Switching system of optical transmission lines for protecting from trouble

Claim 2

A switching system according to claim 1, wherein said protection piece of optical terminal equipment comprises: a dummy signal generating means (60) for generating a dummy signal which is to be transmitted through the protection optical transmission line when no working piece of optical terminal equipment is connected to the protection optical transmission line, and a dummy signal connection switch means (S₄) for connecting said dummy signal generating means to said protection optical transmission line when no working piece of optical terminal equipment is connected to the protection optical transmission line.

Claim 3

A switching system according to claim 1, wherein said protection piece of optical terminal equipment (100) comprises: at least one bidirectional tributary port for transmitting and receiving low-priority tributary signals therethrough, sixth receiving means for receiving low-priority tributary signals from said at least one tributary port, third converting means for converting the received low-priority tributary signals to optical signals, sixth transmitting means for transmitting said optical signals converted from said received low-priority tributary signals, through said first bidirectional optical port to the other of said optical terminal stations, seventh receiving means for receiving optical signals transmitted from said other optical terminal station, through said first bidirectional optical port, fourth converting means for converting said optical signals received by said sixth receiving means, to low-priority tributary signals to be transmitted from said at least one bidirectional tributary port, and seventh transmitting means for transmitting said low-priority tributary signals converted by said fourth converting means, from said at least one bidirectional tributary port, a substitute signal connection switch means for connecting said third transmitting means to said protection optical transmission line when no working piece of optical terminal equipment is connected to the protection optical transmission line.

Claim 4

A switching system according to claim 1, wherein said protection piece of optical terminal equipment operates in synchronization with a clock signal, and the fourth and fifth transmitting means respectively comprise synchronizing means (811, ··· 81n, 820) for regenerating said optical signals received through said fourth and fifth bidirectional optical ports, at timing of said clock signal before the transmitting operations by the fourth and fifth transmitting means.

Claim 5

A switching system according to claim 4, wherein said fourth and fifth receiving means respectively comprise optical-to-electric conversion means for converting the respectively received optical signals into electric signals, and demultiplexer means for demultiplexing the converted electric signals into demultiplexed electric signals, said fourth and fifth transmitting means respectively comprise multiplexer means for multiplexing the respectively received electric signals into multiplexed electric signals, and electric-to-optical conversion means for converting the multiplexed electric signals into optical signals, and said protection piece of optical terminal equipment comprises connection means for supplying said demultiplexed electric signals generated in said fourth and fifth receiving means to said fourth and fifth transmitting means, respectively.

Claim 6

A switching system according to claim 4, wherein a wavelength of said optical signal transmitted from said protection piece of optical terminal equipment to said working pieces of optical terminal equipment and a wavelength of said optical signal transmitted from said respective working pieces of optical terminal equipment to said protection piece of optical terminal equipment, are the same.

Claim 7

A switching system according to claim 1, wherein each of said plurality of bidirectional optical signal paths comprise wavelength division multiplex means (251) for transforming a plurality of optical signals to optical signals respectively having different wavelengths, and multiplexing the plurality of optical signals to transmit the plurality of optical signals between the protection piece of optical terminal equipment and one of the plurality of working pieces of optical terminal equipment through an optical transmission line.

Claim 8

A switching system according to claim 1, wherein each of said plurality of working pieces of optical terminal equipment comprises switch means for making the operation active regarding optical signals passing through one of said first and second bidirectional optical ports.

Claim 9

A switching system according to claim 1, wherein each of said plurality of working pieces of optical terminal equipment comprises, a receiving signal switch means (169) for selecting the optical signals received through one of said first and second bidirectional optical ports,to be converted to said tributary signals by said second converting means, and a transmitting signal switch means (168) for selecting one of said first and second transmitting means to operate.

Claim 10

A switching system according to claim 9, wherein each of said first and second optical terminal stations further comprises switch control means for controlling the operations of said receiving signal switch means and said transmitting signal switch means.

Claim 11

A switching system according to claim 9, wherein said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: a first signal coupling/branching means (300, 300'), provided corresponding to the protection piece of optical terminal equipment, said first signal coupling/branching means having one coupled bidirectional optical port and a plurality of uncoupled bidirectional optical ports provided corresponding to the respective working pieces of optical terminal equipment, the plurality of uncoupled bidirectional optical ports are respectively connected to said second bidirectional optical port of the corresponding working pieces of optical terminal equipment, the coupled bidirectional optical port being connected to said fourth bidirectional optical port of said protection piece of optical terminal equipment, an optical signal input into said coupled bidirectional optical port in each first signal coupling/branching means branching therein to be output from said plurality of uncoupled bidirectional optical ports, and an optical signal input into either of said plurality of uncoupled bidirectional optical ports in the first signal coupling/branching means passing therethrough to be output from said coupled bidirectional optical port.

