Optical add drop multiplexer

1. An optical add-drop multiplexer having first and second routes, comprising:

an optical cross connect;

a first wavelength selective switch optically coupled to a plurality of output ports of the optical cross connect and configured to select specified optical signals;

a second wavelength selective switch optically coupled to a plurality of other output ports of the optical cross connect and configured to select specified optical signals;

a third wavelength selective switch to generate a first WDM optical signal including at least one of the optical signals output from the first wavelength selective switch and to guide the first WDM optical signal to the first route; and

a fourth wavelength selective switch to generate a second WDM optical signal including at least one of the optical signal output from the second wavelength selective switch and to guide the second WDM optical signal to the second route,

wherein the optical cross connect guides an input optical signal to the first wavelength selective switch when the input optical signal is output on the first route, and guides an input optical signal to the second wavelength selective switch when the input optical signal is output on the second route,

wherein the first wavelength selective switch has an output optically connected to an input of the third wavelength selective switch, and wherein the third wavelength selective switch is not optically connected to the second wavelength selective switch, and

wherein the second wavelength selective switch has an output optically connected to an input of the fourth wavelength selective switch, and wherein the fourth wavelength selective switch is not optically connected to the first wavelength selective switch.

2. The optical add-drop multiplexer according to claim 1 , further comprising a first optical coupler between the optical cross connect and the first wavelength selective switch, and a second optical coupler between the optical cross connect and the second wavelength selective switch.

3. The optical add-drop multiplexer according to claim 1 , further comprising a plurality of optical filters respectively having a specified transmission wavelength, for a plurality of input ports of the optical cross connect.

4. The optical add-drop multiplexer according to claim 2 , wherein

an optical coupler to combine a plurality of optical signals guided from a plurality of input ports of the optical cross connect is provided for each output port of the optical cross connect.

5. The optical add-drop multiplexer according to claim 1 , wherein

the first and second multiplexers respectively have a wavelength multiplexer;

different transmission wavelengths are set for a plurality of input ports of the wavelength multiplexer; and

the optical cross connect guides an input optical signal of the optical cross connect to a corresponding input port of the wavelength multiplexer according to a wavelength of the input optical signal.

6. An optical add-drop multiplexer comprising:

a plurality of optical cross connects;

a drop signal generator to generate a first drop optical signal from an input WDM optical signal;

a wavelength selective switch to generate a second drop optical signal from the first drop optical signal; and

an optical splitter to split the second drop optical signal to be guided to the plurality of optical cross connects; wherein

at least one of the optical cross connects guides the second drop optical signal received at an input port to a plurality of output ports.

7. The optical add-drop multiplexer according to claim 6 , wherein

the drop signal generator splits the input WDM optical signal and outputs the split signal as the drop optical signal.

8. An optical add method used in an optical add-drop multiplexer having first and second routes, comprising:

wave length selectively switching a plurality of optical signals output from a plurality of output ports of an optical cross connect to generate a first specified optical signal;

wave length selectively switching a plurality of optical signals output from a plurality of other output ports of the optical cross connect to generate a second specified optical signal;

generating a first WDM optical signal including an optical signal in the first specified optical signal and guiding the first WDM optical signal to the first route; and

generating a second WDM optical signal including an optical signal in the second specified optical signal and guiding the second WDM optical signal to the second route,

wherein the optical cross connect guides an input optical signal to a first wavelength selective switch when the input optical signal is output on the first route, and guides an input optical signal to a second wavelength selective switch when the input optical signal is output on the second route,

wherein the first wavelength selective switch has an output optically connected to an input of a third wavelength selective switch, and wherein the third wavelength selective switch is not optically connected to the second wavelength selective switch, and

wherein the second wavelength selective switch has an output optically connected to an input of a fourth wavelength selective switch, and wherein the fourth wavelength selective switch is not optically connected to the first wavelength selective switch.

9. An optical drop method used in an optical add-drop multiplexer with a plurality of optical cross connects, comprising:

generating a first drop optical signal from an input WDM optical signal;

wave length selectively generating a second drop optical signal from the first drop optical signal; and

optically splitting the second drop optical signal to be guided to the plurality of optical cross connects; wherein

at least one of the optical cross connects guides the second drop optical signal received at an input port to a plurality of output ports.

