Design of an optical interconnect for photonic backplane applications

A compact alignment-tolerant interconnect has been developed for use within a prototype modulator-based free-space photonic backplane. The interconnect design encompasses several unique features. Microlens arrays are used, and several beams share each microlens by clustering the optical input-output in a small field about the optical axis of each lens. For simplifying the layout, the optical input and output of each smart-pixel array are clustered separately, thereby allowing a Fourier plane patterned-mirror array to be used in the beam-combination optics. This allows a suitable balance between high interconnection densities and reasonable optical relay distances between adjacent boards to be achieved. The primary advantages of this scheme are the simplicity of the optical design and its alignability, making it ideally suited for high-density interconnection applications.     

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.     

Optomechanics for a four-stage hybrid-self-electro-optic-device-based free-space optical backplane

We present the design, fabrication, and testing of optomechanics for a free-space optical backplane mounted in a standard 6U VME backplane chassis. The optomechanics implement an optical interconnect consisting of lenslet-to-lenslet, as well as conventional lens-to-lens, links. Mechanical, optical, electrical, thermal, material, and fabrication constraints are studied. Design trade-offs that affect system scalability and ease of assembly are put forward and analyzed. Novel mounting techniques such as a thermal-loaded interference-fitted lens-mounting technique are presented and discussed. Diagnostic tools are developed to quantify the performance of the optomechanics, and experimental results are given and analyzed.     

Design, implementation, and characterization of an optical power supply spot-array generator for a four-stage free-space optical backplane

The design and implementation of a robust, scalable, and modular optical power supply spot-array generator for a modulator-based free-space optical backplane demonstrator is presented. Four arrays of 8 x 4 spots with 6.47-mum radii (at 1/e(2) points) pitched at 125 mum in the vertical direction and 250 mum in the horizontal were required to provide the light for the optical interconnect. Tight system tolerances demanded careful optical design, robust optomechanics, and effective alignment techniques. Issues such as spot-array generation, polarization, power efficiency, and power uniformity are discussed. Characterization results are presented.     

Multimode polymeric Y junctions for star couplers in backplane optical interconnect

Three different multimode polymeric Y junctions with 50:50 splitting ratios were designed and their performance analyzed with ray tracing and measurements. There is agreement between measurements and modeling. The best performance is found for a Y junction in which the waveguide is split to S bends with 50% widths.     

Design and implementation of a modulator-based free-space optical backplane for multiprocessor applications

Design and implementation of a free-space optical backplane for multiprocessor applications is presented. The system is designed to interconnect four multiprocessor nodes that communicate by using multiplexed 32-bit packets. Each multiprocessor node is electrically connected to an optoelectronic VLSI chip which implements the hyperplane interconnection architecture. The chips each contain 256 optical transmitters (implemented as dual-rail multiple quantum-well modulators) and 256 optical receivers. A rigid free-space microoptical interconnection system that interconnects the transceiver chips in a 512-channel unidirectional ring is implemented. Full design, implementation, and operational details are provided.     

Performance of a compact, hybrid optical evanescent-wave sensor for chemical and biological applications

We describe a hybrid evanescent-wave sensor component that we fabricated by using an integrated optical interferometer with a specially adapted photodetector array. The design of the interferometer is based on the use of tapered waveguides to obtain two intersecting collimated beams. Phase shifts can be measured with an angular precision of better than 10(-3) rad, which corresponds to a superstrate index change inferior of 10(-6) with our structure. The interest in the device as a chemical sensor is experimentally demonstrated. The same optical component could be used in a variety of other sensor applications, e.g., biological and immunological sensors.     

