PURPOSE: To enhance S/N of images and make possible two-way communication using single wire fiber through a base band transmission system by forming an antireflection film on the surface of the photo element.
CONSTITUTION: An optical fiber 12 opposing to the light emitting part 11 of a light emitting element, e.g., plane emission type LED 10 is directly coupled at its end face. A dielectric is evaporated on the light emission surface thereof to form an antireflection film. If the refractive index and vapor deposition film thickness of said dielectric are let to be (n), (d) respectively, the refractive index of the medium between the diode and fiber to be n0 and the refractive index of the material of the LED 10 to be Ns, then the conditions under which the vapor deposition film becomes the antireflecting film 13 to light of a wavelength λ0 are determined by the formulas (1), (2). Thereby, the S/N of the images may be considerably improved and the two-way optical communication using the singla wire fiber through a base band transmission system which has hitherto been impossible may be performed.
TANAKA TSUTOMU
SERIZAWA HIROMOTO
TSUJIMOTO YOSHINOBU
