用于光纤通信的光放大器

在未来的光纤通信系统中,光放大器是一个重要组成部分,它可以提供直接线性光放大,也可以用来作为光开关或光信息处理系统中的非线性元件。光放大器可以分成两类,即半导体激光放大器和光纤放大器。近几年来,线性半导体激光放大器的进展较快,通常有两种半导体激光放大器,即法布     

偏振无关半导体激光放大器进展综述

能带工程的发展推动了偏振无关半导体激光放大器的不断发展。本文综述了偏振无关半导体激光放大器所采用的有源区结构，并比较了不同结构的特点，还对现在半导体光放大器中常用的器件结构作了简单介绍。     

半导体激光放大器特性及其应用前景

本文综述几种半导体激光放大器,重点介绍FP型的特性。文中还介绍了半导体激光放大器的潜在用途以及目前世界上的研究状况。     

英国进行半导体激光放大器外场试验

英国电讯局最近宣布，它已进行了半导体激光放大器的首次外场试验。该局利用位于科尔切斯特与伊普斯威奇间120公里长的光纤进行了这次外场试验，这种激光放大器置于60公里处作为中继器使用。     

量子点半导体光放大器的速率方程和增益特性

为了深入研究量子点半导体光放大器(QD-SOA)的特性,建立了量子点半导体光放大器子带导带的三能级系统模型.把系统载流子的速率方程与其他文献采用的速率方程进行了对比优化.通过数值计算得到了瞬态解,并得到载流子在放大器各能级态的浓度分布,验证了量子点中能级分立特性.利用电子和空穴各自的占有几率在基态成一定的线性关系,在稳态下对速率方程求解,得出了量子点半导体光放大器相关的增益特性,以及增益特性与基态电子的占有几率之间的关系.结果表明量子点半导体光放大器具有很高的饱和增益和微分增益,较低的阈值电流等特性.说明量子点半导体光放大器具有比其他体材料和量子阱光放大器更加优异的特性.为光放大器的设计提供了有力的理论指导.     

染料激光器泵浦的掺铒光纤放大器

光放大器可对光载波进行直接放大,省去了目前光纤通信中广泛采用的光一电、电一光转换的繁琐过程。掺杂光纤光放大器巧妙结合固体激光和光纤制适两种技术,使光放大器光纤化,克服了半导体激光放大器由于模式干扰引起的大噪声及其受温度、偏振影响大的缺陷。其中,掺铒(Er~(3+))光纤光放大器业已受到国内外广泛重视。 1989年下半年,我们用0.655μm的染料激光对4米长掺铒光纤进行反向泵浦,实现了1.54μm信号光的放大。泵浦光功率为9 dBm时,净增益为6.9dB。     

可同时产生50个波长的光纤环形激光器

加拿大Exfo电-光工程公司的科学家已演示了可同时产生50个波长的光纤环形激光器。该光纤环形激光器的 50个波长间隔为50 GHz,均匀分布在1308-1322 nm 波长之间．该光纤环形激光器基于平坦、宽增益的半导体光放大器技术,并采用掺铒光纤放大器(EDFA)作为增益介质．由于半导体光放大器的增益是非均匀的,这种非均匀展宽的多波长激光器具有更高的稳定性。     

半行波半导体激光放大器超短光脉冲响应及开关特性的实验研究

本文对半行波半导体激光放大器的脉冲响应及开关特性进行了实验研究。脉宽为27ps,重复频率为1GHz的超短光脉冲串通过放大器后脉冲无展宽。当对放大器的注入电流进行调制时,放大器可起到高速光开关的作用。     

管材激光切割过程和条纹形成模型的研究

了研究管材激光有氧切割过程和切割表面条纹形成模型。与板材激光切割一样,管材激光切割也包括非稳态和稳态两个过程,而激光加热特性和热平衡过程的建立是造成这种现象的主要原因。提出了一种基于铁和氧气扩散反应进行的管材激光切割表面条纹形成模型。     

半导体激光放大器中超短光脉冲放大过程的研究

本文对超短光脉冲在半导体激光放大器内的放大过程进行理论和实验研究，首次推导出描述这一瞬态变化过程的一系列方程组，并利用方程组进行了数值模拟求解，最后给出与理论相一致的实验结果。     

Traveling wave semiconductor laser amplifier detectors

Near-traveling-wave semiconductor laser amplifiers for amplification and detection of optical signals are discussed. Measurements of gain, responsivity, and bandwidth are presented and compared with theory. The system performance of the laser amplifier detector is evaluated by a digital transmission experiment. The importance of using low-reflectivity amplifiers with high-responsivity and weakly wavelength-dependent devices is revealed by computer simulations. The various noise contributions of the laser amplifier detector are analyzed. Expected sensitivity values are given, and it is shown that there exists an optimum amplifier gain with respect to sensitivity     

Semiconductor optical amplifiers

Reviews some of the recent advances in semiconductor laser amplifiers and highlights some of the device and system issues connected with the use of optical amplifiers. Particular attention is given to noise properties, system applications (i.e. in-line amplifiers, power amplifiers, and receiver preamplifiers), and nonlinear effects. Finally, semiconductor amplifiers are compared with fiber amplifiers     

Two-photon gain semiconductor amplifier

Semiconductors are proposed as two-photon gain media. The size of the effect and the conditions necessary to observe two-photon gain are determined by employing a low-temperature approximation that allows a simple combination of two-photon absorption theory and semiconductor laser theory. Two-photon gain amplifiers based on electrically pumped GaAs heterostructures and optically pumped InSb are discussed     

