垂直腔面发射激光器与多模光纤的直接耦合

使用重叠积分法,从理论上研究了垂直腔面发射激光器(VCSEL)与多模光纤MMF之间的直接耦合。首先得出了具有拉盖尔一高斯函数形式的VCSEL与MMF的模场表达式,并给出了相应的模场半径的计算公式;然后利用重、叠积分公式,结合matlab的计算结果,重点研究VCSEL与MMF对准时的耦合情况,指出VCSEL和多模光纤的模场半径的匹配对耦合效率具有重要的影响;最后利用VCSEL与MMF端面坐标系变换,给出了偏心激励情况下的耦合效率公式。     

采用多模光纤透镜的光纤麦克风理论与实验研究

对现有强度调制型光纤麦克风做了分析和讨论,采用单模光纤(SMF)熔接多模光纤(MMF)的方法设计了一种新的反射式光纤麦克风。适当长度的折射率分布为抛物线形的多模光纤具有准直透镜的作用,直接熔接在单模光纤上,可以使光纤麦克风进一步微型化、成本低廉化。用单频正弦波信号做声源测试该光纤麦克风,输出正弦波电压信号与声源频率一致,振幅随声源振幅线性变化。结果表明,该结构的光纤麦克风在原理和实验上可以用于语音通信中。     

Laser Fiber Coupling with a Hyperbolic Lens (Short Papers)

Substantial improvements in the coupling efficiency from injection lasers to multimode glass fibers have been obtained by spherical lenses melted on the fiber ends. However, the spherical lens has its own drawbacks. It excites high-order modes which are slow and Iossy and it becomes less effective when used with graded index fibers such as Selfoc. This paper proposes a hyperbolic lens which, in principle, is free from these drawbacks. Several samples have been made by first grinding one end of each fiber in a wedge form and then mechanically or flame-polishing the ground surface. These preliminary samples improved the coupling efficiency by a factor of 2-5 over the simple flat-end coupling depending on the difference in the refractive indices of the core and cladding. The improvement is slightly better than that achieved by spherical lenses.     

通信用石英系多模光纤的技术发展

介绍了世界上多模光纤的技术发展历程,简述了我国多模光纤技术和产业发展状况,列表展示了IEC关于A1类多模光纤近些年三个版本标准的主要性能比较,简要介绍了我国现行的多模光纤标准,最后展望了多模光纤市场应用前景。     

2.5-Gb/s Hybrid Single-Mode and Multimode Fiber Transmission of 1.5-μm Wavelength VCSEL

We report, for the first time, a successful 2.5-Gb/s transmission performance of a 1.5-mum emission monolithic vertical-cavity surface-emitting laser (VCSEL) over hybrid links composed of 25-km-long conventional single-mode fibers (SMFs) and a 2.2-km-long 50-mum core multimode fibers (MMFs). This result suggests that 1.5-mum wavelength VCSELs can be effectively used for multigigabit-per-second transmission over hybrid links interconnecting SMF-based long-distance and (or) subscriber network lines with MMF-based local-area network lines in the future ubiquitous network era     

多模光纤出射的光通过透镜后的场分布

用部分相干光理论,研究了单模激光入射的多模光纤出射的光经透镜后,在菲涅尔衍射区内场的分布。     

传像光纤束耦接镜的设计

在光学耦接镜设计中引入衍射面,根据二元光学元件的三级像差理论,分析了衍射面初始结构参数的求解规律,通过理论计算和ZEMAX光学设计软件的优化,给出工作波长0.8～1.1 μm,焦距33 mm,光学长度为64 mm,采用一个衍射面的耦接镜设计实例.     

Coupling from Multimode to Single-Mode Linear Waveguides Using Horn-Shaped Structures

Coupling from a multimode to a single-mode linear waveguide using horn-shaped structures is investigated. The approximate coupling efficiency is found by numerical solution of coupled-mode equations that apply to the reciprocal problem, i.e., to the problem of propagation in an expanding horn. A coupling efficiency in excess of 90 percent is calculated when coupling is from the principal mode of a sample 50-mu m-wide multimode waveguide to a 3-mu m-wide single-mode guide (lambda = 0.63mu m). This efficiency results from a uniformly tapered horn whose length is on the order of 2 mm. The length can be decreased by using a shaped coupling region. One such region is found to result in a coupling length of approximately 1.6 mm.     

