Select optics from Osmund Optics, s mount components.
System designed must to focus light from a source with 120deg view angle to illuminate a 400um fibre optic (use SMA connection). This light on exit from the fibre must illuminate a 6mm diameter sensor on exit of fibre optic.
Lens selection, lens mounts, fibre optic coupling, fibre optic for both entry and exit of fibre needed.
Please provide a ray trace of your design too.