Transponder Aggregator-based optical loopback in a MD-ROADM

1. A multi-degree colorless, directionless, contention-less, reconfigurable optical add/drop multiplexer, comprising:

a reconfigurable optical add/drop multiplexer section for performing connect operations for wavelength division multiplexing signals among all degrees;

a transponder aggregator section having a split-and-select switch-based transponder aggregator, the aggregator having a (N+1)×(L+1) split-and-select switch for a drop side of the aggregator and another (N+1)×(L+1) split-and-select switch for an add side of the aggregator, wherein N is a number of the degrees, and L is a number of transponders connected to the aggregator; and

an optical loopback for external links to the multi-degree reconfigurable optical add/drop multiplexer,

wherein the (N+1)×(L+1) split-and-select switch for the drop side comprises an optical switch having an output connected to an input of another optical switch comprised in the other (N+1)×(L+1) split-and-select switch for the add side, and wherein at least the optical switch and the other optical switch are used to provide an optical far end path loopback there through for a particular one of the degrees.

2. The multiplexer of claim 1 , wherein the (N+1)×(L+1) split-and-select switch for the drop side and the other (N+1)×(L+1) split-and-select switch for the add side each comprise a respective array of optical switches, wherein each of the switches, except the optical switch and the other optical switch used to provide the optical far end path loopback, are connected to a respective one of the transponders.

3. A multi-degree colorless, directionless, contention-less, reconfigurable optical add/drop multiplexer, comprising:

a reconfigurable optical add/drop multiplexer section for performing connect operations for wavelength division multiplexing signals among all degrees;

a transponder aggregator section having a split-and-select switch-based transponder aggregator, the aggregator having a (N+1)×(L+1) split-and-select switch for a drop side of the aggregator and another (N+1)×(L+1) split-and-select switch for an add side of the aggregator, wherein N is a number of the degrees, and L is a number of transponders connected to the aggregator; and

an optical loopback for external links to the multi-degree reconfigurable optical add/drop multiplexer,

wherein the (N+1)×(L+1) split-and-select switch for the drop side comprises an optical splitter having an input connected to an output of an optical combiner comprised in the other (N+1)×(L+1) split-and-select switch for the add side, and wherein at least the optical splitter and the optical combiner are used to provide an optical local loopback there through for a particular one of the degrees.

4. The multiplexer of claim 3 , wherein the (N+1)×(L+1) split-and-select switch for the drop side comprises an array of optical splitters and the other (N+1)×(L+1) split-and-select switch for the add side comprises an array of optical combiners, wherein each of the optical splitters, except the optical splitter used to provide the optical local loopback, is connected to the multiplexer section to input there from a signal corresponding to a respective one of the degrees, and wherein each of the optical combiners, except the optical combiner used to provide the optical local loopback, is connected to the multiplexer section to output there to the signal corresponding to the respective one of the degrees.

5. A multi-degree colorless, directionless, contention-less, reconfigurable optical add/drop multiplexer, comprising:

a reconfigurable optical add/drop multiplexer section for performing connect operations for wavelength division multiplexing signals among all degrees;

a transponder aggregator section having a split-and-select switch-based transponder aggregator, the aggregator having a (N+1)×(L+1) split-and-select switch for a drop side of the aggregator and another (N+1)×(L+1) split-and-select switch for an add side of the aggregator, wherein N is a number of the degrees, and L is a number of transponders connected to the aggregator; and

an optical loopback for external links to the multi-degree reconfigurable optical add/drop multiplexer,

wherein the N×L split-and-select switch for the drop side and the add side comprise a respective array of (L+1) optical switches, each of the (L+1) optical switches, except a given one on the drop side and given one on the add side, connected to a respective one of the transponders,

wherein the N×L split-and-select switch for the drop side comprises an array of (N+1) optical splitters, each of the (N+1) optical splitters, except a particular one, connected to a respective one of the degrees,

wherein the N×L split-and-select switch for the add side comprises an array of (N+1) optical combiners, each of the (N+1) optical combiners, except a specific one, corresponding to a respective one of the degrees, and

wherein an input of the particular one of the (N+1) optical splitters on the drop side is connected to an output of the specific one of the (N+1) optical combiners on the add side.

6. The multiplexer of claim 5 , wherein each of the (L+1) optical switches for the drop side, except the given one, has an input connected to all of the (N+1) optical splitters except the particular one and an output connected to a respective one of the transponders.

7. The multiplexer of claim 5 , wherein each of the (N+1) optical splitters, except the particular one, has an input corresponding to a respective one of the degrees and an output connected to all of the (L+1) optical switches on the drop side except the given one.

8. The multiplexer of claim 5 , wherein each of the (N+1) optical splitters has an output connected to all of the (L+1) optical switches on the drop side except the given one.

9. The multiplexer of claim 5 , further comprising an optical local loopback having a connection path from a particular one of the transponders on the add side through a corresponding one of the (L+1) optical switches on the add side, the specific one of the (N+1) optical combiners on the add side, the particular one of the (N+1) optical splitters on the drop side, a corresponding one of the (L+1) optical switches on the drop side, back to the particular one of the transponders.

10. A multi-degree colorless, directionless, contention-less, reconfigurable optical add/drop multiplexer, comprising:

a reconfigurable optical add/drop multiplexer section for performing connect operations for wavelength division multiplexing signals among all degrees;

a transponder aggregator section having a split-and-select switch-based transponder aggregator, the aggregator having a (N+1)×(L+1) split-and-select switch for a drop side of the aggregator and another (N+1)×(L+1) split-and-select switch for an add side of the aggregator, wherein N is a number of the degrees, and L is a number of transponders connected to the aggregator; and

an optical loopback for external links to the multi-degree reconfigurable optical add/drop multiplexer,

wherein the N×L split-and-select switch for the drop side and the add side comprise a respective array of (L+1) optical switches, each of the (L+1) optical switches, except a given one on the drop side and given one on the add side, connected to a respective one of the transponders,

wherein the N×L split-and-select switch for the drop side comprises an array of (N+1) optical splitters, each of the (N+1) optical splitters, except a particular one, connected to a respective one of the degrees,

wherein the N×L split-and-select switch for the add side comprises an array of (N+1) optical combiners, each of the (N+1) optical combiners, except a specific one, corresponding to a respective one of the degrees, and

wherein an output of the given one of (L+1) optical switches on the drop side is connected to an input of the given one of (L+1) optical switches on the add side.

11. The multiplexer of claim 10 , further comprising an optical far end path loopback having a connection path from a particular one of the degrees provided from the reconfigurable optical add/drop multiplexer section through a corresponding one of the (N+1) optical splitters, the given one of the (L+1) optical switches on the drop side, the given one of the (L+1) optical switches on the add side, a corresponding one of the (N+1) optical combiners, back to the particular one of the degrees.