconnects

Small inter-line spacings and high switching speeds emphasize the problems of crosstalk and coupling distortion in high-speed, high-density digital interconnects. The use of substrate compensation allows the design of structures in which crosstalk and coupling can be essentially eliminated, even for inter-line spacings of less than one center conductor width. Characteristics of this novel method are presented for both symmetric and asymmetric multiline geometries. Pulse distortion and crosstalk on a four-line, symmetric structure are analyzed, showing how crosstalk and coupling distortion are reduced by substrate compensation. Pulse distortion on symmetric coupled lines is studied, showing that it is possible to choose a substrate combination which significantly reduces coupling and crosstalk for a wide range of conductor configurations     

Detailed dynamic model for semiconductor optical amplifiers andtheir crosstalk and intermodulation distortion

An advanced dynamic model for multisection semiconductor optical amplifiers is presented. It accounts for the carrier and field distributions in the longitudinal direction as well as for the facet reflectivities. The model can handle arbitrary time-varying input signals and current modulations. The model is used to assess intermodulation distortion and crosstalk. Cascaded amplifiers are considered, and the crosstalk and intermodulation distortion due to cascaded amplifiers are found to accumulate by adding together in amplitude; this may limit the number or cascaded amplifiers in multichannel systems. Carrier-induced nonlinearities depend strongly on facet reflectivities; for 25 dB of single-pass gain, a reflectivity of 5×10^-4 will result in 3 dB excess distortion. Reduction of intermodulation distortion by use of multisection amplifiers is found to be possible only for small channel separations (<300 MHz). Simulations of 11-channel amplification showed a reduction of 13 dB in intermodulation distortion when random-phase optical carriers are applied     

Crosstalk penalities due to coherent Rayleigh noise inbidirectional optical communication systems

The statistical properties, i.e. power spectral densities and probability density functions, of the noise due to Rayleigh backscattered light and due to interference of backscattered and reflected light are derived from the autocorrelation function of the optical source field. The crosstalk penalties due to Rayleigh backscattering in single- and double-source bidirectional systems are calculated. It is shown that it is possible to realize a bidirectional system with commercially available connectors in which Rayleigh backscattering is the dominant crosstalk contribution. The measured crosstalk penalties and bit-error probabilities in a double-source bidirectional system confirm the theoretical results     

Optimizing subcarrier-multiplexed WDM transmission links

We present an analytic approach to optimizing the information capacity of a subcarrier-multiplexed wavelength-division-multiplexed optical communication link. Receiver and relative-intensity noise, clipping distortion, and crosstalk between wavelength channels due to optical nonlinearities in the fiber are the signal impairments considered.     

低串扰载流子注入型光开关的设计

针对载流子注入马赫-曾德尔干涉型光开关,提出使用输出比可调的3dB耦合器,补偿相移臂上通过载流子注入实现π相位调制所产生的吸收损耗,从而降低光开关的串扰。使用传输矩阵方法计算分析了载流子注入所伴随的吸收损耗对光开关串扰的影响,同时计算了可调3dB耦合器对光开关串扰性能的改进。计算结果表明,可调3dB耦合器的引入可以有效补偿相移臂的吸收损耗,对改善光开关的串扰性能有着明显的作用。     

2×2多模干涉光开关的设计与制作

以多模干涉耦合器为主体,通过载流子注入效应所引起的折射率改变来调整二重像之间的相位差,当折射率下降所引起的相位改变达到π相位时完成开关功能。在AlGaAs/GaAs/AlGaAs外延材料上,利用两步湿法腐蚀工艺,实际制作了2×2光开关并进行了测试。测试结果表明,工作在1.55μm波段,当注入电流达到160mA时,完成了开关功能。     

Crosstalk and its power penalty in multichannel transmission due togain saturation in a semiconductor laser amplifier

A theoretical study of channel crosstalk due to gain saturation in a laser amplifier in multichannel transmission is discussed. When the amplifier is gain-saturated, the gain of any channel is influenced by the light intensity of the other channels, which causes channel crosstalk in intensity-modulated multiplexing transmission. On-off-keying modulation systems with more than two channels are discussed. Considering the probability distribution, the power penalty due to crosstalk is presented for practical system design. Calculated examples reveal that the power penalty is dependent on both the level of gain saturation and the number of multiplexed channels     

