| 摘要 |
PURPOSE:To obtain the optical communication device which can transmit more than ternary information by modulating laser light by utilizing electrooptic effect generated in a twisted nematic liquid crystal cell. CONSTITUTION:Laser light is polarized directly by a polarizer 4 and a voltage applied to the twisted nematic liquid crystal cell 6 is varied under the control of a control circuit 1 according to the variation of an input signal (having quad information), so that the light is modulated into three kinds of light signals according to the applied voltage value. Further, the OFF state of the input light is combined to obtain four kinds of light signals. This modulated light signal is sent to a receiver and further sent to two analyzers 10 and 11 through an optical fiber 9 and photodiodes A and B detect whether or not the light pass through the analyzers 10 and 11. Their detection results are combined by a detecting circuit 12 to detect the modes of the four kinds of light. Thus, a two-bit input signal is converted into quad information, which is sent optically. |
