Low-loss fattened fusion splices between differentfibres

Using a fattening technique which requires a flame with a long hot zone, fibres with both different cladding diameters and NAs can be spliced with low loss. For instance, a standard 125/9.5 µm telecommunications fibre (NA = 0.11), can be spliced to an 80/5.3 µm fibre (NA = 0.21) with 0.1 dB loss.