Less than 5-ns wavelength switching with an SG-DBR laser

We achieve fast wavelength switching between all channel combinations of a 64-channel sampled-grating distributed Bragg reflector laser in less than 5 ns. The laser was designed to have low tuning currents and efficient heat extraction in order to reduce parasitic thermal effects. We also report on the behavior of the front and back mirror pre-emphasis amplitudes required for the fast switching.     

All-optical switching using color centers in an irradiated phosphorus-doped fiber

We report on all-optical switching of a 900-nm signal in a two-mode silica fiber based upon a resonant nonlinearity introduced by phosphorus color centers in a 22-cm irradiated P/sub 2/O/sub 5/-SiO/sub 2/ fiber. Full switching was observed with only 1 /spl mu/J of absorbed 532-nm pump energy, with a projected response time under 10 ns. This switch required a peak power two orders of magnitude lower than for a fiber Kerr effect device operated under identical conditions.     

Raman-assisted femtosecond soliton switching and wavelength demultiplexing with optical fiber rocking filters

We analyze the femtosecond polarization and wavelength-dependent nonlinear switching response of birefringent fiber rocking filter. We show by perturbation theory and numerical simulations that, in the presence of the Raman self-frequency shift, the soliton switching efficiency may be optimized by injecting pulses in the fast fiber axis and with a negative wavelength offset from the center of the filter bandpass.     

Nonlinear switching of optical pulses in fiber Bragg gratings

We study numerically the nonlinear switching characteristics of optical pulses transmitted though fiber Bragg gratings. We consider both the uniform and phase-shifted gratings and compare their performance as a nonlinear switch. The nonlinear coupled-mode equations were solved numerically to obtain the pulse-switching characteristics. The steady-state behavior known to occur for continuous-wave optical beams is realized only for pulses wider than 10 ns with long tails. For pulsewidths in the range 0.1-1 ns, the use of phase-shifted gratings reduces the switching threshold, but the on-off contrast is generally better for uniform gratings. We also quantify the effects of rise and fall times associated with an optical pulse on nonlinear switching by considering the Gaussian pulses with smooth tails and nearly rectangular pulses with sharp leading and trailing edges.     

Fast switching gate driver for self resonant inverters applicableto electronic ballasts

A fast switching gate driver suitable for self-oscillating resonant inverters such as electronic ballasts is presented. The proposed gate driver has negligible switching loss and driving loss owing to fast driving and zero voltage switching (ZVS) control capability. Experiments show that the gate transition time is as short as 20 ns and the switching loss is as little as one quarter of that of a conventional gate driver     

All-optical switching in 3,3'-diethyl-2,2'-thiatricarbocy-anine Iodide dye molecules

All-optical switching has been theoretically analyzed in the 3,3'-diethyl-2,2'-thiatricarbocyanine iodide(DTTCI) carbocyanine dye that exhibits large excited-state absorption to achieve high contrast and fast switching.Switching has been analyzed both ns and ps pump pulse widths.It is shown that there is an optimum value of concentration for given peak pump intensity at which maximum modulation can be achieved.We can get 93.84% modulation of transmission of a CW probe laser beam at 532 nm at peak pumping in...     

A four-channel monolithic optical/electronic selector for fastpacket-switched WDMA networks

We report the characteristics of a four-channel monolithic GaAs optical/electronic selector for applications in fast packet-switched wavelength division multiaccess networks. The selector chip consists of four metal-semiconductor-metal photodetectors sharing a single differential transimpedance amplifier selected by four enhancement-mode MESFET switches. The channel switching time is about 2 ns and no appreciable crosstalk is observed from neighboring channels     

A fast and unilateral monolithic switch for analog signals

This correspondence deals with a monolithic switch circuit for voltage-type analog signals. The circuit constitutes a unilateral, impedance buffering changeover switch, which is capable of fast signal switching (10 ns changeover time) and can handle wide-spectrum signals (dc-100 MHz). The switch introduces only a small offset (<1 mV) and causes only small (<50 mV), short lasting (<50 ns) switching spikes.     

