We describe the current state and future of the WWW Jena-Petersburg database of optical constants (JPDOC) that also contains references to papers and links to internet resources related to measurements or calculations of the optical constants of materials of astronomical interest. The most important part of the JPDOC are data measured in broad wavelength ranges and partly at low temperatures in the Jena Laboratory. To demonstrate the use of these data, we show as examples infrared refractive indices of crystalline and amorphous magnesium silicates, spinel, and hydrogenated amorphous carbon and calculate the absorption cross-sections of small particles composed of these materials.