Performance of High-Bitrate Multiple-Output Links Over Multimode Fiber With Intermodal Dispersion

We investigate novel transmission schemes over multimode fiber with multiple output detectors, providing more efficient utilization of the available spatial-temporal degrees of freedom of the system by combining coherent phase shift keying transmission with direct detection. We evaluate the statistics of the electrical charge generated by each detector, and its dependence on factors such as detector type, dimension and offset position. In the frequency-selective case, we reveal that temporal degrees of freedom resulting from nonoverlapping time pulses modify the decision variable statistics. We apply the ensuing model to propose a novel phase-modulated single input multiple output (SIMO) multimode fiber transmission system employing multiple detectors and multiple input multiple output (MIMO) space-time postdetection signal processing in order to mitigate the ISI stemming from intermodal dispersion.      

Representation of Intermodal Dispersion in Multimode Fiber Links

This paper analyzes statistical aspects of intermodal dispersion in multimode fiber links using a linear systems model. It is shown that the dependence of the response of a fiber section on the power distribution in the input modes leads to uncertainties in the characterization of the rms time dispersion of the section when it forms a part of a fiber link. Analytical expressions for the link dispersion in terms of three section parameters are derived, and a recursive method for computing link dispersions when these parameters are known for each section of the link is outlined. Calculations indicating the applicability of the method are also presented.     

多路数据光纤传输系统

充分利用光纤的频带资源是降低光纤数据传输系统成本的重要途径,波分复用和时分复用是信道共享和有效利用的常用方法.通常,利用CPLD实现多路信号时分复用的方式较使用多个激光器产生多个波长的激光的波分复用方式有较大的成本优势,但后者更容易实现双向通讯.因此,将波分复用和时分复用结合复用的方式即可实现一种高速、双向,点到点的光纤数据传输系统.     

Coherent Transmission Direct Detection MIMO Over Short-Range Optical Interconnects and Passive Optical Networks

Building on a recently introduced quadratic multiple-input multiple-output (Q-MIMO) channel model making use of quadratic forms instead of linear channel matrices, we explore diverse signaling formats over the Q-MIMO channel in the frequency flat regime, highlighting the unique characteristics of optical multimode fiber (MMF) systems versus their wireless counterparts. In particular, we treat multiple-input single-output multimode fiber systems, comparing them with single-input single-output MMF systems and obtaining insight into the possibility of efficiently coupling the output of an MMF into a single-mode fiber. We further treat vector amplitude modulation over MMF MIMO and study the receiver zero-forcing (ZF) technique for MMF MIMO transmission, deriving its performance and comparing with a recently introduced ZF beamforming technique based on precoding at the transmitter, which is shown to be superior to receiver ZF.      

Multimode Optical Fiber Displacement Sensor

The structure of an intensity modulation optical fiber sensor is introduced.The principle of the sensor which can detect minor displacement by use of minor curve in dark ground is described.Complex experiment shows that the multimode optical fiber not only has the abilitly of detecting the displacement of less than 0.1 nm,but also exhibits characteristics of wide dynamic range and good linearity.     

LDPC-Coded OFDM Transmission Over Graded-Index Plastic Optical Fiber Links

The possibility of 10-Gb/s transmission over graded-index plastic optical fiber (GI-POF) using the orthogonal frequency-division multiplexing (OFDM) and iteratively decodable codes is demonstrated by simulations. Several classes of low-density parity-check (LDPC) codes suitable for use in LDPC-coded OFDM transmission over GI-POF are presented as well. Several power efficient OFDM schemes are introduced     

Multimode Fiber as Random Code Generator— Application to Massively Parallel MIMO Transmission

We propose a novel multiple-input multiple-output (MIMO) scheme over multimode fiber, acting as a distributed random code generator fed by spatial codes, using silicon photonics in the transmitter and maximum-likelihood (ML) electronic detection in the receiver, providing an alternative to coarse wavelength division multiplexing (CWDM) for implementation of ultrahigh speed parallel transmission over short-range optical interconnects. The optical MIMO system utilizes mutually coherent transmission and conventional direct detection with one-bit quantization, facilitating cost-effective application to 100 Gb/s links over < 50 m.     

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。     

Viabilities of the Wavelength-Division-Multiplexing Transmission System Over an Optical Fiber Cable

This paper describes the feasibility and the applicability of the Wavelength-Division-Multiplexing (WDM) system with two types of preliminary WDM transmission experiments. Through this study, it has become clear that WDM technologies play a major role in optical fiber systems and have the possibilities of realizing the various optical fiber transmission systems.     

激光二极管线列阵与多模光纤列阵的光纤耦合

利用一段数值孔径(NA)较小的多模光纤作为一个低成本的微透镜,对激光二极管线列阵的大数值孔径方向准直,将激光二极管线列阵的输出光束耦合到多模光纤列阵中.激光二极管线列阵每个发光单元的光分别耦合到光纤列阵的单根光纤中.总的耦合效率和输出光功率分别为75%和15W.     

