| 摘要 |
PURPOSE:To reduce the insertion loss to improve the capacity by spreading temporarily a propagated light in a main optical transmission line to the state of an optical beam in the space and inserting a photoelectric light detecting means into this optical beam to branch directly a photoelectrically converted signal. CONSTITUTION:An optical beam A emitted from a main optical transmission line 1 consisting of an optical fiber is converted to a parallel optical beam B by a lens 2. A photodetector 3 such as a PIN photo diode or the like is inserted into this optical beam, and lead wires 3a and 3a' are connected to an electrode of the photodetector 3. The photodetector 3 is fixed by a supporting plate 4 which is provided with a reflection preventing film and consists of a light- transmissive glass or the like. The photodetector 3 is moved in the direction orthogonal to the optical beam B to adjust the quantity of light striking the light receiving face of the photodetector. The optical beam B which is not intercepted by the photodetector 3 and passes through it is condensed by a lens 2' and is made incident to a main optical transmission line 1' again. The photoelectrically converted signal is branched directly by the light detecting means to reduce the insertion loss in a branching circuit. |
