Technique for selectively changing dispersion in optical communication channels

1. A reconfigurable wavelength selective dispersion compensation device RWSDCD for selective compensation of dispersion in optical channels having respective different wavelengths, the RWSDCD having an input line for inputting incoming optical channels, and an output line for outputting outgoing optical channels, the RWSDCD comprising:

a controllable wavelength selective unit WSU having a plurality of local, wavelength related input/output (I/O) ports; the WSU being adapted to controllably configure assignment of the incoming optical channels to the local I/O ports of said plurality in a way that any number of said incoming optical channels may at a time utilize any of said local I/O ports;

a dispersion compensation cascade comprising at least one chain of successively connected dispersion compensation units DCUs, wherein one or more of the DCUs in the chain are respectively connectable to one or more of said local I/O ports;

the arrangement of the RWSDCD being such that the output line outputs from the RWSDCD said outgoing optical channels comprising one or more of said incoming optical channels upon selectively compensating chromatic dispersion in them by controllably passing said one or more of the incoming optical channels via one or more DCUs of said dispersion compensation cascade, wherein said at least one chain comprises a first DCU and a last DCU each having at least two connections, and comprising at least one intermediate DCU having at least three connections; and wherein said at least one chain is interconnected with said WSU in such a manner that said at least one intermediate DCU, via two of said at least three connections, is respectively connected with a preceding DCU in the chain and with a next DCU in the chain, and via a third of said at least three connections is connected to one of the local I/O ports of the WSU.

2. The device according to claim 1 , wherein the WSU is implemented as a Wavelength Selective Switch WSS, a Reconfigurable Optical Add Drop Multiplexer ROADM, a Wavelength selective Optical Cross Connect WOXC or a Wavelength Router WR.

3. The device according to claim 1 , wherein the DCU comprises a Dispersion Compensation Fiber (DCF) or a Dispersion Compensation Module (DCM), associated with a 2×1 or a 2×2 optical coupler.

4. The device according to claim 1 , wherein the WSU is WSS, the dispersion compensation cascade comprises an additional DCU chain, thereby the cascade comprising a first DCU chain and a second DCU chain, and

wherein said two DCM chains are connected to the local I/O ports of the WSS in such a manner that the DCUs of the first chain receive the currently assigned sets of optical channels from the WSS, while DCUs of the second chain send other sets of optical channels to the WSS.

5. The device according to claim 4 , wherein the WSU is a reconfigurable add-drop multiplexer ROADM, wherein the input line of the RWSDCD is a common input port of the ROADM, the output line of the RWSDCD is a through line of the ROADM, and the local I/O ports of the WSU are add/drop ports of the ROADM.

6. A reconfigurable wavelength selective dispersion compensation device RWSDCD for selective compensation of dispersion in optical channels having respective different wavelengths, the RWSDCD having an input line for inputting incoming optical channels, and an output line for outputting outgoing optical channels, the RWSDCD comprising: a controllable wavelength selective unit WSU having a plurality of local, wavelength related input/output (I/O) ports; the WSU being adapted to controllably configure assignment of the incoming optical channels to the local I/O ports of said plurality in a way that any number of said incoming optical channels may at a time utilize any of said local I/O ports; a dispersion compensation cascade comprising at least one chain of successively connected dispersion compensation units DCUs, wherein one or more of the DCUs in the chain are respectively connectable to one or more of said local I/O ports; the arrangement of the RWSDCD being such that the output line outputs from the RWSDCD said outgoing optical channels comprising one or more of said incoming optical channels upon selectively compensating chromatic dispersion in them by controllably passing said one or more of the incoming optical channels via one or more DCUs of said dispersion compensation cascade, wherein said WSU is implemented as a Wavelength Router WR, wherein the input line of the RWSDCD is formed by the incoming optical channels having controllably changeable wavelengths and being entered in parallel into the WR; wherein ports of the wavelength router WR are said local I/O ports of the WSU, and the DCU cascade is connected to said output ports of the WR.

7. The device according to claim 1 , controllable either by an operator, or by a control entity being a local control unit and/or a Network Management System, for selectively adjusting dispersion in the optical channels handled by the RWSDCD.

8. The device according to claim 7 , further comprising a monitoring unit interconnected with the control unit, for monitoring chromatic dispersion in the optical communication channels handled by the RWSDCD.

