Abstract: The present invention relates to the routing of data within communications networks, including but not confined to networks such as the Internet, and particularly, but not exclusively, to a method of routing data directed to a mobile node.

Abstract: In an optical network through which data is transmitted as a stream of bits during successive bit periods by an optical source with a given optical center frequency, to a receiver for detecting a frequency baseband, interferometric noise power, in particular incoherent beat noise power, is minimized by causing a variation in the center frequency of the source such as to cause a redistribution of the incoherent beat noise power from the baseband to higher frequencies, thereby reducing the noise in the baseband.

Abstract: An optical processing and correlation system is described in which each user is assigned a unique code as its identity. When a user wishes to establish a communication link with another user, it encodes the unique identity of the latter (representing the destination address) and broadcasts to all other users. On reception, each receiver correlates its own unique address with the received signal. If the received signal has arrived at the correct destination, then the correlator output is a maximum; this is known as auto-correlation. Alternatively, if the received signal arrives at an incorrect destination, the correlator output is a minimum, known as cross-correlation. Thus, by monitoring the correlator output, desired and undesired signals can be identified by an all-optical network. Various embodiments of the invention are described.

Abstract: An optical code recognition unit (OCRU) for recognising a predetermined n-bit optical code sequence coded using the Manchester code format, has an n-way splitter (7) having an input and n parallel outputs (7a). A plurality of gates (9a, 9b, 9c, 9d) are associated with the splitter outputs (7a), respective pairs of splitter outputs leading to each of the gates ( 9a, 9b, 9c) via a respective optical combiner (8a, 8b, 8c), and any remaining single splitter output leading directly to its gate (9d). Each of the splitter outputs (7a) is subject to a different delay of m half bit periods, where m=0 to 2(n-1), the values of m being chosen such that, if a predetermined optical code sequence is applied to the splitter input, the `1`s in the outputs of each of the pairs of splitter outputs (7a) reach the associated AND gates (9a, 9b, 9c) and the `1` in any remaining single splitter output (7a) reaches its AND gate (9d) at predetermined times such that all the gates are turned on.

Abstract: An optical signal processor (1) used with a method of processing optical data has at least one optical coupling unit (12). Each coupling unit (12) has two optical couplers (12A, 12B) which are connected so that principal channels (14) are connected in series with a time delay of a predetermined value between adjacent couplers (12A, 12B). The optical coupling units (12) are formed into stages. The number of optical coupling units (12) or stages determines further coding of each bit of the input optical signal or code sequence. Stages can be coupled together to process a sequence of optical pulses corresponding in number to the number of optical coupling stages in the system. The outputs of each stage are coupled via optical switches (18) to an optical summing device (24) to simultaneously process the coded data and determine whether the processing has resulted in matching or mismatching of data.