DC WDM device and DC WDM system and transmission network using the same

• US 20030053748A1
• Filed: 08/09/2002
• Published: 03/20/2003
• Est. Priority Date: 09/17/2001
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Byeong-Hoon
• Granted Patent: US 6,845,188 B2
• Time in Patent Office: Days
• US Class Current: 385/24
• CPC Class Codes: G02B 6/12021 Comprising cascaded AWG devices; AWG multipass configuration; Plural AWG devices integrated on a single chip
• CPC Class Codes: G02B 6/29319 With a cascade of diffractive elements or of diffraction operations forming interferometer by splitting and recombining G02B6/29347 - G02B6/29358
• CPC Class Codes: G02B 6/4201 Packages, e.g. shape, construction, internal or external details
• CPC Class Codes: G02B 6/4246 Bidirectionally operating package structures
• CPC Class Codes: H04J 14/0219 Modular or upgradable architectures

Abstract

The invention adds a function of Wavelength-Division-Multiplexing (WDM) to conventional transmission units to enlarge the transmission capacity. The DC WDM device of the invention includes a first WDM coupler module for inputting a first WDM optical signal subjected to transmission and a first optical signal of a fixed wavelength to wavelength-division-multiplex the signals, and a second WDM coupler module for demultiplexing a transmitted WDM optical signal to divide the same into a second optical signal of the fixed wavelength and a second WDM optical signal of the remaining wavelengths. The WDM system of the invention includes a pair of DC WDM sub-systems connected to each other via optical transmission/receiving channels for transmitting/receiving WDM optical signals, where one of the DC WDM sub-systems includes a plurality of transmission units for transmission/receiving optical signals of fixed wavelengths into and from corresponding transmission units of the other DC WDM sub-system, a plurality of DC WDM devices connected to one another into the shape of a daisy chain while coupled to said transmission units in one-to-one relation, and a fiber amplifier connected between said optical transmission/receiving channels and one of said DC WDM devices subjected to connection to said channels.

Claims

1. A Daisy Chain Wavelength-Division-Multiplexing device, comprising:

a first Wavelength-Division-Multiplexing coupler module for inputting a first Wavelength-Division-Multiplexing optical signal subjected to transmission and a first optical signal of a fixed wavelength to wavelength-division-multiplex the signals; and

a second Wavelength-Division-Multiplexing coupler module for demultiplexing a transmitted Wavelength-Division-Multiplexing optical signal to divide the same into a second optical signal of the fixed wavelength and a second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths.

2. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 1,

wherein said first Wavelength-Division-Multiplexing coupler module comprises:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission;

an optical signal input terminal for inputting the first optical signal of the fixed wavelength;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal and the first optical signal inputted to said optical signal input terminal; and

a first Wavelength-Division-Multiplexing output terminal for outputting a third Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler, and

wherein said second Wavelength-Division-Multiplexing coupler module comprises;

a second Wavelength-Division-Multiplexing input terminal for inputting the transmitted Wavelength-Division-Multiplexing optical signal;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical signal output terminal for outputting the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler; and

a second Wavelength-Division-Multiplexing output terminal for outputting the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths divided in said second Wavelength-Division-Multiplexing coupler.

3. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 2, wherein said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said first Wavelength-Division-Multiplexing output terminal while reflects the first optical signal inputted to said optical signal input terminal toward said first Wavelength-Division-Multiplexing output terminal, and

wherein said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical signal output terminal while transmits the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

4. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 1, with said first Wavelength-Division-Multiplexing coupler module comprising:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission;

an optical signal input terminal for inputting the first optical signal of the fixed wavelength;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal and the first optical signal inputted to said optical signal input terminal; and

a first Wavelength-Division-Multiplexing output terminal for outputting a third Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler.

5. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 1, with said second Wavelength-Division-Multiplexing coupler module comprising:

a second Wavelength-Division-Multiplexing input terminal for inputting the transmitted Wavelength-Division-Multiplexing optical signal;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical signal output terminal for outputting the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler; and

a second Wavelength-Division-Multiplexing output terminal for outputting the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths divided in said second Wavelength-Division-Multiplexing coupler.

6. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 2, said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said first Wavelength-Division-Multiplexing output terminal while reflects the first optical signal inputted to said optical signal input terminal toward said first Wavelength-Division-Multiplexing output terminal.

7. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 2, said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical signal output terminal while transmits the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

8. A Daisy Chain Wavelength-Division-Multiplexing device comprising:

a first Wavelength-Division-Multiplexing coupler module for inputting a first Wavelength-Division-Multiplexing optical signal subjected to transmission, transforming an inputted electric signal into a first optical signal, and wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal with the first optical signal; and

a second Wavelength-Division-Multiplexing coupler module for demultiplexing a transmitted Wavelength-Division-Multiplexing optical signal to divide the same into a second optical signal of the fixed wavelength and a second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths while outputting a second electric signal transformed from the second optical signal of the fixed wavelength.

9. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 8,

wherein said first Wavelength-Division-Multiplexing coupler module comprises:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission;

an electric signal input terminal for inputting the first electric signal subjected to wavelength-division-multiplexing with the first Wavelength-Division-Multiplexing optical signal;

an optical transmitter for transforming the first electric signal inputted to said electric signal input terminal into the first optical signal of the fixed wavelength;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal with the first optical signal outputted from said optical receiver; and

a first Wavelength-Division-Multiplexing output terminal for outputting a third Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler into a transmission channel, and

wherein said second Wavelength-Division-Multiplexing coupler module comprises;

a second Wavelength-Division-Multiplexing input terminal for inputting the transmitted Wavelength-Division-Multiplexing optical signal;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical receiver for transforming the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler into the second electric signal;

an electric signal output terminal for outputting the second electric signal transformed in said optical receiver; and

a second Wavelength-Division-Multiplexing coupler for outputting the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths demultiplexed in said second Wavelength-Division-Multiplexing coupler.

10. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 9, wherein said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said first Wavelength-Division-Multiplexing output terminal while reflects the first optical signal inputted from said optical transmitter toward said first Wavelength-Division-Multiplexing output terminal, and

wherein said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical receiver while transmits the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

11. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 8, said first Wavelength-Division-Multiplexing coupler module comprising:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission;

an electric signal input terminal for inputting the first electric signal subjected to wavelength-division-multiplexing with the first Wavelength-Division-Multiplexing optical signal;

an optical transmitter for transforming the first electric signal inputted to said electric signal input terminal into the first optical signal of the fixed wavelength;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal with the first optical signal outputted from said optical receiver; and

a first Wavelength-Division-Multiplexing output terminal for outputting a third Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler into a transmission channel.

12. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 8, said second Wavelength-Division-Multiplexing coupler module comprising:

a second Wavelength-Division-Multiplexing input terminal for inputting the transmitted Wavelength-Division-Multiplexing optical signal;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical receiver for transforming the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler into the second electric signal;

an electric signal output terminal for outputting the second electric signal transformed in said optical receiver; and

a second Wavelength-Division-Multiplexing coupler for outputting the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths demultiplexed in said second Wavelength-Division-Multiplexing coupler.

13. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 9, said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said first Wavelength-Division-Multiplexing output terminal while reflects the first optical signal inputted from said optical transmitter toward said first Wavelength-Division-Multiplexing output terminal.

14. The Daisy Chain Wavelength-Division-Multiplexing device according to claim 9, said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical receiver while transmits the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

15. A Daisy Chain Wavelength-Division-Multiplexing system, comprising:

a pair of Daisy Chain Wavelength-Division-Multiplexing sub-systems connected to each other via optical transmission and receiving channels for transmitting and receiving Wavelength-Division-Multiplexing optical signals, wherein one of the Daisy Chain Wavelength-Division-Multiplexing sub-systems comprises;

a plurality of transmission units for transmission and receiving optical signals of fixed wavelengths into and from corresponding transmission units of the other Daisy Chain Wavelength-Division-Multiplexing sub-system;

a plurality of Daisy Chain Wavelength-Division-Multiplexing devices connected to one another into the shape of a daisy chain while coupled to said transmission units in one-to-one relation; and

a fiber amplifier connected between said optical transmission and receiving channels and one of said Daisy Chain Wavelength-Division-Multiplexing devices subjected to connection to said channels, and

with each of said Daisy Chain Wavelength-Division-Multiplexing devices comprising;

