An optical-coax unit (130-1, 130-2), comprising: an optical physical-layer device, PHY, to receive and transmit optical signals; a coax PHY (308, 1308) to receive and transmit coax signals; characterised by a media-independent interface (306, 1310) to provide a first continuous bitstream from the optical PHY to the coax PHY (308, 1308) and a second continuous bitstream from the coax PHY (308, 1308) to the optical PHY, wherein the first continuous bitstream corresponds to received optical signals and transmitted coax signals, and the second continuous bitstream corresponds to received coax signals and transmitted optical signals, wherein the coax PHY (308, 1308) comprises: a first sublayer to receive the first continuous bitstream from the media-independent interface (306, 1310) and to provide the second continuous bitstream to the media-independent interface (306, 1310); and a second sublayer to transmit coax signals corresponding to the first continuous bitstream during a first plurality of time windows (202, 208) and to receive coax signals corresponding to the second continuous bitstream during a second plurality of time windows (206, 212) distinct from the first plurality of time windows (202, 208), and wherein the first sublayer comprises: one or more layers to generate a third bitstream based on the first continuous bitstream and corresponding to the transmitted coax signals; and a time-division duplexing adapter to adapt a rate of the third bitstream and insert pad bits into the third bitstream in locations corresponding to times during which the second sublayer does not transmit, the times comprising the second plurality of time windows (206, 212). an optical physical-layer device, PHY, to receive and transmit optical signals; a coax PHY (308, 1308) to receive and transmit coax signals; characterised by a media-independent interface (306, 1310) to provide a first continuous bitstream from the optical PHY to the coax PHY (308, 1308) and a second continuous bitstream from the coax PHY (308, 1308) to the optical PHY, wherein the first continuous bitstream corresponds to received optical signals and transmitted coax signals, and the second continuous bitstream corresponds to received coax signals and transmitted optical signals, wherein the coax PHY (308, 1308) comprises: a first sublayer to receive the first continuous bitstream from the media-independent interface (306, 1310) and to provide the second continuous bitstream to the media-independent interface (306, 1310); and a second sublayer to transmit coax signals corresponding to the first continuous bitstream during a first plurality of time windows (202, 208) and to receive coax signals corresponding to the second continuous bitstream during a second plurality of time windows (206, 212) distinct from the first plurality of time windows (202, 208), and a first sublayer to receive the first continuous bitstream from the media-independent interface (306, 1310) and to provide the second continuous bitstream to the media-independent interface (306, 1310); and a second sublayer to transmit coax signals corresponding to the first continuous bitstream during a first plurality of time windows (202, 208) and to receive coax signals corresponding to the second continuous bitstream during a second plurality of time windows (206, 212) distinct from the first plurality of time windows (202, 208), and wherein the first sublayer comprises: one or more layers to generate a third bitstream based on the first continuous bitstream and corresponding to the transmitted coax signals; and a time-division duplexing adapter to adapt a rate of the third bitstream and insert pad bits into the third bitstream in locations corresponding to times during which the second sublayer does not transmit, the times comprising the second plurality of time windows (206, 212). one or more layers to generate a third bitstream based on the first continuous bitstream and corresponding to the transmitted coax signals; and a time-division duplexing adapter to adapt a rate of the third bitstream and insert pad bits into the third bitstream in locations corresponding to times during which the second sublayer does not transmit, the times comprising the second plurality of time windows (206, 212).