Claim 12

A switching system according to claim 11, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths further comprises: a second signal coupling/branching means 200, 200'), provided corresponding to the protection piece of optical terminal equipment, said second signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of the second signal coupling/branching means being connected to said coupled bidirectional optical port of said first signal coupling/branching means, said two uncoupled unidirectional ports of the second signal coupling/branching means are respectively connected to said optical input port and said optical output port of said protection piece of optical terminal equipment, an optical signal input into said coupled bidirectional optical port in the second signal coupling/branching means passing therethrough to be input into the protection piece of optical terminal equipment through the optical input port thereof, and an optical signal output from the optical output port of the protection piece of optical terminal equipment, passing through the second signal coupling/branching means to be output from said coupled bidirectional optical port thereof to the first signal coupling/branching means; and a plurality of third signal coupling/branching means (201, 202, ··· 20N), respectively provided corresponding to said plurality of working pieces of optical terminal equipment, each of said third signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of each third signal coupling/branching means being connected to one of said plurality of uncoupled bidirectional optical ports of said first signal coupling/branching means, said two uncoupled unidirectional ports of each third signal coupling/branching means are respectively connected to said optical input port and said optical output port of one of said plurality of working pieces of optical terminal equipment corresponding to said each third signal coupling/branching means, an optical signal input into said coupled bidirectional optical port in each third signal coupling/branching means passing therethrough to be applied to the working piece of optical terminal equipment corresponding to the third signal coupling/branching means through the one of the uncoupled unidirectional ports of the third signal coupling/branching means and the optical input port of the working piece of optical terminal equipment, and an optical signal output from the optical output port of the working piece of optical terminal equipment corresponding to the third signal coupling/branching means, being input through the other of said two uncoupled unidirectional ports of the third signal coupling/branching means, and passing therethrough to be output from the coupled bidirectional optical port thereof to the first signal coupling/branching means.

Claim 13

A switching system according to claim 9, wherein said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: a first unidirectional signal coupling/branching means, provided corresponding to the protection piece of optical terminal equipment, said first unidirectional signal coupling/branching means having one coupled signal unidirectional port and a plurality of uncoupled unidirectional ports provided corresponding to the respective working pieces of optical terminal equipment, the plurality of uncoupled unidirectional ports are respectively connected to said optical output ports in the second bidirectional optical ports of the corresponding working pieces of optical terminal equipment, the coupled signal unidirectional port being connected to the optical input port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, an optical signal input into one of said uncoupled unidirectional ports in the first unidirectional signal coupling/branching means being output from said coupled signal unidirectional port to be input through the optical input port of the protection piece of optical terminal equipment into the protection piece of optical terminal equipment; and a second unidirectional signal coupling/branching means, provided corresponding to the protection piece of optical terminal equipment, said second unidirectional signal coupling/branching means having one coupled signal unidirectional port and a plurality of uncoupled unidirectional ports provided corresponding to the respective working pieces of optical terminal equipment, the plurality of uncoupled unidirectional ports are respectively connected to said optical input ports in the second bidirectional optical ports of the corresponding working pieces of optical terminal equipment, the coupled signal unidirectional port being connected to the optical output port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, an optical signal input into said coupled signal unidirectional port in the second unidirectional signal coupling/branching means being output from all of said uncoupled unidirectional ports to be applied through the optical input ports of the corresponding working pieces of optical terminal equipment to the respective working pieces of optical terminal equipment.

Claim 14

A switching system according to claim 9, wherein said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: one or more signal coupling/branching means (311, 312, ··· 31N), provided corresponding to the respective working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, each of said one or more signal coupling/branching means having one coupled bidirectional optical port and two uncoupled bidirectional optical ports, one of said two uncoupled bidirectional optical ports being connected to said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal input into said coupled bidirectional optical port in each signal coupling/branching means branching therein to be output from said two uncoupled bidirectional optical ports, and an optical signal input into either of said uncoupled bidirectional optical ports in each signal coupling/branching means passing therethrough to be output from said coupled bidirectional optical port; a furthest bidirectional optical connection path for connecting said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with the other of said two uncoupled bidirectional optical ports of one of said one or more signal coupling/branching means located at location nearest to said working piece of optical terminal equipment located at the furthest location; one or more bidirectional optical connection paths for connecting the other of said two uncoupled bidirectional optical ports of each of the one or more signal coupling/branching means with said coupled bidirectional optical port of one of said one or more signal coupling/branching means located at a position further by one piece than said each signal coupling/branching means from said protection piece of optical terminal equipment, except when said each of said one or more signal coupling/branching means being said signal coupling/branching means located at the nearest location to said working piece of optical terminal equipment located at the furthest location; and a nearest bidirectional optical connection path for connecting said coupled bidirectional optical port of said signal coupling/branching means located at the nearest location to said protection piece of optical terminal equipment, to said fourth bidirectional optical port of the protection piece of optical terminal equipment.

