Step-type optical delay line using silica-based planar light-wavecircuit (PLC) technology

We successfully fabricated a step-type optical delay line using a silica-based planar light-wave circuit (PLC) technology with a total delay of 51.0 mm and an optical coherent crosstalk of -49.1 dB. For the purpose of applying it to a mode-locked Er³⁺-doped fiber ring laser, we aimed for: 1) an optical delay of several tens of mm so that any optical pulse repetition frequency could be set, 2) as-low-as-possible optical crosstalk so that the oscillation of the mode-locked ring laser would be stable, and 3) low optical insertion loss. We integrated an optical circuit consisting of eight optical delay units possessing three thermo-optic switches, which have a Mach-Zehnder interferometer configuration, and two waveguides. The difference in optical path length of the waveguides corresponds to the optical delay. We set the optical delay of each unit to 0.2, 0.4, 0.8, 1.6, 3.2, 6.4, 12.8, and 25.6 mm, respectively, to give a maximum delay of 51.0 mm. Moreover, the total insertion loss was 5.2 dB. Precision measurement of the optical delay of each unit gave good results, with a manufacturing error of <0.47%, Based on the above results, the fabricated PLC step-type optical delay line can be used in a mode locked ring laser     

Long-period grating fabricated by periodically tapering standard single-mode fiber

We fabricated an asymmetric long-period grating (LPG) by periodically tapering a section of standard single-mode fiber using a resistive filament heating. The LPG exhibits large peak transmission attenuation of -30.31 dB with only 22 periods in a 1.0 cm long optical fiber and possesses unique characteristics for sensing applications. The bending and strain sensitivities are 1.74 nm m and 1.11 pm/mu epsilon, respectively. The polarization dependent loss is large, up to 11.65 dB, which is caused by an asymmetric index profile in the cross section of the tapered LPG.     

Comment on the reported fiber attenuations in the visible regime in "Fabrication of glass photonic crystal fibers with a die-cast process"

We comment on the recent paper by Zhou et al. [Appl. Opt.45, 4433 (2006)APOPAI0003-693510.1364/AO.45.004433], in which transmission losses of 0.2-0.3 dB/m were claimed across the wavelength range 420-900 nm in a high-index (n(d)=1.80518 at 587.6 nm) SF6 glass-based photonic crystal fiber fabricated by novel die-cast technique. If confirmed, these losses are at least 1 order of magnitude lower than previous reported losses of SF6 photonic crystal fibers from other fabrication approaches. Here we present a statistic survey on the relationship between the refractive index and the bulk material attenuation, based on a large number of commercial Schott optical glasses with the n(d) ranging between 1.40 and 2.05. It shows that the loss of a high-index (n(d)=1.80) glass optical fiber should be at the levels of 10-50 dB/m at 420 nm and 1-10 dB/m at 500 nm, respectively. Moreover, the material attenuation of such a high-index glass fiber should intrinsically show a large decay, from 10-50 dB/m at 420 nm to the level of 1 dB/m at 700 nm, which arises from the tail on the UV absorption edge of the high-index glass extending to the visible region. Therefore, we conclude that: (1) the low loss of 0.2-0.3 dB/m reported in the cited paper is abnormally one or two magnitudes lower than the material attenuation that a high-index (n(d)=1.80) glass optical fiber should have in the range between 420 and 500 nm and that (2) the flat loss curve between 420 and 700 nm in the cited paper deviates greatly from the intrinsic behavior of a high-index (n(d)=1.80) glass fiber.     

Non-display applications and the next generation of liquid crystal over silicon technology

The next generation of applications for liquid crystal (LC) over silicon technology will be non-display oriented systems such as adaptive optical interconnects, optical switches and optical image processors. These new non-display applications have a different set of material parameters, which means that existing display-based materials are not entirely optimal. This is particularly the case when the application is driven by phase modulation at high frame rates (more than 1 kHz). An example of such a non-display application is in adaptive optical interconnects. Optical data transmission between printed circuit boards is becoming more and more important as the data rate in electronic systems increases into the gigahertz region. One way of avoiding the data bottlenecks in board to board interconnects is to use optical links to transmit the data. Recent research into free-space optical links has shown that a high level of manufacturing tolerance must be used to maintain the link. However, one way of avoiding these limitations is to use a reconfigurable LC phase hologram as a beam-steering element to compensate for movement between the boards and maintain the optical data path.     

