| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive, reliable optical amplification device which can prevent optical surge with a simple optical circuit. SOLUTION: An input signal light 40 is inputted to an optical input off detector 43 where the light is branched into two light signals by a CPL(coupler) 45. One of two light signals branched by the CPL 45 is input to a light receiver 46 to be converted therein to an electric signal corresponding to the branched light power. The other light signal branched by the CPL 45 is input to an optical signal cut-off section 44 as it is. The electric signal converted by the light receiver 46 is compared by a controller 48 with a predetermined value. When the electric signal is smaller than the predetermined value, the controller 48 cuts off an optical path of a SW(switch) 47 to an optical direct amplifier 42. When the electric signal is larger than the predetermined value, the controller 48 controls connection of the optical path in such a manner that a control signal to the SW 47 varies more slowly than a time constant for constant output control of the optical direct amplification circuit 42. |
