| 摘要 |
PURPOSE:To reduce noises without increasing a maximum rate output by supplying a driving current which has the same period as high frequency pulses with >=50% duty and varies with the threshold value of a semiconductor laser. CONSTITUTION:The semiconductor laser LD receives a current ID from a DC power source E and a pulse generator PG for operating and the current ID is generated by superposing high-frequency pulses ia upon the DC current Ib of the power source E and the current ia has >=50% duty. This current Ib is made smaller than an operating current and set close to a threshold current Ith. An operation output level Po is Pb+gamma.Pa (gamma: coefficient determined by duty), where Pb and Pa are outputs of the laser LD corresponding to the driving currents Ib and Ia, and when the level Po is 3mW and the duty is 90% (gamma=0.8), Pb is 1mW and Pa is 2.5mW. Therefore, when the level Po is 3mW, a maximum output level is 3.5mW and a 3.5mW operation output is obtained by a laser LD with 3.5mW maximum rated output, so that only a 5mW maximum rated output is required even when the margin is increased. |
