| 摘要 |
PURPOSE:To increase the transmission margin, to extend the transmission distance and to improve the reliability by using a demultiplex signal so as to apply intensity modulation to plural light sources, sending an optical signal and detecting a received light level so as to control number of light sources emitted at a sender side. CONSTITUTION:A subcarrier 2 is subjected to pre-modulated by using an input signal 1 at a modulator 3. A modulated wave is demultiplexed into n-set of waves by a demultiplexer 4, amplified to be a level proper to a light emitting element as a laser diode or a light emitting diode in E/O converters 6a-6n by amplifies 5a-5n and converted into an optical signal at converters 6a-6n, and then sent to space. The optical signal sent through space is collected by a lens system 8, converted into an electric signal by an O/E converter 9 including a light receiving element, demultiplexed by a demultiplexer 10, the one is reproduced into the original signal at a detector 11 and the other is inputted to an optical signal reception level detector 12, in which the optical signal reception level is detected and it is informed to a control section 7 at the sender side by a feedback means 13. The control section 7 discriminates a minimum number of light sources required based thereon and applies on/off control to the converters 6a-6n. |
