Integrated reconfigurable optical add/drop multiplexer
View Patent ↗An integrated reconfigurable planar lightwave add-drop (RPLAD) multiplexer for use in a WDM optical communication system is arranged such that each drop port can receive any wavelength channel and each add port can transmit on any wavelength channel. Drop port reconfigurability is achieved by integrating a cross-connect functionality into the RPLAD, illustratively using optical 1×2 switches to perform “space” switching. The switches are controlled from a remotely located node controller. Add port reconfigurability is achieved by having tunable lasers and a wavelength independent optical power combiner, which may be a star coupler that is integrated with the other above-mentioned elements. The RPLAD has a modular architecture, so that when RPLAD's are connected by dual unidirectional transmission rings for the purpose of redundancy and failure protection, an RPLAD that fails can be removed and the remaining module can be reconfigured so as to re-route incoming traffic backwards around the still operating optical communication ring.
1. A reconfigurable integrated planar lightwave add-drop (RPLAD) multiplexer having a plurality of add ports and a plurality of drop ports, said RPLAD arranged for use in a WDM optical communication system, said RPLAD comprising
a cross-connect switch formed from an interconnected array of optical 1×2 switches,
means for dropping a first plurality of WDM channels from an input WDM signal to desired ones of said plurality of drop ports by controlling said optical 1×2 switches forming said cross-connect switch,
a passive optical power combiner having an output port and a plurality of input ports, wherein each input port is connected to a respective add port of the plurality of add ports;
wherein a plurality of said RPLAD multiplexers are interconnected by dual transmission rings that operate in opposite directions; and wherein said drop ports each drop channels from the input WDM signal only on one of said transmission rings, and said add ports add channels via the passive power combiner, only to the other one of said transmission rings,
such that the dropped channels are received at the RPLAD only from a prescribed direction only on one of the transmission rings, and the added channels are transmitted from the RPLAD back only toward said prescribed direction only on the other transmission ring.
2. The invention defined in claim 1 wherein said add ports each include a tunable laser.
3. The invention defined in claim 1 wherein said passive optical power combiner is a star coupler.
4. The invention defined in claim 1 , wherein each of said RPLAD multiplexers is arranged to re-route incoming traffic from the one of said optical transmission rings to the other one of said optical transmission rings in the event of a failure of one of said RPLAD multiplexers.
5. The invention defined in claim 1 wherein each of said RPLAD multiplexers include a plurality of variable optical attenuators (VOA's) arranged to correct imbalances in the power levels present in said WDM channels.
6. The invention defined in claim 1 wherein said first plurality of WDM channels are dropped from said input WDM signal by an interleaver.
7. The invention defined in claim 6 wherein said interleaver is integrated on the same substrate as said switches.
8. In an optical communication system adapted to transmit a multiplexed signal containing a plurality of wavelength division multiplexed channels each channel having a different wavelength, an arrangement for a node served by dual transmission rings that operate in opposite directions, the node adapted to (a) receive at the node, an incoming multiplexed signal containing a first plurality of channels, (b) add one or more channels to a second incoming multiplexed signal, and (c) drop one or more channels from said incoming multiplexed signal, an integrated reconfigurable planar lightwave add-drop (RPLAD) multiplexer comprising:
a plurality of add ports for receiving said one or more channels to be added to said second incoming multiplexed signal,
a plurality of drop ports for receiving said one or more channels to be dropped from said incoming multiplexed signal that arrives only on one of the transmission rings,
a cross-connect switch formed from an interconnected array of optical 1×2 switches for routing selected ones of said one or more channels to be dropped from said incoming multiplexed signal, to desired ones of said drop ports, and
a wavelength independent passive optical power combiner having an output port and a plurality of input ports, the input ports for receiving from said add ports said one or more channels to be added, and for combining said one or more channels to said second incoming multiplexed signal that arrives only on the other one of the transmission rings;
such that each of said channels to be dropped from said incoming multiplexed signal arrive at the node only from a prescribed direction, and said channels added to the second incoming multiplexed signal are transmitted back only toward said prescribed direction.