| 摘要 |
PURPOSE:To obtain a required monitor light which is small in dispersion by a method wherein an optical variable attenuator is installed between the rear end face of a semiconductor laser and a photodiode. CONSTITUTION:A monitor light 8 radiated from the rear of an LD 4 is so controlled through a variable attenuating plate 7 provided between the rear of the Ld 4 and a PD 5 that a required volume of the monitor light 8 is made to irradiate the PD 5. Next, the monitor light concerted is converted into a monitor current through the PD 5, which is kept constant through an automatic power control circuit (APC) to keep a front laser ray 6 constant in optical output. By this setup, as a variable attenuating plate which is able to adjust a monitor light in intensity is installed between an LD monitoring side and a PD, a monitor light can be small in dispersion and a required monitor light can be obtained. |
