Apparatus for combining optical radiation

Apparatus for combining optical radiation, particularly high energy sources such as lasers. It includes a glass taper 2 housing a waveguide, a plurality of inputs 1 coupled to a first end of the taper and an output optical fibre 3 with a polymer coating 13 coupled to the second end of the taper, the diameter of the first end of the taper 9 being greater than the diameter of the second end 11. The taper 2 also has a cladding mode stripper 16 located at a diameter, Dcms 17, equal to a fraction, the numerator of which is the product of the fibre diameter, Dr 12, the numerical aperture of the fibre, NAf 15, and a factor, β 18, which is less than or equal to 1.0, and the denominator of which is the numerical aperture of the taper, NAT 7. The mode stripper ensures that higher angle rays propagating along the taper 2 towards the output optical fibre 3 are attenuated thus reducing or eliminating damage to the polymer coating 13.