Broad-band continuously tunable all-fiber DFB lasers

Up to 27-nm continuous tuning is demonstrated from Er/Yb all-fiber distributed-feedback (DFB) lasers using a simple tuning technique for axial extension and compression. The demonstrated devices operate with powers up to 10 dBm and remain operating in single mode over the full tuning range. Our results represents the broadest tuning-range previously reported in any DFB laser configuration and demonstrate that uniform compression tuning of long Bragg gratings is possible with high reliability     

Optically pumped continuously tunable high-pressure molecular lasers

Recent developments in the optical pumping of high-pressure molecular lasers, particularly continuously tunable high- pressure molecular lasers, are described. Included are some experimental results on optically pumped pure CO2lasers, optically pumped ultrahigh-pressure CO2-He lasers, and optically pumped N2O/CO2transfer lasers. Recent efforts to use the output from these devices for high-resolution infrared spectroscopy are also described.     

Interpretation of wavelength switching effects of widely tunable lasers

Wavelength switching dynamics of widely tunable transmitters are particularly important in switching systems for wavelength-division-multiplexing applications. By using a time-resolved spectrum technique, the wavelength switching OD behavior of a sampled grating distributed Bragg reflector laser a CD has been successfully characterized. The switching transient and related physical effects have been linked and clarified for the first time.     

An optical switching and routing system using frequency tunable cleaved-coupled-cavity semiconductor lasers

A 1 × 4 optical switch based on a frequency tunable cleaved coupled cavity (C³) laser and a grating demultiplexer is demonstrated. The switch, which can easily be expanded to a generalN times Nswitch WithNas high as 13 has a 2 ns access time with negligible crosstalk between the channels.     

一种改进的光突发交换数据信道调度算法

简单介绍了两类基于LAUC的OBS数据信道调度算法-重新调度算法和成组调度算法,分析了其优缺点.分析了在LAUC机制下产生不合理调度的原因,并在此基础上提出了一种新的改进的数据信道调度算法,可以在付出相对较小代价的情况下减少丢包率,提高信道利用率,使信道调度趋于合理.     

微电机械系统使光通讯用可调谐激光器成为可能

动态重组的下一代光纤通讯系统要求配置能将信号传输到任意波分复用通道，并能在通道中实现转换的波长可调谐激光器。目前世界各国科学家积极投入此项研究工作，正在考虑各种方案以实现工作稳定、高效率和廉价的可调谐激光器，其中就包括采用悬臂式微电子机     

High-speed continuously tunable liquid crystal filter for WDMnetworks

We describe a high-speed wavelength tunable liquid crystal filter which can be utilized as the tuning element at the receiving end of wavelength division multiaccess (WDMA) optical networks. The filter uses chiral smectic A electroclinic liquid crystals as the active cavity material in a Fabry-Perot etalon in order to obtain a microsecond switching speed. Using the commercially available BDH764E liquid crystal material, we demonstrate a tunable optical filter both in a bulk Fabry-Perot and a fiber Fabry-Perot (FFP) configuration. A bandwidth of about 0.7 mm and effective finesse of 70 were obtained in the FFP configuration. A FFP tuning range of 13 nm with a switching time of less than 10 μs were measured at the operating wavelength of 1.55 μm. A theoretical analysis of the expected filter performance in the FFP configuration is given. Diffraction in the Fabry-Perot cavity is identified as the dominant loss factor, resulting in reduced throughput and finesse broadening. It is calculated theoretically that an effective finesse of 130 and a throughput loss of 2.2 dB are achievable for a mirror finesse of 200 and a liquid crystal cavity thickness of 5 μm. A short waveguide piece is assumed to be included in the cavity. Other expected loss sources for the filter in the FFP configuration have been calculated, showing negligible effect on the filter performance     

Optical generation and distribution of continuously tunable millimeter-wave signals using an optical phase modulator

In this paper, we propose an approach to generate and distribute two wide bands of continuously tunable millimeter-wave (mm-wave) signals using an optical phase modulator and a fixed optical notch filter. We demonstrate theoretically that the odd-order electrical harmonics are cancelled and even-order electrical harmonics are generated at the output of a photodetector when the optical carrier is filtered out from the phase-modulated optical spectrum. Analysis shows that dispersion compensation is required in order to maintain the suppression of the odd-order electrical harmonics, in order to eliminate signal fading of the generated electrical signal when the optical signal is distributed using conventional single-mode optical fiber. It is experimentally demonstrated that, when the electrical drive signal is tuned from 18.8-25 GHz, two bands of mm-wave signals from 37.6 to 50 GHz and from 75.2 to 100 GHz with high signal quality are generated locally and remotely. This approach does not suffer from the direct current (dc) bias-drifting problem observed when an optical intensity modulator is used.     

Single-frequency tunable semiconductor lasers

Work on single-frequency tunable-wavelength semiconductor lasers with an external cavity based on fiber Bragg gratings formed in a single-mode optical fiber is reported. Methods for discrete and continuous tuning of the emission wavelength are considered. The described lasers emit dynamically stable radiation with a narrow linewidth (10 kHz) in the wavelength range of 635–1650 nm.     

