Experimental evaluation of the 3-D optical shuffle interconnectionmodule of the sliding Banyan architecture

A free-space optical interconnection module for the sliding Banyan (SB) multistage interconnection network is experimentally evaluated. This three-dimensional (3-D) optical shuffle topology employs a macro-lens array in a reflective architecture. Interconnections for multiple stages are interleaved across a single two-dimensional (2-D) multichip array of “smart pixels”. The experimental module implements five interleaved stages of shuffle interconnections with approximately 10 μm resolution and 10 μm registration accuracy across a 10×10 cm, 256 node, simulated optoelectronic (OE) backplane. The experiments demonstrate the use of conventional refractive optical elements to implement the required shuffle interconnection pattern in a SB network. The results suggest that this reflective 3-D shuffle interconnected SB approach may lead to ATM switching fabrics with aggregate throughputs scaleable to >1 Tb/s. Such a system could be implemented with vertical cavity surface emitting laser (VCSEL) based smart pixel OE technology     

Optical backplane system using waveguide-embedded PCBs and optical slots

As discussed in this paper, a practical optical backplane system was demonstrated, using a waveguide-embedded optical backplane board, processing boards, and optical slots for board-to-board interconnection. A metal optical bench was used as a packaging die for the optical devices and the integrated circuit chips in both the transmitter and the receiver processing boards. The polymer waveguide was produced by means of a hot-embossing technique and was then embedded following a conventional lamination processes. The average propagation loss of these waveguides was approximately 0.1 dB/cm at 850 nm. The dimension and optical properties of the waveguide in an optical backplane board were unchanged after lamination. As connection components between transmitter/receiver processing boards and an optical backplane board, optical slots were used for easy and repeatable insertion and extraction of the boards with a micrometer-scale precision. A 1/spl times/4 850-nm vertical-cavity surface-emitting laser array was used with 2 dBm of output power for the transmitter and a p-i-n photodiode array for the receiver. This paper successfully demonstrates 8 Gb/s of data transmission between the transmitter processing board and the optical backplane board.     

Design limitations of highly parallel free-space opticalinterconnects based on arrays of vertical cavity surface-emitting laserdiodes, microlenses, and photodetectors

We utilize a novel diffraction formalism to study the crosstalk effect in a highly parallel free-space optical interconnect based on two-dimensional arrays of surface-emitting laser diodes, microlenses, and photodetectors. The diffraction induced crosstalk between adjacent laser diodes in each detector to the system limitations is investigated. Optimum design rules and formulas are given for the first time, to include the relation of channel packaging density and interconnect length to the design parameters of the optical interconnect components. The design formulas developed here yield an optimum detector size and indicate a tradeoff between channel packaging density and interconnect length. The feasibility of such a free-space interconnect with a channel packaging density of 3460 channels/cm² and 2.0 cm interconnection length is determined using typical parameters of detector radius from ~5 to ~45 μm, lens radius of 85 μm, and laser diode radius of ~5 pm operating at wavelength 0.67 pm for signal-to-noise ratio above 17 dB. Some experiments were conducted to measure the diffraction induced crosstalk and optical link efficiency     

Optical fiber interconnection for the scalable parallel computingsystem

In this paper, we discuss the optical fiber interconnection technologies applied in the two types of parallel processing systems: 1) a backplane interconnection in a parallel processor array system and 2) a computing cluster network. We have set up a parallel processor array system using optical fiber to make point-to-point interconnection between processor elements and are developing a low-cost virtual parallel optical fiber interconnection link (VPOFLink) complying with peripheral component interconnect (PCI) local bus specifications for the computing cluster. VPOFLink is integrated with the popular PCI bus interface in order to make the link hold the same bandwidth as that of the PCI bus. It was fabricated as an available peripheral device that can been inserted into the bus slots of commercial computers directly and can operate under the control of PCI bus. Also in this paper, we demonstrate the optical fiber link for a ring network and the architecture of the ring network     

Technology development of a high-density 32-channel 16-Gb/s opticaldata link for optical interconnection applications for theoptoelectronic technology consortium (OETC)

A parallel, 32-channel, high density (140 μm pitch), 500 Mb/s NRZ, point-to-point, optical data link has been fabricated using existing GaAs IC, silicon optical bench (SiOB), and multichip module (MCM-D) technologies. The main components of the transmitter and the receiver modules are a GaAs-based vertical cavity surface emitting laser (VCSEL) array at 850 mn with its IC driver array chip and an integrated metal-semiconductor-metal (MSM) receiver (photodetector and signal processing circuits) array at 850 nm. The package module uses a modified 164 I/O JEDEC premolded plastic quad flat pack (PQFP) in combination with a polymer film integrated circuit (POLYFIC) chip carrier. The electrical input and output are 500 Mb/s NRZ binary signals. The optical I/O in both modules consists of a directly-connectorized (nonpigtail) fiber array block that plugs into the 32×1 optical fiber ribbon directly on one side and accepts 32 optical signals from the SEL array or delivers them to the MSM receiver array via a gold-coated 45° polished fiber array mirror. The MACII-32 ribbon cable is an enhanced version of the standard MACII connector ribbon cable. This paper characterizes key components of the optical data link, describes its package design, and discusses preliminary component and optical data link test results     

