RECONFIGURABLE OPTICAL ADD/DROP MULTIPLEXER AND PROCEDURE FOR OUTPUTTING OPTICAL SIGNALS FROM SUCH MULTIPLEXER

• US 20090226172A1
• Filed: 03/07/2008
• Published: 09/10/2009
• Est. Priority Date: 05/30/2007
• Status: Active Grant

• Current Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Original Assignee: Tellabs Operations Incorporated (Infinera Corp.)
• Inventors: Boduch, Mark E., Younce, Richard C., Larikova, Julia Y.
• Granted Patent: US 8,965,220 B2
• Time in Patent Office: Days
• US Class Current: 398/83
• CPC Class Codes: H04J 14/0205 Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
• CPC Class Codes: H04J 14/0206 Express channels arrangements
• CPC Class Codes: H04J 14/0209 Multi-stage arrangements, e.g. by cascading multiplexers or demultiplexers
• CPC Class Codes: H04J 14/0212 using optical switches or wavelength selective switches [WSS]
• CPC Class Codes: H04J 14/0213 Groups of channels or wave bands arrangements
• CPC Class Codes: H04J 14/0217 Multi-degree architectures, e.g. having a connection degree greater than two
• CPC Class Codes: H04J 14/0219 Modular or upgradable architectures
• CPC Class Codes: H04J 14/0221 Power control, e.g. to keep the total optical power constant

Abstract

A reconfigurable optical add drop multiplexer (ROADM) includes local interfaces at which optical signals of different wavelengths are locally input into the ROADM, and a network interface configured to connect the ROADM to a network from which multiplexed optical signals of different wavelengths are transmitted to the network. In a first configuration, the ROADM is configured to transmit from the network interface to the network multiplexed signals of different wavelengths having a first minimum frequency difference. In a second configuration, the ROADM is configured to transmit from the network interface to the network multiplexed signals of different wavelengths having a second minimum frequency difference. The second minimum frequency difference is greater than the first minimum frequency difference. This arrangement reduces the power of four wave mixing cross products produced when optical signals of three wavelengths are multiplexed and transmitted from the ROADM to NZDSF or DSF fiber types.

Claims

1. A reconfigurable optical add drop multiplexer (ROADM) comprising:

a plurality of local interfaces at which optical signals of different wavelengths are locally input into the ROADM and have a first minimum frequency difference when all of the local interfaces input the optical signals;

a first network interface configured to connect the ROADM to a network from which multiplexed optical signals of different wavelengths are transmitted to the network; and

a device configured to control the input or processing of optical signals input into the ROADM so that the input optical signals that are transmitted from the first network interface to the network have a second minimum frequency difference that is greater than the first minimum frequency difference.

2. The reconfigurable optical add drop multiplexer recited by claim 1, wherein

the ROADM also comprises a second network interface through which optical signals from the network are received,

the ROADM is part of an optical node,

the plurality of local interfaces includes at least one express port connected to another ROADM in the node that transmits optical signals to the express port, and the device is configured to control the processing of optical signals input from the second network interface and from the express port.

3. The reconfigurable optical add drop multiplexer recited by claim 1, wherein the device is configured to prevent no more than half the optical signals of different wavelengths input into the ROADM from being transmitted therefrom to the network via the first network interface.

4. The reconfigurable optical add drop multiplexer recited by claim 1, wherein

when all the local interfaces input optical signals, the wavelengths of the different optical signals input into the local interfaces are represented by a set of monotonically increasing wavelength values, each wavelength value comprising either an even numbered or odd numbered member of the set, the set comprising alternating even and odd numbered members of increasing wavelength values, and

the device is configured to produce the second minimum frequency difference by transmitting to the first network interface optical signals have wavelengths corresponding to only the even or only the odd members of the set.

5. The reconfigurable optical add drop multiplexer recited by claim 1, wherein

the ROADM is part of an optical node, and

the plurality of local interfaces includes at least one express port connected to another ROADM in the node.

6. The reconfigurable optical add drop multiplexer recited by claim 1, wherein the first minimum frequency difference is equal to 100 GHz and the second minimum frequency difference is equal to 200 GHz.

7. The reconfigurable optical add drop multiplexer recited by claim 1, wherein the plurality of local interfaces includes a plurality of add ports and the device is configured to control the input or processing of optical signals input into the ROADM from the plurality of add ports.

8. The reconfigurable optical add drop multiplexer recited by claim 7, wherein the device is configured so that the number of add ports at which optical signals are input is no more than half the total number of add ports.

9. The reconfigurable optical add drop multiplexer recited by claim 7, wherein the device is configured so that the number of add ports at which optical signals are input is no more than half the number the number of wavelengths supported by the ROADM.

10. A reconfigurable optical add drop multiplexer (ROADM), comprising:

a plurality of add ports at which optical signals of different wavelengths are locally input into the ROADM, two of the add ports at which optical signals of adjacent center wavelength values are input being denoted as adjacent add ports;

a device configured to control the inputting or processing of optical signals input into the plurality of add ports so that for at least two pairs of optical signals input at two adjacent add ports, the center wavelength difference of optical signals input at one add port pair is different than the center wavelength difference of optical signals input at the other add port pair; and

a network interface from which optical signals of different wavelengths input at the plurality of add ports and controlled by the device are transmitted to the network.

11. The reconfigurable optical add drop multiplexer recited by claim 10, wherein not more than half of the add ports add optical signals to the ROADM.

