Analysis of optical fibre connectors and modal noise generation

The connector proposed by Culshaw, in which input fibre exit face and second fibre entrance face are in the focal planes of a lens, is analysed using wave theory and Fourier optics to test whether it reduces modal noise generation. The results are that the Culshaw connector is inferior to butt coupling for step-index fibres, and has exactly the same modal noise properties as butt copuling for parabolic-index fibres.