| 摘要 |
PURPOSE:To increase the extent of stop band attenuation of the light beams having a wide wavelength range by partially dividing output-side optical waveguides and inserting interference film filters, through which only the light beams in a required wavelength band are transmitted, between end faces of divided optical waveguides which face each other respectively. CONSTITUTION:Interference film filters 9 and 9' are ground with 45mum thickness into thin pieces, and the filter 9 is a short wavelength transmission filter through which the light having <=1.4mum wavelength is transmitted, and the filter 9' is a long wavelength transmission filter through which the light having >=1.4mum wavelength is transmitted. Though the light beams made incident on an optical waveguide from an input optical fiber are separated to two optical waveguides 2 and 2' in a coupling part, the light beams of <=several % power is outputted to opposite optical waveguides also. The light beams having unnecessary wavelengths which is made incident on these optical waveguides is reflected on interference film filters 9 and 9' and is radiated out of optical waveguides. Since interference film filters 9 and 9' normally have a wide stop band wavelength width and a very large extent of attenuation, the power of unnecessary waves incident on an optical fiber is very small. Since interference film filters 9 and 9' are provided at 15 deg. to optical axes of optical waveguides, the quantity of light which is reflected and is returned to the input optical fiber is very small not to have a bad influence on the transmission characteristic. |
