Abstract: 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.

Abstract: A test apparatus is designed for use with a TPON system including a headend station connected via a fibre optic network to a plurality of terminations. The test apparatus is a self-contained unit including a connection for linking the apparatus to a termination, a first detection circuit which detects status signals generated by the termination, and a second detection circuit which detects alarm signals generated in the head-end station and transmitted to the termination in a downstream data frame. The test apparatus in response to the first and second test circuits provides an output which indicates the condition of the termination. In one example, a series of indicator lamps formed on the housing for the test apparatus are lit to provide the appropriate output.