In this experiment, the optical characteristics of porous silicon microcavities (PSM) are studied using spectroscopy analysis. Porous silicon microcavities were fabricated by the anodization of boron doped P-type (111) single crystal wafers in hydrofluoric acid/ethanol (HF/EtOH) electrolytes. The samples were prepared at room temperature under different fabrication conditions in order to obtain different physical parameters such as porosity (p), thickness (d), and pore geometry. The current density was varied from 25mA/cm2 to 100mA/cm2 and the HF/EtOH concentration was varied from 1:1 to 1:4. The transmission spectra of the prepared samples were investigated over the range of 800 nm to 2400 nm with a period of 2 seconds. The fabricated PSM structures were investigated using SEM and their physical properties were analyzed as a function of the fabrication parameters. The transmission spectra of the prepared samples were compared to the transmission spectra of the reference bulk silicon wafer. We observed that the refractive index of the (PSM) was lower than that of bulk silicon, and it decreased with increasing porosity (p). Based on the experimental spectra of the PSM structure, we report a spectral density function relating the physical properties of the surface and the effective dielectric function.