一种新型梯度折射率激光单模光纤耦合物镜

本文提出抛物型梯度折射率透镜用作激光单模光纤耦合物镜的设计方案。基于几何光学和光束光学理论,论述了这种设计方案的可行性。     

In-House Networks Using Multimode Polymer Optical Fiber for Broadband Wireless Services

A novel system concept is presented to transport microwave signals over an in-house multimode graded-index polymer optical fiber network, in order to feed the radio access points in high-capacity wireless LANs. By employing optical frequency multiplying, the network's intrinsically limited bandwidth is overcome. The feasibility of this concept to carry data at several hundreds of Mbit/s speed for various microwave signal formats at carrier frequencies in the tens of GHz range is shown. The concept enables cost-effective system implementation, and easy upgrading by offering data signal transparency. It can readily be integrated with other system technologies such as wired Gigabit Ethernet in a single multi-service in-house polymer optical fiber network.     

光纤放大和光孤子长途通信

本文简述十余年来光纤通信从常规系统进化至新型系统所经历的过程,传输容量Gb/s·km以每四年增大十倍的速率前进。文中着重说明长途单模光纤线路中间装置掺铒光纤放大器,实现全光传输,不用再生中继机,每一光纤放大器在0.98μm或1.48μm激光管功率的抽引下,对1.55μm信号提供增益30dB。用12个光纤放大器,可使数字速率2Gb/s传输1000km成为实用的长途通信系统。最近实验室报道表明有可能使传输容量加大至50 000Gb/s·km。文中还介绍了光孤子通信实验的进展,在设置光纤放大器的1000km光纤线路上,获得光纤似的长途通信系统,由于光纤非线性抵消了色散效应,很窄的脉冲以很高的数字速率经过越长距离的传播,仍不呈现显著的脉冲展宽,和畸变及噪声影响。这种系统对越洲的陆地线路和越洋海底光缆极为有利。     

High-Speed Multimode Fiber Transmission by Using Mode-Field Matched Center-Launching Technique

We report that the center-launching technique can be improved to selectively excite the fundamental mode of multimode fiber (MMF). This ldquomode-field matchedrdquo center-launching technique enables us to excite only the fundamental mode in the MMF and, consequently, avoid the inherent limitations imposed by the differential mode delay. We realize this mode-field matched center-launching technique simply by fusion-splicing a single-mode fiber (SMF) pigtailed transmitter to the MMF. The splicing condition is optimized to expand the core of SMF slightly so that it can match the mode field distribution of the fundamental mode of MMF. The results show that, by using this launching technique, we can achieve the transmission characteristics similar to SMF and drastically increase the bandwidth-distance product of MMF. For demonstrations, we have successfully transmitted 10- and 40-Gb/s signals over 12.2 and 3.7 km of MMF, respectively, without using any dispersion compensation techniques. We have also evaluated the robustness of the MMF link implemented by using the proposed launching technique against the mechanical perturbations such as the lateral offset between fiber connectors, fiber bending, and fiber shaking.     

Compensation of Multimode Fiber Dispersion Using Adaptive Optics via Convex Optimization

In this paper, we propose a provably optimal technique for minimizing intersymbol interference (ISI) in multimode fiber (MMF) systems using adaptive optics via convex optimization. We use a spatial light modulator (SLM) to shape the spatial profile of light launched into an MMF. We derive an expression for the system impulse response in terms of the SLM reflectance and the field patterns of the MMF principal modes (PMs). Finding optimal SLM settings to minimize ISI, subject to physical constraints, is posed as an optimization problem. We observe that our problem can be cast as a second-order cone program, which is a convex optimization problem. Its global solution can, therefore, be found with minimal computational complexity, and can be implemented using fast, low-complexity adaptive algorithms. We include simulation results, which show that this technique opens up an eye pattern originally closed due to ISI. We also see that, contrary to what one might expect, the optimal SLM settings do not completely suppress higher order PMs.     

