| 摘要 |
PURPOSE:To hold transmission quality while burden for light sources is reduced by detecting the level of a received optical signal, feeding back the detected result to a transmission-side, and permitting the transmission-side to control the level of an input current for the light sources to an irreducible minimum. CONSTITUTION:An auxiliary carrier 2 is previously modulated in a modulator 3 based on the input signal, 1, is branched into n-number in a branching unit 4. The signals are amplified in the appropriate levels in respective amplifiers 5a-5n, are converted into the optical signals in E/O converters 6a-6n and are transmitted to an open space. The optical signals transmitting the space are converged in a lens system 8, are converted into electric signals in an O/E converter 9 and are branched in a branching unit 10. Then, the reception levels of the optical signals are detected in an optical signal reception level detector 12 and they are noticed to a control part 7 on the transmission-side by a feedback means 13. The control part 7 controls the input current level to the irreducible minimum so that the reception optical level becomes optimum based on the optical signal reception level information. |
