Abstract: In the present invention, fast dynamic dispersion compensation on a per-packet basis is performed by using a header recognition scheme at each node in an optical network to extract from each packet the path and bit-rate information. A decision can then be taken on whether dispersion compensation is needed for that packet, and if so, what would be a suitable amount of such compensation.

Abstract: In a method of transmitting data over an optical transmission network, the data to be transmitted is divided into a plurality of data streams, each of which comprises data packets of predetermined lengths with the packet lengths of each stream differing from those of the other streams. Individual packet streams are associated on to respective wavelengths of a wavelength division multiplexed optical signal for transmission over the network.

Abstract: The present invention provides an optical packet switch (3, 4) that facilitates efficient provisioning of packet services through a predominantly circuit-switched optical transport network infrastructure (1). In particular, the optical packet switch (3, 4) fits within a network where circuit and packet-switched traffic are transported together through the optical transport network (1). Fast switching is provided for packet traffic where granularity below the wavelength level is required, while slow wavelength switching and routing is facilitated at the same time. Fast switching and packet traffic aggregation for efficient bandwidth utilisation is performed at the edge where the optical transport network (1) interfaces with the IP domain (6), where dynamic and fast wavelength allocation for packet traffic is required.

Abstract: An optical tunable filter/wavelength converter comprises an input for multiple wavelength traffic carrying signals &lgr;1-&lgr;m, an output for converted wavelength carrying signals (&lgr;1′-&lgr;m′), means (20) for routing each of the traffic carrying signals through a demultiplexer to an individual semiconductor optical amplifier (SOA) (22) or to an interferometer arrangement. A laser source (26) provides a further input wavelength to the SOAs, or to the interferometer arrangements, to enable cross-gain or cross-phase modulation from the input signal which thereby provides the converted signal. Means is provided for selectively routing the converted signal to the output.

Abstract: An optical routing device for wavelength division multiplexed (WDM) optical signals includes an optical switch matrix (50) having a first optical switch array (54) and a second optical switch array (52), the first optical switch array being adapted to couple optical signals to the second optical switch array on the basis of the wavelength of respective optical signals. The second optical switch array (52) includes a number of optical switch devices, each of which is dedicated to route traffic on a respective wavelength. The device includes a drop traffic path and a through traffic path, in which the drop traffic path includes a transponder unit (170; 220) that is selectively reconfigurable to couple signals to a through traffic path and thereby provide a signal regeneration path. The transponder unit (170; 220) may be tunable so as to provide a wavelength translation function for any optical signal received by the transponder unit. This feature enables efficient sharing of transponders.

Abstract: The present invention provides an optical signal processor for the optical processing of a digitally amplitude-modulated optical signal input thereto, to determine the presence or absence of a predetermined digital bit-pattern within said optical signal.

Abstract: The present invention provides an optical signal processor for the optical processing of a digitally amplitude-modulated optical signal input thereto, to determine the presence or absence of a predetermined digital bit-pattern within said optical signal, the optical signal processor possessing optical processing means including;

Abstract: An optical level controller (13) for a wavelength division multiplex optical communication network (17) includes one or more variable gain elements (1;9) adapted to suppress transient amplitude fluctuations in traffic signals caused by the adding or the dropping of traffic signals at one more points in the optical communication network. The at least one variable gain element (1;9) is controlled through a negative feedback loop adapted such that a response time of the negative feedback is shorter than a time scale of the transient amplitude fluctuations.

Abstract: The invention relates to a branching unit (7) for an underwater wavelength division multiplexed (WDM) optical communications system. The branching unit (7) has an optical switch (16) and an optical multiplexer (17) having a number of loop back optical paths which pass through the switch (16). The optical switch (16) is reconfigurable so that individual channels of a WDM signal can be selectively coupled to a trunk output of the branching unit (7). The branching unit allows wavelength and/or capacity reconfiguration between the main trunk (4) and the spur (8) so that it is possible to disconnect a signal from the spur or increase capacity of the spur according to customers' changing requirements.

Abstract: A wavelength division multiplex transmission system has an optical fiber trunk (12) with one or more branching units (18) each providing an add/drop channel (22, 20). In the branch, components are provided for pre-dispersing the wavelength of the add channel, prior to route to the trunk (12), with a dispersion characteristic of opposite sign to the dispersion occurring in the trunk, thereby to compensate for dispersion of that wavelength occurring along the trunk.