PURPOSE: To make the device simple and small in size and decrease the insertion loss of the equalizer by connecting the guides of the specified length longitudinally in correspondence to the wavelength λi of light waves, providing the specific reflecting films of the central wavelength λi at their connection faces, and fetching the light reflected by each reflecting film to the outside from the same optical path.
CONSTITUTION: Light from an optical fiber 1 is passed through a polarizing and separating prism 11 such as Rochon prism and a 1/4 wavelength plate 12 and is thereby made into the circularly polarized wave which is then led to the diffusion delay portion consisting of wavelength selective reflecting films 13-1W13-N and optical guides 14-1W14-(N-1). The length of the delay optical guide for the wavelength λi is made li=LS(λi-λi+1)c/2n and the resolving power of the reflecting films having a center at λ1 is made about (λi-λi+1)/2. Here, L, is the length of the optical guides, S is their wavelength diffusion, (n) is refractive index and (c) is the velocity of light. The light reflected by each reflecting film passes the route in the direction opposite from that at the time of incidence and is led to the outside by way of the optical guide 5. This diffusion delay equalizer is simple, small in size and has less losses.
TSUCHIYA HARUHIKO
IZAWA TATSUO
