光纤放大器中有限增益带宽对自相似脉冲放大演化的数值研究

通过求解包含超高斯增益系数滤波项的分布增益非线性薛定谔方程,模拟研究了短脉冲在有限增益带宽指数增益光纤放大器中的自相似演化行为及其差异。结果表明脉冲在不同指数增益分布放大器中传输时都会受到增益带宽的限制。相同输入脉冲在相同长度、相同总增益的指数上升、下降和双向分布放大器中放大时,在双向分布放大器中输出能量最高,输出脉冲线性啁啾特性最好,指数下降放大器输出能量最低,输出脉冲线性啁啾特性最差,指数上升放大器居两者之间。另外,总增益相同时,无论是指数上升、下降和双向分布放大器,初始增益系数较小,输出脉冲能量较高,脉冲线性啁啾特性较好。     

Investigation of the gain regimes and gain parameters of the free electron laser dispersion equation

We compute the small signal gain curve and various gain parameters by solving numerically the generalized gain-dispersion equation of free electron lasers (FEL), which characterizes the conventional magnetic bremsstrahlung FEL, as well as a large number of other FEL devices. The model includes high gain, collective, and axial velocity spread effects, and some waveguide effects. The FEL gain regimes are investigated and presented in terms of only three universal FEL characteristic parameters. The approximative analytic gain expressions are compared to the numerical computation results, and the approximation error is computed and displayed. In the intermediate regimes (high-low gain, tenuous-collective beam, cold-warm beam), the gain parameters are given in terms of useful curves, and a heuristic approximative formula is suggested for estimating the axial velocity spread gain reduction factor in all gain regimes. We also define and compute gain bandwidth and beam quality acceptance parameters in all gain regimes.     

Extending the Gain Bandwidth of Combined Raman-Parametric Fiber Amplifiers Using Highly Nonlinear Fiber

The authors demonstrate extended flat gain bandwidth by combining Raman and parametric processes. The increase in bandwidth is accomplished by extending the Raman gain region to the longer wavelength side of the Raman gain by using parametric gain. Two different configurations of the amplifier are investigated. The associated gain and bit error performance is characterized. A gain of about 15 dB, with gain flatness of 5 dB is measured.     

一种计算OTA通用滤波器增益的简便方法

以OTA(运算跨导放大器)通用滤波器增益的计算为例,将拆环法推广到多环系统。拆环时可拆开任意一个环,其余部分视为一个无反馈系统,先求环路增益,再求前向通路增益,即可用反馈电路的基本方程求出闭环增益。强调拆分不同的反馈环,将有不同的环路增益和前向通路增益,但闭环增益不变。分析还表明,若能使拆分点把所有环路均断开,则可使环路增益、前向通路增益计算简便,从而使增益的计算更简单、实用。因此,推广的拆环法可快速计算高阶滤波器增益,适宜推广。     

双抽运光参量放大的增益特性

在相同条件下(如抽运光功率、信号光功率等),与单抽运相比,双抽运光参量放大(OPA)的增益大,增益带宽宽.由于信号光的增益特性与参量增益系数直接相关,因此,在建立高非线性光纤(HNLF)光参量放大的理论模型的基础上,对相位匹配条件、参量增益以及信号光饱和增益的特性进行了分析讨论,采用有限差分法,对增益饱和的特性进行了模拟.结果表明,参量增益和光纤参数、输入抽运光以及信号光的波长、功率有关,而信号光的饱和增益和输入抽运功率有关.     

Gain characteristics of an Er3+-doped multicomponentglass single-mode optical fiber

Experimental results on gain characteristics of an Er³⁺-doped multicomponent glass single-mode optical-fiber amplifier are reported. This amplifier shows a gain spectrum with twin gain peaks of 1.535 and 1.543 μm, providing a broadened gain bandwidth. The apparent 6-dB gain bandwidth is 12 nm. Furthermore, the signal gain of 17 dB and 15-mW pump power is realized at a signal wavelength of 1.536 μm, and a signal gain coefficient of 1.4 dB/mW is achieved     

宽带平坦L-波段掺Er光纤放大器及其增益提高

利用980nmLD前向泵浦方式,实现了L-波段信号的放大,在1560～1610nm波长范围内,小信号增益平均为11．1dB,增益波动小于1．0dB。利用插入附加泵浦激光提高增益的方法,在保持增益带宽和增益平坦度不变的情况下,分别插入-25dBm的1532和1551nm激光时,放大器的小信号增益平均为11．2dB和12．8dB。     

