基于拉曼组合放大的长距离光纤传输系统

本文改进了一种实现长距离自适应补偿光纤传输的方法.在利用光纤光栅形成的谐振腔产生激光对信号光进行拉曼放大的基础上,再利用双抽运光对信号光进行拉曼放大,从而获得更高的拉曼增益以实现更长距离的自适应补偿光纤传输.使实验自适应补偿传输距离达125km(为目前国际上已报道的最长自适应补偿光纤传输距离).实验测量并理论分析了该长距离光纤传输系统的开关增益、放大的自发辐射噪声、噪声指数和光功率分布的特性,实验结果与理论模型符合很好.     

旋光纤喇曼放大器中ASE噪音模型及仿真计算

通过分析旋光纤喇曼放大器中信号光、抽运光的非线性薛定谔波动方程及放大自发辐射噪音特性,提出一种能同时在旋光纤喇曼放大器中产生预计波形放大自发辐射噪音,又方便计算的方法.根据放大自发辐射噪音时域特性,建立并在波动方程中加入放大自发辐射非高斯噪音模型.在考虑旋光纤双折射的非线性效应同时,通过分步傅里叶法对波动方程求解,计算了旋光纤喇曼放大器中的放大自发辐射噪音,并与实验结果吻合.     

旋光纤喇曼放大器中ASE噪音模型及仿真计算

通过分析旋光纤喇曼放大器中信号光、抽运光的非线性薛定谔波动方程及放大自发辐射噪音特性,提出一种能同时在旋光纤喇曼放大器中产生预计波形放大自发辐射噪音,又方便计算的方法.根据放大自发辐射噪音时域特性,建立并在波动方程中加入放大自发辐射非高斯噪音模型.在考虑旋光纤双折射的非线性效应同时,通过分步傅里叶法对波动方程求解,计算了旋光纤喇曼放大器中的放大自发辐射噪音,并与实验结果吻合.     

交叉增益调制型波长转换器噪声特性的研究

对基于半导体光放大器的交叉增益调制型波长转换器相向和同向两种工作方式进行了研究。实验上分别实现了两种工作方式在1550nm波段的波长转换,比较了相同外部条件下两种工作方式的噪声特性,在全面考虑放大自发辐射噪声及其消耗载流子,增益谱的色散性和有源区内部损耗等因素的基础上,运用放大器的分段模型,计算了不同条件下两种方式的输出噪声功率,结果表明：相向型工作方式受放大自发辐射噪声的影响要远大于同向工作方式,输出放大自发辐射噪声功率的大小主要取决于载流子浓度的高低,而载流子空间分布的不均匀程度则决定两种工作方式输出噪声功率的差值大小。     

纤维光学 光纤器件

TN253 2006032293抑制噪声的宽带碲基掺铒光纤放大器性能分析=Per-formance analysis of broadband EDTFA with noise sup-pression[刊,中]/周亚训(宁波大学信息科学与工程学院.浙江,宁波(315211)) ,陈芬…∥光电工程.—2006 , 33(1) .—59-62 ,76设计了一个带光隔离器的复合型宽带碲基掺铒光纤放大器(EDTFA) ,通过对该结构模型下的速率方程和光功率传输方程的数值模拟,理论研究了EDTFA在插入光隔离器后的性能变化。研究表明,通过插入光隔离器抑制反向传输的放大自发辐射( ASE)噪声,可以有效地改善宽带EDTFA的信号增益和噪声特性…     

基于自发辐射相干控制的电磁感应透明诱导无反转光放大效应

建立微波驱动基态精细结构跃迁的Λ型三能级系统,研究基于自发辐射相干控制的电磁感应透明诱导无反转光放大效应.微波场作用于基态精细结构能级之间,产生3个透明窗口,利用适当角度的自发辐射相干效应与电磁感应透明耦合,实现透明向光放大的转化.结果表明,透明转化为光放大时,激发态与基态能级之间以及两个基态能级之间均不出现粒子数反转,但在产生光放大的过程中必须经历两个基态能级出现粒子数反转的状态.调节微波场的频率失谐量可以改变基态能级上的粒子数分布,有利于无反转光放大的产生.     

激光强度起伏及相位噪声对光学双频探测的影响

针对利用光纤延时自差系统获得双频拍频光的方法,建立了激光源强度起伏和相位噪声对拍频光功率谱影响的理论模型,并基于该模型进行了数值分析和模拟。结果表明,短延时差比长延时差更有利于减小激光器的噪声干扰。当延时差小于激光相干时间时,激光线宽越大,强度起伏越大,信号的信噪比越低。当延时差远大于激光相干时间时,激光器的相位噪声成为拍频光信号展宽的主要来源,且相位噪声越大,拍频光信号功率越小;强度起伏也有一定的展宽效应,但对于拍频信号功率有增大作用。在长延时情况下,拍频光信号功率和线宽随两个频率光的延时差呈余弦规律变化,存在最佳工作点。     

基于光环路正交频分多址无源光网络的光拍频噪声避免方案及性能仿真(英文)

在正交频分多址无源光网络上行传输中,不同光网络单元的上行信号如果采用相同波长的不同激光器将会产生光拍频噪声,使得光网络单元的无色性难以实现.本文以正交频分多址无源光网络为研究对象,通过对系统结构的研究和相关公式的推导,分析了信号上行传输中光拍频噪声的产生原因和避免方式.针对下行发送上行载波结合光线路终端相干接收的光拍频噪声避免方案进行了仿真研究.分析了系统的抗色散方案以及色散累积和训练序列长度对系统性能的影响,给出了优化的参数设置,为系统实际应用提供了理论参考.     

