Ronny Bockstaele

Circuit-level simulation approach to analyze system-level behavior of VCSEL-based optical interconnects

In order to satisfy the increasing demand for interchip interconnect bandwidth, a number of current research projects are concentrating on the use of waveguided optical interconnect arrays to span PCB-range distances. To accelerate system design and technology development, CAD tools for the design and the simulation of the interconnects are indispensable. We are developing a design methodology for optical inter-chip interconnects, to produce a tool for assisting system designers on deciding on product and parameter options for the different interconnect building blocks. A mandatory first step in this methodology development concerns the investigation of the combined impact of individual product and parameter variations on system-level interconnect system properties. Accurately predicting some interconnect properties requires analog simulation of the full electrical-optical-electrical links. Detailed models for the link building blocks involving geometrical calculations are much too slow for this purpose. Circuit-level simulation tools, with appropriate model descriptions, are much more suitable. In this paper, we describe our framework for the joint simulation of the entire optical interconnect with a mixed analog/digital system. We discuss in detail a number of issues that are involved with the implementation of circuit-level simulation models in the analog modelling language Verilog-AMS, and show a link simulation example.

Demonstrating POF based optoelectronic interconnect in a multi-FPGA prototype system

The goal of our work is demonstrating the viability of massively parallel optical interconnect between electronic CMOS VLSI chips. Here we describe the definition and realisation of a systems architecture in which these interconnections can play a meaningful role. The architecture is a multi-FPGA system with low level optoelectronic interconnects introduced into the FPGA chips. A demonstrator, reaching 10 Gbit/s/chip aggregate bit rate with small-scale custom made optoelectronic FPGAs, shows the feasibility of this approach.

A multi-FPGA demonstrator with POF-based optical area interconnect

It is our goal to demonstrate the viability of massively parallel optical interconnects between electronic VLSI chips. This is done through the development of the technology necessary for the realisation of such interconnections, and the definition and realisation of a systems architecture in which these interconnections play a meaningful role. Multi-FPGA systems have been identified as a good candidate for the introduction of low level optoelectronic interconnects, from both the systems and the purely demonstrator related points of view. An optoelectronic FPGA demonstrator along these lines is currently being realised. This involves besides the actual CMOS FPGA, the design and implementation of various light sources and detectors, as well as the analogue CMOS interface circuits; the building blocks of the optical pathways, which are based upon plastic optical fibre; and the methodology for hybrid assembly, packaging and passive alignment of all components. The optoelectronic FPGA demonstrator aims at using a smart-pixel like interconnect structure to create a logically 3-dimensional architecture.

Direct MT(TM)-compatible connectorisation of VCSEL and LED-arrays to plastic optical fiber ribbon for low cost parallel datalinks

For the realisation of MT compatible direct connectorised modules, a PMMA-based interconnection scheme, using index-alignment is developed. Plastic pieces are accurately positioned with respect to the chips and then fixed with epoxy, following an index-alignment strategy. Alignment accuracies in the range of 5 to 10 /spl mu/m have been achieved, which is sufficient to have good coupling efficiencies in view of the relaxed alignment tolerances when coupling to large core POF (120/125 /spl mu/m). The chips are assembled in commercially available packages, which are then mounted on PCB boards. First coupling measurements on fully assembled modules, using a red (670 nm) 1/spl times/8 VCSEL-array and a 1/spl times/8 RC-LED (Resonant Cavity LED, 980 nm), are successfully carried out.

Microcavity LEDs coupled to POF arrays for parallel optical interconnects

A low cost approach for realising parallel optical interconnects, based on the use of micro-cavity LEDs and polymer optical fibres (POFs) has been proposed. LEDs were optimised for coupling to POF, yielding 3% external quantum efficiency into POF. Optimisation of the POF-termination procedure has led to interface losses of 0.3 dB. An alignment scheme, avoiding active alignment, has been discussed offering lateral misalignment tolerances in the 10 - 15 /spl mu/m range, which is compatible with the use of 125 /spl mu/m POF.

Electrically pumped photonic crystal micro-cavity light emitting diodes

Photonic crystal InGaAs MQW micro-cavity LEDs have been designed and fabricated. The spectra of the devices demonstrate that the extracted light consists of both the surface normal resonant mode and the diffracted guided mode.

Substrate-removed 850-nm RCLEDs and small core (63/125 um) plastic optical fibers for optical data communication

Current developments in computer technology give rise to increasing data communication over relatively short distances at backplane- and inter MCM interconnect level. It is foreseen that electrical interconnect will not be able to accommodate the necessary data traffic in advanced data processing systems in the future and hence a bottleneck will be created. A potential remedy for this interconnect problem is the use of parallel optical datalinks. In this paper we propose small diameter step index plastic optical fiber ribbons in combination with high efficient resonant cavity LEDs as a cheap and feasible option for these optical links. A design for such an optical link is presented with special attention for the optical pathway. Experimental results on the optical properties of the used POF are shown. We describe the development of RCLEDs at 850 nm specially designed for efficient coupling into POF. We measured a RCLED to POF coupling efficiency up to 40%. Additionally we report on the technologies used for the fabrication and assembly of the optical pathways and finally some experiments were carried out on the first realized assemblies.