Experimental investigation of the beam spot size radius in single-mode fibre tapers

Fibre tapers have been evaluated with regard to the spot size radius enlargement effect predicted theoretically. The experiments show that the expected amount of improvement does not occur under the applied drawing conditions. For fibre tapers with taper lengths up to 1 mm and fibre core inclination angles between 0.6 and 1.2° it amounts to 20% at maximum.