The logical consequence is to also use optical transmission for inter- and intra-system interconnects. PCBs will thus be called on to provide very high bandwidth. Current PCB technology is sufficient to support a high number of interconnects with some performance reserve, thus further development is much more efficient and economical than developing a completely new technology. An additional and important precondition for the industrial use of optoelectronic interconnects is the availability of capable and low-cost optical transmitters and receivers. The development of suitable optical receivers (e.g., in GaAs technology) seems achievable. Suitable laser diodes, acting as optical transmitters, were until recently only available in edge emitter technology. These laser-diodes are established for telecommunication and long-haul applications but do not meet the economic requirements of optical intra- and inter-system interconnects. Vertical cavity surface emitting lasers (VCSEL) seem to have solved this problem. Modulation frequencies leading to data transfer rates of 10 Gbit/sec. and more have been successfully demonstrated. The optical transmitters used in commercially available optical-fiber links, providing data transfer rates of 2.5 Gbit/sec. per channel, are already used in VCSEL technology. The mean time between failures (MTBF) of VCSELs, quoted by the suppliers in the range of 10~5 hours (approximately 11.5 years), is proof of the quality of this technology.
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