All-optical switching in 3,3′-diethyl-2,2′-thiatricarbocyanine Iodide dye molecules

All-optical switching has been theoretically analyzed in the 3,3＇-diethyl-2,2＇-thiatricarboeyanine iodide （DTTCI） carbocyanine dye that exhibits large excited-state absorption to achieve high contrast and fast switching. Switching has been analyzed both ns and ps pump pulse widths. It is shown that there is an optimum value of concentration for given peak pump intensity at which maximum modulation can be achieved. We can get 93.84% modulation of transmission of a CW probe laser beam at 532 nm at peak pumping intensity of 500 kW/cm^2 at 763 nm, with At =1 ns and concentration of 80 μM in alcohol, resulting in switch-off and on time of 2 ns and 8 ns, respectively. The results have been also used to design all-optical NOT and the universal NOR and NAND logic gates with multiple pump laser pulses.     

室温下ZnS干涉滤光片的快速开关

本文中以连续Ar~+激光作为维持光,以脉冲Nd:YAG倍频激光作为触发光,用CW+P的方法在室温下实现了ZnS干涉滤光片的快速开关。开启时间为300ns。在理论上分析了实现快速开关的条件。     

Fast bistable wavelength switching characteristics in two-electrodedistributed feedback laser

Fast bistable wavelength switching between two longitudinal modes separated by 1.7 nm was achieved in a two-electrode distributed feedback laser with inhomogeneous excitation. As a result, a fast wavelength switching time less than 200 ps was observed in this device. In addition, high-speed repetitive wavelength switching operation up to 1 GHz was achieved. This indicates that the device is capable of repetitive wavelength switching within 1 ns, including delay time and rise time     

Nanosecond thermal fiber switch using a Sagnac interferometer

We demonstrate a new, fast, and stable all-optical fiber switch based on the TOAD principle. It utilizes a transient thermal phase shift induced by a short pump pulse to cause switching in a cobalt (Co)-doped fiber placed in a Sagnac fiber loop. Switched pulses as short as 7-ns were observed in a 2-m loop containing a 2.55-cm length of Co-doped fiber pumped with 12-ns pulses. Compared to other all-optical switches using doped fibers, this switch offers a dramatic increase in speed and stability, and a sizable reduction in fiber length requirement     

Submilliwatt optical bistability in wafer fused vertical cavity at 1.55-/spl mu/m wavelength

We report on low-power optical bistability in a vertical cavity structure at 1.55-/spl mu/m wavelength due to the bandgap resonant dispersive optical nonlinearity of InGaAsP. In this structure, a GaAs-AlAs Bragg reflector grown on GaAs and the nonlinear medium grown on InP are bonded through wafer-fusion, leading to a high-quality vertical cavity after deposition of a top dielectric mirror. This device shows interesting characteristics for optical switching applications at fiber communication wavelengths, such as a switching contrast higher than 8:1 in the reflective mode and a bistability threshold power as low as 0.6 mW. True steady-state memory effect is observed with continuous-wave input, and the device switching time is in the ns range.     

Ultrafast optoelectronic switching in CdS

Optoelectronic switching in CdS is described. The time behaviour of the switched pulse shows a fast decay of about 500 ps and a long slope of more than 3 ns in dependence on the excitation energy. Measuring the switching efficiency of the CdS switch, it was pointed out that one-proton excitation takes place. The switching efficiency as a function of the applied voltage was studied up to 400 V.     