First digital optical switch based on InP/GaInAsP double heterostructure waveguides

A Y-junction digital optical switch based on InP/GaInAsP has been realised and operated using either carrier injection or carrier depletion. the switch functions with both TE and TM polarised light. In the case of current injection, 30 mA is enough to obtain a crosstalk up to 20 dB for TM polarisation and 10 dB for TE polarisation.<>     

Channel capacity optimization of chirp-limited dense WDM/WDMAsystems using OOK/FSK modulation and optical filters

Frequency chirp in semiconductor lasers that are directly modulated through carrier injection not only induces dispersion in long-haul single-mode fiber communication systems, but also causes energy loss and signal distortion when frequency selective elements such as Fabry-Perot filters are present. This effect is significant for high-bit-rate channels in a dense wavelength-division-multiplexed system in a LAN/MAN environment which requires narrow-band filters to suppress crosstalk from adjacent channels. A simulation approach is used to determine the channel capacity in the presence of chirp and crosstalk. The results show that a minimal channel spacing of less than 37 and 10 GHz with each channel operating at 2 Gb/s using OOK and FSK, respectively, can be achieved by a dense wavelength division multiple access system. It is also shown that this system performance can be optimized through adjusting various parameters of the laser and the filter     

Experimental study on channel crosstalk due to fiber four-wavemixing around the zero-dispersion wavelength

Channel crosstalk due to fiber four-wave mixing (FWM) in multichannel systems operated around the zero-dispersion wavelength is experimentally studied. After determining the wavelength at which FWM light is most efficiently generated, the FWM efficiency is measured for possible frequency combinations which generate FWM light at that wavelength. Using these data, FWM crosstalk in multiwavelength systems is evaluated. The results show that actual crosstalk, is less than the value estimated by the theoretical model assuming the uniformly distributed chromatic dispersion for 80-km-long fibers. It is concluded that the theoretical model can be applied to system design dealing with the worst condition     

宽谱光源对CMOS阵列电串扰的影响

CMOS阵列探测器中,像素单元间的串扰会影响其成像质量。为了解不同光源对CMOS电串扰的影响,针对CMOS图像传感器的电串扰特性建立了一个分析模型,结合CMOS图像传感器的工作原理定量计算了单色光、宽谱光源入射条件下的电串扰特性。分析结果表明CMOS图像传感器的电串扰随单色光波长、宽谱光源谱宽和中心波长的增大而增大,但中心波长与单色光波长相同的宽谱光源,其对电串扰的影响大于单色光。辐照功率为600 W,单色光波长为1 064 nm,电串扰大小约为50.611 mV;宽谱光源中心波长为1 064 nm,谱宽为400 nm时,电串扰的大小约为50.914 mV,相比于单色光电串扰增加了约0.303 mV。     

Sensitivity and crosstalk study of the zero gap microlens used in 3.2 μm active pixel image sensors

The microlens has been widely applied to improve the sensitivity and to decrease the spatial crosstalk of image sensors. In order to further decrease the pixel size while improve the image quality, the zero gap microlens has been proposed to make high performance image sensors. In this paper, both the traditional microlens and zero gap microlens are fabricated using TOWER and TOPPAN processes. And their performances are compared and evaluated. The results show that the least sensitivity of the zero gap microlens has been significantly improved by more than 45.8% compared to that of the traditional microlens. The use of the zero gap microlens results in an obvious decrease of the crosstalk among blue, green and red lights. For example, the crosstalk of blue light in red light under the green irradiation has been decreases about 1.33%, and the crosstalk of red light in blue light under the blue irradiation has showed about 2.429 times decrease. Overall, the output colour image of the zero gap microlens is brighter and clearer than that of the traditional microlens. Image quality has been significantly improved due to the use of the zero gap microlens.     

