输入光特性对超快非线性干涉仪开关窗口的影响

就超快非线性干涉仪(UNI)的输入光特性对其开关窗口的影响进行了数值模拟和实验研究,输入光包括控制光脉冲和探测光脉冲。在数值模拟中,调节控制光脉冲和探测光脉冲的功率及脉宽,功率越高和脉宽越窄,窗口的形状越好。在调节过程中发现控制光脉冲和探测光脉冲都存在一个最佳的功率点使窗口的形状达到最优。如果继续增大控制光脉冲功率,会使窗口的顶部倾斜,窗口形状恶化;而继续增大探测光脉冲功率,窗口的消光比开始下降。在数值模拟的基础上进行了10Gb／s的超快非线性干涉仪全光开关实验,在实验中用连续光代替探测光脉冲以观察窗口形状。通过改变控制光脉冲和连续光功率来验证它们对超快非线性干涉仪开关窗口的影响。实验表明,应选用短而强的控制光脉冲和最优功率点的连续光,这与模拟结果吻合。     

Experimental study of nonlinear switching characteristics of conventional 2 × 2 fused tapered couplers

The nonlinear switching characteristics of fused fiber directional couplers were studied experimentally. By using femtosecond laser pulses with pulse width of 100 fs and wavelength of about 1550 nm from a system of Ti:sapphire laser and optical parametric amplifier (OPA), the nonlinear switching properties of a null coupler and a 100% coupler were measured. The experimental results were coincident with the simulations based on nonlinear propagation equations in fiber by using super-mode theory. Nonlinear loss in fiber was also measured to get the injected power at the coupler. After deducting the nonlinear loss and input efficiency, the nonlinear switching critical peak powers for a 100% and a null fused couplers were calculated to be 9410 and 9440 W, respectively. The nonlinear loss parameter PN in an expression of αNL = αP/PN was obtained to be PN = 0.23 W.     

Chaotic soliton switching generation using a nonlinear micro ring resonator for secure packet switching use

We propose a new design of the secure packet switching device using the nonlinear behaviors of soliton in a micro ring resonator, where the nonlinear penalty of light traveling in the device becomes beneficial. The chaotic signals are generated by a Kerr effects nonlinear type of the input soliton pulse in a micro ring resonator, where the control input power can be used to specify the output filtering signals. Some device parameters are chosen and simulated using the proposed model. The potential of using such a device for communication security is performed and discussed. For instance, the packet switching of the chaotic encoding data increases from the chaotic signal encoding of 100 bits⁻¹. Results obtained have shown the potential of using such a proposed device for the tunable bandpass and band-stop filters, in which packet switching data can be performed and secured.     

螺旋波导压缩频率调制脉冲的初步研究

利用螺旋波导对频率调制脉冲进行压缩可大幅度提高脉冲峰值功率。利用所编Matlab程序对螺旋波导的色散特性进行了计算和分析,获得了波纹幅度和纵向周期长度等结构参数对其色散特性的影响规律;给出了脉冲功率压缩比的计算公式,对不同脉宽和频带宽度、不同频率调制形式的微波脉冲通过螺旋波导后的功率压缩比进行了计算和分析。计算表明:脉冲的频率调制形式对功率压缩比影响较大;相同频率调制形式下,脉冲长度越长,工作频带越宽,功率压缩比越高。为了获得尽可能高的功率压缩比,需对脉冲的频率变化方式进行调节,使其与螺旋波导色散特性匹配。同时还需要在高的功率压缩比和高的压缩效率之间做出权衡。计算得到,当注入脉冲的脉宽为40ns、工作频带为8.8~9.5GHz、频率调制形式与螺旋波导色散特性匹配时,功率压缩比达到了15,压缩效率约为40%。     

PIN限幅器的高功率微波单脉冲效应研究

基于PIN限幅器的等效电路模型,构建了PIN限幅器HPM效应ADS等效电路仿真模型,利用HPM注入实验和等效电路仿真相结合的方法,研究了单个微波脉冲作用下PIN限幅器的响应规律,获取了HPM作用结束后限幅器限幅持续时间与注入脉冲功率、脉宽的对应关系,并对限幅器的限幅持续过程进行了分析。仿真与实验结果表明:PIN限幅器限幅持续时间随着微波脉冲功率和脉宽的增大而变大,实验和仿真结果趋势一致,该研究使用的ADS等效电路模型可以应用于PIN限幅器的高功率微波瞬态响应特性分析研究。     

Soliton switching study using new normalized nonlinear Schrödinger equations

Soliton switching in a nonlinear directional coupler (NLDC) is studied by using new normalized nonlinear Schrödinger equations (NLSE). The resulted equations have one parameter κL_D only, this feature greatly simplifies the numerical study of soliton coupling in a NLDC, and it enables us to derive the soliton switching conditions based on numerical analysis. Numerical results show that most of the input soliton energy remains in the launched waveguide when input soliton normalized peak power is bigger than 2.5. It is contrary to the existing theoretical expectations which were derived using variational approach. The fundamental soliton switching conditions is also expressed in terms of input soliton pulse width. In addition, it is found that frequency chirp degrades soliton switching performance in a NLDC.     