光纤通信技术展望

在介绍目前广泛使用的光纤通信的基础上，针对波分复用的特点，分析提高光纤带宽资源的途径和影响通路数的因素，指出大量带宽资源有待于开发利用和利用有效带宽的途径，以适应未来更大容量和可持续升级的传输网络；同时对影响光通路光纤的非线性效应进行了理论分析和解决措施。未来的第三代光纤通信网络是要实现全光网络，对其中的关键单元进行了一些分析。     

Simple Reconfigurable Photonic Microwave Filter Using an Arrayed Waveguide Grating and Fiber Bragg Gratings

We demonstrate a photonic microwave finite impulse response filter with reconfiguration and tuning capabilities. The filter is based on spectral slicing of a broadband source and optical fiber as a wideband dispersive medium. An arrayed waveguide grating and fiber Bragg gratings are used to select and vary the weight of the optical taps to achieve reconfiguration and tuning     

球端面径向梯度折射率激光－单模光纤耦合透镜的设计研究

本文研究径向梯度折射率透镜用作激光二极管－单模光纤耦合透镜的结构选型，探讨平－凸、凸－平型径向梯折耦合透镜的像差特性。通过比较认为平－凸型梯折耦合透镜更为可取。     

Hybrid RF/VLC Communications Using Reconfigurable Intelligent Surfaces

In this paper, we suggest the use of Reconfigurable Intelligent Surfaces (RIS) for hybrid Radio Frequency (RF) Visible Light Communications (VLC). The signal is transmitted from a transmitter T to a relay C using RIS. RIS is implemented as a transmitter or a reflector between T and C. The relay node C decodes the received signal and transmits it to the receiver R using a VLC link. The proposed VLC/RF communications using RIS offers 20–45 dB gain with respect to conventional RF/VLC when the number of reflectors N is varied from \(N=16\) to \(N=256\).

     

用单透镜会聚多模光纤出射的YAG激光为较小光斑的分析讨论

对传输大功率Ｎｄ：ＹＡＧ激光（λ：１．０６４μｍ）的多模光纤，为能仅在单透镜聚焦下获得校小聚焦光斑，对透镜的大小和位置及光纤输出端头的形状作了计算和分析讨论。所得结论对激光加工的许多方面都有实际意义。     

V型槽侧面抽运的光学耦合模型的研究

V型槽侧面耦合是目前双包层光纤抽运光耦合的方法之一。本文提出了一种二透镜光学系统的耦合模型，并利用几何光学的ABCD矩阵分析和计算了透镜焦距与激光二极管阵列（LD—Arrays），透镜，双包层光纤（DCF）三者之间间距的关系，同时通过计算确定了V型槽所开的最佳角度。通过数值模拟计算发现透镜焦距的选取在很小范围内会引起两透镜间距的剧烈变化而且激光二极管与透镜的间距以及两透镜间的间距主要取决于靠近激光二极管那个透镜的焦距大小。本文的分析和计算对V型槽侧面抽运的光学耦合系统中透镜焦距的选取以及LD，透镜，DCF三者之间间距的设置的最优化提供了理论指导。     

Multimode Fiber Devices for Optical Fiber Links, Printing, and Display

It is generally agreed that multimode graded index fiber has become the main fiber technology for optical communication applications. Multimode graded index fibers provide sufficient bandwidth for most applications without the critical tolerances of single mode fibers. In this paper, multimode fiber devices and components based on packaging miniaturized optical components for a GaAs laser array source package, and multichannel waveguides will be discussed. Experimental results, fabrication process and technology limitation for some of the multimode devices will be included. One major drawback of using multimode fibers is the difficulty to obtain simple and efficient switches and taps which are essential for data bus or other optical links. Some possible solutions for multimode fiber switches with miniaturized bulk wave devices will be presented.