12. The reconfigurable optical add drop multiplexer recited by claim 10, wherein

the add ports into which optical signals are not input are denoted as inactive add ports and the add ports into which the optical signals are input are denoted as active add ports, and

the device is configured to prevent any optical signals generated in the inactive add ports as a result of interaction between optical signals input into the active add ports from being transmitted from the network interface to the network.

13. The reconfigurable optical add drop multiplexer recited by claim 10, wherein

a first pair of adjacent add ports is adjacent a second pair of adjacent add ports when the first and second pair share a common add port, and

the device is configured so that for at least two adjacent pairs of adjacent add ports, the center wavelength difference of optical signals added at one add port pair is different than the center wavelength difference of optical signals added at the other add port pair.

14. An optical node comprising:

an input interface configured to receive at least one input optical signal of a plurality of different input wavelengths having a first minimum frequency difference;

an output interface through which at least one output optical signal of a plurality of different output wavelengths is transmitted; and

an optical node element configured to change the frequency of at least one input wavelength to a different frequency so that when the changed-frequency input wavelength is incorporated into the output optical signal, the output optical signal has a second minimum frequency difference that is greater than the first minimum frequency difference.

15. The optical node recited by claim 14, further comprising a first reconfigurable optical add drop multiplexer (ROADM), wherein the first ROADM includes the input interface.

16. The optical node recited by claim 15, wherein

the first ROADM is configured to separate the input optical signal of a plurality of wavelengths into a plurality of single wavelength optical signals,

the first ROADM also comprises a plurality of drop ports, each of which is configured to drop one of the single wavelength optical signals therefrom,

the optical node element comprises at least one transponder configured to receive one of the dropped single wavelength optical signals, to change the frequency of the dropped single wavelength optical signal, and to output the changed-frequency dropped single wavelength optical signal for incorporation into the output optical signal,

the output interface is configured to output the output optical signal into which the changed-frequency dropped single wavelength optical signal output by the transponder is incorporated, and

the optical node includes a sufficient number of transponders so that the second minimum frequency difference is twice the first minimum frequency difference.

17. The optical node recited by claim 16, wherein each transponder is a bidirectional transponder.

18. The optical node recited by claim 15, further comprising a second ROADM connected to the first ROADM and comprising the output interface, and wherein

the first ROADM is configured to separate the input optical signal of a plurality of wavelengths into a plurality of single wavelength optical signals,

the optical node element is connected to the first ROADM and the second ROADM,

the optical node element is configured to receive one of the single wavelength optical signals, to change the frequency of the single wavelength optical signal, and to output the changed-frequency single wavelength optical signal into the second ROADM, and

the second ROADM is configured to receive the other single wavelength optical signals from the first ROADM and to incorporate the changed-frequency single wavelength optical signal and the other single wavelength optical signals into the output optical signal, which is output from the output interface to a network.

19. The optical node recited by claim 18,

further comprising a plurality of optical node elements, each configured to receive a different single wavelength optical signal from the first ROADM, to change the frequency of the received single wavelength optical signal, and to output the changed-frequency single wavelength optical signal into the second ROADM,

wherein the first ROADM is configured to transmit a sufficient number of single wavelength optical signals to the optical node elements so that the wavelength values of each pair of adjacent frequencies in the output optical signal output by the output interface of the second ROADM are spaced apart by a wavelength spacing that is larger than the wavelength spacing of each pair of adjacent frequencies in the input optical signal input into the first ROADM at the input interface, thereby causing the second minimum frequency difference to be greater than the first minimum frequency difference.

20. A procedure for controlling optical signals of different wavelength input into a reconfigurable optical add drop multiplexer (ROADM) and having a first minimum frequency difference when all local interfaces of the ROADM input the optical signals, comprising:

inputting optical signals of different wavelengths into the ROADM; and

controlling the inputting or processing of the optical signals input into the ROADM so that the input optical signals that are transmitted from a first network interface of the ROADM to a network have a second minimum frequency difference that is greater than the first minimum frequency difference.

21. The procedure recited by claim 20, wherein

the local interfaces include a plurality of add ports,

the inputting operation is performed by adding optical signals of different wavelengths at different add ports of the ROADM, and

the number of add ports at which the optical signals are added is less than the total number of add ports of the ROADM.

22. The procedure recited by claim 20, wherein the inputting operation is performed by inputting optical signals into the ROADM from the network through a second network interface of the ROADM.

23. The procedure recited by claim 20, wherein the controlling operation includes changing the frequency of at least one inputted optical signal.

24. The procedure recited by claim 20, wherein the controlling operation includes extinguishing at least one input optical signal.

25. A procedure for controlling optical signals of different wavelength input into a reconfigurable optical add drop multiplexer (ROADM), comprising:

inputting optical signals of different wavelengths into the ROADM; and

controlling the inputting or processing of the optical signals input in the inputting operation so as to output from the ROADM a multiplexed optical signal of at least three wavelengths such that for at least two pairs of adjacent wavelengths, the center wavelength difference of one pair of adjacent wavelengths is different than the center wavelength difference of the other pair of adjacent wavelengths.

26. The procedure recited by claim 25, wherein the inputting operation includes adding optical signals of different wavelengths at different add ports of the ROADM.

27. The procedure recited by claim 26, wherein

the inputting operation includes adding optical signals of different wavelengths at no more than half of the add ports, and

the procedure further comprises blocking any four-wave-mixing cross products that are produced in the add ports to which optical signals are not added in the inputting step from being outputted from the ROADM.

28. The procedure recited by claim 26, wherein the inputting operation includes adding optical signals of different wavelengths at no more than half of the add ports.