基于半导体开关和LTD技术的高重频快沿高压脉冲源

采用快开通功率MOSFET,通过优化驱动电路、磁芯参数以及耦合结构,设计了基于半导体开关和直线变压器驱动源（LTD）技术的高重频快沿高压脉冲源。该脉冲源由四级LTD串联而成,可实现单次脉冲和最高频率2 MHz脉冲串输出。脉冲最高幅值约2.3 kV,上升沿约7 ns,脉宽约90 ns,下降沿约20 ns,输出电压效率约95%。该脉冲源结构紧凑,输出脉冲稳定,实现了模块化设计,可作为重频电磁脉冲模拟源使用。     

光脉冲传输的Volterra级数模型收敛性质的研究

利用级数收敛理论, 推导出了基于Volterra级数理论的非线性薛定谔方程(NLSE)半解析解的收敛性质的表达式, 得到了保证级数收敛所允许的光脉冲最大输入功率、传输距离和所用Volterra级数模型的阶数以及与光纤参数之间的关系。利用数值计算得到了在给定光纤参数的情况下, 使用不同阶数的Volterra级数时为保证级数收敛所允许的光脉冲最大输入功率和传输距离的关系曲线, 结果表明, 使用不同阶数的Volterra级数来描述光脉冲传输时, 与阶数相对应的为保证级数收敛所允许的光脉冲最大输入功率也不同, 同时脉冲的宽度和光纤的色散都对为保证级数收敛所允许的光脉冲最大输入功率有影响。     

瞬态功率光限幅实验

应用单脉冲时间分辨技术测量了富勒烯溶液瞬态功率光限幅特性。在激发波长为532nm,脉冲宽度为8ns,峰值功率密度达到180MW/cm²的条件下,其瞬态功率光限幅的开关速度约为5ns.     

Phase-induced switching in fiber nonlinear directional coupler

A numerical study of soliton switching characteristics and the maximum output coupling by the relative phase change of a control pulse is carried out for input powers, coupled coefficient and input soliton width. It is shown that input powers ratio, coupled coefficient and input soliton width play important roles in this mode of soliton switching and that these effects may lead to useful soliton switching if the relative phase of the control pulse is monitored judiciously.     

PIN限幅器电磁脉冲效应数值模拟与验证

基于电磁脉冲对半导体器件效应的电-热多物理场模型,利用Sentaurus-TCAD仿真器建立了PIN限幅器电磁脉冲效应数值模型,研究了不同峰值功率的电磁脉冲作用下限幅器的输入/输出特性,以及大功率电磁脉冲注入PIN器件热损伤阈值与脉冲宽度的关系。模拟与实验结果表明:基于器件热效应影响载流子输运过程的电-热多物理模场型,模拟限幅器在大功率电磁脉冲注入下输入/输出功率的结果与实验结果吻合较好;模拟大功率电磁脉冲注入PIN器件热损伤阈值与脉冲宽度的关系式,与Wunsch-Bell半经验关系式符合较好。     

啁啾脉冲在正常色散光纤中频域特性实验研究

对负啁啾脉冲在正常色散光纤中的频域特性进行了实验研究,并对实验结果进行了数值分析,实验和数值分析结果基本一致．     

An experimental investigation of the optical switching characteristics using an optical Sagnac interferometer incorporating one and two ring resonators

We present the use of a fiber optic Sagnac interferometer incorporating one and two fiber optic ring resonators to characterize experimentally the optical switching behaviors. These prototypes were formed by the Sagnac interferometer and serially connected to the ring resonators. The input optical signal was launched via one end of the interferometer, where the polarization control was employed to obtain the maximum optical transmission power. Results obtained have shown that the increasing in switching time (i.e. narrower spectral width) and power can be achieved.     

Tunable wavelength conversion of picosecond pulses based on cascaded sum- and difference-frequency generation in quasi-phase-matched LiNbO3 waveguides

Tunable wavelength conversion for picosecond pulses is proposed and demonstrated exploiting cascaded sum- and difference-frequency generation in quasi-phase-matched LiNbO₃ waveguides. The influences of initial pulse widths and injected pulse powers on the conversion efficiency and converted pulse width are theoretically analyzed. Arbitrarily tunable wavelength conversion is performed for the signal pulse with the temporal width of 1.57 ps and repetition rate of 40 GHz. Approximately −18.9 dB conversion efficiency and 25 nm variable region of the input signal are achieved under the lower launched signal power. The results imply that simultaneous wavelength conversion and pulse compression can be potentially obtained by using the pulsed control wave or designing longer waveguides.     

