Directionless optical architecture and highly available network and photonic resilience methods
A directionless optical architecture is described for reconfigurable optical add/drop multiplexers (ROADMs) and wavelength selective switches (WSSs). The directionless architecture utilizes a directionless wavelength switch coupled between client devices and ROADMs/WSSs to eliminate the need to hard-wire client devices to a wavelength division multiplexed (WDM) network. Accordingly, client device connections can be automatically routed without manual intervention to provide a highly resilient network design which can recover route diversity during failure scenarios. Additionally, the present invention minimizes deployments of costly optical transceivers while providing superior resiliency. Further, the present invention couples the directionless optical architecture and associated optical protection mechanisms with existing mesh restoration schemes to provide additional resiliency.
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The present non-provisional patent application/patent is a continuation of U.S. patent application Ser. No. 12/045,933, filed on Mar. 11, 2008, and entitled “DIRECTIONLESS OPTICAL ARCHITECTURE AND HIGHLY AVAILABLE NETWORK AND PHOTONIC RESILIENCE METHODS,” the contents of which are incorporated in full by reference herein.
FIELD OF THE INVENTIONThe present invention relates generally to optical networks. More particularly, the present invention provides a directionless optical architecture for reconfigurable optical add/drop multiplexers (ROADMs) and wavelength selective switches (WSSs) which can be utilized to provide highly available network, photonic resiliency, and wavelength optimization.
BACKGROUND OF THE INVENTIONAs point-to-point Internet Protocol (IP) flows increase in bandwidth, core router connections are being driven to higher capacities. Today, core router interfaces are starting to move from 10 Gbps to 40 Gbps while 100 Gbps connections are already in the planning stage. With this increase in capacity comes a heightened responsibility to maintain high availability service by minimizing the time that these very expensive, high bandwidth connections are out of service due to failure events or scheduled maintenance activities.
Referring to
The WSSs 14 connect each of the various locations 16 in a mesh configuration through optical fibers. Conventionally, the core routers 12a,12b,12c are connected through the WSSs 14 statically, and bandwidth on each wavelength connection is typically traffic engineered to a predetermined capacity below the maximum possible capacity, such as 50%, 40%, 20%, etc., so as to accommodate a layer three initiated roll over of traffic from a failed link to a working link upon a network failure, such as a fiber cut, equipment failure on the WSSs 14, failure on the core router 12, and the like. For example, in
In
While the architecture of the network 10 is reasonably efficient from a capital equipment (“CAPEX”) perspective, it raises some challenges that can impact the operating expenses (“OPEX”) required to operate and maintain this network 10. One challenge is associated with how the links between the routers 12a,12b,12c are protected. While the link between routers 12a to 12b is down, the network 10 core is operating in a dangerous condition whereby any second failure could potentially isolate a region of the network 10. The Median Time to Repair (MTTR) becomes a critical parameter in the calculation of service availability and the corresponding service level agreements (SLAs) that can be offered to end user clients. Providing the ability to provide a new (third) path through the network 10 in the event of such a condition could help to minimize the MTTR for the connection and maintain high connection availability.
Another challenge is associated with the coordination of network maintenance activities between operations personnel who are responsible for the IP network, i.e. routers 12, and those responsible for the underlying transport connections, i.e. WSSs 14. Because core router 12 interfaces are directly associated with a statically defined WDM lightpath across the network 10, it is not possible to separate the two events. Without careful cooperation between operations personnel, it is possible that simultaneous maintenance could occur on links between routers 12a to 12b (by transport) and between routers 12a to 12c (by IP) causing unnecessary network disruption. Clearly, providing a mechanism to reconfigure the IP or optical layers independently is advantageous.
The use of optical cross connects (OXCs) based on an electrical switch fabric provides one possible solution that could provide optical layer re-configurability in the face of network failure or planned maintenance. However, there is concern that the cost of 40 G or 100 G interfaces required to support core router connections is not as cost effective as 10 G and therefore should be minimized throughout the transmission path, i.e. OXCs would require additional 40 G or 100 G interfaces. Furthermore, dedicating 40 G or 100 G modules on an OXC to aggregate flows of data is wasteful of precious backplane and switch capacity.