Design and characterization of a microchannel optical interconnect for optical backplanes

The design, modeling, and experimental characterization of a microchannel-based free-space optical interconnect is described. The microchannel interconnect was used to implement a representative portion of an optical backplane that was based on field-effect transistor, self-electro-optic device smart-pixel transceivers. Telecentric relays were used to form the optical interconnect, and two modes based on two different optical window clusterings were implemented. The optical system design, including the optical geometry for different degrees of clustering of windows supported by a lenslet relay and the image mapping associated with a free-space optical system, is described. A comparison of the optical beam properties at the device planes, including the spot size and power uniformity of the spot array, as well as the effects of clipping and misalignment for the different operating modes, is presented. In addition, the effects of beam clipping and misalignment for the different operating modes is presented. We show that microchannel free-space optical interconnects based on a window-clustering scheme significantly increase the connection density. A connection density of 2222 connections/cm(2) was achieved for this prototype system with 2 x 2 window clustering.     

A compact optical wavelength splitter in one-dimensional photonic crystal waveguides

A fundamental T-branch in one-dimensional photonic crystal waveguides based on the omnidirectional reflection is constructed. Numerical simulations of this T-branch indicate that without any structural optimization, four high reflectance peaks and three high transmittance peaks appear alternately within a wide enough frequency band. The T-branch with the unique transmission characteristics can be used as a wavelength splitter. Combining the fundamental T-branch with flexible bends of one-dimensional photonic crystal waveguides, we construct simple and compact wavelength splitters with arbitrary branching angles. Those wavelength splitters are expected to be applied to high density photonic integrated circuits.     

Azobenzenes for photonic network applications: Third-order nonlinear optical properties

We review the third-order nonlinear performance of pseudo-stilbene type azobenzenes with an eye to application in ultrafast optical signal processing. We discuss mechanisms responsible for the nonlinear response of the azobenzenes. By aggregating experimental data and theoretical trends reported in the literature, we identify five characteristic regions of optical nonlinear response. Analyzed with respect to Stegeman figures of merit, pseudo-stilbene type azobenzenes show promise for ultrafast optical signal processing in two spectral regions, one lying between the main and two-photon absorption resonances, and the other for wavelengths longer than the two-photon absorption resonance. © 2001 Kluwer Academic Publishers     

Testbed for a scalable terabit optical local area network

The design of a fiber-optic local area network (LAN) demonstration system is described. A complete LAN system would consist of an array of 16 personal computers (PC's), where each PC has a network interface card (NIC) with a parallel fiber-optic datalink to a centralized optoelectronic switch core. The centralized core switches the data generated by 16 NIC's, up to 128 Gbit/s of bandwidth. The demonstrator is designed to scale to terabits of bandwidth by use of an emerging optoelectronic technology, i.e., integrated complementary metal-oxide semiconductor (CMOS) substrates with vertical-cavity surface-emitting laser (VCSEL) and photodetector optical input and output. A subset of the complete system was constructed and is operational. A prototype NIC card, with Motorola Optobus VCSEL transceivers for the optical datalinks, was constructed and is described. A prototype high-speed bipolar switch core, with statically configurable electrical positive-emitter coupled-logic 16 x 16 crossbar switches, CMOS field-programmable gate arrays, and Motorola Optobus transceivers, was constructed and is described. We successfully demonstrated the transmission of high-speed packetized data from one NIC card, through 10 m of parallel fiber ribbon and the centralized switch core, and back to the NIC. We summarize our experiences on the design and testing of our first demonstration system and our development toward a terabit switch core.     

Design, implementation, and characterization of a folded spot-array generator for a modulator-based free-space optical interconnect

A folded structured light generator is presented. This spot generator is to be used in a modulator-based free-space optical interconnect. Three cascaded diffractive optical elements produce 4 x 8 clusters on an 800 microm x 1600 microm pitch, in which each cluster is a 4 x 4 array of 13.1-microm-radius spots on a 90-microm pitch. The folded configuration is more compact than an existing linear spot-array generator and replaces 14 optical surfaces with eight surfaces. Details of the optical design, sensitivity analysis, alignment techniques, assembly, and test results are presented.     

