低损耗As-S玻璃光纤的制备与应用研究

采用反复蒸馏提纯技术和开放式动态蒸馏相结合的工艺, 制备了高纯As-S玻璃, 基本消除了玻璃在2.9、4和6.3 μm处的杂质吸收。利用旋转法制备出壁厚均匀、表面质量优异的硫系玻璃套管。采用棒管法拉制出丝径50 μm, 芯径40 μm具有芯包结构的硫系玻璃光纤。拉制的As-S光纤机械性能和光学性能优异, 光纤丝径波动小于1%, 弯曲半径优于4 mm, 中红外波段损耗基线小于0.5 dB/m。制备出像元呈正方形排列, 出端规格64×9, 入端规格192×3, 用于线-面转换的红外传像束, 像束断丝率为2.7%。利用该异型传像束成功实现了长线阵的红外推扫成像。     

Spatially resolved electrochemiluminescence on an array of electrode tips

An array of electrode tips with 6-microm center-to-center spacing, fabricated through chemical etching of an optical fiber bundle, and coated with gold, was used for initiating electrochemiluminescence (ECL) in an aqueous solution of Ru(bpy)3(2+) and tri-n-propylamine (TPrA). ECL generated at the tips of the electrodes in the array was detected with a CCD camera and exhibited both high sensitivity and high resolution. In the case in which the ECL signal could not be distinguished from the background, ECL signals could be obtained by pulsing the array and summing multiple CCD images. The behavior of this array was compared to a second array that consisted of individual electrodes insulated with an electrophoretic paint.     

Development of an ordered array of optoelectrochemical individually readable sensors with submicrometer dimensions: application to remote electrochemiluminescence imaging

A novel array of optoelectrochemical submicrometer sensors for remote electrochemiluminescence (ECL) imaging is presented. This device was fabricated by chemical etching of a coherent optical fiber bundle to produce a nanotip array. The surface of the etched bundle was sputter-coated with a thin layer of indium tin oxide in order to create a transparent and electrically conductive surface that is insulated eventually by a new electrophoretic paint except for the apex of the tip. These fabrication steps produced an ordered array of optoelectrochemical sensors with submicrometer dimensions that retains the optical fiber bundle architecture. The electrochemical behavior of the sensor array was independently characterized by cyclic voltammetry and ECL experiments. The steady-state current indicates that the sensors are diffusively independent. This sensor array was further studied with a co-reactant ECL model system, such as Ru(bpy)(3)(2+)/TPrA. We clearly observed an ordered array of individual ECL micrometer spots, which corresponds to the sensor array structure. While the sensors of the array are not individually addressable electrochemically, we could establish that the sensors are optically independent and individually readable. Finally, we show that remote ECL imaging is performed quantitatively through the optoelectrochemical sensor array itself.     

Laser speckle reduction by multimode optical fiber bundle with combined temporal, spatial, and angular diversity

We report significant speckle reduction in a laser illumination system using a vibrating multimode optical fiber bundle. The optical fiber bundle was illuminated by two independent lasers simultaneously. The beams from both lasers were first expanded and collimated and were further divided into multiple beams to illuminate the fiber optic bundle with normal and oblique incidence. Static diffusers were also placed at the input and output faces of the fiber bundle, thus introducing the spatial as well as angular diversity of illumination. Experiments were carried out both in free space and in imaging geometry configuration. Standard deviation, speckle contrast and signal-to-noise ratio of the images were computed, and the results were compared with those of white light illumination. Speckle contrast close to that of white light was obtained using a vibrating fiber bundle with combined temporal, spatial, and angular diversities of the illumination.     

Fabrication of an optoelectrochemical microring array

In this paper, we describe a novel approach for fabricating an optoelectrochemical microring array. The array was fabricated by coating individual optical fibers of 25-microm diameter with a 1-microm layer of gold nanoparticles via electroless gold deposition. A SAM layer around the individual gold-coated imaging fibers prevented electrical contact with neighboring ring electrodes. To achieve better mechanical stability and to make the device more practical, the electrode/fiber bundle comprising approximately 600 individual gold-coated optical fibers was dipped into epoxy. By polishing the ends of such a device, a ring microelectrode array comprising 600 individual and insulated ring electrodes was formed. To limit diffusional overlap of current, only 20-30% of the microring fiber/electrodes were wired. The inner diameter of the ring electrode is fixed by the diameter of the individual optical fibers (25 microm), while the outer radius is determined by the thickness of the deposited gold. The array was characterized using ferrocyanide in aqueous solution as a model electroactive species to demonstrate that this microelectrode array format exhibits steady-state currents at short response times. In addition, cyclic voltammetry experiments were performed using conventional potentiostats due to the amplification of current inherent in the array format. Finally, electrochemiluminescence at the ring electrode array was demonstrated through the oxidation of Ru(bpy)3(2+) in tri-n-propylamide in a pH 7 phosphate buffer solution, where the light generated was collected and detected via the fiber bundle.     

