Fujitsu Corporation

Toshimi Kida

Kazuhiro Uchida

Katsuichi Yamaji

Toshihiro Noguchi

In a point-to-multipoint network of an optical line terminal (OLT) and multiple optical network units (ONUS) wherein each ONU is enabled to send a signal only within a time period enabled for the ONU, the OLT (or a system installed therein) identifies a defective one of the ONUs. For each of a given series of time periods, the OLT measures an optical reception level of an optical fiber signal in the time period. The OLT stores, in advance, in a table at least the reception level of a received signal from each ONU in association with the ONU. The reception level is measured in a normal state where signals from the ONUs are exclusively received. For each of the given series of time periods, the OLT decides whether a signal from one of the ONUs associated with the time period is exclusively received with no collision with any other signal. If the signal from an ONU associated with the time period is not exclusively received, the OLT identifies the defective ONU based on a measured optical reception level for the time period, a stored reception level of an ONU stored in the table and associated with the time period and the table.

Technique of identifying a defective subscriber device in a point-to-multipoint network without stopping normal subscriber devices

In an optical transmission method and device of a point-multipoint type, whether or not identification information of an optical network unit designated is received within a fixed phase tolerance for a transmission enabling phase designated to optical network units on multipoint sides is determined. When it is determined that no identification information of the optical network unit designated is received and identification information of any optical network unit is received up to a transmission enabling phase subsequently designated, a transmission stop command is transmitted to the optical network unit whose identification information is received. Also, when abnormality is detected in transmitted data from the optical network unit designated or any optical network unit within a transmission enabling duration designated for the transmission enabling phase designated to the optical network units, a transmission enabling duration reducing command is transmitted to the optical network unit or all of the optical network units respectively. Thereafter, when the identification information of the optical network unit designated is received within a fixed phase tolerance for the transmission enabling phase designated to the optical network units and identification information of another optical network unit is also received up to a transmission enabling phase subsequently designated, a transmission stop command to the other optical network unit and a command for restoring the transmission enabling duration for the optical network unit and all of the optical network units are transmitted.

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Fukuoka, Japan

Toshimi Kida