MIMO系统中分集增益和空间复用增益的折衷关系

论文导出了分集增益与空间复用增益间的最佳折衷关系式。该关系式为阶梯递减右连续函数,阶梯数等于接收天线数目。分集增益的取值与分组长度有关,只有当分组长度不小于发射天线数目时才能获得满分集增益。折衷关系表明,采用合适的空时编码可以同时获得分集增益和空间复用增益,但是两种增益不能同时达到最大。由最佳折衷关系可以推测一定空间复用增益时可得到的最大分集增益,以及一定分集增益时能获得的最大空间复用增益。     

多泵浦与光纤级联结合的宽带拉曼光纤放大器

针对传统光纤通信传输系统中拉曼光纤放大器(RFA)增益带宽不足、输出增益低且输出增益不平坦的问题,设计了一种多泵浦和光纤级联相结合的宽带拉曼光纤放大器。并且推导实现增益平坦输出时所用六个泵浦光和四段光子晶体光纤(PCF)对应参数满足的约束表达式,从理论上给出了一种提高放大器增益和增益带宽的同时保证较小增益平坦度的设计方法。最后通过Matlab数值模拟,所设计的宽带拉曼光纤放大器达到了增益带宽92 nm,平均增益39.95 dB,增益平坦度0.1447 dB。     

AC and DC gain tilt of erbium-doped fiber amplifiers

AC gain tilt and DC gain tilt are defined as the variable gain of an erbium-doped fiber amplifier (EDFA) with input laser wavelength chirp due to modulation, and with different static laser unmodulated wavelengths of no modulation. This paper proposes a novel experimental setup for measuring AC gain tilt. This paper also clarifies experimentally and theoretically the dependency of the AC gain tilt on the input light modulation frequency from near DC to high frequency. The measured AC gain tilt values at high frequency resemble the measured spontaneous gain tilt values for input wavelengths from 1530 to 1580 nm. The influence of the AC gain tilt effect on AM-SCM video transmission systems is evaluated     

Electrical and Optical Gain Lever Effects in InGaAs Double Quantum-Well Diode Lasers

In multisection laser diodes, the amplitude or frequency modulation (AM or FM) efficiency can be improved using the gain lever effect. To study gain lever, InGaAs double quantum-well (DQW) edge-emitting lasers have been fabricated with integrated passive waveguides and dual sections providing a range of split ratios from 1:1 to 9:1. Both the electrical and the optical gain lever have been examined. An electrical gain lever with greater than 7-dB enhancement of AM efficiency was achieved within the range of appropriate dc biasing currents, but this gain dropped rapidly outside this range. We observed a 4-dB gain in the optical AM efficiency under nonideal biasing conditions. This value agreed with the measured gain for the electrical AM efficiency under similar conditions. We also examined the gain lever effect under large signal modulation for digital logic switching applications. To get a useful gain lever for optical gain quenched logic, a long control section is needed to preserve the gain lever strength and a long interaction length between the input optical signal and the lasing field of the diode must be provided. The gain lever parameter space has been fully characterized and validated against numerical simulations of a semi-3-D hybrid beam propagation method (BPM) model for the coupled electron-photon rate equation. We find that the optical gain lever can be treated using the electrical injection model, once the absorption in the sample is known.     

一种用于GPS接收机的宽带、高增益变化范围的AGC设计

介绍了一种宽带、高增益变化范围的用于GPS接收机的模拟CMOS自动增益控电路(AGC)的设计.整个AGC环路用0.35μm CMOS工艺实现,包括可变增益运算放大器(VGA)、固定增益运算放大器(FGA)、增益控制电路和直流失调抑制电路.经过仿真验证AGC的最大增益可达80dB,增益变化范围是56dB,环路锁定时间为70μs.     

