Simultaneous alignment of optical axes by monitoring reflected light from core and cladding.
We propose a method of aligning optical axes by monitoring reflected light from the core and the cladding at the coupling end. This method enables the simultaneous alignment of optical axes at multiple coupling ends because it is not necessary to monitor the transmitted light through the couplings. Experimental results show that this method can be used for coupling between cleaved single-mode fibers and between fibers with slant ends. The simultaneous alignment of two coupling ends is also achieved, and it is shown to obtain the optical power transmitted through the coupling, which is enough to begin the precise alignment. Moreover, we confirm fundamentally that one can use this method for precise alignment of optical axes by monitoring the optical beam profiles of the reflected light.