OPTICAL DEMULTIPLEXER

PURPOSE:To allow transmitted light to pass through the same optical path even of input light has different wavelength by providing a parallel plane compensating plate which correct deviation of the optical path of the transmitted light of a beam splitter due to difference in wavelength. CONSTITUTION:The oscillation division type beam splitter 11 is supported in a case 10 at a 45 deg. tilt angle and the parallel plane type compensating plate 14 which is as thick as the beam splitter 11 is arranged symmetrically with the splitter 11. In this constitution, the transmitted luminous flux B of light from an optical fiber 18 is refracted again by the compensating plate 14 and collimated by a SELEOC lens 16 into parallel luminous flux, which is coupled with an optical fiber 19. Thus, the compensating plate 14 is provided, so refraction similar to that of the beam splitter 11 is caused even is there is difference in angle of refraction owing to the difference in the wavelength of the incident light, so the light after transmitted through the compensating plate 15 passes through the same optical path and is usable as light containing different wavelength.