一种新型低噪声掺Er光纤放大器的研究

提出了一种新型的低噪声掺Er光纤放大器(EDFA)。将光波长交错器的输入端口与普通EDFA的输出端相连接,用于降低噪声,信号光由光波长交错器的偶信道端口输出。利用光波长交错器的梳状反射特性,抑制EDFA的放大自发辐射(ASE),改善EDFA的噪声特性,使其具有低噪声的特点。采用4m长的掺Er光纤(EDF)作为增益介质,小信号功率为-26dBm时,在1530～1560nm带宽范围内,测得低噪声EDFA的噪声系数低于3.83dB,仅比噪声系数的量子极限3dB大0.83dB。     

金刚石氮-空位色心零声子线的受激辐射放大

为了解决在基于金刚石氮-空位(NV)色心的磁场高灵敏度测量中,高速获取磁场信号引起的NV色心发光强度的微小变化的技术瓶颈问题,自行设计出一套能够实现金刚石NV色心自发辐射和受激辐射信号同步测量的光学系统,并利用一个长焦距透镜收集金刚石NV色心受激辐射信号,从而尽最大可能地滤除金刚石NV色心的自发辐射信号,提高测量受激放大增益的信噪比。实验中成功观察到NV色心零声子线的受激辐射放大,分析了抽运光功率、信号光功率、抽运光偏振方向和信号光偏振方向对放大特性的影响。结果表明,通过对抽运光和信号光相关参量的优化调整,最终获得了10.5%的受激辐射增益。该研究为实现NV光放大远程磁场监测奠定了研究基础。     

用于检测1/f电噪声的低噪声放大器设计与仿真

1/f低频电噪声是评估半导体器件质量和寿命的一个重要因素。由于1/f低频电噪声极其微弱,为了检测它,同时最大程度降低放大器的本底噪声,低噪声放大器的设计和实现是至关重要的一个环节。针对1/f低频电噪声信号的特性,在现有低噪声放大器基础上进行优化改进,设计出一款频率极低的低噪声放大器,在0.1 Hz~100 kHz频率下具有高增益和低噪声特性。仿真结果表明,在10Hz处噪声系数达到1.80 d B。     

一种低噪声放大器的自噪声分析

本文以一种低噪声放大器为例,着重分析了电路的热噪声特性,结合理论分析计算了低噪声放大器的热噪声,利用HSPICE仿真软件对电路的热噪声进行仿真,与理论计算所得的热噪声比较。按照本设计采用的低噪声放大器的结构特点,对电路进行了优化,有效地减小了电路产生的热噪声。     

低噪声放大器的设计

一、低噪声放大器设计的基本原理和方法在设计低噪声放大器时,信号源(传感器)的参数,如信号强度、内阻大小是已知的,同时还给定了信号传输指标和低噪声指标。怎样着手设计呢?根据经验,放大器的低噪声指标是最难达到的,着重放大器的低噪声指标进行设计,可以少走弯路,尽快设计出满足各项技术要求的放大器。放大器的噪声特性是用工作带宽上等效输入噪声电压来表示的。如图1所示多级放大器的噪声模型,不管有无反馈,系统等效到输入端的噪声电压都可表示为     

PMD对偏振分光OSNR监测方法的影响

偏振模色散(PMD)引起的传输信号去偏是造成偏振分光法监测光信噪比(OSNR)准确性下降的主要因素.研究了偏振模色散对信号和放大的自发辐射(ASE)噪声功率测量的影响,推导得出了误差计算公式并通过仿真实验得到验证.理论分析和仿真实验结果均表明:测量误差随着PMD的增大而增大,当差分群时延(DGD)为80 ps时,误差达4.5 dB;测量误差还随着系统传输速率和信道自身光信噪比的提高而变大.     

宽带铋基掺铒光纤放大器的增益箝制研究

应用于动态通信网络中的光放大器需要恒定的信号增益.为此,设计了一个基于环形激光腔结构的宽带铋基掺铒光纤放大器(Bi-EDFA),进行了宽带Bi-EDFA信号增益箝制特性的理论研究.结果表明:通过将放大器输出的一个前向放大自发辐射(ASE)噪声光反馈到输入端,可以实现对1.53 μm波段传输信号的增益箝制.环路损耗越小,...     