Mid-infrared tunable quantum cascade lasers for gas-sensingapplications

The quantum cascade (QC) laser does not involve the material bandgap for the generation of light. Therefore, InP- and GaAs-based III-V semiconductor materials can now be used for the generation of long-wavelength, mid-infrared light. These materials are also straightforward to process and pattern. This is essential for the more sophisticated device geometries such as distributed feedback (DFB) lasers. DFB lasers provide a very elegant and reliable method to achieve a well-defined single-wavelength emission (called single-mode operation) as opposed to the usually multiple-mode emission of free-running Fabry-Perot resonators. QC-DFB lasers were first demonstrated in 1996. They have evolved very rapidly and have already shown great promise in many different gas-sensing applications     

主动式频谱感知的改进型信道切换算法

针对无线信道频繁切换而导致系统性能下降的问题,在传统算法的基础上,提出了改进型信道切换算法.通过信道空闲时长的预测和比较策略,在对首要用户干扰最小的前提下,对信道进行切换控制,有效降低了信道切换代价,减小了感知开销.仿真验证表明：采用改进型信道切换算法能够有效减少信道切换次数约20%.     

可调谐电子振动的固体激光器

离子晶体中掺入过镀金属离子的电子振动激光器，是一类新型的可调谐高功率红外固体激光器，其激光波段可望复盖0．5μm-5μm的光谱区。本文综述了这类激光器的发展近况，分析讨论了这类激光器及激光晶体材料的光电特性，并对今后发展的可能趋向作一评述。     

A continuously tunable sequential Stokes Raman laser

We have obtained continuously tunable coherent radiation in the1-12 mum region via sequential Raman scattering of pulsed-dye-laser radiation in hydrogen. A multiple-pass-cell was used to enhance the Raman gain and produce an overall quantum conversion efficiency of at least 45 percent in the wavelength range from 0.9 to 5μm. At 5 μm, an energy output of 1 mj in a 7 ns pulse at a 10 Hz repetition rate has been obtained. Inherent four-wave mixing initiates the sequential Stokes conversion to the infrared and produces single transverse mode (TEM00) radiation in a 0.2 cm^-1bandwidth. We have developed a nonlinear model of the process that includes the effects of diffraction, four-wave mixing, and temporal pulse shape and gives numerical outputs in agreement with experiment.     

可调谐激光器波长控制

文章介绍了可调谐激光器的波长调节及稳定控制的设计方法,并通过试验验证了其可行性.该设计由温度控制、偏置电流控制及锁波电路3部分组成,温度控制粗调波长,偏置电流控制微调波长,而锁波电路主要是针对外界温度发生变化时提供反馈.它适用于温度控制型分布反馈式 (DFB)可调谐激光器的外围电路设计.     

可调谐激光器的宽带高反射镜

选择了适当的制备工艺,并改善膜系以减弱膜内的电场强度,获得低损耗可见光区的宽带高反射镜。     

国内外通信用可调谐激光器研究进展

通信用可调谐激光器是密集波分复用系统及未来的全光网络的关键器件,将给网络带来前所未有的灵活性和动态性能。全面、详细地阐述了各种可调谐激光器的结构、特点以及调谐机制,概括了国内外通信用可调谐激光器的研究进展和发展趋势。     

固体激光器被动Q开关技术的进展

本文综合论述了固体激光被动调Ｑ技术的现状与相关材料的进展。注要有用于１μｍ波段的各种被动的调Ｑ技术以及用于１．５４μｍ及２μｍ波段的各种最新被动调Ｑ技术。     

Fast tunable wavelength conversion for all-optical packet switching

We demonstrate a simple scheme to achieve fast tunable wavelength conversion over a wide spectral range. The wavelength conversion is obtained by four-wave mixing in a semiconductor optical amplifier using a double-pump scheme, 2048-bit sequences at 2.5 Gb/s, incoming at a given wavelength, are alternatively converted toward two different wavelengths for a total conversion interval of 20 nm. With this method, the time needed to change the destination wavelength is much shorter than the bit duration. This feature makes any guard-time spacing between packets unnecessary. Bit-error-rate measurements show that the process occurs with negligible penalties (less than 0.3 dB).     

Signal structure of continuously self-pulsing GaAs lasers

CW-excited GaAs lasers can emit self-induced pulses. To study these pulses we have used an intensity correlator involving phase-matched second-harmonic generation in LiIO3. Besides measuring the pulsewidth and the repetition rate we investigated the amplitude fluctuations within a pulse and the correlation between fluctuations of consecutive pulses.     

Monolithically integrated tunable laterally coupleddistributed-feedback lasers

A new method for fabrication of tunable InGaAsP-InP single-mode lasers without epitaxial overgrowth is reported. These devices show the advantage of a considerably simplified fabrication process compared to conventional tunable laser types. The lasers comprise an active Bragg reflector integrated with an uncorrugated separately pumped gain region. By adjusting the current through the Bragg reflector, the wavelength can be tuned between 1590.8 and 1595.2 nm