Elmar Griese

A high-performance hybrid electrical-optical interconnection technology for high-speed electronic systems

A new and innovative interconnection technology applicable for printed circuit boards is presented. This technology is widely compatible with the existing design and manufacturing processes and technologies for conventional multilayer pc boards and it combines electrical and optical interconnects on pc board level. It provides the potential for on-board bandwidth of several Gb/s and closes the bottleneck caused by the limited performance of electrical interconnection technology. After giving an overview on the most important basic technologies and first available results and engineering samples, the focus of this paper is on the development of appropriate modeling methodologies and simulation algorithms necessary for designing and optimizing optical on-board interconnects within the conventional electrical pc board environment.

Ray tracing technique and its verification for the analysis of highly multimode optical waveguides with rough surfaces

A novel hybrid ray tracing technique for the analysis of signal propagation in highly multimode optical waveguides with rough surfaces and its verification in part is presented. The technique combines geometrical optics with a light scattering model, based on wave optics by applying a Monte Carlo method. While the light scattering model takes mode coupling caused by surface irregularities into account, the ray tracing technique provides the analysis of light propagation in highly multimode waveguides with arbitrary shapes. The verification is obtained by calculating wave propagation within a slab waveguide with rough surfaces applying the well known coupled power theory, which provides the power of the guided modes versus the axial coordinate of the waveguide. Therefore, the ray tracing results are transformed into the discrete waveguide modes in order to compare the results.

Reducing EMC problems through an electrical/optical interconnection technology

A novel interconnection technology for printed circuit boards (PCBs) is proposed that has the potential to meet the high-performance requirements of future electronic equipment while at the same time, the electromagnetic compatibility (EMC) behavior will be improved significantly. The technology has a far-reaching compatibility with the existing printed circuit-board technology and the existing design and manufacturing processes of the electrical part do not need significant modifications. After a short description of the most important basic technologies for its realization, this paper focuses on a general approach for modeling the resulting hybrid electrical/optical interconnections containing integrated optical highly multimodal waveguides with manufacturing-caused rough surfaces. Especially the transient analysis is addressed in order to provide an efficient analysis methodology and algorithms for timing and signal integrity prediction necessary for designing and manufacturing high-speed electronic systems. The developed overall modeling strategy is explained and first available results are presented.

Electrical-Optical Printed Circuit Boards: Technology - Design - Modeling

A novel hybrid electrical-optical printed circuit board technology is introduced which is able to meet the high performance requirements of future electronic equipment. On-board data rates exceeding significantly 1 Gbps are enabled where at the same time EMC- and signal integrity problems can be reduced. The technology has a far-reaching compatibility with the existing technologies and processes for designing and manufacturing printed circuit boards, which means that there is no need to substantially modify the electrical part. This compatibility is a very important pre-requisite in order to enable reasonable costs and to allow a successful introduction of this technology to next generation products.

Self-aligned coupling of optical transmitter and receiver modules to board-integrated optical multimode waveguides

A coupling concept for a self-aligning and passive assembly of optical transmitter and receiver modules to board-integrated multimode waveguides is presented. The coupling mechanism is based on a 90 degree(s) beam deflection provided by micro-mirrors which are part of the board-integrated waveguides. The alignment is obtained by a mechanical high precision interface consisting of alignment pins well known from MT connectors at the module side and corresponding holes which are part of the optical layer. As the production of the alignment holes is part of the manufacturing of the optical layer, the required accuracy can be achieved without noteworthy difficulties.

Optical interconnections on printed circuit boards

In this paper an optical interconnection technology for high-speed printed circuit board application is presented. This technology is widely compatible with the existing design and manufacturing technologies of conventional multi- layer pc boards and it combines electrical and optical interconnects on pc board level. Using this interconnection technology on-board bandwidth of several Gbps can be realized. As conventional pc board technology provides sufficient performance characteristics for the majority of all on-board signals only a hybrid technology which is compatible to the existing printed circuit board design and manufacturing processes is able to lead to a practical solution at reasonable cost. This compatibility demand results in different technological, functional, and economic requirements which also consider potential application for high performance computing and telecommunication hardware. In this paper an overview is given on the requirements, on the basic technologies for manufacturing electrical-optical pc boards as well as on the extended design process with its modeling and simulation methodologies and strategies.