Claim 15

A switching system according to claim 14, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths further comprises: a second signal coupling/branching means (210) for connecting said fourth bidirectional optical port of the protection piece of optical terminal equipment with said coupled bidirectional optical port of said signal coupling/branching means located at the nearest location to the protection piece of optical terminal equipment, said second signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of the second signal coupling/branching means being connected to said coupled bidirectional optical port of said signal coupling/branching means located at the nearest location to the protection piece of optical terminal equipment, said two uncoupled unidirectional ports of the second signal coupling/branching means are respectively connected to said optical input port and said optical output port of said protection piece of optical terminal equipment, an optical signal input into said coupled bidirectional optical port in the second signal coupling/branching means passing therethrough to be input into the protection piece of optical terminal equipment through said one of the two uncoupled unidirectional ports of the second signal coupling/branching means and the optical input port thereof, and an optical signal output from the optical output port of the protection piece of optical terminal equipment, being input into the second signal coupling/branching means through the other of the two uncoupled unidirectional ports thereof, passing through the second signal coupling/branching means to be output from said coupled bidirectional optical port thereof to the first signal coupling/branching means; and a plurality of third signal coupling/branching means (211, 212, ··· 21N) for connecting the second bidirectional optical ports of the respective working pieces of optical terminal equipment with said one of the two uncoupled unidirectional ports of the corresponding ones of said one or more signal coupling/branching means, each of said third signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of each third signal coupling/branching means being connected to said other of the two uncoupled unidirectional ports of one of the one or more signal coupling/branching means located at a position further by one piece than said one of the one or more signal coupling/branching means corresponding to said each third signal coupling/branching means from said protection piece of optical terminal equipment, said two uncoupled unidirectional ports of each third signal coupling/branching means are respectively connected to said optical input port and said optical output port of said one of said plurality of working pieces of optical terminal equipment corresponding to said each third signal coupling/branching means, an optical signal input into said coupled bidirectional optical port in each third signal coupling/branching means passing therethrough to be applied to the working piece of optical terminal equipment corresponding to the third signal coupling/branching means through one of the uncoupled unidirectional ports thereof and the optical input port of the working piece of optical terminal equipment, and an optical signal output from the optical output port of the working piece of optical terminal equipment corresponding to the third signal coupling/branching means, being input through the other of said two uncoupled unidirectional ports of the third signal coupling/branching means, and passing therethrough to be output from the coupled bidirectional, optical port thereof to said one of the one or more signal coupling/branching means located at a position further by one piece than said one of the one or more signal coupling/branching means corresponding to said each third signal coupling/branching means from said protection piece of optical terminal equipment.

Claim 16

A switching system according to claim 15, wherein each of said one or more signal coupling/branching means and a corresponding one of the third coupling/branching means are realized by an optical coupler which comprises one coupled bidirectional optical port, one uncoupled bidirectional optical port, and two uncoupled unidirectional optical ports, said coupled bidirectional optical port and said uncoupled bidirectional optical port in the optical coupler respectively correspond to said coupled bidirectional optical port and said other of said each of said one or more signal coupling/branching means, said two uncoupled unidirectional optical ports in said optical coupler respectively correspond to said two uncoupled unidirectional ports of the corresponding third signal coupling/branching means.

Claim 17

A switching system according to claim 15, wherein a wavelength of said optical signal transmitted from said protection piece of optical terminal equipment to said working pieces of optical terminal equipment and a wavelength of said optical signal transmitted from said respective working pieces of optical terminal equipment to said protection piece of optical terminal equipment, are different, and said third signal coupling/branching means comprises filter means for passing therethrough optical signals of the wavelength of said optical signal transmitted from said protection piece of optical terminal equipment to said working pieces of optical terminal equipment.

Claim 18

A switching system according to claim 9, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: one or more first unidirectional signal coupling/branching means (321, 322, ··· 32N), provided corresponding to the respective working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, each of said one or more first unidirectional signal coupling/branching means having one coupled unidirectional optical port and two uncoupled unidirectional optical ports, one of said two uncoupled unidirectional optical ports being connected to said optical output port of said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal input into either of said uncoupled unidirectional optical ports in each first unidirectional signal coupling/branching means passing therethrough to be output from said coupled unidirectional optical port; a first furthest unidirectional optical connection path for connecting said optical output port of said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with the other of said two uncoupled unidirectional optical ports of one of said one or more first unidirectional signal coupling/branching means located at location nearest to said working piece of optical terminal equipment located at the furthest location; one or more first unidirectional optical connection paths for connecting the other of said two uncoupled unidirectional optical ports of each of the one or more first unidirectional signal coupling/branching means with said coupled unidirectional optical port of one of said one or more first unidirectional signal coupling/branching means located at a position further by one piece than said each first unidirectional signal coupling/branching means from said protection piece of optical terminal equipment, except when said each of said one or more first unidirectional signal coupling/branching means being said first unidirectional signal coupling/branching means located at the nearest location to said working piece of optical terminal equipment located at the furthest location; a first nearest unidirectional optical connection path for connecting said coupled unidirectional optical port of said first unidirectional signal coupling/branching means located at the nearest location to said protection piece of optical terminal equipment, to said optical input port of said fourth bidirectional optical port of the protection piece of optical terminal equipment; one or more second signal coupling/branching means (331, 332, ··· 33N), provided corresponding to the respective working pieces of optical terminal equipment except said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, each of said one or more second signal coupling/branching means having one coupled unidirectional optical port and two uncoupled unidirectional optical ports, one of said two uncoupled unidirectional optical ports being connected to said optical input port of said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal input into said coupled unidirectional optical port in each second signal coupling/branching means branching therein to he output from said two uncoupled unidirectional optical ports; a second furthest unidirectional optical connection path for connecting said optical input port of said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with the other of said two uncoupled unidirectional optical ports of one of said one or more second signal coupling/branching means located at location nearest to said working piece of optical terminal equipment located at the furthest location; one or more second unidirectional optical connection paths for connecting the other of said two uncoupled unidirectional optical ports of each of the one or more second signal coupling/branching means with said coupled unidirectional optical port of one of said one or more second signal coupling/branching means located at a position further by one piece than said each second signal coupling/branching means from said protection piece of optical terminal equipment, except when said each of said one or more second signal coupling/branching means being said second signal coupling/branching means located at the nearest location to said working piece of optical terminal equipment located at the furthest location; and a second nearest unidirectional optical connection path for connecting said coupled unidirectional optical port of said second signal coupling/branching means located at the nearest location to said protection piece of optical terminal equipment, to said optical output port of said fourth bidirectional optical port of the protection piece of optical terminal equipment.

