Abstract: A structure for an optical packet for transmission over an optical network comprises a packet header (30) and a packet payload (32). The header comprises first and second sections (34, 36). The first section (34) comprises a series of clock pulses (40) at the data rate of the second section of the packet header, or a multiple or sub-multiple thereof. This header structure enables the clock pulses in the first section (34) to be used to control the timing instants when the header information in the second section (36) is read. The header information can thus be read using the data in the header alone, without needing to alter the structure of the packet payload. The clock pulses can be delayed in order to enable them to be used to control the reading of data in the second section of the packet header. The invention ca be used in optical communications networks.

Abstract: A structure for an optical packet for transmission over an optical network comprises a packet header (30) and a packet payload (32). The header comprises first and second sections (34,36). The first section (34) comprises a series of clock pulses (40) at the data rate of the second section of the packet header, or a multiple or sub-multiple thereof. This header structure enables the clock pulses in the first section (34) to be used to control the timing instants when the header information in the second section (36) is read. The header information can thus be read using the data in the header alone, without needing to alter the structure of the packet payload. The clock pulses can be delayed in order to enable them to be used to control the reading of data in the second section of the packet header. The invention ca be used in optical communications networks.

Abstract: A structure for an optical packet has a packet header (30) and a digitally encoded packet payload (32). Information is encoded in the header by modulation of a signal comprising a plurality of pulses aligned with regularly occurring timing instants, the payload digits also being aligned with the regularly occurring timing instants. The header information is encoded at a rate lower than the frequency of the timing instants. This structure enables simplified opto-electric circuitry to be used to read the packet header, and also enables the packet header to be used to derive the clock information required to read the high data rate information from the packet payload. This avoids the need for the initial bits of the packet payload to be used to synchronize the clock. The structure is used in an optical communications network.