Polarisation insensitive wavelength multiplexing 2X2 fibre couplers.

摘要

In the manufacture of a polarisation insensitive wavelength multiplexing 2x2 tapered fused optical fibre coupler by progressive stretching the birefringence of the coupler resulting from the progressive stretching is subsequently nulled-out by elastic twisting of the coupler. The progressive stretching is performed under temperature conditions providing a profile in the coupling region of the coupler having the property that the coupling strength for one of the principal polarisation planes of the coupler remains substantially constant during said elastic twisting. <IMAGE>