To provide a karaoke communication system and a data communication system which are easy in the construction of their systems.

Different wavelengths are respectively assigned to karaoke halls 4A, 4B, 4C,... each provided with a plurality of karaoke play terminals, and communications between a karaoke data center 2 and the karaoke halls 4A, 4B, 4C,... are performed by the optical signals of these assigned wavelengths. Then, each of OADM 41A, 41B, 41C,... provided in the karaoke halls 4A, 4B, 4C,... drops the optical signal of the wavelength assigned to the karaoke hall installed with that OADM out of optical signals transmitted by an optical fiber 3 and passes through the optical signals of the other wavelengths as they are.