光纤传输过程中的色散特性

基于光纤传输对于光纤通讯技术的重要意义,数值模拟光纤传输过程中的色散关系,得到随着光纤长度的增加,光纤传输中比特率减小,当入射波长为1.28μm时,光纤色散为0ps·nm<'-1>km<'-1>,研究结论为光纤传输器件设计提供理论依据.     

Optical spectroscopy of Ce 3+ ions in BaY 2 F 8 single crystals

In the present work we report on the spectroscopic properties of the Ce 3+ ion in BaY 2 F 8 single crystals. The absorption and excitation spectra of the emission centered at 340 v nm have been measured in the temperature range 15-300 v K. The 340 v nm emission consists of two broad partially overlapping bands, peaking at 324 and 347 v nm (at 15 v K), respectively. The full width at half maximum is about 0.5 v eV at room temperature. The absorption spectrum of the lowest in energy component of the f M d transition of Ce 3+ reveals at low temperature a marked vibronic structure. High resolution (0.02 v cm m 1 ) Fourier transform infrared spectroscopy in the wave number range 500-5000 v cm m 1 and in the temperature range 9-300 v K has been exploited to monitor the f level splitting. The absorption transitions from the three Stark components of the 2 F 5/2 manifold to the four of the 2 F 7/2 one, have been monitored in the wave number range 2000-3400 v cm m 1 . The wave number separation at 9 v K between the lowest level of the ground 2 F 5/2 manifold and lowest one of the 2 F 7/2 manifold is found to be 2197.47 v cm m 1 in good agreement with the splitting detected between the two components of the d M f emission.     

铋/铒共掺光纤荧光特性实验研究

分别用980nm和830nm的半导体激光器作为泵浦源激发铋/铒共掺光纤,采用前向和背向泵浦方式分析放大的自发辐射谱特性.实验结果表明:随着泵浦功率的增大,荧光强度显著增强.利用980nm半导体激光器,采用前向泵浦方式可激发以1 142nm和1 536nm为中心的两个辐射带,以1 142nm为最高辐射峰的3dB带宽是141nm,以1 536nm为最高辐射峰的3dB带宽是29nm.利用830nm半导体激光器,采用前向泵浦方式可激发以1 421nm为中心的荧光谱,3dB带宽是447nm.980nm和830nm激光器分别前向泵浦铋/铒共掺光纤时,随着光纤长度的增加,荧光先增强后减弱;分别背向泵浦铋/铒共掺光纤时,随着光纤长度的增加,荧光强度先逐渐增强后保持稳定.在25~80℃的温度范围内,铋/铒共掺光纤的荧光强度几乎不受温度的影响.使用980nm和830nm泵浦源同时激发铋/铒共掺光纤,结果表明铋/铒共掺光纤的发光中心具有相对独立性,发光范围存在部分重叠.     

Analysis of Longitudinal Mode Suppression in a Fiber Ring Laser Containing Two Optical Filters

We report the results from the characterization and optimization of a stable erbium-doped fiber ring laser that uses two optical filters. The observed laser performance and the measured longitudinal mode patterns are presented. The influence of the combination of the two optical filters on the mode suppression is evaluated. We obtained the matched condition for operation of the optical filters that most improved the laser performance. An estimate of the relative intensity noise due to the introduction of the laser in a communication system is also presented. As a consequence of the mode suppression, a sharp laser linewidth narrowing is con firmed.     

Limitations Due to Er-Doped Optical Amplifier Noise and Stimulated Raman Scattering in Optic-Frequency Division Multiplexed Communications

In this paper, system limitations of an optic-frequency division multiplexed commu nication link are evaluated due to stimulated Raman scattering and noise in erbium-doped optical fiber amplifiers. It is shown that the product of the number of optical amplifiers and the gain (i.e., total gain) are limited by a factor that depends upon the number of channels, channel spacing and required signal-to-noise ratio (bit-error-rate), etc. Thus an indefinite increase in the number of amplifiers and or amplifier gain may not extend the repeaterless distance significantly while keeping the bit-error-rate above a minimum level. Numerical results show that appropriate choice of optical amplifier gain can improve the bit-error-rate of the worst effected channel without adding significant requirements on the receiver. However, large changes in the amplifier gain cannot be allowed if the receiver dynamic range is to be kept small.     

任意波形输入脉冲光纤背向瑞利散射的研究

背向瑞利散射是光纤中一种重要的物理过程,利用该物理现象实现的光时域反射计是一种重要且常见的光纤测量设备.本文理论研究了任意波形的输入脉冲在光纤中的背向瑞利散射过程,导出了将瑞利散射看作为一种线性系统的冲激响应函数,讨论了方波与有振荡拖尾的注入脉冲的背向散射输出波形.对于方波注入,利用商用光时域反射仪表对理论进行了验证;对于有拖尾的脉冲,进行了实验研究,结果表明仿真与实验结果一致.     

