Optics are the components that are used to relay and focus light through a spectrofluorometer or spectrophotometer. These would normally consist of lenses and/or concave mirrors. The number of such components should be kept to a minimum due to the losses of light (5-10%) that occur at each surface.
Reference: Owen T (1996) Fundamentals of modern UV-visible spectroscopy. A Primer. Hewlett Packard, 142pp.