PURPOSE: To simplify a gain controlling circuit and to reduce the number of steps of an amplifier by using an optical amplifier for controlling so that intensity of an optical signal outputted from a laser medium by an electric signal becomes constant.
CONSTITUTION: When an optical signal is inputted to a laser medium 1, the optical signal is amplified by the laser medium 1, and the amplified optical signal is outputted through a Y branching circuit 2. In this case, a part of light is made to branch by the Y branching circuit 2, photodetected by a pin photodiode 3, converted to an electric signal being proportional to intensity of the light and inputted to a gain controlling circuit 4. The gain controlling circuit 4 amplifies the inputted electric signal and makes a direct current flow to the laser medium 1 in proportion to intensity of the light. In this case, if an optical signal of an output of the laser medium 1 is large, the current flowed to the laser medium 1 by an output of the gain controlling circuit 4 becomes large, and an amplification factor of the laser medium 1 operates so as to go down. In this way, an automatic gain adjusting circuit is formed, and even if a level of an inputted optical signal is varied, intensity of an outputted optical signal becomes constant.
| JPH024033 | OPTICAL RECEIVER |
| JP3707955 | WDM OPTICAL TRANSMISSION SYSTEM |
| JPH03148640 | QUANTUM FLUCTUATION MODULATION |
FUKUI SATORU
TAKAGI KAZUTO
| JPS56162554A | 1981-12-14 | |||
| JPS5240002A | 1977-03-28 |