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To date, this kind of protection has been implemented on the short-reach link between core router interfaces and WDM transceivers. This protection scheme is not designed to protect against router 12d,12e or router port failure, however it does provide resistance to transport layer failures associated with optical layer components, i.e. the WSSs 14, and the optical fiber itself.
In
However, because of the static nature of the optical connectivity, it is not possible to reconfigure the optical layer so as to restore diverse links between the end nodes. Instead, after the link failure 26, the connection between the routers 12d and 12e is now unprotected for as long as the damaged link is under repair. For some carriers this is a significant issue. Depending on the physical route of an optical fiber, the MTTR for the damaged connection can be quite long (on the order of days to weeks). For example, some fibers are routed through inhospitable terrain such as over (or through) mountains or under lakes or seas where the maintenance activity can involve lengthy procedures. In this case, the carrier would like to re-establish a new ‘backup’ route quickly so as to restore diversity between end nodes and thus maintain the promise of high availability to end user clients.
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Accordingly, the downtime associated with any network service (e.g., Ethernet, SONET/SDH, Fibre Channel, etc.) is directly associated with the quality of a network service and the associated Service Level Agreement (SLA) between a service provider (i.e., carrier) and a client. In addition to the conventional optical protection schemes described above, network elements (NEs) with protection schemes such as SONET Bi-directional Line Switched Ring/Unidirectional Path Switched Ring (BLSR/UPSR), SDH Multiplex Section-Shared Protection Ring/Sub-network Connection Protection (MSSPRing/SNCP), etc. have been developed as network ‘self-healing’ mechanisms.
More recently, mesh restoration has been implemented in networks to improve service availability by providing access to multiple backup paths. The ability to access more than one backup path through the network increases the probability that service will stay available to the end user, thus decreasing the average downtime a network experiences over the course of a year.
One of the major challenges facing a number of network operators today is a high incidence of fiber cuts occurring randomly in the network. Such failures are a common occurrence in developing nations such as India where significant new infrastructure building is taking place (resulting in lots of digging up of fiber cables). Because most of these carriers are currently using ring protection methods to protect service, their networks are only able to accommodate one fiber failure on a single ring at any one time. High fiber failure probability therefore leads to the isolation of network elements when two cuts occur simultaneously on the same ring and therefore results in a degradation of end-to end service.
To overcome this challenge, some carriers can geographically partition their existing SONET/SDH ring networks into small cascaded rings such that the probability of two fiber failures occurring on the same ring is reduced. This helps increase service availability but, in many cases, does not allow the carriers to meet their target availability objective (particularly for high value e.g. banking clients who demand ‘always on’ service). They are also now investigating the use of mesh restoration to increase their service availability.
A challenge with both ring protection and mesh restoration is the fact that fiber failures are statistically dependent upon the distance between the switching nodes in the network. So, even if mesh restoration is used, if the distance between mesh restoration switch sites is too long, then there still exists an increased probability that a service node can be isolated due to simultaneous failures on each of the (multiple) links connected to that node . . . thus losing service.
One approach used to increase resiliency performance and availability is to combine SDH or SONET ring protection with SONET or SDH mesh restoration. This capability can be combined through a Virtual Line Switched Ring (VLSR) or SNCP protection plus backup mesh restoration on an Optical switch platform. This clearly provides the benefit of a deterministic 50 ms protection time plus mesh restoration availability.
However, this typically needs to be implemented by a single SDH or SONET vendor. Unfortunately, while perhaps possible, the interaction of SDH/SONET between different vendor's equipment for ring protection is highly complicated and not advised. For a number of reasons including Data Communication Channel (DCC) transparency, different use of (and response to) SONET/SDH overhead bytes, etc. very little success has been achieved in the industry in the area of SONET/SDH inter-working between different vendors. Consequently, it does not make engineering or operational sense to operate SDH/SONET rings between mesh restoration nodes belonging to one vendor and SDH/SONET rings belonging to a second vendor. This has been shown to be operationally challenging to engineer.
Also, in some network designs, it may not be cost effective (or prudent from a traffic management perspective) to put a large cross-connect with mesh restoration capabilities at every node in the network. The use of a limited number of cross-connects plus lower cost equipment in between may provide a more economic solution.
