| 摘要 |
PURPOSE:To accurately detect the deterioration of a laser diode LD and to switch the LD module into a spare LD module by providing an optical attenua tor attenuating the signal intensity and an error rate discriminator receiving a signal attenuated by the attenuator and discriminating the error rate. CONSTITUTION:A signal output branched by a photo-spectroscope 5 fitted to an optical transmission cable 10 is propagated through a signal line 15 and enters an optical attenuator 6. The attenuator 6 attenuates the signal output up to the signal level when the signal is propagated actuaIly through the main transmission cable 10 and reaches a repeater or a receiver of the next stage. An error discriminator 7 receiving the signal from the attenuator 6 discriminates the error rate of the reception signal by the same condition as the reception of the next stage and compares it with the predetermined reference error rate. When the error rate of the branched signal exceeds the reference error rate, a changeover command generator 8 outputs a switching command to switch an active LD chip of the laser diode LD module 2 into a spare chip. |