Two-sided through-wafer interconnect for optical spiral delay line

True-time-delay devices could significantly contribute to improving the performance of many optical systems in applications such as sensing, ranging, communication and signal processing. Delay devices based on spiral optical waveguides are of special interest due to their small size and relatively low power attenuation. In this paper, we propose to fabricate spirals on both sides of a wafer, where the coupling between them is through a vertical interconnect. The novel through-wafer interconnect has a level of attenuation that compares competitively with that obtained with a conventional s-shaped interconnect between two interleaved spirals and considerably simplifies the waveguide design and fabrication.     

Structural,optical, mechanical,electrical, and antimicrobial activities of L-Glutamine Barium Acetate (LGBA) single crystal for biological,optical and photonic applications

Journal of Materials Science: Materials in Electronics - The most generally used slow evaporation technique at ambient temperature is used to develop L-glutamine barium acetate (LGBA) materials for...     

Growth and characterization of pure and metal ions-doped l-Taurine: a third-order nonlinear optical crystal for photonic applications

Journal of Materials Science: Materials in Electronics - Pure and 1, 3, 5&nbsp;mol% of nickel- and cobalt-doped l-Taurine (LT) crystals were grown by a slow evaporation method. Diffraction...     

Simple, stable, and compact multiple-reflection optical cell for very long optical paths

A new type of multiple-reflection optical cell is presented. One of the main advantages of this type of cell is that it can be made of standard mirrors without particular tolerance while allowing a great number of reflections and thus a large optical path, only limited by the reflection coefficient of the mirrors. The configuration is simple, compact, stable, and cheap. This cell consists of three mirrors as in a White cell but its principle is different. It behaves as a multiplier of a Herriott cell from which it inherits the opto-mechanical stability qualities. The Herriott cell and the White cell are two particular cases of this type of cell. As examples, a demonstrator and an absorption cell contained in a volume of 5 l are presented. The first device is usable with a laser in visible light. The second device is usable with an infrared laser diode for the detection of atmospheric trace species.     

Analysis of a vertical-cavity surface-emitting laser-based bidirectional free-space optical interconnect

The design of a bidirectional free-space optical interconnect system is presented. Vertical-cavity surface-emitting laser (VCSEL) arrays as a coherent light source and VCSEL beam collimation are described. Hologram array design and a way to improve the diffraction efficiency by use of a copying technique utilizing Dupont photopolymers are presented. Scattering from the hologram as a noise source is measured. An optical model for the design of system parameters such as the VCSEL beam diameter, size and apodization of the hologram, and size of the detector is given on the basis of cross-talk analysis of the system. The effect of VCSEL wavelength variation on system design is considered. Aberrations caused by the Fourier lens in the system are calculated, and ways for correction of the aberrations are discussed.     

Design, implementation, and characterization of a kinematically aligned, cascaded spot- array generator for a modulator-based free-space optical interconnect

The design and the implementation of a modular spot-array generator for a modulator-based free-space optical interconnect is presented. Two cascaded diffractive optical elements produce 4 x 8 clusters on a 1600 mum x 800 mum pitch, where each cluster is a 4 x 4 array of (1/e(2)) 13.1-mum-radius spots on a 90-mum pitch. The spot-array generator is kinematically aligned to the interconnect system such that no realignment is necessary between removal and reinsertion. Characterization results are presented.     

The designs of a scalable optical packet switching architecture

Abstract

This paper proposes a new switching architecture to be used in all optical packet switching networks. The proposed switch is derived from an original 2 × ?2 two‐stage multi‐buffer switched delay line based optical switching node, known as an M‐Quadro node. By incorporating bypass lines into the M‐Quadro architecture and employing a novel switch control strategy, the optical packet switching node can effectively resolve packet contentions, thus reducing the packet deflection probability substantially. Furthermore, we show that such architecture is scalable for a generic multiple stages optical packet switch with a larger number of input/output ports.