光纤Fabry-Perot谐振腔的精细度对相位灵敏度的影响

分析了光纤Fabry-Perot谐振腔的工作原理及其工作点的选择问题，推导了谐振腔的光学相位灵敏度与精细度的关系，给出了理论公式及曲线，并与光纤Math-Zehnder干涉进行了对比，指出了在相位灵敏度上两者的巨大差距，证明了光纤Fabry-Perot干涉的独特优点.介绍了光纤Fabry-Perot干涉的实验系统，提出了检测及计算Fabry-Perot谐振腔有效精细度的方法，实验结果与理论仿真基本吻合.     

任意波形输入脉冲光纤背向瑞利散射的研究

背向瑞利散射是光纤中一种重要的物理过程,利用该物理现象实现的光时域反射计是一种重要且常见的光纤测量设备.本文理论研究了任意波形的输入脉冲在光纤中的背向瑞利散射过程,导出了将瑞利散射看作为一种线性系统的冲激响应函数,讨论了方波与有振荡拖尾的注入脉冲的背向散射输出波形.对于方波注入,利用商用光时域反射仪表对理论进行了验证;对于有拖尾的脉冲,进行了实验研究,结果表明仿真与实验结果一致.     

Optical 3R regeneration of 40 Gbit/s degraded data signals

A 40 Gbit/s optical 3R regenerator is proposed and demonstrated. The 3R regenerator consists of a dual-ring injection mode-locked fiber ring laser as the clock recovery module and an electroabsorption modulator (EAM) as the decision gate. The clock recovery module extracts the optical short pulse clock with low timing jitter from degraded 40 Gbit/s optical data streams, while the decision gate restores their signal quality. A numerical model describing the cross-absorption modulation effect in a bulk EAM is developed to explore the operating conditions, such as bias voltage, pump signal power. The timing jitter tolerance for the EAM optical gate is also investigated. Significantly improvement of BER is obtained from 40 Gbit/s RZ signals which are degraded by polarization mode dispersion or chromatic dispersion.     

OPA泵浦保偏光子晶体光纤产生超连续谱和非线性特性的研究

采用波长可调光参量放大器作为泵浦源,对保偏光子晶体光纤的超连续谱的产生和非线性特性进行了实验研究.将光参量放大器产生的中心波长为1.27 μm,脉宽约为250 fs,重复频率为250 kHz和单脉冲能量只有92 nJ的光脉冲耦合进0.2 m长的保偏光子晶体光纤,实验中观察到了光谱展宽和非线性效应,在1.3 μm 波长区域获得了谱宽为83 nm (1.2486 ～1.3318 μm)的超连续谱.     

基于三次样条插值的光纤F-P传感器傅里叶变换解调研究

从傅里叶变换原理入手,对不插值傅里叶变换解调和高斯频谱插值方法的误差进行了分析.介绍了三次样条插值的原理,通过三次样条插值得到输出光强信号对光频率均匀采样光谱.从光纤F-P传感器的腔长由20 μm以0.02 μm步长匀速增加至120 μm的仿真分析得出,经过三次样条插值后再进行傅里叶变换解调的精度相对频率插值法更高.在此基础上,采用美国Ocean Optics公司生产的USB2000型光谱仪和Melles Griot公司的17MAX600型光纤对准微动台(精度达0.01 μm)搭建了实验系统并进行了对比实验.结果表明,基于三次样条插值的傅里叶变换解调方法误差在0.06 μm以内.     

饱和放大情形下光纤参量放大器的增益和带宽特性研究

利用龙格库塔法数值求解非线性耦合方程,研究了单抽运光纤参量放大器在增益饱和区的增益谱特性.通过比较考虑抽运光损耗与忽略抽运光损耗增益谱的差别,分析了抽运光损耗对增益谱的影响.此外,给出了在饱和放大区,信号光的增益谱与光纤长度、输入信号光功率、抽运光波长与零色散波长偏离之间的关系.发现在饱和放大区,增益的整体水平有所下降,增益谱的可用带宽相对于小信号放大有所减少,增益谱在可用带宽范围内出现了旁瓣.这些结果将对工作在饱和放大区的单抽运光参量放大器的设计提供有益的帮助.     

基于综合光学调制技术的光纤无线双向通信系统设计

提出并研究了一种使用单光源的光纤无线双向传输系统.该系统只需在中心站配置一个可调谐激光器,以产生频率恒定的激光光源,通过综合光学调制（频率调制、强度调制）技术将基带信号调制到光载波上,最终形成60 GHz毫米波下行信号|同时,相同的光载波在基站被重用,作为上行链路传输光源.系统结合光载波重用技术和综合调制技术特点,合理利用资源,基站结构更为简化.仿真结果表明,该系统可以将速率达2.5 Gbit/s的数据在单模光纤中双向传输20 km,功率代价小于0.5 dB,相对已有的技术方案,该传输系统在传输功率、传输距离、传输性能方面具有明显优势.     

