Node device and method for controlling node device
In order to prevent a signal which a terminal station does not require from being intercepted by the terminal station without greatly changing the power of optical signals to be transmitted from a node to the terminal station, a node device is provided with: a first optical unit which outputs a first optical signal received from a first terminal station and addressed to a second terminal station, and a second optical signal received from the first terminal station, addressed to a third terminal station, and having a different wavelength band from the first optical signal; and a second optical unit to which the first and second optical signals outputted from the first optical unit are inputted, and which shifts the frequency of the first optical signal by a predetermined amount to create a fourth optical signal, passes the second optical signal without any change, couples the second and fourth optical signals, and transmits a resultant signal to the third terminal station.
1. A node device comprising:
a first optical circuit that outputs a first optical signal addressed to a second terminal station that is received from a first terminal station and a second optical signal having a wavelength band different from that of the first optical signal addressed to a third terminal station that is received from the first terminal station; and
a second optical circuit in which the first and second optical signals outputted from the first optical circuit are inputted, the frequency of the first optical signal is shifted by a predetermined amount into a fourth optical signal, the second optical signal is passed as it is, and the second and fourth optical signals are coupled and transmitted to the third terminal station.
2. The node device according to claim 1 , wherein
the predetermined amount is determined in such a way that the fourth optical signal cannot be received at the third terminal station.
3. The node device according to claim 2 , wherein
the predetermined amount is determined in such a way that the frequency of the carrier of the fourth optical signal is a frequency at the middle of the frequency grid receivable by the third terminal station.
4. The node device according to claim 2 , wherein the second optical circuit comprises: a WSS (wavelength selective switch) module that outputs the first optical signal and the second optical signal outputted from the first optical circuit from different ports; a frequency shifter that shifts the frequency of the first optical signal outputted from the WSS module by the predetermined value to generate the fourth optical signal; and a second coupler combining the second and fourth optical signals and transmitting the coupled optical signal to the third terminal station.
5. The node device according to claim 2 , wherein the second optical circuit comprises: a 3-port wavelength filter for separating the first and second optical signals outputted from the first optical circuit into the first optical signal and the second optical signal; a frequency shifter for shifting the frequency of the first optical signal demultiplexed by the 3-port wavelength filter by a predetermined value and outputting the signal as the fourth optical signal; and a second coupler for coupling the second optical signal and the fourth optical signal separated by the 3-port wavelength filter and transmitting the coupled optical signal to the third terminal station.
6. The node device according to claim 2 , wherein
the first optical circuit comprises: a first coupler for branching and outputting the first and second optical signals received from the first terminal station; a first wavelength filter for removing the second optical signal from one of the optical signals branched into two by the first coupler and outputting the first optical signal; and a third coupler for branching and outputting the first optical signal outputted from the first wavelength filter in two, and
the second optical circuit comprises: a second wavelength filter for removing the first optical signal from the other of the optical signals branched into two by the first coupler and outputting the second optical signal; a frequency shifter for shifting the frequency of one optical signal outputted from the third coupler by a predetermined value and outputting the optical signal as the fourth optical signal; and a fourth coupler for coupling the fourth optical signal and the second optical signal outputted from the second wavelength filter and transmitting the coupled signal to the third terminal station.
7. The node device according to claim 2 , further comprising a third optical circuit for coupling a third optical signal addressed to the second terminal station received from the third terminal station and the first optical signal outputted from the first optical circuit and transmitting the coupled signal to the second terminal station.
8. The node device according to claim 1 , wherein
the predetermined amount is determined in such a way that the frequency of the carrier of the fourth optical signal is a frequency at the middle of the frequency grid receivable by the third terminal station.
9. The node device according to claim 8 , wherein the second optical circuit comprises: a WSS (wavelength selective switch) module that outputs the first optical signal and the second optical signal outputted from the first optical circuit from different ports; a frequency shifter that shifts the frequency of the first optical signal outputted from the WSS module by the predetermined value to generate the fourth optical signal; and a second coupler combining the second and fourth optical signals and transmitting the coupled optical signal to the third terminal station.
