British Telecommunications Public Limited Company

Donald E Clarke

Michael A Hale

Jeremy B Chuter

David W Faulkner

John W Ballance

Paul Adrian Rosher

Kevin D Stalley

A head-end station (1) is provided for a passive optical network system arranged to transmit downstream TDMA frames and receive upstream TDMA frames. The head-end station (1) comprises a TDMA master (5) and a plurality of optical stages (4a, 4b) connected in common to the TDMA master (5). The TDMA master (5) assembles incoming data into downstream TDMA frames and demultiplexes upstream TDMA frames. Each optical stage (4a, 4b) is arranged to be connected to a different respective fiber network (3a, 3b) and includes an optical transmitter which modulates an optical signal with downstream TDMA frames from the TDMA master (5) together with an optical receiver arranged to detect an optical signal carrying upstream TDMA frames.

Passive optical network

A communications system having a line terminal(1), a plurality of customer terminals (2), and a passive optical network for supporting traffic between the line terminal and the customer terminals. The line terminal(I) has a terminal unit (BTS(n)) for relatively narrow bandwidth traffic, and a second terminal unit (BTS(1) to BTS(n-1)) for relatively wider bandwidth traffic. A time domain multiplexer (14) is arranged to multiplex the traffic from the first and second terminal unit for downstream transmission over the network (18). Each customer terminal (2) has a first service unit for relatively narrow bandwidth traffic and a second service unit for relatively wider bandwidth traffic. Each customer terminal (2) has a demultiplexer (22) arranged to receive multiplexed downstream traffic from the network (18), and to segregate the traffic between the first and second service unit. Each customer terminal (2) has control elements for generating relatively narrow bandwidth control signals for upstream transmission over the network, the second terminal unit (BTS(1) to BTS(n-1)) of the line terminal (1) being responsive to the control signals from a given customer terminal (2) to control the transmission of the relatively wider bandwidth traffic to that customer terminal. The downstream transmission is by TDM and the upstream transmission is by TDMA.

Communications system

A head-end station for a passive optical network system arranged to transmit and receive TDMA frames having a header portion and a plurality of basic frames, each basic frame includes traffic bits and control bits. The head-end station includes a data transmitter which assembles and transmits downstream frames and also generates a diagnostic signal for transmission in a downstream frame, the station being switchable to a diagnostic mode in which it transmits the diagnostic signal in a downstream frame in the absence of other traffic, and also including a data receiver which receives upstream frames and detects a return of the diagnostic signal. In a preferred example, the head-end station may transmit a diagnostic signal in the header portion of each downstream frame. Also, in a test mode the transmit signal is looped back to the receiver to enable testing of the transmit receive function. Loop back is provided at three levels, namely the transmitter drive level, the monitored output level and at the laser output receiver input level.

Passive optical network switchable between an operational mode and a

An optical fibre communications system includes a head end connected to n customers by an optical fibre network. The head end has a transmitter unit and a receiver unit, and each of the customers has an optical network unit with an optical receiver and a transmitter unit. The head end transmitter and receiver units are connected respectively to the receivers and the transmitter units of the customer optical network units by at least one passive optical network. The head end transmitter unit includes an optical transmitter driven by a sub-carrier multiplexer, the sub-carrier multiplexer having a plurality of input sub-carriers at different frequencies. One of the sub-carriers carries interactive signals provided by a further optical transmitter unit. The remaining sub-carriers carry broadband service signals. Each customer transmitter unit includes an optical transmitter and apparatus for multiplexing interactive signals and control signals to drive the optical transmitter. The head end includes a system control unit for controlling the transmission of broadband services by the head end transmitter unit in dependence upon the control signals received by the head end receiver unit from the customer transmitter units.

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Essex, United Kingdom

Donald E Clarke