双级双抽运结构掺铒光纤光源的分析研究

为了研究双级双抽运结构C+L波段放大自发辐射宽带光源的两级光纤长短搭配不同对输出光谱特性的影响,采用软件模拟仿真和实验验证相结合的方法,进行了理论分析和实验对比。结果表明,当第1级光纤较短、第2级光纤较长时,可实现功率为18.04mW(12.56dBm)、抽运光利用效率为13.9%、平坦度小于±3.97dB(1525nm～1600nm)的C+L波段放大自发辐射输出;当第1级光纤较长、第2级光纤较短时,可实现功率为20.07mW(13.02dBm)、抽运光利用效率为16.7%、平坦度小于±1.89dB(1525nm～1600nm)的C+L波段放大自发辐射输出。采用第1级光纤较长、第2级光纤较短的双级双抽运是一种更为理想的C+L波段放大自发辐射光源结构。     

ORCAD在HgCdTe红外探测器放大电路低噪声设计中的应用

以HgCdTe光伏型红外探测器的性能指标为基础对入射到探测器表面的辐射能量进行转换计算,并以所得的微弱电流信号为根据对探测器的前置放大电路和二级放大电路进行设计,利用仿真速度快、精度高的ORCAD仿真软件对所设计的低噪声、高增益放大电路的频率响应、电路的直流传输、温度和噪声分析等特性进行了较为全面的仿真.实验结果表明了本设计能有效放大微弱电流信号,可以在实践中验证其正确性和可行性.     

色散控制WDM孤子通信系统中的定时抖动

采用拉格朗日变分法在同时考虑本信道放大自发辐射 (ASE)噪声、相邻信道信号对本信道信号和ASE噪声等多种因素影响的情况下 ,分析了色散控制孤子的传输演化特性 ,给出了准稳态色散控制孤子传输动力学方程和定时抖动解析表达 ,并给出了三种扰动因素影响程度的比较。     

基于结构诱导人工表面等离激元的宽带低耦合电路北大核心CSCD

实现超宽带传输和超高集成度设计是微波和太赫兹电路发展的终极目标。针对以上目标,本文提出了结构诱导人工表面等离激元的概念。基于此设计并验证了具有超高局附性和超小传输常数的结构诱导人工表面等离激元电路结构,打破了传统人工表面等离激元电路对传输常数和衰减常数的限制。理论分析和数值验证表明,相较于经典人工表面等离激元,具备优异的场局附性和传输特性的结构诱导人工表面等离激元具有明显的弱色散和低耦合特性,在电路设计中可以有效减少宽带信号传输的色散失真,同时提高布线密度。     

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 in an AlGaAs Semiconductor Laser Amplifier

The noise characteristics in a Fabry-Perot (FP) cavity type semiconductor laser amplifier, biased at just below its oscillation thresh-old current, have been studied theoretically and experimentally. Quantum mechanical multimode rate equations containing a Langevin shot noise source and an input signal term were numerically solved for an exponential band-tail model with no k-selection rule. Noise power calculated using this rate equation was compared with a simpler photon statistic master equation method. The experimental results on noise power for an AlGaAs laser amplifier are in reasonable agreement with the two different theoretical predictions. Dominant noise powers in a semiconductor laser amplifier are beat noise powers between signal and spontaneous emission, and between spontaneous emission components. Noise characteristics in a Fabry-Perot cavity type laser amplifier can be improved both by the reduction of the facet mirror reflectivities and by use of an asymmetric cavity configuration with low-input and high-output mirror reflectivities. Two beat noise powers are expressed in simple analytic form by introducing an equivalent noise bandwidth and an excess noise coefficient as figures of merit in an optical amplifier.     

Noise in an AlGaAs semiconductor laser amplifier

The noise characteristics in a Fabry-Perot (FP) cavity type semiconductor laser amplifier, biased at just below its oscillation threshold current, have been studied theoretically and experimentally. Quantum mechanical multimode rate equations containing a Langevin shot noise source and an input signal term were numerically solved for an exponential band-tail model with nok-selection rule. Noise power calculated using this rate equation was compared with a simpler photon statistic master equation method. The experimental results on noise power for an AlGaAs laser amplifier are in reasonable agreement with the two different theoretical predictions. Dominant noise powers in a semiconductor laser amplifier are beat noise powers between signal and spontaneous emission, and between spontaneous emission components. Noise characteristics in a Fabry-Perot cavity type laser amplifier can be improved both by the reduction of the facet mirror reflectivities and by use of an asymmetric cavity configuration with low-input and high-output mirror reflectivities. Two beat noise powers are expressed in simple analytic form by introducing an equivalent noise bandwidth and an excess noise coefficient as figures of merit in an optical amplifier.     