宽带波长可调固体染料光放大的实现

对有机染料4－Dieyanomethylene-2-methjyl-6-(p-dimethylaminostyryl)-4H-pyran(DCM)掺杂的PMMA（聚甲基丙烯酸甲酯）以及DCM掺杂的PMMA／凝胶玻璃复合材料平面光波导中的放大自发辐射进行了研究。实验表明,通过合理地控制波导层的折射率及厚度,可以在较宽范围内选择放大自发辐射的波长,从而实现波长调谐,波长调谐范围可达30nm。该方法可应用于固体可调谐激光器及光放大器的宽带调谐。     

波分复用全光通信网中的放大自发辐射噪声积累效应研究

给出了一种全光通信网波长域计算机模拟方法，模拟了波分复用信号经过３个光分插复用节点后的信号及放大自发辐射积累的光谱图，并与实验结果进行了对比。计算了波分复用信号经过５０个光分插复用节点极限情况下的信噪比，结果表明放大自发辐射噪声积累造成的信噪比下降仍然可以保证接收机在１０Ｇｂ／ｓ时的误码率小于１０＾－９。这些结果可以被应用到未来国家或地区级全光通信网中。     

Double-pass ytterbium-doped fiber amplifier with high gain coefficient and low noise figure

We have proposed and demonstrated a double-pass ytterbium-doped fiber amplifier using an optical circulator and a fiber Bragg grating as reflector. When the signal has passed through the ytterbium-doped fiber once, it reflects off a 0.2-nm passive fiber Bragg grating filter. This reduces amplified spontaneous emission (ASE) noise from the first pass. The input signal light is amplified both forward and backward through ytterbium-doped fiber. With this double-pass configuration, 1053.15-nm unsaturated signal gain of 28 dB, gain coefficient of 1.1 dB/mW, and noise figure of less than 4 dB are achieved at 977-nm pump power of 68 mW. It is also found that this double-pass configure provides enhancing gain coefficient and improving noise figure by comparison with single-pass configuration.     

Spectral shaping to improve the point spread function in optical coherence tomography

We demonstrate inhibition of the sidelobes of the axial point spread function in optical coherence tomography by shaping the power spectrum of the light source with a remaining power of 4.54 mW. A broadband amplified spontaneous emission source radiating at 1565 +/- 40 nm is employed in a free-space optical coherence tomography system. The axial point spread functions before and after optical spectral shaping are presented. Results show that spectral shaping of the source can inhibit sidelobes of the point spread function up to 12.9 dB, with an associated small increase of 2.2 dB in noise floor in the far field. The effect of spectral shaping on axial resolution is demonstrated according to three metrics. Image quality improvement is also illustrated with optical coherence tomography images of an onion before and after spectral shaping.     

Brillouin-based fiber-optic distributed temperature sensor with optical preamplification

Optical preamplification has been used in a fiber-optic distributed temperature sensor based on spontaneous Brillouin scattering and the use of direct detection, resulting in improved signal-to-noise ratios. The fiber-based optical preamplifier system comprises a three-port circulator, an erbium-doped fiber amplifier with a small-signal gain of 27 dB, and a fiber Bragg grating with 47-GHz bandwidth. An improvement of 17 dB in the optical signal-to-noise ratio for the Brillouin signal is demonstrated in a 23-km sensor. The limit to the signal-to-noise ratio is attributed to spontaneous-spontaneous beat noise generated at the photodetector by amplified spontaneous emission from the optical amplifier.     

Broadband phase noise suppression in a Yb-fiber frequency comb

We report a simple technique to suppress high-frequency phase noise of a Yb-based fiber optical frequency comb using an active intensity noise servo. Out-of-loop measurements of the phase noise using an optical heterodyne beat with a cw laser show suppression of phase noise by ≥7?dB out to Fourier frequencies of 100?kHz with a unity-gain crossing of ～700?kHz. These results are enabled by the strong correlation between the intensity and phase noise of the laser. Detailed measurements of intensity and phase noise spectra, as well as transfer functions, reveal that the dominant phase and intensity noise contribution above ～100?kHz is due to amplified spontaneous emission or other quantum noise sources.     