9. A reconfigurable wavelength selective dispersion compensation device RWSDCD for selective compensation of dispersion in optical channels having respective different wavelengths, the RWSDCD having an input line for inputting incoming optical channels, and an output line for outputting outgoing optical channels, the RWSDCD comprising: a controllable wavelength selective unit WSU having a plurality of local, wavelength related input/output (I/O) ports; the WSU being adapted to controllably configure assignment of the incoming optical channels to the local I/O ports of said plurality in a way that any number of said incoming optical channels may at a time utilize any of said local I/O ports; a dispersion compensation cascade comprising at least one chain of successively connected dispersion compensation units DCUs, wherein one or more of the DCUs in the chain are respectively connectable to one or more of said local I/O ports; the arrangement of the RWSDCD being such that the output line outputs from the RWSDCD said outgoing optical channels comprising one or more of said incoming optical channels upon selectively compensating chromatic dispersion in them by controllably passing said one or more of the incoming optical channels via one or more DCUs of said dispersion compensation cascade controllable either by an operator, or by a control entity being a local control unit and/or a Network Management System, for selectively adjusting dispersion in the optical channels handled by the RWSDCD, comprising a monitoring unit interconnected with the control unit, for monitoring chromatic dispersion in the optical communication channels handled by the RWSDCD, and wherein the control unit is adapted to combine the following operations, whenever informed by the monitoring unit about deterioration of chromatic dispersion in a particular optical channel:

adjusting dispersion in said channel by controllably changing a local I/O port of the WSU;

changing the wavelength of said optical channel.

10. A reconfigurable wavelength selective dispersion compensation device RWSDCD for selective compensation of dispersion in optical channels having respective different wavelengths, the RWSDCD having an input line for inputting incoming optical channels, and an output line for outputting outgoing optical channels, the RWSDCD comprising: a controllable wavelength selective unit WSU having a plurality of local, wavelength related input/output (I/O) ports; the WSU being adapted to controllably configure assignment of the incoming optical channels to the local I/O ports of said plurality in a way that any number of said incoming optical channels may at a time utilize any of said local I/O ports; a dispersion compensation cascade comprising at least one chain of successively connected dispersion compensation units DCUs, wherein one or more of the DCUs in the chain are respectively connectable to one or more of said local I/O ports; the arrangement of the RWSDCD being such that the output line outputs from the RWSDCD said outgoing optical channels comprising one or more of said incoming optical channels upon selectively compensating chromatic dispersion in them by controllably passing said one or more of the incoming optical channels via one or more DCUs of said dispersion compensation cascade controllable either by an operator, or by a control entity being a local control unit and/or a Network Management System, for selectively adjusting dispersion in the optical channels handled by the RWSDCD, wherein the control unit is preliminarily provided with a data base of routes, stored in the control unit; the control unit being in communication with NMS and, whenever informed by the NMS about the a change of route of a specific optical channel, being adapted to determine in said internal data base at least one of the following:

a new combination of DCUs in the cascade suitable for compensating dispersion on the new route; and

a new wavelength to be used for the new route.

11. A reconfigurable wavelength selective dispersion compensation device RWSDCD for selective compensation of dispersion in optical channels having respective different wavelengths, the RWSDCD having an input line for inputting incoming optical channels, and an output line for outputting outgoing optical channels, the RWSDCD comprising: a controllable wavelength selective unit WSU having a plurality of local, wavelength related input/output (I/O) ports; the WSU being adapted to controllably configure assignment of the incoming optical channels to the local I/O ports of said plurality in a way that any number of said incoming optical channels may at a time utilize any of said local I/O ports; a dispersion compensation cascade comprising at least one chain of successively connected dispersion compensation units DCUs, wherein one or more of the DCUs in the chain are respectively connectable to one or more of said local I/O ports; the arrangement of the RWSDCD being such that the output line outputs from the RWSDCD said outgoing optical channels comprising one or more of said incoming optical channels upon selectively compensating chromatic dispersion in them by controllably passing said one or more of the incoming optical channels via one or more DCUs of said dispersion compensation cascade provided with one or more controllable switches respectively inserted between one or more of the local I/O ports and one or more of said DCUs in the chain; each of said switches, when in its closed position, connecting a specific local I/O port to a specific DCU, while when in its open position, disconnecting said specific local I/O port with said specific DCU.

12. A network node incorporating the device according to claim 1 .