Fault detecting method, system, and apparatus for pon system

A fault detecting system for a passive optical network (PON) system, comprising:

• a previous apparatus (410) of an electrical relay apparatus (400), adapted to send a signal to the electrical relay apparatus (400);
• the electrical relay apparatus (400), adapted to receive and detect the signal sent by the previous apparatus (410), wherein if a defect is detected in the received signal, it is determined that a fault occurs to a transmission path between the previous apparatus (410) and the electrical relay apparatus (400), and a signal with no defect is formed and sent to a next apparatus (420);
• while if no defect is detected in the received signal, the received signal is processed according to original processes and sent to the next apparatus (420);
• and
• the next apparatus (420) of the electrical relay apparatus (400), adapted to receive and detect the signal sent by the electrical relay apparatus (400), wherein if a defect is detected in the received signal, it is determined that a fault occurs to a transmission path between the electrical relay apparatus (400) and the next apparatus (420).

An electrical relay apparatus, comprising:

• a receiving unit (401), adapted to receive a signal sent by a previous apparatus and provide the received signal to a defect detecting unit (402);
• the defect detecting unit (402), adapted to receive and detect the signal provided by the receiving unit (401), wherein if a defect is detected in the received signal, it is determined that a fault occurs to a transmission path between the previous apparatus and the electrical relay apparatus where the defect detecting unit (402) is located, and the received signal is provided to a signal forming unit (403);
• the signal forming unit (403), adapted to receive the signal provided by the defect detecting unit (402), process the signal to form a signal with no defect, and provide the signal with no defect to a sending unit (405);
• and
• the sending unit (405), adapted to receive the signal provided by the signal forming unit (403) and send the received signal to a next apparatus of the electrical relay apparatus where the sending unit (405) is located.