Can we send light with 473 nm through a single mode fiber designed to operate between 1500 to 1600 nm spectrum? The radius of the fiber core is 4.25 micrometer, NA=0.12 and the single-mode cut-off is at 1350 nm.
- the fiber will be in the multi-mode regime for that wavelength, and
- it's possible that the glass will exhibit significant losses if you want to run this wavelength of light over substantial lengths of your fiber (probably in the multi-kilometer regime or higher).
Other than that, there's nothing stopping this light from propagating down your fiber.