| 摘要 |
PURPOSE:To obtain an optical directional coupler with small insertion loss and high isolation, by forming ofliquely an end surface of an optical fiber. CONSTITUTION:The end surface 31 of the optical fiber 30 slants at a specified angle alpha to a plane perpendicular to the center axis, and incident light (a) is guided at an angle theta of incidence to the slanting end surface 31. Part at of the incident light (a) is refracted by the end surface 31 to enter the core of the optical fiber 30 and propagates in the fiber 30, and the remainder ar is reflected by the end surface 31 to travel outward. Further, part et of light (e) arraiving at the end surface 31 by propagating in the fiber 30 in a reflection direction is refracted at the angle theta to the normal line and the remainder er is reflected by the end surface 31 and further refracted to be guided out from the end surface of the fiber 30. In this case, we have theta<=50 deg. and 90 deg.-2alpha<=40 deg. preferably. |
