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A new method for approximating steady-state mode power distribution (SMPD) in graded-index fibres is described. It has been shown that a biconical taper is a very simple and effective means to launch SMPD in short lengths of fibres. Prefabricated tapers can be directly used as component between the source and the test fibre. Experimental results are presented.

A new design of a mode scrambler for optical fibre measurements is presented. A rotation-splice technique has been used to mix the incoming mode power distribution in the fibre. The device is tested under different launch conditions to check its efficiency to produce a definite mode power distribution. Experimental results are presented.

A modified monomode-fibre offset technique as well as a new and very simple method for selective mode excitation in multimode graded-index fibres is presented. It is shown that an inclined plane wave launch followed by a mandrel-wrap mode filter is a powerful way to excite a definite number of mode groups in graded-index fibres. Besides its extreme simplicity this method yields improved selectivity. Experimental results are presented.