Sagnac-type fiber-optic array sensor for detection of bulk ultrasonic waves

In this paper, we describe a fiber optic array sensor suitable for detection of bulk ultrasonic waves. This sensor is based on an intrinsic fiber optic Sagnac interferometer. The fiber array is formed by multiple folding of a continuous length of an optical fiber into flat coils. Depending on the orientation of the fiber array with respect to the ultrasonic wave, the proposed sensor can act as a conventional in-phase detector or as a narrowband detector. In the narrowband mode, the center frequency of detection can be tuned by adjusting the spacing of the fiber array elements to be equal to the ultrasonic wavelength of interest. This feature distinguishes this array sensor from conventional hydrophones in which a receiver is typically much smaller than the acoustical wavelength. It is shown that the array sensor provides an enhanced signal-to-noise ratio (SNR) compared with a single element detection scheme. Results are presented for detection of ultrasonic waves in water arising from both piezoelectric and laser ultrasonic sources. Potential areas of application of this sensor include process monitoring, smart structures, bio-medical ultrasound, and chemical sensing.     

Design, implementation, and characterization of a hybrid optical interconnect for a four-stage free-space optical backplane demonstrator

A four-stage unidirectional ring free-space optical interconnect system was designed, analyzed, implemented, and characterized. The optical system was used within a complementary metal-oxide semiconductor-self-electro-optic-effect-device-based optical backplane demonstrator that was designed to fit into a standard VME chassis. This optical interconnect was a hybrid microlens-macrolens system, in which the microlens relays were arranged in a maximum lens-to-waist configuration to route the optical beams from the optical power supply to the transceiver arrays, while the macrolens optical relays were arranged in a telecentric configuration to route optical signal beams from stage to stage. The following aspects of the optical system design are discussed: the optical parameters for the hybrid optical system, the image mapping of the two-dimensional array of optical beams from stage to stage, the alignment tolerance of the hybrid relay system, and the power budget of the overall optical interconnect. The implementation of the optical system, including the characterization of optical components, subsystem prealignment, and final system assembly, is presented. The two-dimensional array of beams for the stage-to-stage interconnect was adjusted with a rotational error of <0.05 degrees and a lateral offset error of <3.5 mum. The measured throughput is in good agreement with the lower-bound predictions obtained in the theoretical results, with an optical power throughput of -20.2 dB from the fiber input of the optical power supply to the modulator array and -25.5 dB from the fiber input to the detector plane.     

Optical fiber array for the delivery of high peak-power laser pulses for fluid flow measurements

Fiber delivery of 64.7 mJ laser pulses (approximately 6 ns duration) from a Q-switched Nd:YAG laser operating at 532 nm is demonstrated. A custom diffractive optical element was used to shape the laser beam and facilitate coupling into a linear fiber array. This launch arrangement achieves an improvement in launch efficiency compared with a circular fiber bundle evaluated in previous work and the delivery of higher pulse energies is demonstrated. The bundle is capable of delivering light of sufficient pulse energy and, importantly, with suitable focusability, to generate a thin light sheet for the fluid flow measurement technique of particle image velocimetry (PIV). Fiber delivery offers an advantage, in terms of optical access, for the application of PIV to enclosed measurement volumes, such as the cylinder of a combustion engine.     

Coupling and cross-talk effects in 12-15 microm diameter single-mode fiber arrays for simultaneous transmission and photon collection from scattering media

We examine signal degradation effects in fiber arrays from fiber-to-fiber coupling and from cross talk attributable to backscatter from the sample medium originating from adjacent fibers in the array. An analysis of coupling and cross talk for single-mode fibers (SMFs) operating at 1310 nm with different core diameters, interaction lengths, core center spacing, and numerical apertures (NAs) is evaluated. The coupling was evaluated using beam propagation algorithms and cross talk was analyzed by using Monte Carlo methods. Several multimode fiber types that are currently used in fiber image guides were also evaluated for comparative purposes. The analysis shows that an optimum NA and core diameter can be found for a specific fiber center separation that maximizes the directly backscattered signal relative to the cross talk. The coupling between fibers can be kept less than -35 dB for interaction lengths less than 5 mm. The calculations were compared to an experimentally fabricated SMF array with 15 microm center spacing and showed good agreement. The experimental fiber array without a lens was also used in a coherent detection configuration to measure the position of a mirror. Accurate depth ranging up to a distance of 250 microm from the tip of the fiber was achieved, which was five times the Rayleigh range of the beam emitted from the fiber.     