8-Gb/s source-synchronous I/O link with adaptive receiver equalization, offset cancellation, and clock de-skew

A source-synchronous I/O link with adaptive receiver-side equalization has been implemented in 0.13-/spl mu/m bulk CMOS technology. The transceiver is optimized for small area (360 /spl mu/m /spl times/ 360 /spl mu/m) and low power (280 mW). The analog equalizer is implemented as an 8-way interleaved, 4-tap discrete-time linear filter. The equalization improved the data rate of a 102 cm backplane interconnect by 110%. On-die adaptive logic determines optimal receiver settings through comparator offset cancellation, data alignment of the transmitter and receiver, clock de-skew and setting filter coefficients for equalization. The noise-margin degradation due to statistical variation in converged coefficient values was less than 3%.     

High-Speed Optical Interconnect Coupler Based on Soft Lithography Ribbons

In this paper, high-speed optical ribbon couplers for card-to-backplane interconnect applications are presented. The ribbon couplers are based on evanescent coupling between flexible multimode waveguide arrays. A soft lithographic technique is utilized to fabricate the ribbons. A flexible nonterminating optical data bus has been developed. Using BeamPROP software, we simulated the evanescent light coupling between two closely spaced ribbon waveguides to study the effects of waveguides separation, interaction length, and misalignment on coupling efficiency. Further experimental analysis and tests have been performed to quantify these effects. To investigate data transmission performance, a 12-channel optical interconnect link has been assembled. Experimental results demonstrated successful evanescent coupling; facilitating auto alignment coupling between card and backplane ribbon waveguides at data speeds as high as 10 Gb/s per channel. The evident high-speed interconnect performance and rapid ribbon prototyping approach can result in overall lower cost coupler fabrication for prospective optical interconnect applications.      

Gigabit-per-second cryogenic optical link using optimizedlow-temperature AlGaAs-GaAs vertical-cavity surface-emitting lasers

We describe the design of GaAs-AlGaAs vertical-cavity surface-emitting lasers (VCSELs) that are optimized for operation at very low temperatures and the experimental demonstration of a free-space optical interconnect for cryogenic electronic systems using a VCSEL. We demonstrate high-speed modulation of the optical link at a data rate of up to 2 Gb/s at 77 K, with a very low bit-error rate of <10^-13 , and thermally stable operation is achieved over a wide range of cryogenic temperatures without laser bias current compensation. Cryogenic VCSELs with excellent lasing characteristics have been achieved over the entire temperature range from 150 K to 6 K, including high output power (22 mW), high power-conversion efficiency (32%), high slope efficiency (~100%), low threshold voltage (1.75 V) and current (1.7 mA), as well as a high-modulation bandwidth (12 GHz) for a 16 μm diameter device at 80 K     

Low-loss single-mode GaAs/AlGaAs miniature optical waveguides withstraight and bending structures

Low-loss single-mode GaAs/AlGaAs miniature optical waveguides fabricated for use in monolithically integrated optical circuits are discussed. The propagation characteristics of these waveguides with straight and S-bending structures have been investigated at wavelengths of 1.30 and 1.55 μm. The lowest propagation losses are estimated to be 0.58 dB/cm and 0.69 dB/cm at wavelengths of 1.30 and 1.55 μm, respectively. The total loss of an S-bending waveguide with a curvature radius of 2 mm and with a lateral displacement of 200 μm was 0.61 dB and 0.46 dB at wavelengths of 1.30 and 1.55 μm. The fabricated single-mode strip-loaded waveguides proved to be suitable for application of the semiconductor waveguide into monolithically integrated optical circuits     

Conventional contact interconnect technology as an alternative tocontact plug (W) technology for 0.85 μm CMOS EPROM IC devices

