Partitioned optical passive star (POPS) multiprocessorinterconnection networks with distributed control

This paper presents a partitioned optical passive star (POPS) interconnection topology and a control methodology that, together, provide the high throughput and low latency required for tightly coupled multiprocessor interconnection applications. The POPS topology has constant and symmetric optical coupler fanout and only one coupler between any two nodes of the network. Distributed control is based on the state sequence routing paradigm which multiplexes the network between a small set of control states and defines control operations to be transformations of those states. These networks have highly scalable characteristics for optical power budget, resource count, and message latency. Optical power is uniformly distributed and the size of the system is not directly limited by the power budget. Resource complexity grows as O(n) for the couplers, O(n√n) for transceivers, and O[√nlog(n)] for control. We present analysis and simulation studies which demonstrate the ability of a POPS network to support large scale parallel processing (1024 nodes) using current device and coupler technology     

A media-access protocol for time- and wavelength-divisionmultiplexed passive star networks

A media access protocol is presented for time- and wavelength-division multiplexed optical passive star networks. The protocol is based on a bus-mesh virtual topology. The network provides minimum latency and high throughput while requiring only a single fixed wavelength transmitter and receiver at each station. The use of nonagile, fixed wavelength devices, readily available with current technology, reduces costs, improves reliability and avoids tuning delays and limitations. The multihop access protocol operates effectively in an environment with lengthy propagation delays. The wavelength-division multiplexing system is required to support only a small, easily achievable number of wavelength channels     

Optical cascade star network--A new configuration for a passive distribution system with optical collision detection capability

A new fiber-optic passive network configuration with novel star couplers is reported. The new optical network configuration, an Optical Cascade Star Network, optimizes contradictory requirements for network system size and cable cost, and matches the actual layout in offices or factories. The star coupler is novel in that the optical signal does not return to the source terminals. This feature enables cascade connection of star networks, the use of simple repeaters for system extension, and the easy support of carrier sense multiple access with collision detection (CSMA/CD) bus access procedure. Experimental results obtained from novel star couplers, optical transceivers with (CSMA/CD) bus compatibility, and a total network system are also discussed.     

A Fully Integrated 4 × 10-Gb/s DWDM Optoelectronic Transceiver Implemented in a Standard 0.13 μm CMOS SOI Technology

Optical and electronic building blocks required for DWDM transceivers have been integrated in a 0.13 mum CMOS SOI technology. Using these building blocks, a 4 x 10-Gb/s single-chip DWDM optoelectronic transceiver with 200 GHz channel spacing has been demonstrated. The DWDM transceiver demonstrates an unprecedented level of optoelectronic system integration, bringing all required optical and electronic transceiver functions together on a single SOI substrate. An aggregate data rate of 40 Gb/s was achieved over a single fiber, with a BER of less than 10^-12 and a power consumption of 3.5 W.     

Baud-rate channel equalization in nanometer technologies

Chip design technology has been accelerating the advances of the communication technology in the past decades because a chip with larger computing capacity can support a communication system of higher transmission bandwidth. Since the communication transceivers are now in the multigiga bits/second range, the computing bandwidth requirement for a transceiver has grown into several hundreds of giga-FLOPs second range. To support such big computing tasks on a chip, nanometer technology and pure baud-rate computing without pipelining and oversampling overheads will be much more important. Meanwhile, baud-rate computing does not require extra-digital control for the digital-signal processing functions. This can greatly reduce the power consumption and chip area of a VLSI system. Yet, there are several design issues, such as the output signal-to-noise ratio, algorithmic mapping for computing model, and the critical path for the datapath design of the VLSI computing function, which need to be resolved under small silicon area requirements A novel baud-rate channel equalization architecture based on training coefficient relaxation techniques is presented in this paper to resolve these issues in nanotechnology such as 130- and 90-nm technologies. This design paradigm clearly demonstrates its advantage to enable multiport transceiver system-on-a-chip designs in nanometer technology. Trends for the baud-rate computing in smaller geometry are also explained.     