Claim 19

A switching system according to claim 1, wherein each of said plurality of working pieces of optical terminal equipment comprises a receiving signal switch means (173) for selecting the optical signals received through one of said first and second bidirectional optical ports, to be converted to said tributary signals by said second converting means, and both of said first and second transmitting means operating concurrently.

Claim 20

A switching system according to claim 19, wherein said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: a first signal switching means (300), provided corresponding to the protection piece of optical terminal equipment, said first signal switching means having one first-type bidirectional optical port and a plurality of second-type bidirectional optical ports, said first-type bidirectional optical port being connected to said fourth bidirectional optical port of said protection piece of optical terminal equipment, said plurality of second-type bidirectional optical ports are respectively connected to said second bidirectional optical ports of the corresponding working pieces of optical terminal equipment, an optical signal input into said first-type bidirectional optical port in the first signal switching means being output from a selected one of said plurality of second-type bidirectional optical ports, and an optical signal input into either of said plurality of second-type bidirectional optical ports in the first signal switching means passing therethrough to be output from said first-type bidirectional optical port.

Claim 21

A switching system according to claim 20, wherein each of said first and second optical terminal stations further comprises switch control means for controlling the operations of said receiving signal switch means and said one or more signal switching means.

Claim 22

A switching system according to claim 21, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths further comprises: a first signal coupling/branching means (200), provided corresponding to the protection piece of optical terminal equipment, said first unidirectional signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of the first signal coupling/branching means being connected to said first-type bidirectional optical port of said first signal switching means, said two uncoupled unidirectional ports of the first signal coupling/branching means are respectively connected to said optical input port and said optical output port of said protection piece of optical terminal equipment, an optical signal input into said coupled bidirectional optical port in the first signal coupling/branching means passing therethrough to be input into the protection piece of optical terminal equipment through the optical input port thereof, and an optical signal output from the optical output port of the protection piece of optical terminal equipment, passing through the first signal coupling/branching means to be output from said coupled bidirectional optical port thereof to the first signal switching means; and a plurality of second signal coupling/branching means (201, 202, ··· 20N), respectively provided corresponding to said plurality of working pieces of optical terminal equipment, each of said third first signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of each second signal coupling/branching means being connected to one of said plurality of uncoupled bidirectional optical ports of said first signal switching means, said two uncoupled unidirectional ports of each second signal coupling/branching means are respectively connected to said optical input port and said optical output port of one of said plurality of working pieces of optical terminal equipment corresponding to said each second signal coupling/branching means, an optical signal input into said coupled bidirectional optical port in each second signal coupling/branching means passing therethrough to be applied to the working piece of optical terminal equipment corresponding to the second signal coupling/branching means through the one of the uncoupled unidirectional ports thereof and the optical input port of the working piece of optical terminal equipment, and an optical signal output from the optical output port of the working piece of optical terminal equipment corresponding to the second signal coupling/branching means, being input through the other of said two uncoupled unidirectional ports of the second signal coupling/branching means, and passing through the second signal coupling/branching means to be output from the coupled bidirectional optical port thereof to the first signal switching means.

Claim 23

A switching system according to claim 19, wherein said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: a first unidirectional signal switching means, provided corresponding to the protection piece of optical terminal equipment, said first unidirectional signal switching means having one first-type unidirectional port and a plurality of second-type unidirectional ports, said plurality of second-type unidirectional ports being provided corresponding to the respective working pieces of optical terminal equipment, the plurality of second-type unidirectional ports being respectively connected to said optical output ports in the second bidirectional optical ports of the corresponding working pieces of optical terminal equipment, the first-type unidirectional port being connected to the optical input port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, an optical signal input into one of said second-type unidirectional ports in the first unidirectional signal switching means being output from said first-type unidirectional port to be input into the protection piece of optical terminal equipment through the optical input port of the protection piece thereof; and a second unidirectional signal switching means, provided corresponding to the protection piece of optical terminal equipment, said second unidirectional signal switching means having one first-type unidirectional port and a plurality of second-type unidirectional ports, said plurality of second-type unidirectional ports being provided corresponding to the respective working pieces of optical terminal equipment, the plurality of second-type unidirectional ports being respectively connected to said optical input ports in the second bidirectional optical ports of the corresponding working pieces of optical terminal equipment, the first-type unidirectional port being connected to the optical output port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, an optical signal input into said first-type unidirectional port in the second unidirectional signal switching means being output from a selected one of said second-type unidirectional ports to be applied to the respective working pieces of optical terminal equipment through the optical input port thereof.

Claim 24

A switching system according to claim 23, wherein each of said first and second optical terminal stations further comprises switch control means for controlling the operations of said receiving signal switch means, and said first and second unidirectional signal switching means.