Temperature dependence of polarization characteristics in buriedfacet semiconductor laser amplifiers

The temperature dependence of gain and amplified spontaneous power for both TE and TM modes in semiconductor laser amplifiers are measured. Experiments are performed on three selected amplifier types, with higher TE, higher TM, and equal TE-TM gains, respectively. The gain differences are significantly reduced at higher temperature for the TE-dominant and TM-dominant amplifiers. For amplifiers with equal TE-TM gains, the TE and TM gains remain equal at high temperature. The measurements of the amplified spontaneous power show similar similar characteristics. More importantly, less polarization-sensitive gain characteristics can be obtained with some decrease in maximum gain by raising the operating temperature. The experimental results are explained by using the gain equations of the semiconductor laser amplifier     

Theory of signal degradation in semiconductor laser amplifiers indirect detection systems

Theoretical studies are carried out on long haul direct detection optical fiber communication systems, with inline optical semiconductor amplifier repeaters. Calculations are made of the noise, eye diagrams, and bit-error-rate characteristics of lightwave systems with optical amplifiers. Indications are given of the effect of amplifier characteristics such as spontaneous noise and signal distortion due to gain saturation on the system performance. The nonlinear process within semiconductor laser amplifiers leads generally to pulse amplitude-temporal distortions due to gain saturation. This theoretical study demonstrates that the system penalty caused by these nonlinear effects appears progressively as the optical input power at each amplifier is increased. For example, nonregenerated fiber transmission using traveling wave semiconductor laser amplifiers was simulated, and results obtained at 0.5 and 2.5 Gb/s are presented. In order to improve the system performance, the influence of structure and bulk dimensions of the amplifier cavity is also considered     

Noise and error rate performance of semiconductor laser amplifiers in PCM-IM optical transmission systems

Applications of semiconductor laser amplifiers in intensity modulated digital optical transmission systems were studied theoretically. An optical linear amplifier repeater between electronically regenerating terminal repeaters and an optical linear preamplifier in front of a photodetector in an electronically regenerating repeater are discussed. Both traveling-wave type and Fabry-Perot cavity type laser amplifiers are considered. The noise and error rate performance in these systems are evaluated using formulations for semiconductor laser amplifiers. The mean and variance in the optical amplifier output photons calculated by the photon master equation [1] is used to obtain the worst case variance in the equalized output voltage [2] for these systems. The required receiving power reduction from direct detection scheme by a preamplifier system and the repeater spacing expansion between two electronically regenerating terminals by an optical linear amplifier repeater system are delineated.     

Carrier-induced group-velocity dispersion and pulse compression in semiconductor laser amplifiers

The effect of gain dispersion on pulse amplification in semiconductor laser amplifiers is investigated theoretically. A novel phenomenon, referred to as carrier-induced group-velocity dispersion, is shown to influence considerably the amplified pulse. Chirped input pulses are predicted to be compressed in the presence of carrier-induced dispersion even when the amplifier operates far below saturation. The dependence of the compression factor on device parameters such as the pulse width, the amplifier gain, and the linewidth enhancement factor are studied using a simple analytic model. The results are important for optical communication systems as they imply that semiconductor laser amplifiers can be used to compensate simultaneously for the effects of both fibre loss and fibre dispersion when used as in-line amplifiers.<>     

Recent progress in semiconductor laser amplifiers

Recent progress in semiconductor laser amplifiers (SLAs), mainly GaInAsP traveling-wave semiconductor laser amplifiers (TWAs) for use in optical fiber transmission systems, is discussed. The status of antireflection coating on laser-diode facets which are indispensable for TWAs is discussed. Reported data on small-signal gain, signal-gain saturation, and noise are summarized and discussed in relation to active-layer parameters. Common amplification using SLAs for the amplification of various multiplexed signals, including interchannel crosstalk, is also described. A thick, short active-layer structure for a broadband high-output-power low-noise TWA with polarization-insensitive signal gain is proposed     

Influence of nondegenerate four-wave mixing on coherenttransmission system using in-line semiconductor laser amplifiers

Three-channel coherent frequency-shift-keying (FSK) transmission experiments using in-line semiconductor laser amplifiers under the influence of nondegenerate four-wave mixing in laser amplifiers are discussed. The experiments show that the effect of four-wave mixing is reduced by applying modulation to the interfering carriers and enlarging the frequency separation of each carrier. However, transmission quality degradation becomes serious in multistage amplifier systems     

注入锁定半导体激光器全光波长转换技术

波长转换器是光通信网络中的一个重要器件。而除半导体光放大器（SOA）外，半导体激光器也是进行波长变换的一种很好选择。基于半导体激光器的注入锁定波长变换技术具有转换带宽较大、啁啾小、消光比特性好、结构简单、成本低廉等诸多优点。将探测光与信号光同步注入法布里-珀罗（F-P）半导体激光器，可以通过信号光功率的变化控制激光器锁模与失锁，导致腔内纵模变化，探测光随之被共振放大或减弱，从而将信息由信号光转换到探测光频率上。从静态实验入手，对半导体激光器的注入锁定现象及光信号控制法布里-珀罗纵模移动等问题分别进行了研究。分析了动态转换激光器工作点的选取问题，在动态实验中实现了较宽范围的正相与反相波长转换，转换速率达到了10Gb／s。