SEDI-ATI Fibres Optiques is a French company specializing in designing and manufacturing custom-made passive fiber-optic assemblies tailored to specific, complex, and extreme environments. Indeed, our solutions are meant to survive very hostile conditions such as cryogenics, very high temperatures, vacuum, pressure, corrosion, or radiation. We address very demanding applications in the defense, aerospace, industrial, medical, and energy markets. We have developed specific solutions able to withstand hostile conditions: highly achromatic multimode couplers, multimode wavelength division multiplexers for sensing applications, opto-pyrotechnics, miniature fiber-optic links and connectors, pressure and vacuum fiber-optic hermetic feedthroughs, bundles and arrays for spectroscopy applications, special patchcords, deployable fiber-optic spools to drive unmanned vehicles, and medical probes.