Optical communications network
AssigneeBritish Telecommunications plc
InventorJohn W. Ballance
Life of this patent
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Abstract
A passive, all optical communications network is provided in which a single optical source in a central station serves many outstations (e.g. telephones in customers' premises). Time division multiplexed optical signals from a laser source are transmitted along a single optical fibre (14) from a central station (4). The signal is split between several secondary fibers at a first splitter (10) (e.g. array of passive couplers) and between further sets of fibers at a second set of splitters (12). At this stage there are 120 individual fibres to customers' premises (8). Digital speech or data is sent back to the central station by a laser in the customers' premises operating in a low duty-cycle mode. The 120 data streams are interleaved at the branching points.
Claims6
A central station for a digital communications network comprising a plurality of outstations and a branch network of waveguides comprising a single waveguide from the central station, one or more passive splitters and two or more secondary waveguides for bidirectional transmission to and from the outstations:
- the central station comprising transmitting means for transmitting data to outstations in the form of a stream of frames, each comprising a synchronisation signal in the form of a predetermined pattern of bits;
- and characterised by scrambling means for scrambling the synchronisation signal and at least some of the data bits of each of the frames in accordance with a predetermined binary sequence;
- and by means for detecting in data received from the outstations the presence of the scrambled synchronisation signal thereby obtaining information concerning reflections in the branch network.
Dependencies are inferred from the claim text.