Prospects of CMOS technology for high-speed optical communication circuits

This paper describes the capabilities of deep-submicron CMOS technologies for the realization of highly integrated optical communication transceivers in the range of tens of gigabits per second. Following an overview of a CMOS process, the design of traditional and modern transceivers is presented and speed and integration issues are discussed. Next, the problem of equalization is addressed. Finally, the design of critical building blocks such as broadband amplifiers and high-speed oscillators is described and a method of estimating the jitter is introduced.     

Gigabits-per-second optical interconnection networks:fault-tolerance with and without optical amplifiers

This paper quantifies the power budget concerns with respect to the number of consecutive faults that must be tolerated before a network can fail. In particular, it is shown that multiple consecutive failures may have a serious adverse effect on the speed of gigabit optical networks. Results indicate that, with 20 nodes using simple direct-detection, only passive star networks can operate at Gb/s in the event of multiple consecutive faults. Use of optical preamplifiers is shown to remedy this shortcoming substantially: even with 3 consecutive node failures, optical networks with passive star couplers or single couplers can achieve Gb/s transmission speed for a node spacing of up to 2.3 km     

Design and performance analysis of adaptive optical telescopesusing lasing guide stars

The use of adaptive optical systems using electrically deformable mirrors to compensate for turbulence effects is discussed. Since these systems require bright reference sources adjacent to the object of interest and can be used only to observe the brightest stars, artificial guide stars suitable for controlling an adaptive imaging system must be created in the upper atmosphere by using a laser to excite either Rayleigh backscattering in the stratosphere or resonance backscattering in the mesospheric sodium layer. The design requirements of a laser-guided adaptive telescope, as well as the expected imaging performance, are discussed in detail. It is shown that a 2-m ground-based laser-guided telescope can achieve imaging performance levels at visible wavelengths nearly matching the theoretical imaging performance of the Hubble Space Telescope (HST). The required lasers can be either bought off the shelf or built with current technology. The laser power requirement for the Rayleigh guide star approach is on the order of 82 W for zenith viewing when the atmospheric seeing cell diameter is 20 cm. For the same conditions the laser power requirement for the Na guide star approach is on the order of 14 W. Both systems will achieve near diffraction limited imaging with a Strehl ratio of ~0.67 and an angular resolution of approximately 0.07 arcsec for an observation wavelength of 0.5 μm     

WDM passive network design for small wavelength-count in local area/home applications

Passive optical networks are attractive due to their enhanced reliability, reduced electrical power consumption, and small latency. This paper determines the feasibility of WDM (Wavelength Division Multiplexing) passive networks with low wavelength count for small environments such as buildings/homes from the viewpoint of the physical network configuration. After describing the general characteristics of WDM passive networks in the bus, star, and ring configurations, we elucidate the optical path losses to find design solutions when the three physical configurations are used to create small networks. It is concluded that the star configuration is the most feasible approach. The bus and ring are also feasible only for small areas and low wavelength counts.     

A selective-broadcast passive star coupler for self-routing densewavelength division multiplexed optical networks

The authors describe a technique for design and implementation of a selective-broadcast passive optical star coupler, that uses a space-varying refractive-index slab. A network traffic routing matrix can be incorporated in the design fabric of this bandwidth-selective coupler. The matrix may resemble any desired physical cross connection for routing user traffic. As an example, the authors show how a perfect shuffle network connectivity can be built into the fabric of a passive star coupler. A wave-mixing method is proposed to configure such a coupler. With this implementation, the authors have realized the physical connectivity appropriate for any desired routing matrix in dense wavelength division multiplexed optical star network applications     

