Disclosed is an optical transmission system capable of transmitting optical signals of E-band and other bands through one optical fiber. The system includes a first thin film filter for receiving optical signals of E-band and other bands at both sides thereof respectively, and multiplexing the optical signals of both E-band and other bands by selectively transmitting wavelength ranges received at one side, reflecting wavelength ranges received at the other side, and then coupling the optical signals of both E-band and other bands; an optical fiber for transmitting the optical signals multiplexed by the first thin film filter to a receiving portion; and a second thin film filter for selectively separating and demultiplexing the E-band and other bands from the optical signals transmitted through the optical fiber.