Abstract: In N.times.N optical couplers, such as are used in local area networks and backplanes of telecommunications and computer equipment, which use BRAGG volume diffraction means to couple light beams between the inputs and outputs, the number of gratings is reduced by means of so-called "grating degeneration" one grating can be shared by at least two wave pairs at the same time. In order to achieve this reduction, the directions of light waves in the dielectric slab (or the lateral positions of fibre ends) are suitable arranged. In other embodiments, a reduced number of gratings is achieved by using a "sandwiched" structure which uses multi-layered dielectric slabs. Both embodiments may be combined in the one coupler.

Abstract: An optical receiver includes a photodiode having a surface area of suitable dimensions to permit reception of a signal at a high bit rate. Also, the optical receiver includes an optical taper having a head and a tail. The head is of greater diameter than the tail, and co-axial with the tail. The tail is aligned with the photodiode.