| 摘要 |
PURPOSE:To provide the optical direct amplifier for multi-relay optical fiber transmission use in which an alarm signal is sent to a downstream by letting it ride on a naturally radiation light. CONSTITUTION:The amplifier is provided with an input terminal 11, a photocoupler 1, an erbium additive optical fiber (EDF) 2, a wavelength split multiplex coupler (WDM) 4, a light receiving element 5 and an input interruption detection circuit 6, which are the same as those for a conventional optical direct amplifier, a signal light of 1.55mum band from the input terminal 11 is amplified by the stimulation of a stimulation laser beam of 1.48mum band from a stimulation semiconductor laser drive circuit (LDD) 7 and the amplified signal is outputted to an output terminal 12. An input interruption detection circuit 6 receives an electric signal from a light receiving element 5 in the input interruption state of an optical signal to detect the input interruption of the optical signal, a frequency modulation circuit 8 replies it to output an FSK wave. The LDD 7 stimulates the stimulation semiconductor laser (LD) 3 by the FSK wave and the LDD7 supplies the laser beam subjected to intensity modulation by the FSK wave to the EDF 2. The EDF2 outputs a naturally radiation light subjected to FSK intensity modulation. |