The conventional (plug-less) and tungsten (W) plug contact interconnect technologies were studied for the fabrication of 0.85 μm CMOS EPROM integrated circuit devices. 4 Mbit EPROM devices and appropriate test structures were fabricated using these two interconnect architectures and were evaluated for process simplicity, associated problems/solutions, contact electrical characteristics, and circuit yield and speed. The most important process issue for the conventional contact technology was the overlay accuracy of the stepper used for printing the contacts. It was found that a misalignment of <0.3 μm was essential if contacts were to be reflowed after the contact etch process in a way that: a) did not violate the geometrical design rules, and b) did not result in bulging of the contacts, or an increase in the contact profile angle which would degrade metal step coverage. Electrical characteristics of the contacts were studied through contact resistance, specific contact resistivity, contact failure rate, and junction leakage measurements for both contact interconnect architectures. The data presented indicated that both processes produced contacts with similar characteristics. Finally, the results of this work indicated that the conventional contact interconnect technology could be reliably used for fabrication of 0.85 μm CMOS EPROM devices. This process was simpler, less expensive, and as structurally reliable as the W contact plug technology     

Board-level 2-D data-capable optical interconnection circuits usingpolymer fiber-image guides

We present various board-level optical circuits capable of transmitting large-bandwidth two-dimensional (2-D) parallel data for intracomputer optical interconnect applications. The backbone technology of these circuits is a polymer fiber-image guide that can transmit optical data generated from an optoelectronic transmitter array such as a 2D vertical cavity surface-emitting laser array. We demonstrate both point-to-point circuits and circuits incorporating nodes with splitting and combining capabilities. We also present main performance characteristics, such as insertion loss and spatial resolution, and discuss other advantages and limitations of the new optical circuit technology     

A method for rebroadcasting signals in an optical backplane bussystem

A guided-wave optical backplane bus system intended for use in high-performance board-to-board interconnects is described. Its multiplexed polymeric holograms can implement optical signal broadcast between boards so that all boards share common optical channels. By introducing an active coupler to the doubly multiplexed hologram at the center board, signals received from any board can be rebroadcast to all other boards. We describe the design concepts for a centralized optical backplane and the resulting performance and assembly advantages over previously developed guided-wave and free-space optical backplane bus systems used for broadcasting signals. These advantages include equalized fan-out power, increased interconnect distance, and simpler fabrication     

An optical holographic backplane interconnect system

An optical holographic backplane interconnect system capable of high-speed information transmission between optoelectronic transmitter/receiver boards is described. Using conjugate pairs of transmission gratings in a folded reflection geometry, a practical method of insulating the interconnect system from wavelength variations due to temperature or power fluctuations can be achieved. The final demonstration unit was developed in a fully packaged form and has the potential for reconfigurable interconnects and may serve as a testbed for a variety of interconnect networks and hardware protocols     

Power minimization and technology comparisons for digitalfree-space optoelectronic interconnections

This paper investigates the design optimization of digital free-space optoelectronic interconnections with a specific goal of minimizing the power dissipation of the overall link, and maximizing the interconnect density. To this end, we discuss a method of minimizing the total power dissipation of an interconnect link at a given bit rate. We examine the impact on the link performance of two competing transmitter technologies, vertical cavity surface emitting lasers (VCSELs) and multiple quantum-well (MQW) modulators and their associated driver-receiver circuits including complementary metal-oxide-semiconductor (CMOS) and bipolar transmitter driver circuits, and p-n junction photodetectors with multistage transimpedance receiver circuits. We use the operating bit-rate and on-chip power dissipation as the main performance measures. Presently, at high bit rates (>800 Mb/s), optimized links based on VCSELs and MQW modulators are comparable in terms of power dissipation. At low bit rates, the VCSEL threshold power dominates. In systems with high bit rates and/or high fan-out, a high slope efficiency is more important for a VCSEL than a low threshold current. The transmitter driver circuit is an important component in a link design, and it dissipates about the same amount of power as that of the transmitter itself. Scaling the CMOS technology from 0.5 μm down to 0.1 μm brings a 50% improvement in the maximum operating bit rate, which is around 4 Gb/s with 0.1 μm CMOS driver and receiver circuits. Transmitter driver circuits implemented with bipolar technology support a much higher operating bandwidth than CMOS technology; they dissipate, however, about twice the electrical power. An aggregate bandwidth in excess of 1 Tb/s-cm² can be achieved in an optimized free-space optical interconnect system using either VCSELs or MQW modulators as its transmitters     

An optoelectronic CMOS memory circuit for parallel detection andstorage of optical data

A CMOS static RAM (SRAM) circuit capable of detecting and storing optically transmitted data is described. Bits of data are transferred to the memory circuit via an array of parallel light beams. A 16-b optoelectronic SRAM was fabricated in a standard bulk CMOS process and tested using argon and helium-neon lasers. Data contained in an array of 16 light beams with an average power of 3.35 μW/pixel were successfully transferred to the SRAM in parallel fashion. The storage of the optical information was verified by electronically addressing each cell. The optical data transfer technology is extended to other systems in which high speed and parallelism are essential     