纤维增强水泥薄板及其复合梁抗弯性能研究

实验研究了纤维对水泥基复合材料抗弯性能的影响.结果表明,聚乙烯醇(PVA)纤维增强挤压脱水成型板材在弯曲荷载作用下呈现多点开裂、应变硬化的特性,具有良好的延性,聚丙烯(PP)纤维增强挤压脱水成型板材呈应变软化的特性,木纤维增强挤压脱水成型板材则呈脆性破坏;与普通混凝土梁相比,冷浇和热浇纤维增强板-混凝土组合梁的抗弯强度...     

Conductive filament formation in printed circuit boards: effects of reflow conditions and flame retardants

Conductive filament formation, a major cause of failures in printed circuit boards, is an electrochemical process that involves the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. With an increasing potential to market “green” electronics, environmental and health legislations, and the advent of lead-free and halogen-free initiatives, newer types of printed circuit board materials are being exposed to ever higher temperatures during solder assembly. The higher temperatures can weaken the glass-fiber bonding, thus enhancing conductive filament formation. The effects of the inclusion of halogen-free flame retardants on conductive filament formation in printed circuit boards are not completely understood. Previous studies, along with analysis and examinations conducted on printed circuit boards with failure sites that were due to conductive filament formation, have shown that the conductive path is typically formed along the delaminated fiber glass and epoxy resin interfaces. This paper is a result of a year-long study on the effects of reflow temperatures, halogen-free flame retardants, glass reinforcement weave style, and conductor spacing on times to failure due to conductive filament formation.     

Integrated optical polarization splitter based on photobleaching-induced birefringence in azo dye polymers

An integrated optical polarization splitter has been fabricated by utilizing the photobleaching-induced birefringence in an azo dye polymer. It consists of a Y-branch waveguide formed by the reactive ion etching with one of the two arms photobleached. The refractive index of the photobleached arm is decreased for the TE mode and increased for the TM mode. The performance of the splitter was measured as a function of the energy of the photobleaching beam and compared to a wave propagation simulation of the device. The measured cross talks are less than -28 dB for the TM mode and -24 dB for the TE mode at a wavelength of 1310 nm. The measured excess losses for the TE and TM modes, which measure the effect of the Y branch and the photobleaching, are 0.3 and 0.4 dB, respectively. The insertion loss was 5 dB, which includes the input fiber to waveguide coupling loss.     

新型光隔离器结构设计与实验性能测试

提出一种功能复用光隔离器设计方案。在传统光隔离器中加入了透镜对,两透镜间拥有一个相邻共焦面,具有空间光交叉功能,能实现功能复用光隔离器输入输出多尾纤之间的对应耦合;二者结合组成空间复用功能系统,使光隔离器具有功能复用的作用。该光隔离器的主要性能测量结果表明,所设计的1550nm双通道功能复用光隔离器两个通道的插入损耗分别为0.43dB和0.31dB,隔离度分别为43dB和40dB,两个功能隔离器之间的串扰都大于60dB,达到了隔离器需要满足的性能指标,在低插损、高隔离的基础上具有功能复用效用。     

Optical characteristics of a refractive optical attenuator with respect to the wedge angles of a silicon optical leaker

We design, fabricate, and characterize the micromachined refractive variable optical attenuator (VOA) with a wedge-shaped silicon optical leaker (SOL). The vertical structures of the VOA device can be simply fabricated by deep reactive ion etching with no sidewall metallization, and the 8 degrees angled fibers are employed for a high return loss even in air-ambient conditions. The SOL successively transmits and refracts part of the incident light far outside the acceptance angle of the output fiber, showing an effective optical attenuation. The fabricated VOA gives high optical performances, such as a response time of 6 ms, a return loss of 39 dB, an insertion loss of 0.6 dB, an attenuation range of 43 dB, and a polarization-dependent loss (PDL) of a 10% attenuation level, including a wavelength-dependent loss. The optical characteristics of the VOA are also theoretically investigated with respect to the wedge angles of the SOL. The experimental characteristics are in good agreement with the theoretical values calculated, considering light scattered from the endface of an optical fiber and sidewall of the SOL. The PDL estimation was confirmed especially to sufficiently explain the fundamental characteristic of the PDL for the refractive VOA.     

