A first fiber stub incorporating a first GI fiber is connected to a first optical fiber by a PC connection. The first GI fiber expands a beam diameter of light transmitted by the first optical fiber and collimates this light. A second fiber stub is connected to a second optical fiber by the PC connection. The second fiber stub, facing the first fiber stub across a predetermined gap G therebetween, converges the light transmitted from the first fiber stub using a second GI fiber incorporated therein. The second fiber stub transmits the converged light to the second optical fiber. When the first fiber stub or the second fiber stub is damaged, the first fiber stub or the second fiber stub is pulled out from a first sleeve or a second sleeve, respectively for replacement.
