Devices called "Light Pipes" are often used to get luminary output to (easy) and into (harder) various places.
These will influence the response of the spectrometer due to their materials or configuration. You'll have to find what influence your chosen device has and how consistently it performs by experiment.
You have choices. There are fibres, fibre bundles, coherent fibre bundles, mirror chains, prisms, prism assemblies, air (or gas filled) interfaces, and several combinations of all of these.