并联双晶体高速削波快脉冲源的设计

设计了一种并联双晶体高速快脉冲源,用于激光物理实验中预脉冲的高速削波。该削波脉冲源采用升压工作模式,由光电转换模块、高压电源模块、开关器件及电路等部分组成。光电转换模块将光信号转变为开关通断信号,用于控制高压脉冲输出;集成的高压电源模块和开关器件简化了电路设计,增加了该电源的可靠性;设计合理的开关电路和元件参数,保证稳定输出符合要求的高压脉冲波形。该快脉冲源的输出脉冲幅度大于4 000 V,下降沿小于10 ns,时间抖动小于1 ns,已成功用于激光物理实验预脉冲的削波。     

Design consideration on a DBR-laser transmitter for fastfrequency-switching in an optical FDM cross-connect system

The design of a laser transmitter for fast frequency switching in an optical frequency-division-multiplexing (FDM) cross-connect system that uses tunable laser diodes and passive frequency-channel selection filters is considered. Small-signal analysis of the laser rate equation is used to estimate laser switching time. The results show that the frequency switching time depends on the allowable frequency detuning as well as the frequency spacing and the carrier lifetime. Frequency switching time is obtained from the calculation of power penalty due to the frequency detuning at the receiver section with ASK and FSK direct detection schemes. To achieve frequency switching without bit loss in the cross-connect module, switching times of 4-200 ns are required to change frequencies of 500 GHz. This suggests that a duplex transmitter configuration using two laser diodes must be employed to perform fast frequency switching and bit-error-free operation in a cross-connect system. The thermally induced frequency drift is experimentally evaluated. The feasibility of the duplex transmitter configuration is experimentally verified with a 156 Mb/s cross-connect unit     

Design and characterization of a step-recovery switching transistor

Fast rise time pulses can be generated with a special high-frequency silicon transistor structure having a collector impurity profile designed to control charge storage in the collector. When switched out of saturation it operates in a manner analogous to a step-recovery diode. The theory of operation is discussed along with the design and fabrication of the diffused impurity profiles. Its unique geometry combines planar and mesa technologies. Experimental transistors have a storage time of approximately 2-30 ns followed by a fall time as fast as 0.5 ns. The storage time can be adjusted by varying the initial base current or the driving pulse. The storage time and fall time are accurately characterized by the charge-control model. A transformer input circuit gives the best switching performance. Control devices of conventional planar structure fail to produce fast switching times. They demonstrate the failure of the charge-control model in describing the fall time of planar transistors in general.     

9kHz～1.4GHz高精度快速随机跳频DDS频率合成器

为适应微波系统对频率合成器在高频率精度、频率捷变、随机跳频等方面的要求,文中设计了一种基于DDS芯片AD9914的频率合成器。论文阐述了优化频率控制字的计算方法,结合线性反馈移位寄存器LFSR产生随机跳频点,并利用FPGA对AD9914进行软硬件控制,使该频率合成器能够达到10 ^-5 Hz的频率精度以及百纳秒内的随机扫频。测试结果表明在输出9 kHz1.4 GHz频率时,该频率源频点准确,全频带扫频且跳频切换时间为90 ns,达到了高精度捷变频的目标,应用前景广阔。     

Experimental characteristics of optical crosspoint switch matrix and its applications in optical packet switching

This paper presents the experimental results of the switching performances of the fast reconfigurable optical crosspoint switch (OXS) matrix. This paper demonstrates unicast optical packet switching for a 10-Gb/s payload at various modulation formats and a 155-Mb/s nonreturn-to-zero label. Reconfigurable time as fast as 2 ns is achieved because of the optimized control circuit and device fabrication. The power and wavelength dependence for the payload and the capability of multihop operation are investigated as well. The functionalities of the OXS acting as an optical switch and an optical buffer are demonstrated in the optical network node experiment. Very good switching property is obtained for the OXS, which clearly validates OXS as a potential technique for future high-speed Internet-protocol-over-wavelength-division-multiplexing networks.     

A high-speed low-power 4096 x 1 bit bipolar RAM

Describes a 4096-word by 1-bit TTL static bipolar RAM with a typical address access time of 25 ns and power dissipation of 350 mW. Emphasis is given to circuit techniques which made the high performance possible. These techniques are: variable impedance cell (VIC) with low standby current capable of fast switching of digit lines, cell margin increasing circuitry which increases the operating margin of the cell with low standby current, sharing of only one pair of read current sources by 64 pairs of digit lines, and Darlington word drivers causing fast switching of word lines. The process and device structure are mentioned briefly.