Tunable coherent optical transversal EDFA gain equalization

In this paper, we propose a fiber amplifier gain equalizer using a coherent optical transversal filter. The gain equalizer is tunable and has a bandwidth in the order of 30 nm. We also study the effects of different parameters such as input signal power pattern and the input pump power on the gain profile of the amplifier. The results show that, when the input signal power pattern changes, the amplifier does not maintain its gain profile. The gain profile has to be maintained in order to make the gain equalization effective. We show that, the pump input power can be adjusted so that the changes in the gain profile are compensated for. The gain profile varies quite slowly, hence compensation is feasible. As an example, we discuss the design of a gain equalizer for a system consisting of seven wavelength channels     

宽带拉曼光纤放大中的多泵浦源选择方法

理论分析了拉曼光纤放大谱与多波长泵浦光功率和波长的关系.考虑到泵浦光与泵浦光,泵浦光与信号光的拉曼相互作用,得出一个增益数组,增益数组就是离散的宽带拉曼光纤放大增益谱.对任何形态的宽带拉曼光纤放大增益谱,可以设定对应的增益数组,把泵浦光功率和波长组成二维坐标系,遍取坐标系中的各点,求出各组点对应的增益数组,找出最接近设定的增益数组,这组泵浦光功率及波长就是最优的解决方案.     

L-band erbium-doped fibre amplifier with clamped- and flattened-gain using FBG

A gain clamped long wavelength band erbium-doped fibre amplifier (L-band EDFA) based on a ring laser cavity is demonstrated using a fibre Bragg grating (FBG) at the output end of the amplifier. This new design provides a good gain clamping as well as a gain flattening. The gain is clamped at 16.9 dB with gain variation of less than 0.1 dB from input signal power of -40 to -18 dBm by setting the VOA=5 dB. Also, the amplifier has the flattest gain spectrum at VOA=5. The gain variation is less than 1.0 dB within the wavelength range from 1570 to 1600 nm. This gain clamped amplifier also can support a 12 channel WDM system.     

基于高斯拟合的级联光子晶体光纤拉曼放大器

为了满足超高速、大容量的光纤传输系统的需求,本文在两段光纤级联结构的基础上,分析了光子晶体光纤的拉曼增益谱并采用高斯曲线对其进行拟合,设计了一种高增益、宽带宽的拉曼光纤放大器。高斯曲线拟合完整准确地保留了光子晶体光纤的增益谱信息,同时尽可能地增加了信号的传输带宽。利用四阶龙格-库塔法对经典的拉曼耦合波微分方程进行数值求解,不仅降低了放大器的增益平坦度,也实现了高增益放大。相比于直线拟合光纤拉曼增益谱的方法,提升了系统的传输容量。通过仿真分析得到:放大器的放大带宽为61 nm,其增益高达22.8 dB,增益平坦度仅为0.42 dB。     

手动VSAT站天线接收增益的诊断测量

阐述了利用卫星信标和高增益标准喇叭天线,测量手动VSAT站天线接收增益的方法。由测量的天线接收增益计算天线接收效率,从而实现对天线发射增益进行估算。最后,给出了工程测量实例,证明了该方法的可行性,并对增益测量误差进行了分析,其均方根误差±0.28dB。     

低增益脉冲准分子激光阈值条件的研究

对于激光系统性能而言,激光工作阈值条件具有非常重要的意义。低增益、宽带脉冲 准分子激光的阈值条件和其激光泵浦脉冲有密切关系。在激光四能级系统速率方程的基础上,利用增益开关和Q开关的分析方法来研究低增益脉冲准分子激光阈值条件,给出了其在不同增益脉宽情况下一致的阈值条件。所得到的结论显示,在增益脉宽很短时,低增益准分子激光和连续激光的阈值条件完全不同,取决于时间积分增益系数要大于一临界值。     

基于光纤环形镜的增益平坦L波段掺铒光纤放大器优化设计

L波段掺铒光纤放大器（EDFA）的增益介质具有本征增益平坦特性,但平坦增益值低,放大器实用性差,因此对放大器优化设计提高平坦增益有十分重要的意义。使用光纤环形镜（FLM）作为增益平坦滤波器进行L波段掺铒光纤放大器的增益平坦化实验,实现了高增益值的平坦输出。     

Theoretical Investigation of the Gain Profile of Erbium-Doped Fiber Amplifiers

An exact analytical expression for the gain profile of erbium-doped fiber amplifiers (EDFAs) is presented. It is shown theoretically that the shape of the gain profile of an EDFA is determined by the average gain per unit fiber length. It turns out that the optimum fiber length for minimum gain differences in an arbitrary bandwidth is exactly proportional to the desired gain and to the achieved gain differences. Furthermore it is shown that an erbium-doped fiber with a special wavelength-dependent fiber background loss produces a flat gain profile for any desired gain if the optimum fiber length is chosen. An analytical expression for the required background loss is given.