Optical computing and interconnects

This paper discusses the present status of optical computing and interconnects, including device technology, and recent progress in three types of optical computing-analog, digital, and neural-is introduced. Examples of technologies used in an analog computing system, a technique for the optimal design of coherent phase-only spatial filters, and a new version of incoherent filtering are presented. The use of the modified sign digit number representation and its applications to digital optical computing are also described. Some architectures for optical neural computing are introduced, and the importance of optical interconnect technology in parallel computing is stressed. Permutation techniques, the board-to-board level interconnection techniques, and switching techniques are reviewed. Recent developments in optoelectronic devices and passive optical elements are outlined and finally some technological issues in optical computing and interconnects for practical use are discussed     

Contention-based reservation protocols in multiwavelength opticalnetworks with a passive star topology

In a multiwavelength optical network with tunable transceivers, an algorithm to make the transmitter and the receiver tuned to the same wavelength simultaneously is needed. The paper proposes contention-based reservation protocols using a separate control channel for multiwavelength optical networks with a passive star topology. First, they present a protocol which can be used in the network where the ratio of the end-to-end signal propagation delay to the transmission time of a data packet is smaller than 1. Also, for a very high speed network where this ratio is greater than 1, the authors present three protocols according to the variability of the packet length and the buffering of the reservation. To access the control channel, all the proposed protocols use the slotted ALOHA protocol. The authors analyze these protocols with a finite population model and investigate the delay-throughput characteristics     

基于μLED发光技术的新型星模拟器设计

针对常规星模拟器存在的模拟参数少、精度低和模拟技术难度大等具体问题,将LED发光技术引入到星模拟器的设计中,提出一种基于LED发光技术的新型星模拟器研制方法。结合星模拟器准直光学系统设计结果,详细设计了整体机械结构,以确保其具有在仿真环境下,最大程度弱化温变、振动等外界因素的特性。重点研究星点位置精度和星点发光亮度的控制技术,并对星点圆度、星点发光均匀度以及星点光谱控制技术进行具体分析。分析与测试结果均表明,所设计的星模拟器具有星间角距精度小于3,多种5个连续星等模拟,同时满足星点圆度、发光均匀度以及发光光谱的多参数模拟性能。所提出的设计方法也为更高级别的星模拟器研制提供一种可行的技术方案。     

Electronic Data Processing for Error and Dispersion Compensation

The use of smart electronic signal processing is emerging as a key technology to enable economical high-performance transceivers for high-speed optical networks (10 Gb/s and beyond). This paper surveys the role, scope, limitations, and challenges of this technology for enterprise, access, and core networks to enable cost-effective optical transceivers and to reuse the installed fiber infrastructure. Further, the state-of-the-art technology results in these areas will also be presented     

基于单芯片技术和垂直腔面发射激光器的光纤与光电器件被动无源对准光互连

在平行光互接应用的光收发器中,光纤对准占据了光电封装成本的一大部分。文章研究的光发送器和接收器由工作波长950nm的垂直腔面发射激光器（VCSELs）和谐振腔增强型（RCE）光检测器组成,并键合到单个双极型互补金属氧化物半导体（BiCMOS）芯片上。考虑到性能与生产成本,对不同的组装结构进行了研究。最终选择了利用倒装技术将光芯片键合到集成电路（IC）的方法。为实现光纤的被动无源对准,提出了在一片倒装焊了光芯片的IC上方叠放的硅片上蚀刻孔的设想。目前这样一种测试装置已由法国LETI开发出来,并通过它证明了采用这种方法能够获得高精度（μm）的光纤对准。     

大视场全天时星敏感器光学系统设计

全天时星敏感器作为星敏感器的一个发展分支,在飞机、热气球等近空间载体定姿定位方面有较好的应用前景,是GPS拒止条件下的可用导航手段。大视场全天时星敏感器相较于小视场全天时星敏感器在高精度轻小型化定姿定位方面具有较大的优势,针对近空间高度大视场全天时测星对光学系统的需求,对光学系统工作波长的选取进行了分析,利用消色差和消热差设计,实现了一种能够适应高低温环境的大视场、大相对孔径的透射式光学系统,并对像质进行了分析评价。系统工作波长为0.9～1.7μm, F/#为1.4,焦距为70 mm,视场为18°,结构总长为105 mm。试验结果表明,该光学系统具有良好的像质,能够满足大视场星敏感器白天测星要求。     