Hybrid free-space optical bus system for board-to-board interconnections

A free-space optical bus system is described for board-to-board interconnections at the backplane level. The system uses active optoelectronic modules as the interface between the circuit boards and the electrical backplane. Substrate-mode holograms are used to implement signal broadcast operations between boards, and each board on the backplane shares common free-space channels for transmitting and receiving signals. System-design considerations are given, and the potential performance of the optical bus system is evaluated. An experimental demonstration is also presented for the signal broadcast operation through cascaded substrate-mode holograms at a data rate of 622 Mb/s.     

Design and analysis of an adaptive board-to-board dynamic holographic interconnect

We describe the design and analysis of an adaptive free-space optical interconnect between two circuit boards in a standard electronic backplane. An array of vertical-cavity surface-emitting lasers is used as the transmitter, and this communicates with a detector array on the receiver circuit board. Routing is achieved with a holographic crossbar that has a ferroelectric liquid-crystal spatial light modulator to display binary phase computer-generated holograms. A detailed analysis of a 48-channel interconnect designed to operate at 1 (Gbytes/s)/channel indicates that such a switch will operate successfully given typical components and card misalignments.     

热处理对玻璃纤维布/聚苯硫醚非织造布复合板材力学性能的影响

以玻璃纤维布和聚苯硫醚（PPS）非织造布分别作为增强体和树脂基体原料,采用热压成型法制备出玻璃纤维布/PPS非织造布复合板材,然后在烘箱中进行热处理。利用万能试验机（Instron）、XRD、偏光显微镜（PLM）和SEM等手段对玻璃纤维布/PPS非织造布复合板材的力学性能、结晶度、晶粒类型和尺寸及微观形貌等进行了测试和表征。结果表明：随着热处理温度和时间的提高,玻璃纤维布/PPS非织造布复合板材的弯曲强度、弯曲模量和缺口冲击强度得到明显提高。当热处理温度为220℃、热处理时间为2 h时,其力学性能最佳,其弯曲强度、弯曲模量和缺口冲击强度分别达到285.7 MPa、7.8 GPa和85.0 MPa。和未进行热处理的玻璃纤维布/PPS非织造布复合板材相比,分别提高了63.2%、469.0%和37.8%。微观形貌结果表明,玻璃纤维布/PPS非织造布复合板材界面粘结得到了明显改善。     

Low-cost and minimal-conditioning interface for a PbSephotoconductor array

A low cost conditioning structure for PbSe photoconductor arrays with few components is described. We use a PbSe array of 64 pixels in a simultaneous atmospheric pollutant detector of several gases. The sensor system is based on infrared optical absorption spectroscopy. The authors present a second version of the sensor. From the first version they deduced: i) it is necessary to work at high chopper frequencies to reduce the effect of 1/f noise, ii) it is necessary to provide a conditioning circuit for each channel, and iii) the conditioning interface must be near the array. Therefore, they propose to amplify and mix the incoming signal to produce a signal at a fixed intermediate frequency (IF), in their case 1 Hz. The fact that the circuit has few components makes possible to place 64 conditioners in a small volume (10×4.9×7.6 cm³) using the with SMT technique. The conditioner is divided into eight boards. Each board has eight channels and an analog multiplexor. These characteristics permit to approach the circuitry to the array. Each channel conditioner has up to 100 dB voltage gain. The low IF technique makes it possible to have high-performance circuits with low-cost components     

