PURPOSE: To monitor light outputs and increase permissible quantity of connection deviations by working the end phase of an optical fiber whose refractive index distribution coefficient α corresponds to α>2 to a spherical surface and providing a PIN photo diode to its tapered part.
CONSTITUTION: The photo coupler comprises working the end face of a graded type fiber 9 of α>2 to spherical lens form, disposing the spacing between a light source 8 and fiber 9 so that the incident power becomes maximum, then mounting a PIN diode 11 to the tapered part at the root of the spherical portion by means of a transparent resin 10 and connecting this coupler to a local system fiber 13 by means of a connector 12. Hence, unnecessary clad mode and leaky mode are led to the PIN diode and are utilized for monitoring. In addition, the use of the optical fiber of the refractive index distribution corresponding to α>2 enables the permissible quantity of connection deviations to be increased and the switching office loss to be reduced.
NAWATA KIYOSHI
SUZUKI NOBUO
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