Characterization of picosecond pulse crosstalk between coupledmicrostrip lines with arbitrary conductor width

The propagation and crosstalk properties of picosecond electrical pulses along coupled microstrip lines with arbitrary strip widths are investigated. The current distributions and propagation constants of the dominant c- and π-modes in these asymmetric coupled striplines are calculated using the spectral domain approach; and the full-wave analysis results obtained are incorporated into a fast Fourier transform (FFT) algorithm to simulate pulse distortion and crosstalk in the coupled transmission lines. Several samples of asymmetric coupled microstrip lines are fabricated and their characteristics are measured. The results of experiments are found to be in good agreement with those of computer simulations. For the first time, rigorous results of picosecond pulse distortion and crosstalk in asymmetric coupled transmission lines are provided     

Crosstalk reduction in arrayed-waveguide grating multiplexer/demultiplexer using cascade connection

This paper proposes a cascade-connected arrayed-waveguide grating (AWG) as a solution to the problem of crosstalk accumulation in a large-scale AWG multiplexer/demultiplexer (MUX/DEMUX) and demonstrates a 64-channel cascaded AWG module with a very low background crosstalk of less than -80 dB and a total crosstalk of about -34 dB. In this paper, the authors densely integrate 64 additional compactly designed crosstalk-suppressing AWGs whose bandwidths were carefully optimized and directly attach them to a conventional 64-channel AWG. Consequently, in addition to a very low crosstalk, a low insertion loss and a compact size without passband shape distortion are achieved with this module. Based on the performance of the cascaded AWG module, it is then estimated that it is possible to realize a 1000-channel AWG MUX/DEMUX that is free from the problem of crosstalk accumulation.     

Orthogonal Hybrid Waveguides: An Approach to Low Crosstalk and Wideband Photonic Crystal Intersections Design

A low crosstalk and wideband photonic crystal (PC) waveguide intersection design based on two orthogonal hybrid waveguides in a crossbar configuration is proposed. The finite-difference time-domain (FDTD) and coupled-mode theory (CMT) methods are used to simulate the hybrid waveguides of square lattice. The bandwidth (BW) and crosstalk of the intersection are investigated for various radii of the coupled cavities. It is shown that simultaneous crossing of the lightwave signals through the intersection with negligible interference is possible. The transmission of a 200-fs pulse at 1550 nm is simulated by using the FDTD method, and the transmitted pulse shows negligible crosstalk and very little distortion.     

耦合传输线信道传输矩阵建模及串扰抵消效果分析

针对高速互连系统中传输线上的串扰问题,基于电磁耦合理论,研究了耦合传输线信道传输矩阵的性质,建立了以下两种情况的耦合传输线信道传输矩阵模型及其矩阵分解形式,分别是：（1）考虑受扰线两边各一条相邻微带线对受扰线的串扰;（2）考虑受扰线两边各两条相邻微带线对受扰线的串扰.给出了上述两种情况下基于耦合传输线信道传输矩阵分解形式的串扰抵消方案,并利用仿真工具ADS对其进行了验证.结果表明：信号抖动和失真大幅下降,串扰抵消效果良好,并且第二种情况下的串扰抵消效果优于第一种情况.该结果说明了在基于耦合传输线信道传输矩阵进行串扰抵消时,考虑两边各两条相邻微带线的串扰效果较好,对保持高速信号完整性具有一定的实际应用价值.     

Intelligible Crosstalk Between Two FDM/FM Carriers Accessing Double Cascaded Nonlinear Amplifiers

A method of evaluating double intelligible crosstalk between two frequency division multiplexed frequency modulated (FDM/FM) carriers accessing the same earth station high-power amplifier (HPA) and satellite transponder traveling wave tube amplifier (TWTA) has been developed. The analysis takes into consideration the AM/AM and AM/PM characteristics of the two cascaded memoryless nonlinear amplifiers, and the amplitude and group delay variations of transmission paths preceding the first nonlinear amplifier and of the path between the two nonlinear amplifiers. Results of the double intelligible crosstalk evaluation show the existence of significant distortion cross terms caused by the two cascaded nonlinearities and filters, in addition to individual distortion terms by each nonlinearity. Specific illustrative examples are discussed, and some practical suggestions are given for controlling crosstalk impairment effects in satellite channels with double cascaded nonlinear amplifiers.     

彩色等离子体显示板的光串扰研究

本文提出彩色等离子体显示板的两个新参数──绝对光串扰和相对光串扰，确定其定义，并制定测试方法。着重讨论了相对光串扰与驱动电压、放电电极间距、电极宽度之间的关系。同时对用障壁抑制光串扰的效果予以初步探讨