超级信道在高速光标记交换系统中的应用研究

将利用光频梳产生的超级信道引入光标记交换(OLS)系统中。首先,通过仿真实现了能够产生60根可用谱线的光频梳,为光标记和超级信道提供了性能良好的光源;其次,搭建了超级信道光标记交换系统,使用正交频分复用(OFDM)的方法产生超级信道,得到携带1.25Gbit/s光标记的6Tbit/s的超级信道。仿真结果表明:在误码率为10-9时,超级信道各子信道和光标记的接收光功率分别为-5.3和-18.12dBm,实现了性能良好的高速光传输。     

40Gb/s长距离光纤传输系统的残余色散影响研究

伴随信息化进程的加速,WDM系统中的单信道传输速率普遍由10Gb/s扩容至40Gb/s,而单信道40Gb/s的长距离光纤传输系统对残余色散要求更为苛刻.就40Gb/s的WDM系统中的残余色散分别对MODB、CSRZ、DPSK和DQPSK光信号调制方式的影响进行了研究,发现残余色散大小对这4种光调制技术产生了不同的影响,并且DQPSK光信号调制技术在残余色散为正时具有更大的系统Q值和OSNR更适合长距离光纤传输系统.     

37.5Gbit/s并行光发射模块的研制

制作并测试了12信道总传输速率为37.5Gbit/s的高速并行光发射模块,其中单信道传输速率为3.125Gbit/s.模块采用波长为850nm的垂直腔面发射激光器(VCSEL)作为光源.耦合过程采用了一种利用倒装焊设备进行激光器阵列与列阵光纤之间的无源对准耦合的方法.在单信道8mA的工作电流下,可以得到3.125Gbit/s的清晰眼图.     

37.5Gbit/s并行光发射模块的研制

制作并测试了12信道总传输速率为37.5Gbit/s的高速并行光发射模块,其中单信道传输速率为3.125Gbit/s.模块采用波长为850nm的垂直腔面发射激光器(VCSEL)作为光源.耦合过程采用了一种利用倒装焊设备进行激光器阵列与列阵光纤之间的无源对准耦合的方法.在单信道8mA的工作电流下,可以得到3.125Gbit/s的清晰眼图.     

40Gbit/s甚短距离并行光发送模块的研制

基于VCSEL激光器阵列,设计和制作了一种12信道的40 Gbit/s甚短距离并行光发送模块。模块单信道传输速率大于3.5 Gbit/s,12信道并行总传输速率高达40 Gbit/s。并行光发送模块以其高速率、高集成度以及低成本等特点,为短距离高速率并行光传输提供最具竞争力的解决方案之一。     

一种基于SOA的XGM效应构成的XOR光逻辑门实现光标记交换的方法

提出了一种基于半导体光放大器(SOA)的交叉增益调制(XGM)效应构成异或(XOR)光逻辑门实现光标记交换的方法,并将该方法应用于载荷采用DPSK调制/光标记采用ASK调制的正交调制光标记交换系统中,以此来验证其可行性。通过仿真,在载荷信息速率为10Gbit/s,标记信息速率为2.5Gbit/s的非归零码DPSK/ASK正交调制光标记交换系统中实现了标记交换。     

16QAM/PPM光标记交换系统的仿真研究

提出一种脉冲位置调制光标记(PPM)与正交幅度调制(QAM)净荷相结合的光标记交换系统。利用仿真对携带40Gbit/s 16QAM净荷和2.5Gbit/s 2PPM标记的系统传输特性进行验证。通过优化系统频率间隔,得到BER=10-9时,标记和净荷的接收灵敏度与光信噪比(OSNR)分别为-28.51dBm/13.65dB和-22.03dBm/15.02dB。经96km光纤传输后,传输代价均未超过1.5dB。结果证明:16QAM/2PPM光标记交换系统具备良好的传输特性。     

多跳相干探测光谱幅度码标记交换系统传输特性分析

提出了一种基于标记栈技术的两跳相干探测光谱幅度码(SAC)标记交换系统.利用仿真软件,搭建了包含两个转发节点、两个156 Mb/s光谱幅度码标记、与40 Gb/s差分正交相移键控(DQPSK)净荷的光标记交换系统.利用接收光功率与光信噪比(OSNR)分析系统传输性能,并得到结论:经两个节点传输后,标记与净荷产生的功率代价与OSNR代价均未超过3 dB.     

