| 摘要 |
PURPOSE:To stabilize the optical output signal received from an optical transmitter in a CATV optical transmission system even in a case having the fluctuation of the optical output signal level of the optical transmitter. CONSTITUTION:The optical signal outputted from a laser diode 4 contained in an optical transmitter is branched by an optical branching device 6. This branched optical output is detected by a photodiode 7, and the output signal of the photodiode 7 is amplified by a signal amplifier 8. Then a signal of an optional frequency is selected out of the output of the amplifier 8 by a BPF 9. This selected signal detects the level of the signal having the frequency selected by a level detecting circuit 10 and then applies the signal accordant with the difference between the level of the signal and a reference level to a laser diode input signal control circuit 11. Thus the level of the signal inputted to the diode 4 is controlled and the optical output signal is stabilized. |