Claim 25

A switching system according to claim 19, wherein said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: one or more signal switching means (311, 312, ··· 31N), provided corresponding to the respective working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, each of said one or more having one second-type bidirectional optical port and two second-type bidirectional optical ports, one of said two second-type bidirectional optical ports of the signal switching means being connected to said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal input into said second-type bidirectional optical port in each signal switching means passing therethrough to be output from one of said two second-type bidirectional optical ports, and an optical signal input into one of said second-type bidirectional optical ports in each signal switching means passing therethrough to be output from said second-type bidirectional optical port; a furthest bidirectional optical connection path for connecting said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with the other of said two second-type bidirectional optical ports of one of said one or more signal switching means located at location nearest to said one of the working pieces of optical terminal equipment located at the furthest location; one or more bidirectional optical connection paths for connecting the other of said two second-type bidirectional optical ports of each of said one or more signal switching means with said second-type bidirectional optical port of one of said one or more signal coupling/branching means located at a position further by one piece than said each signal coupling/branching means from said protection piece of optical terminal equipment, except where said each of said one or more signal switching means being said signal switching means located at the nearest location to said one of the working pieces of optical terminal equipment located at the furthest location; and a nearest bidirectional optical connection path for connecting said first-type bidirectional optical port of said signal switching means located at the nearest location to said protection piece of optical terminal equipment, to said fourth bidirectional optical port of the protection piece of optical terminal equipment.

Claim 26

A switching system according to claim 25, wherein each of said first and second optical terminal stations further comprises switch control means for controlling the operations of said receiving signal switch means and said one or more signal switching means.

Claim 27

A switching system according to claim 25, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths further comprises: a first signal coupling/branching means (210), provided corresponding to the protection piece of optical terminal equipment, for connecting said fourth bidirectional optical port of the protection piece of optical terminal equipment with said coupled bidirectional optical port of said signal switching means located at the nearest location to said protection piece of optical terminal equipment, said first signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of the first signal coupling/branching means being connected to said coupled bidirectional optical port of the signal switching means located at the nearest location to said protection piece of optical terminal equipment, said two uncoupled unidirectional ports of the first signal coupling/branching means are respectively connected to said optical input port and said optical output port of said protection piece of optical terminal equipment, an optical signal input into said coupled bidirectional optical port in the first signal coupling/branching means passing therethrough to be input into the protection piece of optical terminal equipment through the optical input port thereof, and an optical signal output from the optical output port of the protection piece of optical terminal equipment, passing through the first signal coupling/branching means to be output from said coupled bidirectional optical port thereof to said signal switching means located at the nearest location to said protection piece of optical terminal equipment; and a plurality of second signal coupling/branching means (211, 212, ··· 21N), respectively provided corresponding to said plurality of working pieces of optical terminal equipment, for connecting said one of said two second-type bidirectional optical ports of each signal switching means with said second bidirectional optical port of a corresponding working piece of optical terminal equipment, each of said second signal coupling/branching means having one coupled bidirectional optical port and two uncoupled unidirectional ports, said coupled bidirectional optical port of each second signal coupling/branching means being connected to said one of the uncoupled unidirectional optical ports of a corresponding one of the signal coupling/branching means, said two uncoupled unidirectional ports of each second signal coupling/branching means are respectively connected to said optical input port and said optical output port of one of said plurality of working pieces of optical terminal equipment corresponding to said each second signal coupling/branching means, an optical signal input into said coupled bidirectional optical port in each second signal coupling/branching means passing therethrough to be applied to the working piece of optical terminal equipment corresponding to the second signal coupling/branching means through the one of the uncoupled unidirectional ports of the second signal coupling/branching means and the optical input port of the working piece of optical terminal equipment, and an optical signal output from the optical output port of the working piece of optical terminal equipment corresponding to the second signal coupling/branching means, being input through the other of said two uncoupled unidirectional ports of the second signal coupling/branching means, and passing therethrough to be output from the coupled bidirectional optical port thereof to the signal switching means corresponding to the second signal coupling/branching means.