Fine control of optical pulse width via doublet gain lines

We demonstrate a general technique for realizing fine control of optical pulse width via doublet gain or loss lines. The optimized doublet gain or loss lines for fine control of optical pulse width can be designed by using an inverse design method. The preliminary experimental demonstration of fine control of optical pulse width is performed by using doublet Brillouin gain lines in an optical fiber. Tunable pulse compression or stretching ratio of 1.47–0.43 accompanying a time delay is achieved by controlling the separation between two gain lines, for an input pulse train with a 40 ns pulse width and a repetition rate of 5 MHz, in a 4 km silica fiber with a fixed pump power of 88.1 mW.     

基于全保偏八字腔结构锁模的光纤激光器及其功率放大

采用包层泵浦的全保偏八字腔结构搭建了一种脉宽可调的掺镱锁模光纤激光器,实现了中心波长为1 064nm、重复频率为4.683 MHz、脉冲宽度可调范围为0.8~5ns、对应平均功率范围为74.8~429.7mW的耗散孤子共振方波脉冲输出.腔内无需偏振控制器,仅通过调节泵浦输入即可实现锁模状态的自启动,并能够长时间保持稳定,在剧烈振动条件下亦不会失锁.采用两级光纤放大器进行功率放大,实现了100 W的平均功率输出,峰值功率高达26.68kW.     

Gain-induced soliton switching in fiber nonlinear directional coupler

With study for switching characteristics and output coupling ratio of fiber nonlinear directional couplers (NLDC), we found that the influence elements on the switching characteristics and output coupling ratio had gain of core 1 and 2, nonlinear coefficient of those, the input power and width of input soliton. We also found numerically that switching efficiencies were improved by controlling gain of core 1, different output coupling ratio would be obtained by controlling gain of core 1 or 2. And we can change the gain by changing pump power of the optical fiber amplifiers. From this, we also made fiber coupler which output coupling ratio was changeable.     

A new soliton communication band for optical networking redundancy using a Gaussian soliton generation

We present a novel communication band of the tunable multi-Gaussian soliton system, whereas the large bandwidth signals of the spatial soliton pulses can be generated after propagating within the nonlinear ring resonator system. A Gaussian pulse input with 20 ns pulse width, 2 W peak power, the center wavelength at 1300 nm is propagated into the nonlinear ring resonator system. Using the appropriate parameters relating to the practical device such as micro-ring radii, coupling coefficients, linear and nonlinear refractive index, we found that the multi-soliton pulse obtained have shown the potential of application for a new dense wavelength division multiplexing (DWDM) band. The soliton pulse width and free spectrum range of 400 and 7 fm are obtained, respectively, which can be used to increase the channel capacity in soliton communication. Furthermore, the soliton power obtained is available for system and link redundancy, where the output soliton power of 12 W is achieved.     

高功率光子晶体光纤放大器内超短脉冲的放大传输特性

由速率方程和功率传输方程得到信号脉冲平均功率和增益系数随脉冲传输距离的变化关系.利用Ginzburg-landau方程,在信号脉冲功率的不断增强和增益系数的不断变化的情况下,研究超短脉冲的传输演化特性,发现信号脉冲平均功率、能量和增益系数等参量受到色散和非线性效应的影响相对较小,而信号脉冲的峰值功率、时域和频域特性则易受到色散和非线性效应的影响.探讨了在非线性作用下,脉冲分裂和展宽等所导致的脉宽不稳定性对传输特性的影响,表明研究脉冲传输问题时,引入脉宽不稳定性有利于提高数值模拟准确度.     

基于磁隔离驱动的亚微秒高压脉冲电源

为满足不可逆电穿孔对高压纳秒脉冲电源的需求,并且突破电源模块耐压的限制,提出了一款以正极性Marx为主电路、具有ns级前沿的高重复频率的亚微秒高压脉冲电源。该脉冲电源使用光纤传输信号,经过驱动芯片放大信号后,利用磁芯变压器传递驱动信号给MOSFET。磁芯变压器给电路提供了磁隔离,使驱动电路不会受高压输出的影响,提高了电路的耐压水平。驱动电路设计简单,所需元器件较少,可提供负压偏置,使开关管可靠关断,提高电路的抗电磁干扰能力,保障电路稳定运行。此电源由16级电路构成,实验表明:在10 kΩ纯阻性负载上,当输入电压为630 V时,即可得到10 kV的高压输出。其最小脉宽为300 ns,频率1 Hz～10 kHz可调。该脉冲电源结构紧凑,能够做到输出电压、脉宽、频率可调。研究了磁芯材料和匝数对驱动脉宽的影响。结果表明:匝比的增加会影响信号脉宽,在一定的条件下,单匝电感量的差异和磁芯材料的不同对信号脉宽的影响较小。