Advancement of photonic interconnects for spaceborne systems

Optical interconnects have long promised significant advantages over their electrical counterparts. Specific advantages include increased bandwidths at long (ten meters or more) interconnection distances, immunity to EMI effects, negligible crosstalk, reduced size, and lower weight. Optical interconnects have been developed for, and are being used in, a range of ground based and aircraft applications, however they are only now beginning to gain acceptance in spaceborne systems. In addition to the maturity demanded from components destined for ground-based applications and the wider temperature excursions characteristic of airborne applications, spaceborne components must also be able to survive the radiation environments associated with their intended applications. The additional qualification required has resulted in delayed introduction of photonic interconnects. We describe the tradeoffs involved in implementing for the first time a spaceborne fiber optic data bus with a clock speed of 1.2 Gbps. The tradeoffs include emitter, detectors, fiber, connectors and packaging. We have selected a series of commercial grade optoelectronic devices which were then qualified for use in spaceborne environments and have developed a space qualifiable packaging scheme. We have designed and implemented the optoelectronic subsystem of the data bus and have simulated its operation. We also describe recent advances in Vertical Cavity Surface Emitting Lasers (VCSELs) for spacebourne databuses. VCSELs also offer advantages in simplicity of packaging and electronic control. We summarize available initial radiation data on these devices and project their impact on spaceborne photonic interconnects.