光纤连接器端面超声机械研磨

为了提高光纤连接器端面的加工效率和加工质量，改善连接器光传输性能，探讨了在机械研磨的界面上引入超声能的复合研磨方式，设计了相应的超声机械研磨装置．实验结果显示，超声机械研磨效率是机械研磨的4～8倍，光纤表面粗糙度达到2～5nm，插入损耗小于0．1dB、回波损耗小于-60dB．研究表明，超声机械研磨技术可以提高光纤连接器的研磨效率和质量，使传输性能获得显著改善．     

New Optical Power Meter for Optical Fiber Transmission System Applications

This paper describes a design and the characteristics of a new optical power meter for 0.8-?m wavelength region optical fiber transmission systems. Features of this optical power meter are high sensitivity (-80 dBm), high stability (±0.005 dB at > -65 dBm), and small deviation against the plug rotation inside the receptacle (±0.02 dB). The SNR design method presented is useful in high sensitivity and high stability optical power meter design.     

自动舵电路板故障测试系统研究

针对自动舵故障电路板需要返厂测试的问题,设计自动舵电路板便携式故障测试系统。在分析自动舵电路板故障测试需求的基础上,采用专用接口电缆和测试软件而复用数据采集系统的方法,仅用少数硬件就实现了多块电路板的测试;基于神经网络方法设计自动测试软件,能够定位电路板常见故障;采用Measurement Studio和Visual Studio联合编程的方法,设计了辅助信息丰富的故障诊断程序界面。实践表明:该系统具有成本低、体积小、功能强的特点,可在船上直接对电路板进行故障测试。     

Misalignment correction for optical interconnects using vertical cavity semiconductor optical amplifiers

In board-to-board optical interconnects, the misalignment between the board and the backplane connections can cause both optical loss and interchannel cross talk. A vertical cavity semiconductor optical amplifier (VCSOA) is proposed to correct optical misalignment in an optical connector between the board and the backplane. Angular or lateral misalignment can be corrected with the designed module. The correction ability is determined by the acceptance angle of the VCSOA, which was characterized to be 9.4 degrees full angle at a 3 dB gain drop for a 30 microW optical signal at 1 GHz. The lateral misalignment correction ability is 0.16f, where f is the focal length of the mini lens to converge the input light onto the VCSOA.     

Scalability analysis of diffractive optical element-based free-space photonic circuits for interoptoelectronic chip interconnections

An interchip free-space optical interconnection module is investigated to solve the pin-input-output bottleneck at the interface of silicon integrated circuits. The scalability of the photonic circuit is theoretically analyzed by use of the minimum feature size requirement of each diffractive element used. The study showed that interconnection densities of 1000-2000 channels/cm is possible for a 40-mm interconnection length with a 3-mm-thick optical substrate. Diffraction-limited imaging capability has been demonstrated using a fabricated prototype, confirming its applicability for interchip free-space interconnections. Photonic circuit insertion losses of -23.4 dB for TE polarization and -25.9 dB for TM polarization as well as a polarization-dependent loss of 2.5 dB are found to be caused primarily by a pair of binary linear gratings used for beam deflections. Design modifications aiming at insertion loss reduction and further improvement of tolerance capabilities are also discussed.     

Coupling losses between standard single-mode fibers and rectangular waveguides for integrated optics

The butt-coupling loss between different tapered rectangular waveguides and a standard single-mode optical fiber has been calculated. Losses as low as 0.16 dB can be reached for waveguides with a refractive-index contrast in the range of 0.5% to 1.96%. The fabrication tolerances are such that practical devices with coupling losses below 0.25 dB are feasible.     

卤化银光纤原料的超提纯

高纯原料的制备是制造高品质光纤最重要的环节,本文采用氯气氛下水平区熔法生长单晶的提纯方法对卤化银原料进行超提纯．区域熔融提纯后的卤化银原料红外吸收光谱测量显示在800～4000cm^－1范围内吸收随波长的增加而降低．经CO₂激光量热计法测量提纯后的卤化银原料在10．6μm处的吸收系数为5×10^－4Cm^－1,较提纯前降低两个数量级,制成的光纤传输损耗03～0．5dB／m