40 Gbit/s WDM系统技术与应用前景展望

单信道传输速率40Gbit/s的波分复用系统是目前研究的热点.文章介绍了其现状,分析了其关键技术中的高速电信号处理、光信噪比、色散及色散斜率补偿、数据调制格式、偏振模色散补偿等,探讨了其实用化面临的问题,并展望了其应用前景.     

基于半导体光放大器频移的色散监测方法研究

利用半导体光放大器产生的频移效应监测单信道传输速率40 Gbit/s、CSRZ的高速光纤通信系统的残余色散.通过仔细选择光纤光栅滤波器的带宽和中心波长,可以实现色散监测系统性能的优化.动态色散监测系统的色散监测范围为±60 ps/nm,监测精度优于5 ps/nm,能够满足单信道速率为40 Gbit/s的CSRZ系统动态色散监测的要求.     

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

A 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode (APD) array. The mean breakdown voltage of the APD was 57.9 V and the standard deviation was less than 0.1 V. The mean dark current was /spl sim/2 and /spl sim/300 nA, and the standard deviation was /spl sim/0.19 and /spl sim/60 nA at unity gain (V/sub bias/ = 13.5 V) and at 90% of the breakdown voltage, respectively. External quantum efficiency was above 40% in the wavelength range from 1.0 to 1.6 /spl mu/m. It was /spl sim/57% and /spl sim/45% at 1.3 and 1.55 /spl mu/m, respectively. A bandwidth of 13 GHz was achieved at low gain.     

Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Highly linear Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMTs

We report an Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMT with enhanced linearity. By engineering the channel region, i.e., inserting a 6-nm-thick AlGaN layer with 5% Al composition in the channel region, a composite-channel HEMT was demonstrated. Transconductance and cutoff frequencies of a 1 /spl times/100 /spl mu/m HEMT are kept near their peak values throughout the low- and high-current operating levels, a desirable feature for linear power amplifiers. The composite-channel HEMT exhibits a peak transconductance of 150 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 12 GHz and a peak power gain cutoff frequency (f/sub max/) of 30 GHz. For devices grown on sapphire substrate, maximum power density of 3.38 W/mm, power-added efficiency of 45% are obtained at 2 GHz. The output third-order intercept point (OIP3) is 33.2 dBm from two-tone measurement at 2 GHz.     

Comparison between Pt/TiO2/Pt and Pt/TaOX/TaOY/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO₂ and TaO₂ nonvolatile memristive devices were compared and the factors that make TaO₂ memristive devices better than TiO₂ memristive devices were studied. TaO₂ memristive devices have shown better endurance performances (10⁸ times more switching cycles) and faster switching speed (5 times) than TiO₂ memristive devices. Electroforming of TaO₂ memristive devices requires~4.5 times less energy than TiO₂ memristive devices of a similar size. The retention period of TaO₂ memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO₂ and TaO₂ memristive devices. This article summarizes the reasons that give TaO₂ memristive devices the advantage over TiO₂ memristive devices, in terms of electroformation, switching speed, and endurance.     

Electrooptic ferroelectric Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films

We report on waveguiding and electrooptic properties of epitaxial Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films grown by radio-frequency magnetron sputtering on Al/sub 2/O/sub 3/(11_02) single crystal substrates. High optical waveguiding performance has been demonstrated in infrared and visible light. The in-plane electrooptic effect has been recorded in transmission using a transverse geometry. At dc fields, the effective linear electrooptic coefficient was determined to 28 pm/V, which is promising for modulator applications.