| 摘要 |
PURPOSE:To stabilize the oscillating state of a light source, by intermittently driving the light source, utilizing the delay time during the propagation in a fiber, and preventing the returning of the light into the light source during the time the light source is driven. CONSTITUTION:An LD3 is intermittently driven by a pulse generator 9. At this time, a period T of the pulse is made to be the value shown by an expression, and a duty cycle is made to be 1/2 or less. Then, the light emitted from a light source during the initial time of T/2 is emitted from a fiber during the following time T/2 and returned to a PD and the LD. The expression is T=2tau=2.nL/C, where tau is a propagation time of light in the fiber, (n) is the refractive index of the fiber, L is the length of the fiber, and C is a speed of light. During the time the light is returning to the LD 3, the LD is not oscillated. Therefore the effect of the returned light is not received. The light received by the PD becomes intermittent, but the light can be readily averaged. No deterioration occurs in comparison with the continuous driving of the light source. |
