OPTICAL TRANSMISSION CIRCUIT

摘要

PURPOSE:To provide an optical transmission circuit capable of connecting an optical transmitter to an optical booster amplifier only by optical fibers. CONSTITUTION:The optical transmitter 11 includes mark rate information into an optical signal by superposing a low frequency digital signal having an occupation rate corresponding to the mark rate of a digital main signal to be transmitted to the main signal and the occupation rate of the low frequency digital signal in the optical signal is detected by a light receiving element 21 and an occupation rate detecting circuit 22. A negative feedback circuit 20 controls the amplification factor of an optical fiber amplifier 16 through a control circuit 23 based upon the occupation ratio and the average value of the amplified optical signal level detected by a light receiving element 18 and an average value detecting circuit 19 so that the output level of the mark ratio of an outputted optical signal is fixed.