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Optical transmission system wherein protection terminal equipment converts alarm indication signal before relaying same to working terminal equipment

  • US 6,147,783 A
  • Filed: 06/07/1995
  • Issued: 11/14/2000
  • Est. Priority Date: 02/18/1992
  • Status: Expired due to Fees
First Claim
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1. An optical transmission system for communicating between first and second terminal stations, having a working system providing a first connection between the first and second terminal stations and a protection system used as a stand-by system of the working system and providing a second connection between the first and second terminal stations, said optical transmission system comprising:

  • first and second working optical transmission lines, each having respective first and second ends respectively disposed at and coupled to the first and second terminal stations, the first working optical transmission line transmitting a first optical signal from the first terminal station to the second terminal station and the second working optical transmission line transmitting a second optical signal from the second terminal station to the first terminal station;

    first and second protection optical transmission lines, each having respective first and second ends respectively disposed at and coupled to the first and second terminal stations, the first protection optical transmission line transmitting a third optical signal from the first terminal station to the second terminal station and the second protection optical transmission line transmitting a fourth optical signal from the second terminal station to the first terminal station;

    first and second optical working system terminal units located in the respective first and second terminal stations and terminating the respective first and second ends of each of said first and second working optical transmission lines;

    first and second optical protection system terminal units located in the respective first and second terminal stations and terminating the respective first and second ends of each of said first and second protection optical transmission lines;

    a first bidirectional optical transmission line connecting said first optical working system terminal unit with said first optical protection system terminal unit;

    a second bidirectional optical transmission line connecting said second optical working system terminal unit with said second optical protection system terminal unit;

    said first optical protection system terminal unit further comprising first relay means for relaying said fourth optical signal transmitted through said second protection optical transmission line to said first bidirectional optical transmission line;

    said second optical protection system terminal unit further comprising second relay means for relaying said third optical signal transmitted through said first protection optical transmission line to said second bidirectional optical transmission line;

    four optical signal repeaters respectively inserted between said respective first and second ends of said first working transmission line, said second working transmission line, said first protection transmission line and said second protection transmission line, each of said optical signal repeaters further comprising first alarm indication signal generating means for detecting an abnormality in the optical signal transmitted through the respective transmission line and, in response thereto, generating a first alarm indication signal and for transmitting said first alarm indication signal through said respective transmission line and toward a downstream side of said respective transmission line;

    each of said first and second optical protection system terminal units and said first and second optical working system terminal units further comprising first alarm indication signal detecting means for receiving and detecting said first alarm indication signal transmitted through and toward the downstream side of said respective transmission line; and

    each of said first and second relay means further comprising second alarm indication signal generating means for generating and transmitting a second alarm indication signal without transmitting said first alarm indication signal through a corresponding one of said first and second optical bidirectional transmission lines in response to said detection of said first alarm indication signal, wherein said first alarm indication signal detecting means of said first and second optical working system terminal units do not detect said second alarm indication signal.

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