| 摘要 |
PURPOSE:To prevent the transmission of an error signal by providing a light delay line of needed length between a laser light source and external light modulator and then by controlling the external light modulator by a signal controller when the laser light source becomes abnormal. CONSTITUTION:Between laser light source 1 and external light modulator 3, light delay line 2 of optical fiber of needed length is provided via optical system 5 for coupling. On detecting the fluctuation of the output of laser light source 1 exceeding an allowable value, photo detector 6 or signal controller 4 interrupts temporarily the transmission of information 7 supplied from the outside and controller 4 sends by interrupting a signal, needed to inform a reception side of measures such as the temporary standing-by of information and temporary interruption of the information transmission, to modulator 3. This process is continued until the abnormality of a laser output appears via delay line 2, and external lighr modulator 3 is cut off temporarily to maintain the stand-by state until the laser output returns to a steady value. Consequently, malfunctions on the reception side can be prevented. |