Asynchronous transfer mode distribution network by use of an optoelectronic VLSI switching chip

We describe a new optoelectronic switching system demonstration that implements part of the distribution fabric for a large asynchronous transfer mode (ATM) switch. The system uses a single optoelectronic VLSI modulator-based switching chip with more than 4000 optical input-outputs. The optical system images the input fibers from a two-dimensional fiber bundle onto this chip. A new optomechanical design allows the system to be mounted in a standard electronic equipment frame. A large section of the switch was operated as a 208-Mbits/s time-multiplexed space switch, which can serve as part of an ATM switch by use of an appropriate out-of-band controller. A larger section with 896 input light beams and 256 output beams was operated at 160 Mbits/s as a slowly reconfigurable space switch.     

Interconnection of a two-dimensional array of vertical-cavity surface-emitting lasers to a receiver array by means of a fiber image guide

The implementation of a 10-channel parallel optical interconnect consisting of a two-dimensional array of vertical-cavity surface-emitting lasers, a 1.35-m fiber image guide, and a metal-semiconductor-metal receiver array is described. Transmission rates of 250 Mbits/s per channel are demonstrated with an optical cross talk of less than -27 dB and a loss of -3 dB. Coupling issues associated with image guides are analyzed and discussed.     

纤维束增强复合材料的双层次随机扩大临界核模型

针对纤维束增强复合材料, 提出了双层次随机扩大临界核模型。以复合材料制造工艺为基础建立了纤维间距和纤维束中纤维根数的计算模型, 将复合材料中的纤维分为2 个层次: 纤维束和纤维束群, 并提出父核和子核的概念对临界核的构成进行了区分, 用Beyerlein 公式计算纤维束群中纤维束相继失效引起的纤维束的平均应力集中因子, 用Sivasambu 公式来计算纤维束中纤维相继断裂造成的纤维的应力集中因子。然后, 以纤维断裂蔓延的主要模式为基础, 将逐渐增大的无效长度引入纤维束内部, 根据统计学理论推导相应的复合材料破坏概率计算公式。编制了相关程序, 通过该程序分别预测了S 玻纤、E 玻纤、玄武岩纤维无捻单向纤维布增强复合材料试件的拉伸强度。对3 种复合材料板进行了拉伸强度及基体的拉伸和剪切实验, 并对比了预测结果与实验结果。研究结果显示, 直接将实验对象的材料、几何参数代入就能得到与实验结果吻合的预测结果。      

Design of a lidar receiver with fiber-optic output

Design considerations for a coaxial lidar receiver are examined, including details of coupling to an optical fiber for transfer of return light to a remote detector box. Attention is concentrated on the influence of fiber position on return-light capture efficiency and dynamic range of the return signal. The effect of a central obstruction on short-range signals is included. The analysis is augmented with simulations of lidar receiver performance.     

Simple wide-range method for angle measurement with a point fiber-optic output

We propose a simple optical method for precise, wide-range angle measurement based on the use of a single-mode optical fiber as a registration scheme output. Because of its micrometric core dimensions, the fiber serves as a point receiver that is highly sensitive to angular displacements of focused laser emission. The method allows the independent photoelectric measurement of both rotation and spatial angles of various optical elements, combining a wide angular dynamic range (from 0 degrees to 360 degrees ) with high accuracy (exceeding 3 arcsec).     

Dynamic null steering in an ultrawideband time-steered array antenna

We develop a method for forming squint-free wideband nulls in the antenna pattern of an ultrawideband array antenna. The technique uses an optical dispersive-prism beam former to provide time-delayed microwave signals to each antenna element for forming a squint-free main beam. The amplitude-modulated optical carrier is propagated through a set of optical links. Each link feeds an array element and includes an amount of dispersion proportional to element position. Tuning the wavelength of the optical carrier controls the microwave signal's arrival-time delay gradient across the array. A dispersive-prism tapped delay-line microwave filter is used to frequency shape a nulling signal. The wideband nulls do not significantly distort the main beam and are steered independently of the main beam. The technique is applied to sidelobe nulling for a transmitter and for jammer suppression for a receiver array.     

