CIRCUIT FOR CONTROLLING AMPLIFICATION EXTENT OF LIGHT CIRCULATION CIRCUIT

摘要

PURPOSE:To control an amplification extent in a light circulation circuit by stable negative feedback control and to suppress the vibration of a circulation signal in the light circulation circuit. CONSTITUTION:A circulation light circulating the light circulation circuit 100 is converted to an electric signal, and is held to a sample-and-hold circuit 23 as a circulation light intensity signal, and the circulation light intensity signal held in the sample-hold circuit 23 one circulation before is held in the sample- hold circuit 24. A difference between these circulation light intensity signals is obtained by a subtraction circuit 26 to be supplied to an addition circuit 18 through the sample-hold circuit 25. Then, the resultant difference is added to an output of a reference power source circuit 19 in the addition circuit 18, and is supplied to an excitation light source 10 to be converted to an optical signal, and is supplied to a wavelength multiplexer/demultiplexer 2 as an excitation light of a rare-earth addition fiber 1.