Method for measuring a signal transmission delay time station, terminal station and network system to perform this method

摘要

The method is used in an optical transmission network with a plurality of terminal stations (TS1-TSn) connected to a central station (CS) via a tree-like connection structure, to determine a signal transmission delay time between one terminal station (TSi) and the central station. The terminal stations are adapted to send cells containing information signals to the central station in dedicated time slots. The method consists of sending a start signal (start CR) from the central station to the terminal station (TSi), sending a first predetermined time interval after the receipt of that start signal, a ranging signal from the terminal station to the central station, sending a second predetermined time interval after the sending of the start signal an inhibit signal from the central station to the terminal stations to indicate that no cells may be transmitted during an idle time window; deducing in the central station the signal transmission delay time from contents of the predetermined ranging signal received by the central station during the idle time window. The ranging signal either has an amplitude which is smaller than the infomation signals contained in the cells in order not to disturb the information signals when the ranging signal is transmitted outside the idle time window, or has a similar amplitude in which case error codes are included in the cells in order to recover possible disrupted cells. <IMAGE>