a first Wavelength-Division-Multiplexing coupler module for inputting a first Wavelength-Division-Multiplexing optical signal subjected to transmission into said optical transmission channel from an upstream one of said Daisy Chain Wavelength-Division-Multiplexing devices, inputting a first optical signal of a fixed wavelength from a corresponding one of said transmission units, wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal and the first optical signal, and outputting a second Wavelength-Division-Multiplexing optical signal to a downstream one of said Daisy Chain Wavelength-Division-Multiplexing devices or said fiber amplifier; and

a second Wavelength-Division-Multiplexing coupler module for demultiplexing a third Wavelength-Division-Multiplexing optical signal transmitted from said optical receiving channel via said fiber amplifier or said upstream Daisy Chain Wavelength-Division-Multiplexing device to divide the same into a second optical signal of the fixed wavelength and a fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths, outputting the second optical signal of the fixed wavelength into said corresponding transmission unit, and outputting the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths to said downstream Daisy Chain Wavelength-Division-Multiplexing device.

16. The Daisy Chain Wavelength-Division-Multiplexing system according to claim 15,

wherein said first Wavelength-Division-Multiplexing coupler module comprises:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission from said upstream Daisy Chain Wavelength-Division-Multiplexing device into said optical transmission channel;

an optical signal input terminal for inputting the first optical signal of the fixed wavelength subjected to wavelength-division-multiplexing with the first Wavelength-Division-Multiplexing optical signal from said corresponding transmission unit;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal and the first optical signal inputted to said optical signal input terminal; and

a first Wavelength-Division-Multiplexing output terminal for outputting the second Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler to said downstream Daisy Chain Wavelength-Division-Multiplexing device or said fiber amplifier, and

wherein said second Wavelength-Division-Multiplexing coupler module comprises;

a second Wavelength-Division-Multiplexing input terminal for inputting the third Wavelength-Division-Multiplexing optical signal transmitted from said optical receiving channel via said fiber amplifier or said upstream Daisy Chain Wavelength-Division-Multiplexing device;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical signal output terminal for outputting the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler to said corresponding transmission unit; and

a second Wavelength-Division-Multiplexing output terminal for outputting the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths divided in said second Wavelength-Division-Multiplexing coupler to said downstream Daisy Chain Wavelength-Division-Multiplexing device.

17. The Daisy Chain Wavelength-Division-Multiplexing system according to claim 16,

wherein said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier while reflects the first optical signal inputted to said optical signal input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier, and

wherein said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical signal output terminal while transmits the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

18. The Daisy Chain Wavelength-Division-Multiplexing system according to claim 15, said first Wavelength-Division-Multiplexing coupler module comprising:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission from said upstream Daisy Chain Wavelength-Division-Multiplexing device into said optical transmission channel;

an optical signal input terminal for inputting the first optical signal of the fixed wavelength subjected to wavelength-division-multiplexing with the first Wavelength-Division-Multiplexing optical signal from said corresponding transmission unit;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal and the first optical signal inputted to said optical signal input terminal; and

a first Wavelength-Division-Multiplexing output terminal for outputting the second Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler to said downstream Daisy Chain Wavelength-Division-Multiplexing device or said fiber amplifier.

19. The Daisy Chain Wavelength-Division-Multiplexing system according to claim 15, said second Wavelength-Division-Multiplexing coupler module comprising:

a second Wavelength-Division-Multiplexing input terminal for inputting the third Wavelength-Division-Multiplexing optical signal transmitted from said optical receiving channel via said fiber amplifier or said upstream Daisy Chain Wavelength-Division-Multiplexing device;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical signal output terminal for outputting the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler to said corresponding transmission unit; and

a second Wavelength-Division-Multiplexing output terminal for outputting the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths divided in said second Wavelength-Division-Multiplexing coupler to said downstream Daisy Chain Wavelength-Division-Multiplexing device.

20. The Daisy Chain Wavelength-Division-Multiplexing system according to claim 16, said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier while reflects the first optical signal inputted to said optical signal input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier.

