| 摘要 |
PURPOSE:To transmit digital information of fault information with an optical main signal. CONSTITUTION:Fault information 15 is converted into two kinds of frequencies less than a low pass interruption frequency by a frequency shift keying modulation circuit 16, and an exciting semiconductor laser driving circuit drives an exciting semiconductor laser 19. Exciting light by the laser is inputted to an erbium addition fiber by a wavelength division multiplex coupler 13, and optical direct amplificatior is executed in a form that exciting light is overlapped with the optical main signal. The optical signal which is thus obtained is outputted from an output terminal 14. |
