Optical transmission system, optically branching apparatus and optical signal processing apparatus

• US 6,327,060 B1
• Filed: 03/04/1998
• Issued: 12/04/2001
• Est. Priority Date: 03/04/1997
• Status: Expired due to Fees

• Current Assignee: KDD Submarine Cable Systems Inc., Kokusai Densin Denwa Kabushiki Kaisha
• Original Assignee: KDD Submarine Cable Systems Inc., Kokusai Densin Denwa Kabushiki Kaisha
• Inventors: Goto, Koji, Otani, Tomohiro, Kawazawa, Toshio
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): SEDIGHIAN, REZA
• Application Number:
  US09/034,932
• Time in Patent Office: 1,371 Days
• Field of Search: 359/110, 359/127, 359/128, 359/119, 359/166, 359/124, 359/130
• US Class Current: 398/83
• CPC Class Codes: H04B 10/035 using loopbacks
• CPC Class Codes: H04B 10/071 using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
• CPC Class Codes: H04B 10/0775 Performance monitoring and measurement of transmission parameters
• CPC Class Codes: H04B 10/27 Arrangements for networking
• CPC Class Codes: H04B 2210/078 using a separate wavelength

Abstract

In an optical transmission system, an optical transmission line has up and down systems and loops back a supervisory light between the up and down systems. Trunk stations are provided at both ends of the optical transmission line and one or more optically branching units are provided in the optical transmission line for add/dropping a specific wavelength respectively. A branch station is connected to each of one or more the branching units. A bypass line for bypassing the supervisory light is provided in each of the one or more optically branching units.

Claims

1. An optical transmission system comprising:

an optical transmission line having up and down systems, means for looping back a supervisory light between the up and down systems, and an optical branching, unit for adding and dropping a specific wavelength, said optical branching unit having a bypass line for bypassing the supervisory light;

a trunk station at each end of the optical transmission line; and

a branch station connected to the optical branching unit, wherein the optical branching, unit further comprises in each of the up and down systems;

a reflecting means for selectively reflecting the specific wavelength;

means for dropping light of said specific wavelength;

means for adding light of said specific wavelength; and

first and second optical circulators each having first, second, third and fourth in/out ports, each said circulator adapted for outputting to said second port light inputted into the first port, for outputting to said third port light inputted into the second port, and for outputting to said first port light inputted into the fourth port, the first optical circulator having the first port connected to an up flow side of the optical transmission line, the second port connected to one end of the reflecting means, the third port connected to the means for dropping light, and the fourth port connected to one end of the bypass line, and the second optical circulator having the first port connected to the other end of the reflecting means, the second port connected to a down flow side of the optical transmission line, the third port connected to the other end of the bypass line, and the fourth port connected to the means for adding light, and

wherein the means for adding light and the means for dropping light each comprise an optical amplifier, and further comprise a first loop back circuit between an output stage of the optical amplifier of the means for dropping light of the up system and an output stage of the optical amplifier of the means for adding light of the down system, and a second loop back circuit between an output stage of the optical amplifier of the means for dropping light of the down system and an output stage of the optical amplifier of the means for adding light of the up system.

2. An optical transmission system comprising:

an optical transmission line having an up system and a down system;

a loop back optical circuit capable of looping back a supervisory light between the up system and the down system;

an optical branching unit disposed on the optical transmission line having a first optical add/drop device for the up system and a second optical add/drop device for the down system;

trunk stations at each end of the optical transmission line; and

a branch station connected to the optical branching unit;

wherein the first optical add/drop device comprises,

a reflector to selectively reflect a specific wavelength,

a bypass line,

an optical input port to add light output from the branch station to be added to the up system,

an optical output port to drop light dropped from the up system to be applied to the branch station,

first and second optical couplers each having first, second, third and fourth ports, each said coupler adapted to output to said second port light inputted into the first port, to output to said third port light inputted into the second port, and to output to said first port light inputted into the fourth port, the first optical coupler having the first port connected to an up flow side of the up system in the optical transmission line, the second port connected to an end of the reflector, the third port to output the dropped light toward the output port, and the fourth port connected to an end of the bypass line, and the second optical coupler having the first port connected to another end of the reflector, the second port connected to a down flow side of the up system in the optical transmission line, the third port connected to another end of the bypass line, and the fourth port to receive the added light from the input port.

