| 摘要 |
PURPOSE:To improve the reliability of a communication system by preventing the generation of bit error in case of stopping and starting one luminous source by chang ing the optical output of luminous source with a time constant in the photo stand-by system dependent upon optical synthesis. CONSTITUTION:Laser diode LD13 of circuit 6 is caused to emit light according to driving signals from terminal 5, and the output light is sent to optical transmission path 10 through level supervisory circuit 7. Supervisory signals which accord to the optical level from circuit 7 are compared with a fixed reference voltage in detector circuit 8; and if they are below the reference voltage, control signals are generated and applied to time constant circuit 9. Then, the current of current limiting transistor 19 in circuit 6 is gradually reduced by a prescribed time constant, and the current applied to LD13 is gradually reduced to zero. Meanwhile, when circuit 6 is mounted, transistor 19 becomes conductive from an off-state according to the time constant of circuit 9, thereby operating LD13. |
