Abstract: In an optical fibre switch it is important that the ends of the fibres are very accurately aligned after the switching operation so that the minimum amount of light is lost in the switch. This is achieved by mounting an optical fibre in each of the corners of, for example an accurately formed square hole, and having a moveable fibre which can be moved into each corner and which is accurately aligned with one of the other fibres by the sides of the corner itself. Optical switches are used for transmitting light from a light source to one of several different locations. Typical uses are the transmission of data, telecommunications and similar signal transmission systems.