Polymer Optical Interconnects—A Scalable Large-Area Panel Processing Approach

A flexible approach to producing optical interconnects on 609.6$ast ,$609.6 mm large-area panels is demonstrated. Stepwise projection patterning from 101.6$ast ,$101.6 mm masks has generated optical waveguide patterns over the whole panel using large-area projection lithography equipment. The waveguide routing design allows optical waveguides on different 101.6$ast ,$101.6 mm tiles to be interconnected. Four different waveguide connecting geometries in the border region between tiles have been fabricated and tested. Multimode waveguides from inorganic-organic hybrid polymers (ORMOCER) (cross section:$le hbox 50~muhbox mast hbox 10~muhbox m$) with refractive index step between core and cladding$Delta n=hbox 0.01$were produced. The index step was adjusted by mixing two diffrent ORMOCER systems. The materials show good adhesion to numerous substrates, such as glass and silicon. Application concepts such as flexible manufacturing of optoelectrical hybrid backplanes with two-dimensional interconnect, a three-dimensional optical interconnect with optical vias, and a hybrid backplane with the optical interconnect in a strip-format on a separate plane right above the electrical plane are proposed. Promising new technologies are presented along with preliminary demonstrativ viability.     

Optical phased array technology

Optical phased arrays represent an enabling new technology that makes possible simple affordable, lightweight, optical sensors offering very precise stabilization, random-access pointing programmable multiple simultaneous beams, a dynamic focus/defocus capability, and moderate to excellent optical power handling capability. These new arrays steer or otherwise operate on an already formed beam. A phase profile is imposed on an optical beam as it is either transmitted through or reflected from the phase shifter array. The imposed phase profile steers, focuses, fans out, or corrects phase aberrations on the beam. The array of optical phase shifters is realized through lithographic patterning of an electrical addressing network on the superstrate of a liquid crystal waveplate. Refractive index changes sufficiently large to realize full-wave differential phase shifts can be effected using low (<10 V) voltages applied to the liquid crystal phase plate electrodes. High efficiency large-angle steering with phased arrays requires phase shifter spacing on the order of a wavelength or less; consequently addressing issues make 1-D optical arrays much more practical than 2-D arrays. Orthogonal oriented 1-D phased arrays are used to deflect a beam in both dimensions. Optical phased arrays with apertures on the order of 4 cm by 4 cm have been fabricated for steering green, red, 1.06 μm, and 10.6 μm radiation. System concepts that include a passive acquisition sensor as well as a laser radar are presented     

15 Gb/s multichannel optical interconnect laser array transmitteroperating at λ=1.3 μm

We have fabricated and measured detailed bit error rate experiments on a 12 channel optical interconnect transmitter operating at rates up to 1.25 Gb/s per channel, using InGaAsP/InP λ=1.3 μm lasers. The lasers are highly uniform, the channel crosstalk is less than 1 dB, and the mode selective losses are low (<1 dB). This transmitter has been demonstrated in an architecture which would allow the transmission of 120 channels of 100-Mb/s uncompressed video signals     

卫星地面站高速数据传输终端平台设计

提出了一种具有开放式架构的新型高速数据传输终端平台,它以RapidIO作为各处理板卡的监控指令接口,以两个8×PCIe作为各处理板卡的数据接口。设计了有源交换网络背板实现系统互联;设计了通用处理板卡通过软件重构以实现数据上行调制或数据下行接收功能;下行接收的数据通过块数据传输,传输速率最高达40 Gb/s;通过独立磁盘冗余阵列扩展固态盘阵列实现数据高速记录,数据记录速率不低于500 MB/s;通过万兆以太网接口实现数据高速实时转发,数据转发速率不低于4 Gb/s;上行调制数据实时注入实时调制,数据速率不低于2 Gb/s。该平台硬件可扩展,软件可升级,控制和数据总线解耦合,可通过软件重构实现功能配置和在线更新,具有良好的扩展性和通用性,已在地面终端站高速数据传输系统中得到工程应用。     

Room temperature photonic crystal defect lasers at near-infraredwavelengths in InGaAsP

Room temperature lasing from optically pumped single defects in a two-dimensional (2-D) photonic bandgap (PBG) crystal is demonstrated. The high-Q optical microcavities are formed by etching a triangular array of air holes into a half-wavelength thick multiquantum-well waveguide. Defects in the 2-D photonic crystal are used to support highly localized optical modes with volumes ranging from 2 to 3 (λ/2n)³. Lithographic tuning of the air hole radius and the lattice spacing are used to match the cavity wavelength to the quantum-well gain peak, as well as to increase the cavity Q. The defect lasers were pumped with 10-30 ns pulses of 0.4-1% duty cycle. The threshold pump power was 1.5 mW (≈500 μW absorbed)