| 摘要 |
PROBLEM TO BE SOLVED: To reduce the occupancy of a band by a distance measurement window generated in a distance measurement operation to the utmost and to ensure the reliabil ity of a result of the distance measurement. SOLUTION: When distance measurement processing is started, whether the starting results from an initial connection operation from application of an ONU (Optical Network Unit) power supply or from restarting after the ONU in an operating state has fallen into a fault state is discriminated, in restarting, number of times (SUC) for success to delay measurement is regarded to obtain one success and the processing is started, and a delay reference value (d0) is used for a delay in a preceding operating state. Then the distance measurement window is open, a PLOAM (Physical Layer Operation Administration and Maintenance) grant is sent, a PLOAM cell sent from the ONU is received and when the delay is obtained, the delay measurement result is set to (d). When the difference between the delays d and d0 is within a phase limit, the SUC is incremented. When the SUC reaches a maximum value (SUC- NUM) of number of delay measurement success times specified in advance, a delay adjustment instruction value is calculated from the measured delay and the distance measurement operation is completed. |