21. The Daisy Chain Wavelength-Division-Multiplexing system according to claim 16, said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical signal output terminal while transmits the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

22. A Daisy Chain Wavelength-Division-Multiplexing transmission network, comprising:

two pairs of Daisy Chain Wavelength-Division-Multiplexing systems connected to each other via optical transmission and receiving channels for transmitting and receiving Wavelength-Division-Multiplexing optical signals, wherein one of the Daisy Chain Wavelength-Division-Multiplexing systems comprises;

a plurality of transmission units for transmission and receiving optical signals of fixed wavelengths into and from corresponding transmission units of the other Daisy Chain Wavelength-Division-Multiplexing systems;

a plurality of Daisy Chain Wavelength-Division-Multiplexing devices connected to one another into the shape of a daisy chain while coupled to said transmission units in one-to-one relation; and

a fiber amplifier connected between said optical transmission and receiving channels and one of said Daisy Chain Wavelength-Division-Multiplexing devices subjected to connection to said channels; and

a pair of Optical Add/Drop Multiplexers respectively connected between said Daisy Chain Wavelength-Division-Multiplexing systems for adding and dropping the Wavelength-Division-Multiplexing optical signals transmitted between said Daisy Chain Wavelength-Division-Multiplexing systems,

with each of said Daisy Chain Wavelength-Division-Multiplexing devices comprising;

a first Wavelength-Division-Multiplexing coupler module for inputting a first Wavelength-Division-Multiplexing optical signal subjected to transmission into said optical transmission channel from an upstream one of said Daisy Chain Wavelength-Division-Multiplexing devices, inputting a first optical signal of a fixed wavelength from a corresponding one of said transmission units, wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal and the first optical signal, and outputting a second Wavelength-Division-Multiplexing optical signal to a downstream one of said Daisy Chain Wavelength-Division-Multiplexing devices or said fiber amplifier; and

a second Wavelength-Division-Multiplexing coupler module for demultiplexing a third Wavelength-Division-Multiplexing optical signal transmitted from said optical receiving channel via said fiber amplifier or said upstream Daisy Chain Wavelength-Division-Multiplexing device to divide the same into a second optical signal of the fixed wavelength and a fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths, outputting the second optical signal of the fixed wavelength into said corresponding transmission unit, and outputting the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths to a corresponding one of said Optical Add/Drop Multiplexers or said downstream Daisy Chain Wavelength-Division-Multiplexing device.

23. The Daisy Chain Wavelength-Division-Multiplexing transmission network according to claim 22,

wherein said first Wavelength-Division-Multiplexing coupler module comprises:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission from said corresponding Optical Add/Drop Multiplexers or said upstream Daisy Chain Wavelength-Division-Multiplexing device into said optical transmission channel;

an optical signal input terminal for inputting the first optical signal of the fixed wavelength subjected to wavelength-division-multiplexing with the first Wavelength-Division-Multiplexing optical signal from said corresponding transmission unit;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal and the first optical signal inputted to said optical signal input terminal; and

a first Wavelength-Division-Multiplexing output terminal for outputting the second Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler to said downstream Daisy Chain Wavelength-Division-Multiplexing device or said fiber amplifier, and

wherein said second Wavelength-Division-Multiplexing coupler module comprises;

a second Wavelength-Division-Multiplexing input terminal for inputting the third Wavelength-Division-Multiplexing optical signal transmitted from said optical receiving channel via said fiber amplifier or said upstream Daisy Chain Wavelength-Division-Multiplexing device;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical signal output terminal for outputting the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler to said corresponding transmission unit; and

a second Wavelength-Division-Multiplexing output terminal for outputting the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths divided in said second Wavelength-Division-Multiplexing coupler to said corresponding Optical Add/Drop Multiplexers or said downstream Daisy Chain Wavelength-Division-Multiplexing device.

24. The Daisy Chain Wavelength-Division-Multiplexing transmission network according to claim 23,

wherein said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier while reflects the first optical signal inputted to said optical signal input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier, and

wherein said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical signal output terminal while transmits the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

25. The Daisy Chain Wavelength-Division-Multiplexing transmission network according to claim 22, said first Wavelength-Division-Multiplexing coupler module comprising:

a first Wavelength-Division-Multiplexing input terminal for inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission from said corresponding Optical Add/Drop Multiplexers or said upstream Daisy Chain Wavelength-Division-Multiplexing device into said optical transmission channel;

an optical signal input terminal for inputting the first optical signal of the fixed wavelength subjected to wavelength-division-multiplexing with the first Wavelength-Division-Multiplexing optical signal from said corresponding transmission unit;

a first Wavelength-Division-Multiplexing coupler for wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal and the first optical signal inputted to said optical signal input terminal; and

a first Wavelength-Division-Multiplexing output terminal for outputting the second Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler to said downstream Daisy Chain Wavelength-Division-Multiplexing device or said fiber amplifier.

