Abstract: The invention is directed to the use of wavelength channels to bypass nodes in ring networks. For networks with a small number of nodes, direct node to node routes are provided without changing the physical layout of the fibre in the ring. Architectures providing complete transparent interconnections with extra capacity for heavily used routes on a portion of the ring are disclosed. For networks with a large number of nodes, underconnected networks provide a number of accelerated, direct routes between some of the nodes. Proposed architectures for underconnected networks and methods for self-routing the traffic are also provided.

Abstract: An edge emitting optoelectronic source is integrally formed on a surface of a semiconductor substrate. An optical waveguide is integrally formed on the same surface of the substrate adjacent to the source. The waveguide is aligned with the source for optical coupling of the source to the waveguide. The waveguide comprises an optical diverter for diverting at least a portion of any light propagating along the waveguide toward the source through a surface of the waveguide. An optoelectronic detector is secured to that surface of the waveguide through which light is diverted for receiving light diverted through that surface. The resulting optoelectronic apparatus is suitable for launching and detecting optical signals in large volume bidirectional optical fiber transmission systems.

Abstract: An optical disc assembly has an optical disc and a protective cover. The optical disc has a surface adapted to have optically recorded thereon data consisting of a series of laser ablated pits recorded as a series of concentric data tracks. The pits have small size and high surface density. The protective cover has a permanent optical recording at one surface thereof consisting of a series of visible marks. The marks are an order of magnitude larger than the pits and have a much lower surface density. Memory data is recorded on the optical disc and positional data, comprising a map of the memory data surface, is recorded on the cover. This allows the use of separate positional data and memory data monitoring channels which facilitates the recording of a blank optical disc and subsequent memory data access.

Abstract: A terminal has a reciprocating print head bearing a series of linearly arranged, individually-magnetizable styli for printing on magnetic particle oriented paper. The terminal may be used as a printer, or as a display by combining the printer with an erasing head comprising a series of linearly arranged magnets which create a rotating magnetic field to erase the magnetic particle oriented paper when the erasing head is reciprocated. The print and erase heads are mounted on a common carriage. The terminal is cheap to manufacture and, if used as a printer, has the advantage of reusable paper. If used as a display, it required no refresh.

Abstract: In a scanning head for an optical disc system, a light beam from a laser is transmitted through a monomode optical fiber and then focussed on a record carrying surface of an optical disc by a converging lens. The end of the fiber can be reoriented within orthogonal planes perpendicular to the plane of the record carrying surface by transducers so as to correct for tracking and timing errors. The laser diode can function both as an emitter and, in an external cavity mode, as a detector of light reflected from the disc. Drive to the transducers is dependent on tracking and speed error signals generated from the detected light. For tracking and speed error compensation, only lens fiber end, and, optionally, a collimating lens, which are of negligible weight, need be moved rather than the entire scanning head. This provides a simple structure having a high frequency response and low power consumption.