Claim 28

A switching system according to claim 27, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: one or more first unidirectional signal switching means (321, 322, ··· 32N), provided corresponding to the respective working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, each of said one or more first signal switching means having one coupled unidirectional optical port and two uncoupled unidirectional optical ports, one of said two uncoupled unidirectional optical ports being connected to said optical output port of said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal input into a predetermined one of said uncoupled unidirectional optical ports in a first unidirectional signal switching means corresponding to the working piece of optical terminal equipment, passing through the first unidirectional signal switching means to be output from said coupled unidirectional optical port thereof when the working piece of optical terminal equipment is to be connected to the protection transmission line, and an optical signal input into the other of said uncoupled unidirectional optical ports in the first unidirectional signal switching means passing through the first unidirectional signal switching means to be output from said coupled unidirectional optical port when any working piece of optical terminal equipment located at a further location than the working piece of optical terminal equipment corresponding to the first unidirectional signal switching means is to be connected to the protection transmission line; a first furthest unidirectional optical connection path for connecting said optical output port of said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with the other of said two uncoupled unidirectional optical ports of one of said one or more first unidirectional signal switching means located at location nearest to said working piece of optical terminal equipment located at the furthest location, an optical signal input into a predetermined one of said uncoupled unidirectional optical ports in at most a selected one of said one or more first unidirectional signal switching means passing therethrough to be output from said coupled unidirectional optical port, and an optical signal input into the other of said uncoupled unidirectional optical ports in one of said one or more first unidirectional signal switching means passing therethrough to be output from said coupled unidirectional optical port when any of the working pieces of optical terminal equipment located at a further location than the working piece of optical terminal equipment corresponding to the first unidirectional signal switching means is to be connected to the protection transmission line; one or more first unidirectional optical connection paths for connecting the other of said two uncoupled unidirectional optical ports of each first unidirectional signal switching means with said coupled unidirectional optical port of one of said one or more first unidirectional signal switching means located at a position further by one piece than said each first unidirectional signal switching means from said protection piece of optical terminal equipment, except when said each of said one or more first unidirectional signal switching means being said first unidirectional signal switching means located at the nearest location to said working piece of optical terminal equipment located at the furthest location; a first nearest unidirectional optical connection path for connecting said coupled unidirectional optical port of said first unidirectional signal switching means located at the nearest location to said protection piece of optical terminal equipment, to said optical input port of said fourth bidirectional optical port of the protection piece of optical terminal equipment; one or more second unidirectional signal switching means (331, 332, ··· 33N), provided corresponding to the respective working pieces of optical terminal equipment except said working piece of optical terminal equipment is located at the furthest location from said protection piece of optical terminal equipment, each of said one or more second unidirectional signal switching means having one coupled unidirectional optical port and two uncoupled unidirectional optical ports, one of said two uncoupled unidirectional optical ports being connected to said optical input port of said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal which is applied to said coupled unidirectional optical ports in a second unidirectional signal switching means corresponding to one of the working pieces of optical terminal equipment, passing through the second unidirectional signal switching means to be output from a predetermined one of said two uncoupled unidirectional optical ports to the working piece of optical terminal equipment corresponding to the second unidirectional signal switching means when the working piece of optical terminal equipment is to be connected to the protection transmission line, and an optical signal which is applied to said coupled unidirectional optical ports in the second unidirectional signal switching means corresponding to the working piece of optical terminal equipment, passing through the second unidirectional signal switching means to be output from the other of the two uncoupled unidirectional optical port when any working piece of optical terminal equipment located at a further location than the working piece of optical terminal equipment corresponding to the second unidirectional signal switching means is to be connected to the protection transmission line; a second furthest unidirectional optical connection path for connecting said optical input port of said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with said other of said two uncoupled unidirectional optical ports of one of said one or more second unidirectional signal switching means located at location nearest to said working piece of optical terminal equipment located at the furthest location; one or more second unidirectional optical connection paths for connecting said other of said two uncoupled unidirectional optical ports of each second unidirectional signal switching means with said coupled unidirectional optical port of one of said one or more second unidirectional signal switching means located at a position further by one piece than said each second unidirectional signal switching means from said protection piece of optical terminal equipment, except when said each second unidirectional signal switching means being located at the nearest location to said working piece of optical terminal equipment located at the furthest location; and a second nearest unidirectional optical connection path for connecting said coupled unidirectional optical port of said second unidirectional signal switching means located at the nearest location to said protection piece of optical terminal equipment, to said optical output port of said fourth bidirectional optical port of the protection piece of optical terminal equipment.

Claim 29

A switching system according to claim 28, wherein each of said first and second optical terminal stations further comprises switch control means for controlling the operations of said receiving signal switch means, and said first and second unidirectional signal switching means.

Claim 30

A switching system according to claim 19, wherein said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: unidirectional signal switching means, provided corresponding to the protection piece of optical terminal equipment, said unidirectional signal switching means having one first-type unidirectional port and a plurality of second-type unidirectional ports, said plurality of second-type unidirectional ports being provided corresponding to the respective working pieces of optical terminal equipment, the plurality of second-type unidirectional ports being respectively connected to said optical output ports in the second bidirectional optical ports of the corresponding working pieces of optical terminal equipment, the first-type unidirectional port being connected to the optical input port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, an optical signal input into one of said second-type unidirectional ports in the unidirectional signal switching means being output from said first-type unidirectional port to be input into the protection piece of optical terminal equipment through the optical input port of the protection piece thereof; and a unidirectional signal coupling/branching means, provided corresponding to the protection piece of optical terminal equipment, said unidirectional signal coupling/branching means having one coupled signal unidirectional port and a plurality of uncoupled unidirectional ports provided corresponding to the respective working pieces of optical terminal equipment, the plurality of uncoupled unidirectional ports are respectively connected to said optical input ports in the second bidirectional optical ports of the corresponding working pieces of optical terminal equipment, the coupled signal unidirectional port being connected to the optical output port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, an optical signal input into said coupled signal unidirectional port in the unidirectional signal coupling/branching means being output from all of said uncoupled unidirectional ports to be applied through the optical input ports of the corresponding working pieces of optical terminal equipment to the respective working pieces of optical terminal equipment.