Analysis and dimensioning of switchless networks for single-layeroptical architecture

The “switchless” all-optical network is an alternative networking approach being developed in the framework of the ACTS project named SONATA, which aims to provide a future single layer, advanced transport architecture on a national scale. The single hop, shared access network employs time and wavelength agility (a WDMA/TDMA scheme), using fast tunable transmitters and receivers, to set up individual customer connections through a single wavelength router (suitably replicated for resilience). The dimensioning of this type of network is one of the main tasks for the design of networks serving a certain number of customers, connected together by means of passive optical networks (PONs). This paper reports an analytical model which allows the network dimensioning according to some relevant design parameters: the number of customers per PON, the number of PONs, the offered traffic per single user (either considering residential or business user), and the required system performance expressed in terms of blocking probability. Furthermore, relevant issues related to the dimensioning of switchless networks are discussed and some results achieved for relevant network scenarios are reported, to assess the feasibility of the system concept     

Single mode fiber MT-RJ SFF transceiver module using opticalsubassembly with a new shielded silicon optical bench

Demand for a compact cost reduced optical transceiver has arisen. Small form factor (SFF) optical transceivers are expected to meet this demand. A new concept optical module based on V-grooved silicon optical bench (SiOB) technology, that enables a passive alignment of optical fibers and optical devices is expected to reduce the cost. MT-RJ SFF optical transceivers require this new packaging technique because the distance between input and output optical axes is shorter than conventional transceivers. However, crosstalk between a transmitter and a receiver is a big issue to be solved because the distance between optical axes of the laser diode (LD) and the photo diode (PD) is only 0.75 mm. It is difficult to reduce the crosstalk in a SiOB because large electromagnetic coupling exists due to the conductivity of a silicon substrate. A newly developed, low crosstalk optical subassembly (OSA) with a single mode fiber MT-RJ receptacle and the SFF transceiver module are reported. We have analyzed a mechanism of electrical crosstalk in a SiOB and developed a shield structure to reduce it. The crosstalk in the OSA with shielded SiOB was reduced over 20 dB compared to the unshielded SiOB     

Scheduling in Optical WDM Networks Using Hidden Markov Chain Based Traffic Prediction

This paper presents the design and performance analysis of a predictor-based scheduling algorithm for optical wavelength division multiplexed (WDM) networks. WDM technology provides multiple, simultaneous and independent gigabit-per-second channels on a single fiber. A reservation-based multiple access control (MAC) protocol is considered here for a local area WDM network based on the passive star topology. The MAC protocol schedules reservation requests from the network nodes on the multiple channels. In previous work, we have presented an on-line scheduling algorithm for such a network. We have shown earlier that schedule computation time can significantly affect performance and the scheduling algorithms should be simple for better performance. In this work, we further improve system performance by using a hidden Markov chain based prediction algorithm. The objective here is to reduce the amount of time spent in computing the schedule by predicting traffic requests. Performance analysis based on discrete-event simulation, varying parameters such as number of nodes and channels is presented. The results show that the error of prediction is reasonable for most cases: more than 70% of the time, the error between actual request and predicted request is less than 20%. Network throughput is higher with the proposed prediction algorithm due to pipelining of schedule computation.     

FSK with direct detection in optical multiple-access FDM networks

High-performance optical data networks of the future may interconnect hundreds of users at gigabit rates for a reasonable cost. A novel approach is described that utilizes a passive star coupler for distribution, a multiplicity of frequency-shift keyed (FSK) tunable lasers to provide a frequency division multiplexed (FDM) network, and a tunable optical fiber Fabry-Perot filter to select the channels and convert the FSK signal to ASK (amplitude-shift keying) for direct detection. The design of high-speed FDM-FSK direct detection networks and the performance of critical devices, such as tunable FM lasers, tunable filters, integrated star couplers, and optical amplifiers, are reviewed and discussed