A simple technique utilizing a bifurcated fiber light guide for obtaining the reflectivity spectra of specular and diffusely reflecting surfaces is described. The technique can be used in certain situations where conventional reflectometers are not practical.
L. A. Lott and D. L. Cash, "Spectral Reflectivity Measurements Using Fiber Optics," Appl. Opt. 12, 837-840 (1973)