Polymeric variable optical attenuator based on long range surface plasmon polaritons

Proposed is a polymeric variable optical attenuator based on long range surface plasmon polaritons (LRSPPs) along a thin metal stripe embedded in polymers. The device is operated by controlling radiation loss of the LRSPP mode resulting from the temperature gradient of the polymer cladding caused by a heater. For guiding LRSPPs and efficient coupling of singlemode fibres, gold stripes 20 nm thick, 4 /spl mu/m wide and 1 cm long are utilised. To obtain a long physical lifetime, the heater is formed on the top of the polymer cladding with a 200 nm Au film which is about ten times thicker than the thin metal waveguide. The fabricated device is characterised at a wavelength of 1.55 /spl mu/m, exhibiting high attenuation of less than 30 dB with an operating power of 100 mW. A fibre-to-fibre total insertion loss of 6.1 dB is achieved when using singlemode fibres.     

Noise properties of a Raman amplifier

We present the first measurements of the noise properties of a Raman optical amplifier. Measurements on CW Raman amplified optical signals from a 1.5-μm single frequency laser in 32 km of silica fiber, pumped by a 1.45-μm color center laser, reveals that the main noise source is the shot noise generated in the receiver due to the spontaneous Raman radiation. For signal levels down to -50 dBm, no excess noise due to the Raman process could be detected.     

ASE spectral slice gain-clamping of EDFA

An erbium-doped (Er-doped) fiber amplifier operating in the C-band is gain clamped, at about 26 dB with noise figures below 6 dB by multiple fiber Bragg gratings. These gratings are placed at the amplifier output with center wavelengths in between communication channels so that unwanted amplified spontaneous emission is removed but put to good use. A 0.5-dB gain compression point at -15 dBm of input signal powers for two simultaneous signal channels is also demonstrated.     

Experimental study on noise characteristics of a gain-saturatedfiber optical parametric amplifier

A fiber optical parametric amplifier (OPA) has a unique saturation property such that, with increase in signal input, the signal output power increases, reaches a peak level, then decreases. Around the output peak condition, a negative feedback mechanism works to suppress intensity fluctuations in the signal output. This paper experimentally studies noise characteristics of such a gain-saturated fiber OPA. Two kinds of incident signals are injected into a fiber OPA. One is intentionally fluctuated light with large excess noise and the other is excess-noise-free (or shot-noise-limited) light. It is demonstrated that the noise suppression has an effect both on the excess noise and on beat noise due to amplified spontaneous emission generated inside the amplifier     

基于SSPPs的低剖面宽带八木天线阵列设计

提出了一种基于新型人工表面等离子体激元(Spoof Surface Plasmon Polaritons, SSPPs)馈电带有引向器的低剖面宽带八木天线阵列。天线阵列包括两部分:基于人工表面等离子体激元波导的四路宽带功分器和八木天线阵列。人工表面等离子体激元具有高的场局限性,将信号束缚在人工表面等离子体激元的凹槽结构中保证了信号的高效传输,减少了传输损耗。八木天线通过进一步加载引向器结构能够实现端射辐射特性。测试结果表明:天线阵列的回波损耗在4.5 ~6.05 GHz 频率范围内小于-10 dB。天线阵列实际增益在4.5 ~ 6.05 GHz 范围内最高可达11.1 dBi。     

掺Yb3+光纤放大器的自发辐射噪声分析

为了研究掺Yb3+光纤放大器中自发辐射噪声分布情况,利用离散化的方法求解掺Yb3+)光纤放大器的速率方程,理论研究了不同的抽运方式、端面反射率、抽运功率以及有无滤波等条件下,端面抽运掺Yb3+光纤放大器中自发辐射的功率放大特性.结果表明,不同边界条件下的自发辐射功率差异较大;通过减少光纤端面的菲涅耳反射和利用滤波技术等方法,可有效抑制光纤激光放大器中自发辐射噪声的功率放大.