Fiber-Bragg-Gratings as a candidate technology for satellite optical communication payloads: Radiation-induced spectral effects

Intra-core Fiber Bragg Gratings (FBGs) is a candidate technology for a number of future applications in satellite payloads that plan to use multi-wavelength optical links for communicating with other satellites or with ground stations. Applications include wavelength multiplexing and demultiplexing units in multi-wavelength inter-satellite links as well as Add/Drop Multiplexers in the context of broadband satellite constellations using optical networking with on board optical routing. The main advantages of fiber Bragg gratings is that these devices are passive requiring no electrical power, have low mass, and can be compactly packaged. When considered for applications in space the main parameters of concern to be controlled are the stability in wavelength selectivity and throughput loss. While all space environmental effects such as vacuum, thermal cycling, mechanical launch loads and radiation need to be considered for on-board satellite components, in this study only radiation induced spectral effects were investigated. In particular, the issue of radiation-induced Bragg peak wavelength shift for telecommunication-grade FBGs in response to dose levels typical of those expected for LEO telecommunications satellites is examined. Also the impact of radiation on the FBG reflectivity is assessed. The study of such components is motivated by the fact that a key issue for the development and deployment of broadband (optical) satellite networks, is the leverage of existing ground-based fiber optic technologies. The experimental results are compared with work previously done in this field for space applications.