Bidirectional line switched ring network control system

A bidirectional line switched ring network control apparatus in a bidirectional line switched ring network BLSR utilizing SONET, comprising:

• a line termination circuit for terminating ring-like transmission lines, effecting mutual conversion between an optical signal and an electric signal, separating an automatic protection switching APS byte conveyed by K1 and K2 bytes in the overhead of a multiplexed signal bidirectionally transmitted through said transmission lines, and inserting said APS byte or new APS byte into the overhead of said multiplexed signal;
• a time slot replacing section for effecting replacement and branching of a time slot of a signal terminated by said line termination circuit, effecting branching and insertion of a signal from an end office connected to a current node, and forming a turn-back circuit to turn said APS byte received from a preceding node back to processing node;
• a bypass circuit for bypassing said APS byte provided by said line termination circuit;
• and
• an address comparison circuit for comparing an address contained in said APS byte from said bypass circuit with the address of the current node, closing said bypass circuit to inhibit the passage of said APS byte when the address contained in said APS byte coincides with the current node address, and opening said bypass circuit to allow the passage of said APS byte when said address of said current node and said APS address do not coincide with each other and further directing formation of said turn-back circuit in said time slot replacing section if detecting a trouble of said transmission lines connected to the current node.

A control method of a bidirectional line switched ring network for the time of the occurrence of a trouble of a bidirectional line switched ring network control apparatus in a bidirectional line switched ring network BLSR utilizing SONET, comprising:

• a step of judging coincidence/non-coincidence between an address of an APS byte by K1 and K2 bytes in the overhead of a multiplexed signal bidirectionally transmitted through ring-like transmission lines by an address comparison circuit;
• a step of closing a bypass circuit for controlling the passage of said APS byte so as to inhibit the passage of said APS byte when the address contained in said APS byte coincides with a current node address, and providing an address of a subsequent node to said APS byte, conversely opening said bypass circuit to allow the passage of said APS byte to a subsequent node when the address contained in said APS byte does not coincide with the current node address;
• and
• a step of further judging coincidence/non-coincidence of the address of said APS byte and said current node address by said address comparison circuit after said bypass circuit is opened and closing said bypass circuit for controlling the passage of said APS byte so as to inhibit the passage of said APS byte when the address contained in said APS byte coincides with said current node address, and providing the address of the subsequent node.