Method and apparatus for connecting branch networks with a trunk network in optical transmission system

• US 5,189,541 A
• Filed: 08/12/1991
• Issued: 02/23/1993
• Est. Priority Date: 11/30/1987
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Konishi, Kuniyoshi
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US07/743,913
• Time in Patent Office: 561 Days
• Field of Search: 359/110, 359/118, 359/119, 359/120, 359/121, 359/173, 359/179, 385/24, 370/85.12, 370/85.14, 370/85.15, 340/825.05
• US Class Current: 398/59
• CPC Class Codes: H04B 10/271 Combination of different networks, e.g. star and ring configuration in the same network or two ring networks interconnected

Abstract

In an optical transmission system including a trunk LAN having duplex optical transmission lines, and branch LANs connected with the trunk LAN through nodes, an optical signal on the optical transmission line of the trunk LAN is input to a node including an optical switch, an optical transmitting and receiving circuit, a serial-parallel converter, an internal bus, and a LAN interface. The optical signal input to the node is converted to an electric signal (serial data) by the optical transmitting and receiving circuit through the optical switch, and is converted to parallel data by the serial-parallel converter. Thereafter, the parallel data is output onto the internal bus. The LAN interface performs an operation for outputting the parallel data onto the internal bus to the branch LANs. Data on the branch LAN is output to the optical transmission line by the operation opposite to that described above. The node can include a signal optical transmitting and receiving circuit. A self return mode is set by the LAN interface, so that the presence/absence of malfunction of the node can be self-checked.

Claims

1. An optical network system comprising:

a trunk network having a first and second ring type optical transmission lines;

a plurality of trunk nodes including a first trunk node connected to the first and second ring type optical transmission lines, the first trunk node having a first loop back circuit, and a second trunk node connected to the first and second ring type optical transmission lines, the second trunk node having a second loop back circuit;

a first branch node connected to the first ring type optical transmission line, the first branch node located between the first and second trunk nodes;

a second branch node connected to the first ring type optical transmission line, the second branch node located between the first and second trunk nodes;

a plurality of branch networks having a first branch network connected to the first trunk node and a second branch network connected to the second trunk node;

the first branch node including first switch means for switching a data flow between the first ring type optical transmission line and the first branch network, first conversion means for converting an optical signal from the first switch means into an electric signal and first interface means for transferring the electric signal from the first conversion means to the first branch network, the first switch means having a first mode for directly returning the optical signal received from the first ring type optical transmission line to the first ring type optical transmission line so as to disconnect the data flow between the first ring type optical transmission line and the first branch network and a second mode for transferring the optical signal received from the first ring type optical transmission line to the first conversion means so as to connect the data flow between the first ring type optical transmission line and the first branch network, the first interface means controlling the first switch means between the first mode and the second mode; and

the second branch node including second switch means for switching a data flow between the first ring type optical transmission line and the second branch network, second conversion means for converting an optical signal from the first switch means into an electric signal and second interface means for transferring the electric signal from the second conversion means to the second branch network, the second switch means having a first mode for directly returning the optical signal received from the first ring type optical transmission line to the first ring type optical transmission line so as to disconnect the data flow between the first ring type optical transmission line and the second branch network and a second mode for transferring the optical signal received from the first ring type optical transmission line to the second conversion means so as to connect the data flow between the first ring type optical transmission line and the second branch network, the second interface means controlling the second switch means between the first mode and the second mode.

2. An optical network system according to claim 1, wherein each of the interface means controls the corresponding switch means from the second mode to the first mode when the first or second branch nodes are abnormal, checks whether the corresponding conversion means is abnormal, and controls the corresponding switch means from the first mode to the second mode if the corresponding conversion means is normal, respectively.

3. An optical network system according to claim 9, wherein each of the loop back circuit includes a loop back mode for disconnecting the first and second branch nodes from the trunk network and a non-loop back mode for connecting the first and second branch nodes to the trunk network, respectively, each of the trunk node controls the corresponding loop back circuit from the non-loop back mode to the loop back mode when the first or second branch nodes are abnormal, and controls the corresponding loop back circuit from the loop back mode to the non-loop back mode after the switch means corresponding to an abnormal branch node is set in the first mode.

4. An optical network system comprising:

a trunk network having first and second ring type optical transmission lines;

a plurality of trunk nodes including a first trunk node connected to the first and second ring type optical transmission lines and a second trunk node connected to the first and second ring type optical transmission lines; and

at least one branch node connected to the first ring type optical transmission line between the first and second trunk nodes, and each of the at least one branch node also connected to a corresponding branch network, each of the at least one branch node including switch means for switching a data flow between the first ring type optical transmission line and the corresponding branch network, conversion means for converting optical signals from the at least one branch node'"'"'s switch means into electrical signals and interface means for transferring the electrical signals from the at least one branch node'"'"'s conversion means to the corresponding branch network, the switch means of each of the at least one branch node having a first mode for directly returning optical signals received from the first ring type optical transmission line to the first ring type optical transmission line so as to disconnect the data flow between the first ring type optical transmission line and the corresponding branch network, and a second mode for transferring optical signals received from the first ring type optical transmission line to the conversion means so as to connect the data flow between the first ring type optical transmission line and the corresponding branch network.

5. An optical network system according to claim 4, wherein each of the at least one branch node further comprises error detection means for detecting malfunctions in the at least one branch node, and controls the at least one branch node'"'"'s switch means from the second mode to the first mode when the branch node is malfunctioning, and controls the at least one branch node'"'"'s switch means from the first mode to the second mode when the at least one branch node is not malfunctioning.

6. An optical network system according to claim 5, wherein each of said at least one branch node further comprises self-test means for testing the at least one branch node when the at least one branch node'"'"'s error detection means detects a malfunction in the at least one branch node.

7. An optical network system according to claim 6, wherein the first and second trunk nodes each have U-link means for disconnecting the at least one branch node from the first ring-type optical transmission line and connecting the first ring-type optical transmission line to the second ring-type optical transmission line.

8. An optical network system according to claim 7, wherein the U-link means of the first and second trunk nodes disconnects the at least one branch node from the first ring-type optical transmission line and connects the first ring-type optical transmission line to the second ring-type optical transmission line when the self-test means of the at least one branch node is testing the at least one branch node or when the error detection means of the at least one branch node detects a malfunction in the at least one branch node.