Claim 31

A switching system according to claim 19, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths in each of first and second optical terminal stations comprise: one or more unidirectional signal switching means (321, 322, ··· 32N), provided corresponding to the respective working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, each of said one or more first signal switching means having one coupled unidirectional optical port and two uncoupled unidirectional optical ports, one of said two uncoupled unidirectional optical ports being connected to said optical output port of said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal input into a predetermined one of said uncoupled unidirectional optical ports in a unidirectional signal switching means corresponding to the working piece of optical terminal equipment, passing through the unidirectional signal switching means to be output from said coupled unidirectional optical port thereof when the working piece of optical terminal equipment is to be connected to the protection transmission line, and an optical signal input into the other of said uncoupled unidirectional optical ports in the unidirectional signal switching means passing through the unidirectional signal switching means to be output from said coupled unidirectional optical port when any working piece of optical terminal equipment located at a further location than the working piece of optical terminal equipment corresponding to the unidirectional signal switching means is to be connected to the protection transmission line; a furthest unidirectional optical connection path for connecting said optical output port of said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with the other of said two uncoupled unidirectional optical ports of one of said one or more unidirectional signal switching means located at location nearest to said working piece of optical terminal equipment located at the furthest location, an optical signal input into a predetermined one of said uncoupled unidirectional optical ports in at most a selected one of said one or more unidirectional signal switching means passing therethrough to be output from said coupled unidirectional optical port, and an optical signal input into the other of said uncoupled unidirectional optical ports in one of said one or more unidirectional signal switching means passing therethrough to be output from said coupled unidirectional optical port when any of the working pieces of optical terminal equipment located at a further location than the working piece of optical terminal equipment corresponding to the unidirectional signal switching means is to be connected to the protection transmission line; one or more unidirectional optical connection paths for connecting the other of said two uncoupled unidirectional optical ports of each unidirectional signal switching means with said coupled unidirectional optical port of one of said one or more unidirectional signal switching means located at a position further by one piece than said each unidirectional signal switching means from said protection piece of optical terminal equipment, except when said each of said one or more unidirectional signal switching means being said unidirectional signal switching means located at the nearest location to said working piece of optical terminal equipment located at the furthest location; a nearest unidirectional optical connection path for connecting said coupled unidirectional optical port of said unidirectional signal switching means located at the nearest location to said protection piece of optical terminal equipment, to said optical input port of said fourth bidirectional optical port of the protection piece of optical terminal equipment; one or more unidirectional signal coupling/branching means (331, 332, ··· 33N), provided corresponding to the respective working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, each of said one or more unidirectional signal coupling/branching means having one coupled unidirectional optical port and two uncoupled unidirectional optical ports, one of said two uncoupled unidirectional optical ports being connected to said optical output port of said second bidirectional optical port of the corresponding working piece of optical terminal equipment, an optical signal input into either of said uncoupled unidirectional optical ports in each unidirectional signal coupling/branching means passing therethrough to be output from said coupled unidirectional optical port; a second furthest unidirectional optical connection path for connecting said optical output port of said second bidirectional optical port of said working piece of optical terminal equipment located at the furthest location from said protection piece of optical terminal equipment, with the other of said two uncoupled unidirectional optical ports of one of said one or more unidirectional signal coupling/branching means located at location nearest to said working piece of optical terminal equipment located at the furthest location; one or more second unidirectional optical connection paths for connecting the other of said two uncoupled unidirectional optical ports of each of the one or more unidirectional signal coupling/branching means with said coupled unidirectional optical port of one of said one or more unidirectional signal coupling/branching means located at a position further by one piece than said each unidirectional signal coupling/branching means from said protection piece of optical terminal equipment, except when said each of said one or more unidirectional signal coupling/branching means being said unidirectional signal coupling/branching means located at the nearest location to said working piece of optical terminal equipment located at the furthest location; a second nearest unidirectional optical connection path for connecting said coupled unidirectional optical port of said unidirectional signal coupling/branching means located at the nearest location to said protection piece of optical terminal equipment, to said optical input port of said fourth bidirectional optical port of the protection piece of optical terminal equipment.

Claim 32

A switching system according to claim 9, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths in each of said first and second optical terminal stations comprise, a long unidirectional optical connection path for connecting said optical output port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, with said optical input port of said second bidirectional optical port of said working piece of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, a plurality of unidirectional optical connection paths each for connecting said optical output port of the second bidirectional optical port of each of said working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at a furthest position from the protection piece of optical terminal, equipment, with said input optical output port of the second bidirectional optical port of one of said plurality of working pieces of optical terminal equipment located at a position further by one piece than said each working piece of optical terminal equipment from said protection piece of optical terminal equipment, and a nearest unidirectional optical connection path for connecting said optical output port of the fourth bidirectional optical port of the protection piece of optical terminal equipment, with said optical input port of the second bidirectional optical port of the working piece of optical terminal equipment located at a nearest position from the protection piece of optical terminal equipment; and each of said plurality of working pieces of optical terminal equipment, further comprises relay means (513) for receiving an optical signal input from said optical input port of said second bidirectional optical port thereof, and transmitting the received optical signal from said optical output port of said second bidirectional optical port thereof when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 33

A switching system according to claim 32, wherein each of said first and second optical terminal stations further comprises switch control means (501, 501') for controlling the operations of said receiving signal switch means, said transmitting signal switch means, and said relay means.

Claim 34

A switching system according to claim 32, wherein said relay means comprises optical bypass switch means (545) for directly connecting said optical input port of said second bidirectional optical port with said optical output port of said second bidirectional optical port to bypass the optical signals received from the optical input port to the optical output port when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 35

A switching system according to claim 32, wherein said optical input port comprises optical-to-electric conversion means for converting the optical signals received through said optical input port into electric signals, and said optical output port comprises electric-to-optical conversion means for converting electric signals into optical signals to be output through the optical output port, and said relay means comprises optical bypass switch means for supplying the electric signals converted by said optical-to-electric conversion means, to the electric-to-optical conversion means when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 36

