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Switching system of optical transmission lines for protecting from trouble

  • US 5,327,275 A
  • Filed: 10/30/1991
  • Issued: 07/05/1994
  • Est. Priority Date: 10/30/1990
  • Status: Expired due to Fees
First Claim
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1. A system for optical communication between optical terminal stations automatically and selectively switchable between normal and protection modes, comprising:

  • first and second optical terminal stations;

    a plurality of working optical transmission lines, each connecting said first and second optical terminal stations and operable in the normal mode for transmitting optical signals in two opposite directions between said first and second optical terminal stations;

    a protection optical transmission line, provided as a standby bidirectional optical transmission line for at least some of said working optical transmission lines, connecting said first and second optical terminal stations and operable in the protection mode for transmitting an optical signal between said first and second optical terminal stations;

    each of said first and second optical terminal stations comprising;

    a plurality of working pieces of optical terminal equipment respectively corresponding to said plurality of working optical transmission lines, each operable in the normal mode for transmitting and receiving signals over the respective working optional transmission line,a protection piece of optical terminal equipment corresponding to said protection optical transmission line and operable in the protection mode for transmitting and receiving signals over the protection optical transmission line,a plurality of bidirectional optical signal paths corresponding to respective working pieces of optical terminal equipment, each connecting a corresponding working piece of optical terminal equipment with said protection piece of optical terminal equipment and operable in the protection mode for signal transmission therebetween, anda control unit which maintains the normal mode of each of the plurality of working pieces in the absence of any trouble occurring on the respective working optical transmission lines and which is responsive to a trouble occurring in one of the plurality of working optical transmission lines for disabling the normal mode and enabling the protection mode of operation of the respective working piece and of the protection piece;

    each of said plurality of working pieces of optical terminal equipment comprising;

    at least one bidirectional tributary port inputting and outputting tributary signals,first and second bidirectional optical ports each inputting and outputting optical signals, said first bidirectional optical port being connected to a corresponding working optical transmission line, and said second bidirectional optical port being connected to a corresponding bidirectional optical signal path,first receiving means, connected to said at least one bidirectional tributary port, for receiving tributary signals from said at least one tributary port,first converting means, connected to said first receiving means, for converting the tributary signals to optical signals,first transmitting means, connected to said first converting means and said first bidirectional optical port and operable in the normal mode for transmitting the optical signals, converted from the tributary signals, through said first bidirectional optical port and the corresponding working optical transmission line to the other of said first and second optical terminal stations,second transmitting means, connected to said first converting means and said second bidirectional optical port and operable in the protection mode for transmitting the optical signals, converted from the tributary signals, through said second bidirectional optical port and the corresponding bidirectional optical signal path to said protection piece of optical terminal equipment,second receiving means, connected to said first bidirectional optical port, for receiving optical signals transmitted in the normal mode from the other of said first and second optical terminal stations through said respective working line and said first bidirectional optical port,third receiving means, connected to said second bidirectional optical port, for receiving optical signals transmitted in the protection mode from said protection piece of optical terminal equipment through the corresponding bidirectional optical signal path and said second bidirectional port,second converting means, selectively connected to said second receiving means in said normal mode and to said third receiving means in said protection mode, for converting the respective optical signals received by said second and third receiving means to tributary signals to be output from said at least one bidirectional tributary port, andthird transmitting means, connected to said second converting means and said at least one bidirectional tributary port, for transmitting the tributary signals converted by said second converting means to said at least one bidirectional tributary port; and

    said protection piece of optical terminal equipment comprising;

    third and fourth bidirectional optical ports each inputting and outputting optical signals therethrough, said third bidirectional optical port being connected to said protection optical transmission line and said fourth bidirectional optical port being operatively connected to at least one of said plurality of bidirectional optical signal paths,fourth receiving means, connected to said fourth bidirectional optical port, for receiving optical signals, transmitted in the protection mode through said fourth bidirectional optical port from the corresponding working piece of optical terminal equipment connected to the at least one of said plurality of bidirectional optical signal paths,fourth transmitting means, connected to said fourth receiving means and said third bidirectional optical port, for transmitting the optical signals, received by said fourth receiving means in the protection mode, through said protection optical transmission line to the other of said first and second optical terminal stations,fifth receiving means, connected to said third bidirectional optical port, for receiving optical signals, transmitted in the protection mode from the other of said first and second optical terminal stations, through said protection optical signal path and said third bidirectional optical port, andfifth transmitting means, connected to said fourth bidirectional optical port, for transmitting the optical signals, received by said fifth receiving means in the protection mode through said fourth bidirectional optical port, to the corresponding working piece of optical terminal equipment connected to the at least one of said plurality of bidirectional optical signal paths.

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