| 摘要 |
PURPOSE:To reduce a speckle noise in optical communication, by utilizing a Pockels effect by use of an electric and optical crystal, and varying the interference condition in an optical fiber. CONSTITUTION:Between a semiconductor laser 1 and a coupling lens 3, and an optical fiber 7, an LiNbO3 transparent electro-optical crystal 4[length (d)] whose C axis is in parallel with a junction surface 2 to the semiconductor laser 1 is installed, voltage from a high frequency voltage applying circuit 6 is applied to an electrode 5, and when an electric field EZ is applied in the Z axis direction, the refractive index is varied by a Pockels effect. For instance, when a varied portion of the refractive index in the (z) direction is denoted as DELTAnz, since a light beam of the semiconductor laser is generally oscillated in TE mode being in parallel with the junction surface, it is influenced by DELTAnz, therefore, when (d) is selected so as to be DELTAnz.d=lambda/2, phase of the light beam in an incident and 8 of the optical fiber 7 is varied by pi. In this way, the interference condition in the optical fiber is varied, and the speckle is smoothed. |