激光二极管线列阵与多模光纤列阵的光纤耦合

利用一段数值孔径(NA)较小的多模光纤作为一个低成本的微透镜,对激光二极管线列阵的大数值孔径方向准直,将激光二极管线列阵的输出光束耦合到多模光纤列阵中.激光二极管线列阵每个发光单元的光分别耦合到光纤列阵的单根光纤中.总的耦合效率和输出光功率分别为75%和15W.     

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.     

梯度折射率塑料光纤上的波分复用数据传输试验研究

首先介绍了梯度折射率塑料光纤的制造方法和性能;其次阐述了在梯度折射率塑料光纤上进行波分复用数据传输试验的最新研究成果。     

大芯径多模石英光纤端面耦合技术研究

对大芯径多模光纤端面耦合技术进行了研究，实验测量了光纤端面间的横向偏离、轴向偏离及光纤轴夹角对耦合效率的影响，其中光纤端面间的横向偏离对耦合效率影响较大，这些实验结果对大芯径多模光纤端面间的连接或熔接以及提高耦合效率具有一定意义。     

An Enhanced Optical Multimode Fiber Sensor Based on Surface Plasmon Resonance With Cascaded Structure

A cascaded side-polished multimode fiber sensor based on surface plasmon resonance (SPR) is proposed. The sensing area is a multimode optical fiber in which half of the core has been polished away and a 40-nm gold thin film is deposited on to the polished surface. The cascaded structure is demonstrated in the small difference variation of the refractive index between the two solutions, deionized (DI) water and phosphate buffered saline (PBS). The transmitted intensity of SPR fiber sensor in dynamic measurement between single SPR fiber structure and the cascaded structure achieved to increase the variation from 73% to 58% for DI water and 70.5% to 53% for PBS, and enhance the difference between DI water and PBS from 2.5% to 5% is obtained in the experiment. The stability and the double variation to enhance the high sensitivity of the intensity measurement is achieved to be 2 times 10^-5 refractive-index units.     

高带宽梯度折射率塑料光纤的数据传输试验

本文首先介绍了高带宽梯度折射率塑料光纤的制造方法和性能;其次阐述了在高带宽梯度折射率塑料光纤上进行的单信道和多信道的数据传输试验.     

基于光纤传输的卫星导航数据采集系统设计与实现

本文提出了基于光纤传输的远程数据采集系统的设计方案,该方案利用在 Delphi 程序设计中应用 TApdComPort 控件实现串口通信的方法,实现了计算机和接收机之间数据更加快捷的传输。     

聚合物光纤中的模式耦合及其对带宽的提高

光在聚合物光纤(POF)中传输时存在较强的模式耦合,由于模式耦合的影响,聚合物光纤的传输带宽得以提高。根据能流方程对阶跃型聚合物光纤光传输中的模式耦合进行了研究,从实验上测量了聚合物光纤的模式耦合系数,测量得到的模式耦合系数为7.61×10-4rad2/m。用测得的模式耦合系数对聚合物光纤中的模式耦合进行数值模拟,得到聚合物光纤的模式耦合长度约为20 m。由模式耦合长度可以得到聚合物光纤的真正带宽,其在150 m传输距离的带宽约为130 Mbit/s。为了验证这一结论,进行了125 Mbit/s.150 m的局域网(LAN)通信实验,通过对发射、接收波形及通信眼图的分析表明,由于模式耦合提高了聚合物光纤的传输带宽,使其可以在150 m的距离上进行百兆速率的通信传输。     

Optical Fiber Transmission System Demonstration Over 32 km with Repeaters Data Rate Transparent Up to 2.3 Mbits/s

An initial optical fiber transmission system under development for Army long haul tactical communications is described and evaluated. The system interfaces with the 2.304 Mbit/s data input and output of an Army inventory multiplexer and its orderwire. The system includes transmitter and receiver end terminals, three data rate transparent repeaters, 8 km of graded index optical fiber, plus three optical attenuators and various optical connectors for simulating transmission up to 32 km. Long repeater spacing is achieved using low loss fiber, semiconductor lasers stabilized using optical feedback, and avalanche photodiodes. The system met all of the specified requirements and shows that optical fiber transmission systems have excellent prospects of meeting full military specifications. The versatility of data rate transparent repeaters is achievable even for transmission up to the 64 km distance desired for Army long haul tactical communications.     

Wave Coupling Between Parallel Single-Mode and Multimode Optical Fibers

A directional coupler composed of a single-mode optical fiber and a multimode optical fiber has been considered to be capable of serving as a drop/insert device of a node in optical fiber Iocal area networks. It should couple almost all the local transmitter power into the multimode fiber bus, while removing only a small fraction of the optical power from the bus through the single-mode fiber. In this paper, the underlying fundamental process of the power transfer between two such optical fibers is analyzed utilizing a coupled-mode theory. Numerical calculations show that wave coupling among the guided modes on the fibers is quite complicated and that the wave amplitude variations along the propagation direction are different from the sinusoidal types resulting from two-mode coupling. The theoretical results do support the expected performance of the proposed couplers and provide an important guide for the design of such devices.