Parallel optical interconnects for high performance printed circuit boards

A novel and innovative interconnection technology for printed circuit board application is presented which is able to meet the high performance requirements of future electronic equipment while at the same time improving the electromagnetic compatibility (EMC) significantly. This technology will have a far-reaching compatibility with the existing printed circuit board technology, which means that the design and manufacturing processes of the electrical part do not need significant modifications. After a short description of the most important basic technologies and results for its realization, the paper focuses on the design and modeling of parallel electrical/optical interconnection systems. Transient analysis is addressed in order to provide an efficient analysis methodology as well as algorithms for timing and signal integrity prediction necessary for designing and manufacturing high-speed electronic systems of high quality. The developed overall modeling strategy is explained and first available results are presented. Besides a time domain transmission line model for parallel optical multimode structures considering delay, losses, dispersion, and crosstalk the corresponding modeling approaches for laser- and photo-diodes are presented.

Time domain simulation of optical multimode chip-to-chip interconnects

To increase the bandwidth of high-performance chip-to-chip interconnects optical on-board interconnects can be used. Since the design procedure of such optical interconnects has to be widely compatible with current computer aided board design processes, adequate simulation methods are required. In this paper an efficient and design process compatible method for simulating the transmission behavior of optical multimode chip-to-chip interconnects is presented. The approach is based on a time domain description where an optical multimode waveguide is represented by a multiport. The different transfer paths between the input- and output ports describe the transmission behavior of the entire waveguide. The transmission behavior of each individual path can be characterized by its step response, which can be computed by the aid of an extended ray tracing method. Due to some fundamental properties of these step responses, its piecewise approximation by simple exponential functions is possible. As a consequence the pulse responses of each transfer path can be determined analytically and they are also approximated by exponential functions. Finally this procedure enables the application of a semi-analytic recursive convolution method for the computation of the waveguide transmission behavior. The simulation procedure is illustrated and discussed by a set of examples.

Electro-optical circuit boards with four-channel butt-coupled optical transmitter and receiver modules

Chip-to-chip interconnects on printed circuit boards within high-speed electronic systems act increasingly as a limiting bottleneck for the achievable system performance, since local processing speed often exceeds the bandwidth capabilities of conventional electrical interconnects. In addition, rising signal frequencies or clock rates also result in increased susceptibility to electromagnetic interference. The well known limitations and problems of electrical interconnects can be overcome with optical interconnects, which have made their way from long haul telecommunication networks to parallel fiber optical modules for board-to-board interconnects within systems. Extending the advantages of optical signal transmission for very short reach interconnect applications, i.e. board or module level interconnects, therefore is a consequent logical step. This paper presents the integration of optical waveguides into conventional printed circuit boards to achieve hybrid electrical-optical boards with high- bandwidth optical interconnects. The realization of such electrical-optical boards is demonstrated with boards containing 4-channel transmitter and receiver modules, utilizing lead-frame based array GaAs-VCSEL and Si-PIN-diode components. The waveguides are manufactured by hot embossing and laminated into the boards within a standard printed circuit board production process. To couple light into and out of the optical waveguides a butt-coupling technique is applied.

Approach to model optical multimode interconnects for time-domain simulation

Next generation high-speed pc board interconnects will be based on integrated optical multimode waveguides with cross- sectional sizes comparable to those of electrical microstrip lines. The design of such interconnects requires appropriate simulation models of the multimode waveguides and the laser- and photo-diodes, as well. Since single-mode interconnects can be modeled very efficiently by well known numerical methods such as FEM and BPM, these methods are not applicable for optical multimode waveguides with more than 1000 propagating modes. Due to the numerical complexity only methods based on geometrical optics, called ray tracing, can be applied efficiently. This paper deals with a time domain modeling and simulation approach for analyzing the signal behavior of multimode waveguide based electrical-optical interconnection systems as a whole. Modeling of multimode waveguide components as well as macromodeling of laser- and photo-diodes is explained in detail. The modeling approaches are discussed by examples.