10. An optical add-drop multiplexer having first and second routes, comprising:

a first optical cross connect;

a first wavelength selective switch optically coupled to a plurality of output ports of the first optical cross connect;

a second wavelength selective switch optically coupled to a plurality of other output ports of the first optical cross connect;

a third wavelength selective switch to generate a first WDM optical signal including an optical signal output from the first wavelength selective switch and to guide the first WDM optical signal to the first route;

a fourth wavelength selective switch to generate a second WDM optical signal including an optical signal output from the second wavelength selective switch and to guide the second WDM optical signal to the second route;

a second optical cross connect;

a drop signal generator to generate a first drop optical signal from an input WDM optical signal from the first route or the second route;

a fifth wavelength selective switch to generate a second drop optical signal including a plurality of optical signals from the first drop optical signal and to guide the second drop optical signal to a plurality of input ports of the second optical cross connect; and

a plurality of optical filters to extract a respectively specified wavelength from each second drop optical signal output from the second optical cross connect,

wherein the optical cross connect guides an input optical signal to the first wavelength selective switch when the input optical signal is output on the first route, and guides an input optical signal to the second wavelength selective switch when the input optical signal is output on the second route,

wherein the first wavelength selective switch has an output optically connected to an input of the third wavelength selective switch, and wherein the third wavelength selective switch is not optically connected to the second wavelength selective switch, and

wherein the second wavelength selective switch has an output optically connected to an input of the fourth wavelength selective switch, and wherein the fourth wavelength selective switch is not optically connected to the first wavelength selective switch.

11. A WDM network system having a plurality of optical add-drop multiplexers, wherein

each optical add-drop multiplexer has first and second routes; and

each optical add-drop multiplexer comprises:

a first optical cross connect;

a first wavelength selective switch optically coupled to a plurality of output ports of the first optical cross connect;

a second wavelength selective switch optically coupled to a plurality of other output ports of the first optical cross connect;

a third wavelength selective switch to generate a first WDM optical signal including an optical signal output from the first wavelength selective switch and to guide the first WDM optical signal to the first route;

a fourth wavelength selective switch to generate a second WDM optical signal including an optical signal output from the second wavelength selective switch and to guide the second WDM optical signal to the second route;

a second optical cross connect;

a drop signal generator to generate a first drop optical signal from an input WDM optical signal from the first route or the second route;

a fifth wavelength selective switch to generate a second drop optical signal including a plurality of optical signals from the first drop optical signal and to guide the second drop optical signal to a plurality of input ports of the second optical cross connect; and

a plurality of optical filters to extract a respectively specified wavelength from each second drop optical signal output from the second optical cross connect,

wherein the optical cross connect guides an input optical signal to the first wavelength selective switch when the input optical signal is output on the first route, and guides an input optical signal to the second wavelength selective switch when the input optical signal is output on the second route,

wherein the first wavelength selective switch has an output optically connected to an input of the third wavelength selective switch, and wherein the third wavelength selective switch is not optically connected to the second wavelength selective switch, and

wherein the second wavelength selective switch has an output optically connected to an input of the fourth wavelength selective switch, and wherein the fourth wavelength selective switch is not optically connected to the first wavelength selective switch.

12. The optical add-drop multiplexer according to claim 1 , wherein

the first wavelength selective switch has a plurality of input ports and only one output port,

the second wavelength selective switch has a plurality of input ports and only one output port.

13. The optical add-drop multiplexer according to claim 12 , wherein

the first wavelength selective switch combines a plurality of optical signals of different wavelengths input via different input ports and outputs the combined optical signals via the output port,

the third wavelength selective switch combines a plurality of optical signals of different wavelengths input via different input ports and outputs the combined optical signals via the output port.

14. The optical add-drop multiplexer according to claim 6 , wherein

each of the optical cross connects includes:

a plurality of splitters implemented for respective input ports; and

a plurality of switches implemented for respective output ports,

each of the splitters splits an input optical signal to be guided to the plurality of switches, and

each of the switches receives a plurality of optical signals from the plurality of splitters and selects specified one of the plurality of optical signals.