A switching system according to claim 9, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths in each of said first and second optical terminal stations comprise: a long unidirectional optical connection path for connecting said optical input port of said second bidirectional optical port of said protection piece of optical terminal equipment, with said optical output port of said second bidirectional optical port of said working piece of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, a plurality of unidirectional optical connection paths each for connecting said optical input port of the second bidirectional optical port of each of said working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at a furthest position from the protection piece of optical terminal equipment, with said output optical output port of the second bidirectional optical port of one of said plurality of working pieces of optical terminal equipment located at a position further by one piece than said each working piece of optical terminal equipment from said protection piece of optical terminal equipment, and a nearest unidirectional optical connection path for connecting said optical input port of the fourth bidirectional optical port of the protection piece of optical terminal equipment, with said optical output port of the second bidirectional optical port of the working piece of optical terminal equipment located at a nearest position from the protection piece of optical terminal equipment; and each of said plurality of working pieces of optical terminal equipment, further comprises relay means (513) for receiving an optical signal input from said optical input port of said second bidirectional optical port thereof, and transmitting the received optical signal from said optical output port of said second bidirectional optical port thereof when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 37

A switching system according to claim 36, wherein each of said first and second optical terminal stations further comprises switch control means for controlling the operations of said receiving signal switch means, said transmitting signal switch means, and said relay means.

Claim 38

A switching system according to claim 36, wherein said relay means comprises optical bypass switch means (545) for directly connecting said optical input port of said second bidirectional optical port with said optical output port of said second bidirectional optical port to bypass the optical signals received from the optical input port to the optical output port when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 39

A switching system according to claim 36, wherein said optical input port comprises optical-to-electric conversion means for converting the optical signals received through said optical input port into electric signals, and said optical output port comprises electric-to-optical conversion means for converting electric signals into optical signals to be output through the optical output port, and said relay means comprises optical bypass switch means for supplying the electric signals converted by said optical-to-electric conversion means, to the electric-to-optical conversion means when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 40

A switching system according to claim 9, wherein said first and second bidirectional optical ports of each of said plurality of working pieces of optical terminal equipment each having an optical input port for the reception by said third receiving means, and an optical output port for the transmission by said second transmitting means, and said protection piece of optical terminal equipment each having an optical input port for the reception by said fourth receiving means, and an optical output port for the transmission by said fifth transmitting means; said plurality of bidirectional optical signal paths in each of said first optical terminal station comprises, a first long unidirectional optical connection path for connecting said optical output port of said fourth bidirectional optical port of said protection piece of optical terminal equipment, with said optical input port of said second bidirectional optical port of said working piece of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, a plurality of first unidirectional optical connection paths each for connecting said optical output port of the second bidirectional optical port of each of said working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at a furthest position from the protection piece of optical terminal equipment, with said input optical output port of the second bidirectional optical port of one of said plurality of working pieces of optical terminal equipment located at a position further by one piece than said each working piece of optical terminal equipment from said protection piece of optical terminal equipment, and a first nearest unidirectional optical connection path for connecting said optical output port of the fourth bidirectional optical port of the protection piece of optical terminal equipment, with said optical input port of the second bidirectional optical port of the working piece of optical terminal equipment located at a nearest position from the protection piece of optical terminal equipment; said plurality of bidirectional optical signal paths in each of said second optical terminal station comprises: a second long unidirectional optical connection path for connecting said optical input port of said second bidirectional optical port of said protection piece of optical terminal equipment, with said optical output port of said second bidirectional optical port of said working piece of optical terminal equipment located at location furthest from said protection piece of optical terminal equipment, a plurality of second unidirectional optical connection paths each for connecting said optical input port of the second bidirectional optical port of each of said working pieces of optical terminal equipment except one of the working pieces of optical terminal equipment located at a furthest position from the protection piece of optical terminal equipment, with said output optical output port of the second bidirectional optical port of one of said plurality of working pieces of optical terminal equipment located at a position further by one piece than said each working piece of optical terminal equipment from said protection piece of optical terminal equipment, and a second nearest unidirectional optical connection path for connecting said optical input port of the fourth bidirectional optical port of the protection piece of optical terminal equipment, with said optical output port of the second bidirectional optical port of the working piece of optical terminal equipment located at a nearest position from the protection piece of optical terminal equipment; each of said plurality of working pieces of optical terminal equipment, further comprises relay means (513) for receiving an optical signal input from said optical input port of said second bidirectional optical port thereof, and transmitting the received optical signal from said optical output port of said second bidirectional optical port thereof when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 41

A switching system according to claim 40, wherein each of said first and second optical terminal stations further comprises switch control means for controlling the operations of said receiving signal switch means, said transmitting signal switch means, and said relay means.

Claim 42

A switching system according to claim 40, wherein said relay means comprises optical bypass switch means (545) for directly connecting said optical input port of said second bidirectional optical port with said optical output port of said second bidirectional optical port to bypass the optical signals received from the optical input port to the optical output port when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 43

A switching system according to claim 40, wherein said optical input port comprises optical-to-electric conversion means for converting the optical signals received through said optical input port into electric signals, and said optical output port comprises electric-to-optical conversion means for converting electric signals into optical signals to be output through the optical output port, and said relay means comprises optical bypass switch means for supplying the electric signals converted by said optical-to-electric conversion means, to the electric-to-optical conversion means when said working piece of optical terminal equipment is not to be connected to said protection transmission line and one of the working pieces of optical terminal equipment located at a location further than the said each working piece of optical terminal equipment is to be connected to the protection transmission line.

Claim 46

A system according to claim 41, wherein the transmission rates of said plurality of bidirectional optical signal paths are equal.

Claim 47

A system according to claim 42, wherein the transmission rates of said plurality of bidirectional optical signal paths are equal to a minimum transmission rate of said working pieces of optical terminal equipment.