Baseband-frequency-response measurement of graded-index fibre using step-index fibre as an exciter

For measuring reproducibily the baseband frequency response of a graded-index fibre, a mode exciter utilising an ordinary step-index multimode fibre has been proposed. The input mode power distribution and the frequency response of the fibre with the exciter are altered very little for axis offset. Input mode distribution excited indicates that excitation of nearly all modes takes place.