一种新型的利用重构等效啁啾超结构光纤光栅消啁啾技术研究

提出了一种利用重构等效啁啾超结构光纤光栅对啁啾光脉冲进行频域消啁啾和时域脉宽压缩的方法.由于重构等效啁啾技术可实现任意物理可实现滤波特性的光纤光栅，因此所提出的新型消啁啾方法可以针对任意啁啾模型的脉冲.仿真结果表明，对于脉宽为20 ps，啁啾系数为-5，啁啾模型为线性、高斯型、洛仑兹型的啁啾高斯脉冲，其被消啁啾后时间带宽积分别由初始的225，265，250下降到0458，0708，0731，脉宽压缩效果明显.针对商业软件给出的增益开关分布反馈半导体激光器输出光脉冲的模型，实际制作相应的重构等效 关键词： 重构等效啁啾 光纤光栅 啁啾 增益开关分布反馈半导体激光器     

双用户2.5 Gb/s 100 km光码分多址传输实验

稳定性高、低成本的窄脉冲光源、高性能编解码器和具有旁瓣/噪声抑制功能的接收机是光码分多址系统实用化的3个关键模块.实验中利用增益开关脉冲光源和63 chip等效相移超结构布拉格光纤光栅相位编解码器的半边带应用,判决门限调整与宽带判决相结合的接收机实现了双用户、2.5 Gb/s 100 km传输.实验中测量了误码率与判决时刻和判决门限的关系曲线,系统在10 ps的判决时刻容限内和17%的幅度判决容限内实现了无误码传输.     

基于码移键控-光码分多址技术的光隐匿通信系统实验

为进一步提高光隐匿通信系统的安全性,提出了基于码移键控-光码分多址(CSK-OCDMA)技术的光隐匿通信方案,搭建了2.5Gb/s的实验系统。实验装置中采用低成本的分布反馈半导体激光器作为隐匿光源,宿主光源采用贴近波分复用(WDM)光网络实际的光波长转换板(OTU)。实验结果表明,隐匿信道可实现背靠背无误码传输,且隐匿信道的引入对宿主信道接收机灵敏度的影响仅为0.1dBm。在保证隐匿信道无误码传输的情况下,宿主与隐匿信号功率差最大可以达24.6dBm。加入前向纠错设备(FEC)后,实现了光隐匿通信系统100km无误码传输。     

A wideband tunable phase shifter based on orthogonal optical single-sideband

We present a novel technique to generate an orthogonally polarized optical single sideband （OSSB） generated by a tunable bandpass filter （TBF）. When the OSSB passes through the other polarization modulation （PolM） which is polarization dependent, the phase shift of the optical carrier and first-order sideband is different under different bias. As a result, a wideband tunable phase shifter is realized by adjusting the bias applied to the polarization modulator.     

Hybrid-anode structure designed for a high-performance quasi-vertical GaN Schottky barrier diode

A quasi-vertical GaN Schottky barrier diode with a hybrid anode structure is proposed to trade off the on-resistance and the breakdown voltage. By inserting a SiN dielectric between the anode metal with a relatively small length, it suppresses the electric field crowding effect without presenting an obvious effect on the forward characteristics. The enhanced breakdown voltage is ascribed to the charge-coupling effect between the insulation dielectric layer and GaN. On the other hand, the current density is decreased beneath the dielectric layer with the increasing length of the SiN, resulting in a high on-resistance. Furthermore, the introduction of the field plate on the side wall forms an metal-oxide-semiconductor (MOS) channel and decreases the series resistance, but also shows an obvious electric field crowding effect at the bottom of the mesa due to the quasi-vertical structure.     

Photonic generation of amplitude-and phase-modulated microwave signals with frequency and modulation bit-rate tunability

A photonic approach for the generation of an amplitude- and phase-modulated microwave signal with tun-able frequency and modulation bit-rate is proposed and demonstrated. Two coherent optical wavelengths are generated based on external modulation by biasing a Mach-Zehnder modulator (MZM) at the minimum transmission point to generate ±1-order optical sidebands while suppressing the optical carrier. The two sidebands are sent to a circulator and are then spectrally separated by a fiber Bragg grating notch filter. With one sideband being amplitude-modulated at another MZM and the other being phase-modulated at a phase modulator, a frequency-tunable amplitude-and phase-modulated microwave signal is generated by beating the two sidebands at a photodetector. The proposed technique is investigated theoretically and experimentally. As a result, a 20-GHz amplitude-modulated, 20-GHz phase-modulated, and 25-GHz amplitude-and phase-modulated microwave signals with tunable modulation bit-rate are experimentally generated.     

Effect of anode area on the sensing mechanism of vertical GaN Schottky barrier diode temperature sensor

Effect of anode area on temperature sensing ability is investigated for a vertical GaN Schottky-barrier-diode sensor. The current-voltage-temperature characteristics are comparable to each other for Schottky barrier diodes with different anode areas, excepting the series resistance. In the sub-threshold region, the contribution of series resistance on the sensitivity can be ignored due to the relatively small current. The sensitivity is dominated by the current density. A large anode area is helpful for enhancing the sensitivity at the same current level. In the fully turn-on region, the contribution of series resistance dominates the sensitivity. Unfortunately, a large series resistance degrades the temperature error and linearity, implying that a larger anode area will help to decrease the series resistance and to improve the sensing ability.     

Vertical GaN Shottky barrier diode with thermally stable TiN anode

Vertical GaN Schottky barrier diodes with Ti N anodes were fabricated to investigate the electrical performance. The turn-on voltage and specific on-resistance of diodes are deduced to be approximately 0.41 V and 0.98 m?·cm2, respectively.The current-voltage curves show rectifying characteristics under different temperatures from 25℃ to 200℃, implying a good thermal stability of Ti N/Ga N contact. The low-frequency noise follows a 1/f behavior due to the multiple traps and/or barrier inhomogeneous at Ti N/Ga N interface. The trapping/de-trapping between traps and Fermi level causes the slight capacitance dispersion under reverse voltage.     

基于光生编码超宽带信号的多用户通信系统

提出并验证了一种基于光学方法产生编码超宽带(UWB)信号的多用户通信系统,在发射端通过光纤直接传输用光学方法生成的UWB信号,在接收端对编码UWB信号进行相关运算,同时完成用户信息和数据信息的判决。系统具有简单扩容、易于接收、远距传输、可调谐性等优点。设计制作的多信道光纤光栅滤波器和色散光纤组合成的鉴频器是系统的核心器件。传输的信号用不同的码片组合来区分各个用户,系统只需调节激光波长来实现用户切换,产生了不同用户的光生编码UWB信号,并恢复出不同用户的信息,实现了多用户通信全过程。