| 摘要 |
An optical coupler is formed by a GRIN lens having an axis and an optical medium contiguous to the GRIN lens but having an index of refraction that is different from that of the lens. An input optical fiber carries an input optical signal along a path substantially parallel to the axis of the lens but is offset from its axis. The lens collimates the input optical signal into a beam that impinges on the interface between the lens and the optical medium at a small angle. Fresnel reflection of the collimated beam at such interface is focused by lens to an output optical path also substantially parallel to the axis of the lens but at the same offset to the axis from the input optical path. The tapping percentage can be controlled by choosing an optical medium having the desired index of refraction. Additional interfaces can be formed between the optical medium and additional media, such as a thin glass disk for additional Fresnel reflections that are also coupled to the same output fiber. Such additional interfaces can be used to increase the tapping percentage.
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