Optical implementation of (3, 3, 2) regular rectangular CC-Banyan optical network

CC-Banyan network plays an important role in the optical interconnection network. Based on previous reports of (2, 2, 3) the CC-Banyan network, another rectangular-Banyan network, i.e. (3, 3, 2) rectangular CC-Banyan network, has been discussed. First, according to its construction principle, the topological graph and the routing rule of (3, 3, 2) rectangular CC-Banyan network have been proposed. Then, the optically experimental setup of (3, 3, 2) rectangular CC-Banyan network has been designed and achieved. Each stage of node switch consists of phase spatial light modulator (PSLM) and polarizing beam-splitter (PBS), and fiber has been used to perform connection between adjacent stages. PBS features that s-component (perpendicular to the incident plane) of the incident light beam is reflected, and p-component (parallel to the incident plane) passes through it. According to switching logic, under the control of external electrical signals, PSLM functions to control routing paths of the signal beams, i.e. the polarization of each optical signal is rotated or not rotated 90° by a programmable PSLM. Finally, the discussion and analysis show that the experimental setup designed here can realize many functions such as optical signal switch and permutation. It has advantages of large number of input/output-ports, compact in structure, and low energy loss. Hence, the experimental setup can be used in optical communication and optical information processing.     

Optical Spectroscopic Study of Al 2 O 3 : Ti 3+ Under Hydrostatic Pressure

This work investigates the effect of hydrostatic pressure on the excitation, emission and lifetime of Ti 3+ - doped Al 2 O 3 in the 0-110 kbar range. The application of pressure induces band shifts that are correlated with the corresponding local structural changes undergone by the TiO 6 complex. The increase of the Stokes-shift and the reduction of the Jahn-Teller (JT) splittings under pressure are analysed in terms of a simple model based on linear electron-phonon couplings to the a_{1_{\rm g}} and the JT e g vibrational modes.     

相变前后VO2薄膜光学性质的研究

测量了玻璃、熔融石英及蓝宝石衬底上VO2 薄膜变温过程的红外透过率谱 ,对样品相变前后的光学性质进行了研究。特定温度下VO2 薄膜发生相变 ,其光学性质随之发生突变。不同衬底、不同制作工艺影响相变发生的温度以及相变前后光学性质的变化量。蓝宝石衬底上磁控溅射所得的VO2 膜 5 μm处透过率的减小量ΔT为 70 % ,相对变化ΔT TRT为 94 % ,玻璃衬底上磁控溅射所得的VO2 膜 2 5 μm处ΔT =6 4 2 % ,而ΔT TRT高达 98% ,接近于 1。     

Frequency Characterization of the Nonlinear Refractive Index in Optical Fiber

The Kerr and the electrostrictive contributions to the intensity-dependent nonlinear refractive index in optical fibers are discussed on both theoretical and experimental bases. Particular attention is devoted to the electrostrictive contribution that under particular conditions is enhanced by resonances. The resonant behavior of the electrostrictive effect is calculated, measured, and discussed for standard single-mode fibers and dispersion shifted fibers. Experimental results are also reported. Measure ments have been carried out with a simple and effective technique based on the cross-phase modulation effect that also allows one to evaluate the nonlinear refractive index at any bit rate. Electrostriction contributes 20 % to the total nonlinear refractive index but in the resonant regime becomes comparable to the Kerr effect.     

Laser excited population redistribution in the 2p3p multiplet in neon

Using neon hollow cathode lamp and employing laser optogalvanic technique, we have studied population redistribution in the 2p⁵3p multiplet. The spectra recorded in the laser energy region of 23300 cm^− 1 -23600 cm^− 1 show transitions originating from both the laser excited levels as well as from an adjacent level whose population builds up as a result of collisional deactivation. Employing the optical delay technique, we have been able to extract decay rates associated with the collisional population mixing of the p levels.     

波长转换器和光纤延迟线在WDM光分组交换中的结构设计和性能研究

介绍了两种新颖的光分组交换结构——MOD1和MOD2,用于解决分组冲突问题.其特点在于,MOD1共享了一组非简并的延迟线,而MOD2则是共享了一组简并的延迟线和波长转换器.研究表明,对于非突发业务,两种结构都只需要少量的延迟线即可获得理想的性能.此时,MOD1比MOD2更加能降低系统体积和成本.而对于突发业务,如果MOD1所共享的延迟线数量和MOD2所共享的延迟线和转换器的总数量相等,MOD2的分组丢弃率要远远低于MOD1.随着业务突发程度的增加,MOD2中的转换器数量也需要增加才能维持给定的分组丢弃率,但即使业务突发程度很高,MOD2在体积、成本和性能等三方面均可取得较理想的折衷.