Optimization of Optical Add-Drop Multiplexers Based on Arrayed Waveguide Gratings with Fabrication Errors for Transparent Optical Networks

A transparent optical network (TON) composed by optical add-drop multiplexers based on arrayed waveguide grating (AWG) with fabrication errors is optimized for 10 Gbit/s per channel and channel spacing of 25 GHz. The optimization takes into account the effect of inter-symbol interference, amplified spontaneous emission noise accumulation, and coherent and incoherent homodyne crosstalk. Numerical results reveal that AWG fabrication errors can have a high influence on the TON performance; however, in all investigated situations, they do not affect the AWG parameters values corresponding to the optimum AWG frequency response. This surprising behavior is due to the fabrication errors affect mainly the AWG response outside the passband for the required AWG crosstalk level. It is shown that the optimum AWG frequency response is a flat-top response with a mean amplitude response outside the passband lower than -30 dB and the switch isolation should exceed 30 dB.     

A novel method degrading the combined effect of FWM and ASE noise in WDM systems containing in-line optical amplifiers

In this paper, a novel method degrading the combined effect of four-wave mixing (FWM) and amplified spontaneous emission (ASE) noise of the amplifier on the most heavily affected channel in an equally channel spaced wavelength division multiplexing (WDM) system containing in-line optical amplifiers is proposed. FWM effect is directly related to input powers of channels. So, FWM effect can be degraded by controlling channel input powers. In the proposed method, varying the input power of each channel in an optical fiber, the output optical signal to noise ratio (OSNR) values are evaluated and input powers of all channels are optimized in order to maximize the OSNR value of the channel having the lowest OSNR. To interpret the results obtained, output OSNR values for the minimum optical input power launched to the system by each channel are also computed. Being compared to the computed results for minimum optical input powers, the lowest output OSNR value among all channels for optimized input powers shows a 5.1867 dB increase in a 5-channel system, a 3.5988 dB increase in a 9-channel system, a 3.0855 dB increase in a 15-channel system and a 1.6795 dB increase for a 21-channel system. Furthermore, output OSNR values of all channels exhibit a significant increase.     

Quality of light path with ASE noise accumulation in nonlinear optical propagation using global performance metrics

In this paper, we have targeted our investigations to the inclusion in performance evaluation of light path on the effect of amplified spontaneous emission (ASE) noise accumulated in nonlinear optical propagation. Quality of light-path transmission feasibility has been reported by using a global performance metrics, called Q-factor, optical signal-to-noise ratio (OSNR), BER, extinction ratio and nonlinear frequency shift, which takes into account the interaction between the parameters aforementioned and returns a unique value corresponding to the performance metrics.     

Evaluation of Transparent Optical Network Performance in Presence of Incoherent Homodyne Crosstalk

A simple method to evaluate the performance of transparent optical networks (TON) that takes into account the incoherent homodyne crosstalk, signal distortion, inter-symbol interference (ISI), amplified spontaneous emission (ASE) noise, and arbitrary optical and electrical filters is proposed. This method combines the effect of the incoherent homodyne crosstalk with an exhaustive Gaussian approximation for the influence of ASE noise, signal distortion, and ISI. It is shown that the incoherent homodyne crosstalk penalty depends on the ASE noise accumulated in the TON, ISI, and extinction ratio. The proposed method estimates are compared with experimental results published by other authors. Good agreement is observed for one, two, and four incoherent homodyne crosstalk signals, revealing that the proposed method provides accurate estimates even when the methods based on a Gaussian approximation for the incoherent homodyne crosstalk fail. The proposed method is used to assess the performance of a TON composed by optical add-drop multiplexers based on arrayed waveguide gratings. Results reveal that incoherent homodyne crosstalk, ASE noise, and ISI impair the TON performance and, therefore, none can be neglected in the TON design.     

有源光纤环脉冲复制器的噪声特性研究

借助半导体光放大器(Semiconductor optical amplifier,SOA)静态模型分析了有源光纤环脉冲复制器的输出放大自发辐射(Amplified spontaneous emission,ASE)噪声功率特性与环内SOA偏置电流及环内注入直流光功率之间的关系,并对环输出噪声分布的形态进行了仿真分析。用较少的实测数据点,使用插值方法对原有噪声曲线进行了快速重构。实验研究了其重构误差分布。     

Optimization of Optical Add-Drop Multiplexers Based on Arrayed Waveguide Gratings with Fabrication Errors for Transparent Optical Networks

A transparent optical network (TON) composed by optical add-drop multiplexers based on arrayed waveguide grating (AWG) with fabrication errors is optimized for 10 Gbit/s per channel and channel spacing of 25 GHz. The optimization takes into account the effect of inter-symbol interference, amplified spontaneous emission noise accumulation, and coherent and incoherent homodyne crosstalk. Numerical results reveal that AWG fabrication errors can have a high influence on the TON performance; however, in all investigated situations, they do not affect the AWG parameters values corresponding to the optimum AWG frequency response. This surprising behavior is due to the fabrication errors affect mainly the AWG response outside the passband for the required AWG crosstalk level. It is shown that the optimum AWG frequency response is a flat-top response with a mean amplitude response outside the passband lower than ?30 dB and the switch isolation should exceed 30 dB.