10. The node device according to claim 8 , wherein the second optical circuit comprises: a 3-port wavelength filter for separating the first and second optical signals outputted from the first optical circuit into the first optical signal and the second optical signal; a frequency shifter for shifting the frequency of the first optical signal demultiplexed by the 3-port wavelength filter by a predetermined value and outputting the signal as the fourth optical signal; and a second coupler for coupling the second optical signal and the fourth optical signal separated by the 3-port wavelength filter and transmitting the coupled optical signal to the third terminal station.
11. The node device according to claim 8 , wherein
the first optical circuit comprises: a first coupler for branching and outputting the first and second optical signals received from the first terminal station; a first wavelength filter for removing the second optical signal from one of the optical signals branched into two by the first coupler and outputting the first optical signal; and a third coupler for branching and outputting the first optical signal outputted from the first wavelength filter in two, and
the second optical circuit comprises: a second wavelength filter for removing the first optical signal from the other of the optical signals branched into two by the first coupler and outputting the second optical signal; a frequency shifter for shifting the frequency of one optical signal outputted from the third coupler by a predetermined value and outputting the optical signal as the fourth optical signal; and a fourth coupler for coupling the fourth optical signal and the second optical signal outputted from the second wavelength filter and transmitting the coupled signal to the third terminal station.
12. The node device according to claim 8 , further comprising a third optical circuit for coupling a third optical signal addressed to the second terminal station received from the third terminal station and the first optical signal outputted from the first optical circuit and transmitting the coupled signal to the second terminal station.
13. The node device according to claim 1 , wherein the second optical circuit comprises: a WSS (wavelength selective switch) module that outputs the first optical signal and the second optical signal outputted from the first optical circuit from different ports; a frequency shifter that shifts the frequency of the first optical signal outputted from the WSS module by the predetermined value to generate the fourth optical signal; and a second coupler combining the second and fourth optical signals and transmitting the coupled optical signal to the third terminal station.
14. The node device according to claim 1 , wherein the second optical circuit comprises: a 3-port wavelength filter for separating the first and second optical signals outputted from the first optical circuit into the first optical signal and the second optical signal; a frequency shifter for shifting the frequency of the first optical signal demultiplexed by the 3-port wavelength filter by a predetermined value and outputting the signal as the fourth optical signal; and a second coupler for coupling the second optical signal and the fourth optical signal separated by the 3-port wavelength filter and transmitting the coupled optical signal to the third terminal station.
15. The node device according to claim 1 , wherein
the first optical circuit comprises: a first coupler for branching and outputting the first and second optical signals received from the first terminal station; a first wavelength filter for removing the second optical signal from one of the optical signals branched into two by the first coupler and outputting the first optical signal; and a third coupler for branching and outputting the first optical signal outputted from the first wavelength filter in two, and
the second optical circuit comprises: a second wavelength filter for removing the first optical signal from the other of the optical signals branched into two by the first coupler and outputting the second optical signal; a frequency shifter for shifting the frequency of one optical signal outputted from the third coupler by a predetermined value and outputting the optical signal as the fourth optical signal; and a fourth coupler for coupling the fourth optical signal and the second optical signal outputted from the second wavelength filter and transmitting the coupled signal to the third terminal station.
16. The node device according to claim 1 , further comprising a third optical circuit for coupling a third optical signal addressed to the second terminal station received from the third terminal station and the first optical signal outputted from the first optical circuit and transmitting the coupled signal to the second terminal station.
17. The node device according to claim 16 , wherein
the third optical circuit comprises a WSS module.
18. A communication system in which first to third terminal stations are connected to the node device according to claim 1 via a transmission path.
19. A method for controlling a node device comprising:
outputting a first optical signal addressed to a second terminal station that is received from a first terminal station and a second optical signal having a wavelength band different from that of the first optical signal addressed to a third terminal station that is received from the first terminal station are outputted;
shifting the frequency of the first optical signal by a predetermined amount into a fourth optical signal; and
coupling the second and fourth optical signals and transmitting the second and fourth optical signals coupled to the third terminal station.