| 摘要 |
PURPOSE:To eliminate the need for manual adjustment of an individual optical output of an optical fiber amplifier by incorporating gain control of an optical fiber amplifier into an AGC control system controlling a current amplification factor of a light receiving element and a gain of an equalization amplifier. CONSTITUTION:The control of a gain G1 of an amplifier deciding an optical output of an optical fiber 10 in an optical reception section is incorporated in an AGC control system in which a current amplification factor M of an APD(Avalanche Photo Diode) of a light receiving element 20 and an electric gain G of an equalization amplifier circuit 30 vary with a power of an optical input. Then the G1 and the M are controlled constant till a certain point after the increase in the optical signal input is started and the G is decreased proportionally. Till a succeeding point after the optical input exceeds the former point, the M and the G are controlled constant and the G1 is controlled to be decreased proportionally. When the input is further increased, the G1 and the G are controlled contact and the M is controlled to be decreased proportionally. Thus, an output level of the equalizing amplifier 30 is kept constant for all areas of the optical input. |
