PURPOSE: To connect an optical fiber with no disconnection even for a moment by using optical fibers for switching connection in which the difference in specific refractive index between a core and a clad differs continuously from both end parts to the center part.
CONSTITUTION: The optical fibers 9-1 and 9-2 for switching connection which have 0.6W1.4% differences in specific refractive index between cores and clads at both end parts and 0W0.5% difference at center parts and decrease continuously from both end parts to center parts are connected previously to new and old cable cores 8-1 and 8-2. The old cable 9-2 and new cable 9-1 are bent in switching connection to leak light from the bent parts, and thus placed in a multiple connection state; and the old cable is cut at a position 11 and the new and old fiber cores 9-1 and 8-2 are welded together. Then, the optical fibers 9-1 and 9-2 for switching connection are released from being bent and all of the light 10 flow in the core of the new cable 8-1.
JINNAI GUNJI
TAGUCHI MORIHIKO
