Performance characterization of optical module designed for space applications

Abstract

Next generation space missions are planning for increasingly aggressive data collection platforms that host advanced sensor technologies. Examples are focal plane arrays and synthetic aperture radar systems producing vast amounts of high-speed data on orbit, on the order of tens of Gbps. Data collection interfaces to these advanced sensors are designed around high speed differential signaling that use copper cable harnesses to provide 40 to 50 individual copper interconnects. This density of copper cabling readily introduces Electromagnetic Interference (EMI) and Electromagnetic Compatibility (EMC) issues. This copper cable harness requires various levels of electrically grounded shielding that introduce complications in mechanical and electrical design to avoid ground loops in the system. Optical cabling is an attractive solution to mitigate and avoid these EMI/EMC and grounding complications while also dramatically reducing the diameter and mass of the harness. Large shielded and impedance controlled copper cables can then be replaced with thinner optical cables that can be more compactly routed through the spacecraft. Micropac Industries, Inc. has recently developed prototype miniaturized optical transceiver modules for space applications. These modules convert a differential signal into a single ended optical signal that can then be used with fiber optic cable. This approach holds promise for reduced size, mass, and EMI/EMC issues, but the technology is still being proven. This paper presents the results of experiments that characterize the performance of high rate data communication over fiber optic interfaces and electrical copper interfaces. Experiments include the assessment of bit error rate performance at multi-Gbps data rates over various lengths of fiber optic and copper cable. The results show that these optical transceivers are a viable solution for an architecture in which sensor electronics and spacecraft electronics must communicate via cables using full duplex high speed communications.