Modern tasks of analyzing turbid media dictate the need to develop specialized tools necessary for the practical implementation of new theoretical approaches using commercially available equipment. This report presents a photometric module that makes it possible to implement in practice the theoretical concept of a composite film developed by the authors. Within this scenario, the absorption coefficient of the average element of the dispersed medium can be determined based on the dependence of light loss in heterogeneous films on their thickness. This was achieved through the design, fabrication, and testing of a photometric Ω-module for a fiber optic spectrometer. The Ω-module provides illumination of the sample within a fixed solid angle Ω0 and provides summation of the transmitted light at the inlet of the fiber optic spectrometer at the same solid angle. The effectiveness of the Ω-module is demonstrated by determining the absorption coefficient of a composite film material and the volumetric absorption coefficient of an average microparticle of yttrium aluminum garnet YAG:Ce3+ powder with an average size of 5.3 μm. The value of the absorption coefficient (774 cm−1) of YAG:Ce3+ crystalline inclusions embedded in supporting epoxy resin film was obtained for a wavelength of 456 nm using the composite films model based on the results of measuring the intensity of light passing through free-standing epoxy-phosphor films of various thicknesses (in the range of 100 to 500 μm) installed in the Ω-module.