SBIR-STTR Award

Early new millennium may foresee GHz PC. However, the slowness of transmitting signals off the processor-chip, for example, processor to memory, makes the system bus speed (~100 MHz) significantly slower than the clock speed. Consequently, the off-processor interconnection speed becomes a major bottleneck to further upgrading the system performance. In this program, RRI proposes a packaging-compatible fully embedded optical bus based on polymeric waveguides within the circuit board where high-speed ICs are located. This optical bus will follow IEEE-standardized ones such as VMEbus and Futurebus. The optical interconnect elements including waveguides, couplers, lasers and detectors are all embedded in the three-dimensional interconnection layers involving both electrical and optical interconnections. Electrical-to-optical and optical-to-electrical signal conversions are realized within the optical interconnection layers using polymer-based waveguide-couplers. Modulation and demodulation signals are tapped in and out through the electrical vias. The input and output signals on the surface of the PC-board are purely electrical. Such a structure has fully bandwidth advantage promised by optics while keeping the packaging-compatibility with IC chips. Performance enhancement and cost-effectiveness are achieved simultaneously through the proposed approach.In phase I program, the polymer-based optical bus layer will be developed. The optical bus protocol suitable for the proposed system architecture will be investigated. Due to the acceleration of interconnection speed, the proposed polymer-based optical bus is expected to attract a number of computer companies to jointly support the phase II efforts. A fast track phase II program will be arranged. Realization of optical communications depends on the successful transmission of high-speed signals among processing elements, memories and other peripherals with minimum losses. A packaging-compatible embedded photonic integrated circuit involving lasers, waveguides, and detectors is essential for such a task. The transferability of the embedded thin-film structure can be realized on any substrate of interest including Silicon. Other potential applications include perfect shuffle networks, optical sensing devices, nonlinear optics, switching devices, and Si CMOS process compatible optical interconnection and intra- and inter-MCM optical interconnects. The pay load reduction due to the nature of thin film optics is also important for space-borne applications where BMDO has an important role.

Keywords:
Optical Interconnects, Polymer-Based Photonics, Pc Board, Thin-Film Optoelectronics, Vmebus.

In this proposed Phase II program we will develop board-level optical waveguides to alleviate the ever-tightening electrical interconnection bottleneck. VLSI provides fast intrinsic signal speeds but these speeds cannot be supported by electrical interconnects between other chips on the same board. Conversion to optical interconnects at the intra-board level can overcome these limits. The practical limits of optical interconnects arises from the optoelectronic transmitters and receivers, which currently have bandwidths up to 10GHZ. The emerging 40-GHz OC-768 telecommunications standard is a strong indication that optical interconnects will keep pace with VLSI for many years. However, their cost-effective assimilation into conventional technologies remains the major unresolved issue. Therefore, we propose an optoelectronic board-level bus employing a fully imbedded optical interconnection layer based on polymeric waveguides, thin-film vertical-cavity-surface-emitting lasers (VCSELs) and thin-film metal-semiconductor-metal (MSM) photodetectors, integrated onto a PCB structure and planarized to allow conventional integration of noncritical electrical interconnects. Optical couplers will couple light between the transceivers and the chips mounted on the boards's surface. By demonstrating these integrations we will prove the practicality of high speed board-level optical interconnects, which should lead to Phase III commercialization. The proposed technology to be developed replaces board-level electrical interconnects with optical interconnects for critical high-speed signals. Because the optical interconnectivity layer is embedded in an otherwise conventional printed circuit board (PCB), this technology supports conventional PCB design and fabrication practices. Electronics engineers can design systems utilizing both electrical and high-speed optical interconnects without concerning themselves with the unfamiliar optical technologies. This should result in broad market acceptance. Once accepted the technology should continue to be useful for many years as advancements in telecommunications optoelectronic devices are readily incorporated into the board level optical interconnects.

Keywords:
Optoelectronic Interconnects, Polymers, Embedded Waveguides, Board-Level Interconnects, Vcsel, Embedded Transceivers, Photodetectors, Pcb