3. The optical transmission system as defined in claim 2 wherein the second optical add/drop devices comprises:

a second reflector to selectively reflect a second specific wavelength;

a second bypass line;

a second input port of second added light output from the branch station to be added to the down system;

a second output port of second dropped light dropped from the down system to be applied to the branch station;

third and fourth optical couplers each having first, second, third and fourth ports, each said coupler adapted to output to said second port light inputted into the first port, to output to said third port light inputted into the second port, and to output to said first port light inputted into the fourth port, the third optical coupler having the first port connected to an up flow side of the down system in the optical transmission line, the second port connected to an end of the second reflector, the third port to output the second dropped light toward the second output port, and the fourth port connected to an end of the second bypass line, and the fourth optical coupler having the first port connected to another end of the second reflector, the second port connected to a down flow side of the down system in the optical transmission line, the third port connected to another end of the second bypass line, and the fourth port to receive the second added light from the second input port.

4. The optical transmission system as defined in claim 3 wherein the first optical add/drop device further comprises a first optical amplifier to optically amplify the added light from the input port to apply to the fourth port of the second optical coupler and a second optical amplifier to optically amplify the dropped light output from the third port to output toward the branch station;

the second optical add/drop device further comprises a third optical amplifier to optically amplify the second added light from the second input port to apply to the fourth port of the fourth optical coupler and a fourth optical amplifier to optically amplify the second dropped light output from the third port to output toward the branch station; and

the optical branching unit further comprises a first loop back circuit to optically connect the output of the first optical amplifier and the output of the fourth optical amplifier and a second loop back circuit to optically connect the output of the second optical amplifier and the output of the third optical amplifier.

5. The optical transmission system as defined in claim 3 wherein the third and fourth optical couplers each comprises an optical circulator.

6. The optical transmission system as defined in claim 2 wherein the first optical add/drop device further comprises a first optical amplifier to optically amplify the added light from the input port to apply to the fourth port of the second optical coupler and a second optical amplifier to optically amplify the dropped light output from the third port of the first optical coupler to output toward the branch station;

the second optical add/drop device further comprises an optical add/drop multiplexer to add/drop light having a second specific wavelength from the light propagating in the down system, a third optical amplifier to optically amplify second added light output from the branch station to be added to the down system to apply to the optical add/drop multiplexer and a fourth optical amplifier to optically amply the light dropped by the optical add/drop multiplexer to output toward the branch station; and

the optical branching unit further comprises a first loop back circuit to optically connect the output of the first optical amplifier and the output of the fourth optical amplifier and a second loop back circuit to optically connect the output of the second optical amplifier and the output of the third optical amplifier.

7. The optical transmission system as defined in claim 2 wherein the first and second optical couplers each comprises an optical circulator.

8. An optical branching apparatus disposed on an optical transmission line to transmit signal light in a predetermined direction, comprising:

a reflector to reflect a specific wavelength;

a bypass line;

an input port to add light;

an output port to drop light; and

first and second optical couplers each having first, second, third and fourth ports, each said coupler capable of outputting to said second port light inputted into the first port, to output to said third port light inputted into the second port, and to output to said first port light inputted into the fourth port, the first optical coupler having the first port connected to an up flow side of the optical transmission line, the second port connected to an end of the reflector, the third port connected to the output port, and the fourth port connected to an end of the bypass line, and the second optical coupler having the first port connected to another end of the reflector, the second port connected to a down flow side of the optical transmission line, the third port connected to another end of the bypass line, and the fourth port connected to the input port.

9. The optical branching apparatus as defined in claim 8 wherein the first and second optical couplers each comprises an optical circulator.