40Gbps甚短距离并行光传输系统接收电路的设计与实现

给出了符合OIF-VSR5规范的40Gbps甚短距离光传输系统接收电路的设计与实现。该接收电路实现简单,由一片转换芯片及光接收模块构成。其特点是充分利用现场可编程门阵列(FPGA)内嵌的高速收发器成功实现了16×2.488Gbps和12×3.318Gbps信号的发送和接收,并且在一片FPGA上实现了诸如时钟数据恢复、串/并转换、帧同步、通道对齐、12-16路映射等全部功能。基于二分查找法的帧同步电路则大大提高了转换芯片的工作速度。Signaltap Ⅱ逻辑分析仪的测试结果表明接收电路工作正常,性能良好。在此基础上,给出了VSR5实验系统的点到点测试方法,通过12通道垂直腔面发射激光器并行接收模块和7m 12芯多模带状光纤,将发送电路与接收电路相连,实现了OC768/STM-256 40Gbps的点到点测试,测试结果表明系统误码率小于10~(-12)。     

Free space optical communications through clouds: analysis of signal characteristics

Free space optical communications (FSOC) is a method by which one transmits a modulated beam of light through the atmosphere for broadband applications. Fundamental limitations of FSOC arise from the environment through which light propagates. This work addresses transmitted light beam dispersion (spatial, angular, and temporal dispersion) in FSOC operating as a ground-to-air link when clouds exist along the communications channel. Light signals (photons) transmitted through clouds will interact with the cloud particles. Photon-particle interaction causes dispersion of light signals, which has significant effects on signal attenuation and pulse spread. The correlation between spatial and angular dispersion is investigated as well, which plays an important role on the receiver design. Moreover, the paper indicates that temporal dispersion (pulse spread) and energy loss strongly depend on the aperture size of the receiver, the field-of-view (FOV), and the position of the receiver relative to the optical axis of the transmitter.     

Fiber-coupling efficiency for free-space optical communication through atmospheric turbulence

High-speed free-space optical communication systems have recently used fiber-optic components. The received laser beam in such a system must be coupled into a single-mode fiber at the input of the receiver module. However, propagation through atmospheric turbulence degrades the spatial coherence of a laser beam and limits the fiber-coupling efficiency. We numerically evaluate the fiber-coupling efficiency for laser light distorted by atmospheric turbulence. We also investigate the use of a coherent fiber array as a receiver structure and find that a coherent fiber array that consists of seven subapertures would significantly increase the fiber-coupling efficiency.     

Image fiber optic space-CDMA parallel transmission experiment using 8 x 8 VCSEL/PD arrays

We experimentally demonstrate space-code-division multiple access (space-CDMA) based twodimensional (2-D) parallel optical interconnections by using image fibers and 8 x 8 vertical-cavity surface-emitting laser (VCSEL)/photo diode (PD) arrays. Two spatially encoded four-bit (2 x 2) parallel optical signals were emitted fiom 2-D VCSEL arrays and transmitted through image fibers. The encoded signals were multiplexed by an image-fiber coupler and detected by a 2-D PD array on the receiver side. The receiver recovered the intended parallel signal by decoding the signal. The transmission speed was 64 Mbps/ch (total throughput: 512 Mbps). Bit-error-rate (BER) measurement with a laterally misaligned PD array showed the array had a misalignment tolerance of 25 microm for a BER performance of 10(-9).     

Remote fluorescence imaging of dynamic concentration profiles with micrometer resolution using a coherent optical fiber bundle

Dynamic concentration profiles within the diffusion layer of an electrode were imaged in situ using fluorescence detection through a multichannel imaging fiber. In this work, a coherent optical fiber bundle is positioned orthogonal to the surface of an electrode and is used to report spatial and temporal micrometric changes in the fluorescence intensity of an initial fluorescent species. The fluorescence signal is directly related to the local concentration of a redox fluorescent reagent, which is electrochemically modulated by the electrode. Fluorescence images are collected through the optical fiber bundle during the oxidation of tris(2,2'-bipyridine)ruthenium(II) to ruthenium(III) at a diffusion-limited rate and allow the concentration profiles of Ru(II) reagent to be monitored in situ as a function of time. Tris(2,2'-bipyridine)ruthenium(II) is excited at 485 nm and emits fluorescence at 605 nm, whereas the Ru(III) oxidation state is not fluorescent. Our experiments emphasize the influence of two parameters on the micrometer spatial resolution: the numerical aperture of optical fibers within the bundle and the Ru(II) bulk concentration. The extent of the volume probed by each individual fiber of the bundle is discussed qualitatively in terms of a primary inner-filter effect and refractive index gradient. Experimentally measured fluorescence intensity profiles were found to be in very good agreement with concentration profiles predicted upon considering planar diffusion and thus validate the concept of this new application of imaging fibers. The originality of this remote approach is to provide a global view of the entire diffusion layer at a given time through one single image and to allow the time expansion of the diffusion layer to be followed quantitatively in real time.