| 摘要 |
PURPOSE:To perform the high-quality communication of information by means of the space propagation of an optical signal, by making the emission wavelength of the optical signal, which is outputted from the light source of a transmitter, to be a specific length. CONSTITUTION:A light transmitter-receiver 2 having a semiconductor laser element as its light source radiates an optical signal outputted from the laser element in the directional angle of, for instance, + or -60 deg. from the ceiling of a room 1 toward each light transmitter-receiver 5 of a terminal 4 arranged on a floor surface. For each light receiving part of the transmitter receiver 5, information communication is performed by the propagation of an optical signal having the wave length of 1.38-1.43mum. In this case, since the level of sunlight component with respect to the optical signal of the wavelength of 1.38-1.43mum is about 1/10, the background noise of the sunlight does not bother the optical signal. |