26. The Daisy Chain Wavelength-Division-Multiplexing transmission network according to claim 22, said second Wavelength-Division-Multiplexing coupler module comprising:

a second Wavelength-Division-Multiplexing input terminal for inputting the third Wavelength-Division-Multiplexing optical signal transmitted from said optical receiving channel via said fiber amplifier or said upstream Daisy Chain Wavelength-Division-Multiplexing device;

a second Wavelength-Division-Multiplexing coupler for demultiplexing the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths;

an optical signal output terminal for outputting the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler to said corresponding transmission unit; and

a second Wavelength-Division-Multiplexing output terminal for outputting the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths divided in said second Wavelength-Division-Multiplexing coupler to said corresponding Optical Add/Drop Multiplexers or said downstream Daisy Chain Wavelength-Division-Multiplexing device.

27. The Daisy Chain Wavelength-Division-Multiplexing transmission network according to claim 23, said first Wavelength-Division-Multiplexing coupler transmits the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier while reflects the first optical signal inputted to said optical signal input terminal toward said downstream Wavelength-Division-Multiplexing device or said fiber amplifier.

28. The Daisy Chain Wavelength-Division-Multiplexing transmission network according to claim 23, said second Wavelength-Division-Multiplexing coupler reflects the second optical signal of the fixed wavelength of the third Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical signal output terminal while transmits the fourth Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal.

29. A method for a Daisy Chain Wavelength-Division-Multiplexing device, comprising:

inputting a first Wavelength-Division-Multiplexing optical signal subjected to transmission and a first optical signal of a fixed wavelength to wavelength-division-multiplex the signals by a first Wavelength-Division-Multiplexing coupler; and

demultiplexing a transmitted Wavelength-Division-Multiplexing optical signal to divide the same into a second optical signal of the fixed wavelength and a second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths by a second Wavelength-Division-Multiplexing coupler.

30. The method according to claim 29, further comprising:

inputting the first Wavelength-Division-Multiplexing optical signal subjected to transmission through a first Wavelength-Division-Multiplexing input terminal;

inputting the first optical signal of the fixed wavelength through an optical signal input terminal;

wavelength-division-multiplexing the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal and the first optical signal inputted to said optical signal input terminal through a first Wavelength-Division-Multiplexing coupler;

outputting a third Wavelength-Division-Multiplexing optical signal multiplexed in said first Wavelength-Division-Multiplexing coupler through a first Wavelength-Division-Multiplexing output terminal;

inputting the transmitted Wavelength-Division-Multiplexing optical signal through a second Wavelength-Division-Multiplexing input terminal;

demultiplexing the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal to divide the same into the second optical signal of the fixed wavelength and the Wavelength-Division-Multiplexing optical signal of the remaining wavelengths through a second Wavelength-Division-Multiplexing coupler;

outputting the second optical signal of the fixed wavelength divided in said second Wavelength-Division-Multiplexing coupler through an optical signal output terminal; and

outputting the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths divided in said second Wavelength-Division-Multiplexing coupler through a second Wavelength-Division-Multiplexing output terminal.

31. The method according to claim 30, further comprising:

transmitting the first Wavelength-Division-Multiplexing optical signal inputted to said first Wavelength-Division-Multiplexing input terminal toward said first Wavelength-Division-Multiplexing output terminal while reflecting the first optical signal inputted to said optical signal input terminal toward said first Wavelength-Division-Multiplexing output terminal by said first Wavelength-Division-Multiplexing coupler; and

reflecting the second optical signal of the fixed wavelength of the transmitted Wavelength-Division-Multiplexing optical signal inputted to said second Wavelength-Division-Multiplexing input terminal toward said optical signal output terminal while transmitting the second Wavelength-Division-Multiplexing optical signal of the remaining wavelengths toward said second Wavelength-Division-Multiplexing output terminal by said second Wavelength-Division-Multiplexing coupler.