Real-time mode analysis of fiber-to-fiber coupling processes using the correlation filter method

We use the correlation filter method for mode analysis and characterize a fiber coupling process modally resolved. In our experiment light is coupled from a single-mode fiber into a multi-mode fiber. During the coupling process the transverse position of the single-mode fiber towards the multi-mode fiber is varied and the actually guided mode content is measured simultaneously. This measurement process allows to maximize the power guided by the fundamental mode and, hence, to achieve most brilliant beam quality in real-time.