| 摘要 |
PROBLEM TO BE SOLVED: To constantly maintain the output level of a wavelength multiplexing transmitter at individual wavelengths without giving any influence of the characteristics of signals even when the multiplicity of wavelengths changes. SOLUTION: When electric signals for optical signal transmission are inputted to optical transmitters 2A, 3A,..., 4A and a specific frequency fo is inputted to one of the optical transmitters 2A, 3A,..., 4A selected by means a superposing destination selecting circuit 5, the optical transmitter synthesizes the frequency fo with the electric signals. A plurality of optical signals respectively transmitted from the transmitters 2A, 3A,..., 4A is multiplexed by means of an optical multiplexer 7. The wavelength-multiplexed signals are amplified by means of an optical amplifying medium 8, and after converted to an electrical signal by a photodetector 14, only the level of the fo-frequency component is extracted by means of an fo extracting electric filter 13. A control circuit 12 controls the light output level of a pumping laser 11 which pumps the medium 8 so that the extracted level may become a desired value. |
