A fixed network comprising: a trunk transmission line; a plurality of tributary transmission lines; one or more signal couplers operable to couple said plurality of tributary transmission lines and said trunk transmission line; a plurality of transmitters each being operable to transmit a traffic data signal onto one of said tributary transmission lines, said traffic data signal representing traffic data encoded in accordance with a code division multiple access coding scheme; said one or more signal couplers being operable to pass said traffic data signals from said transmitters onto said trunk transmission line; said fixed network being characterised by: a timing signal source operable to provide a timing signal to said fixed network; said one or more signal couplers being further operable to distribute said timing signal to said tributary transmission lines; and each of said transmitters being arranged in operation to receive said timing signal via a tributary transmission line and transmit said traffic data signals onto said tributary transmission line at a time dependent upon said timing signal, in order to synchronise the traffic data signals from different transmitters on said trunk transmission line, wherein said trunk transmission line comprises a trunk optical fibre, said one or more signal couplers comprise optical couplers and said tributary transmission lines comprise tributary optical fibres. a trunk transmission line; a plurality of tributary transmission lines; one or more signal couplers operable to couple said plurality of tributary transmission lines and said trunk transmission line; a plurality of transmitters each being operable to transmit a traffic data signal onto one of said tributary transmission lines, said traffic data signal representing traffic data encoded in accordance with a code division multiple access coding scheme; said one or more signal couplers being operable to pass said traffic data signals from said transmitters onto said trunk transmission line; said fixed network being characterised by: a timing signal source operable to provide a timing signal to said fixed network; said one or more signal couplers being further operable to distribute said timing signal to said tributary transmission lines; and each of said transmitters being arranged in operation to receive said timing signal via a tributary transmission line and transmit said traffic data signals onto said tributary transmission line at a time dependent upon said timing signal, in order to synchronise the traffic data signals from different transmitters on said trunk transmission line, wherein said trunk transmission line comprises a trunk optical fibre, said one or more signal couplers comprise optical couplers and said tributary transmission lines comprise tributary optical fibres. a timing signal source operable to provide a timing signal to said fixed network; said one or more signal couplers being further operable to distribute said timing signal to said tributary transmission lines; and each of said transmitters being arranged in operation to receive said timing signal via a tributary transmission line and transmit said traffic data signals onto said tributary transmission line at a time dependent upon said timing signal, in order to synchronise the traffic data signals from different transmitters on said trunk transmission line, wherein said trunk transmission line comprises a trunk optical fibre, said one or more signal couplers comprise optical couplers and said tributary transmission lines comprise tributary optical fibres.