BRIEF SUMMARY OF THE INVENTIONIn various exemplary embodiments, the present invention provides a directionless (i.e., a direction-independent) optical architecture for reconfigurable optical add/drop multiplexers (ROADMs) and wavelength selective switches (WSSs). The directionless architecture utilizes a wavelength switch coupled between client devices and ROADMs/WSSs to eliminate the need to hard-wire client devices to a wavelength division multiplexed (WDM) network. Accordingly, client device connections can be automatically routed without manual intervention to provide a highly resilient network design which can recover route diversity during failure scenarios. Additionally, the present invention minimizes deployments of costly optical transceivers while providing superior resiliency. Further, the present invention couples the directionless optical architecture and associated optical protection mechanisms with existing mesh restoration schemes to provide additional resiliency. Here, the present invention provides mesh restoration, such as through SONET/SDH, across a G.709/OTN enabled sequence of rings. The G.709 rings provide high availability connectivity for the SONET/SDH connections.
In an exemplary embodiment of the present invention, a directionless optical system includes a client device; a reconfigurable optical node including one or more degrees; and a switch connected to each of the one or more degrees; wherein the client device connects to the switch, and wherein the switch is configured to route signals between the client device and the one or more degrees. Optionally, the directionless optical system further includes a splitter including an input port connected to a transmitter on the client device and dual output ports connected to the switch, wherein the splitter is configured to receive an input from the transmitter on the input port and provide duplicate signals of the input from the transmitter on the dual output ports; and a tail-end switch including dual input ports connected to the switch and an output port connected to a receiver on the client device, wherein the tail-end switch is configured to receive duplicate input signals from the switch on the dual input ports and provide one of the duplicate input signals to the receiver. The switch includes a first switch module and a second switch module for redundancy, and wherein each of the dual output ports and dual input ports connect separately to the first switch module and the second switch module. The one or more degrees can includes two or more degrees; wherein the first switch module and the second switch module are configured to connect the duplicate signals on the dual output ports to separate degrees of the two or more degrees; and wherein the first switch module and the second switch module are configured to connect the duplicate input signals on the dual input ports to separate degrees of the two or more degrees. The two or more degrees can also include an additional degree not utilized by the dual output ports and the dual input ports; and wherein, responsive to a failure on one of the separate degrees, the first switch module and the second switch module are configured to redirect one of the dual output ports and one of the dual input from the one of the separate degrees to the additional degree to provide route diversity.
Alternatively, the directionless optical system further includes a first transceiver and a second transceiver on the client device, wherein the first transceiver and the second transceiver are connected to the switch; wherein the one or more degrees includes two or more degrees; and wherein the switch is configured to connect the first transceiver and the second transceiver to separate degrees of the two or more degrees. The switch can include a first switch module and a second switch module for redundancy, and wherein the first transceiver is connect to the first switch module and the second switch module is connected to the second switch module. The two or more degrees can also include an additional degree not utilized by the first transceiver and the second transceiver; and wherein, responsive to a failure on one of the separate degrees, the first switch module and the second switch module are configured to redirect one of the first transceiver and the second transceiver from the one of the separate degrees to the additional degree to provide route diversity. Optionally, the client device includes a router, and wherein the first transceiver and the second transceiver utilize layer three protection mechanisms. The reconfigurable optical node can include a wavelength selective switch for each of the one or more degrees; and a multi-channel fixed filter including one of a band-wide and cyclic Arrayed Waveguide connected to the wavelength selective switch and the switch.
Optionally, the directionless optical system further includes a regenerator/wavelength converter connected to the switch; wherein the switch is configured to connect a signal from the one or more degrees to the regenerator/wavelength converter. The one or more degrees can include two or more degrees, and wherein the reconfigurable optical node includes a first wavelength selective switch connected to a first set of one or more demultiplexers and to a first set of one or more multiplexers; and a second wavelength selective switch connected to a second set of one or more demultiplexers and to a second set of one or more multiplexers; wherein each of the first set of one or more demultiplexers, the first set of one or more multiplexers, the second set of one or more demultiplexers, and the second set of one or more multiplexers include a connection to the switch. The switch can include two or more optical switches, and wherein the first set of one or more demultiplexers, the first set of one or more multiplexers, the second set of one or more demultiplexers, and the second set of one or more multiplexers are each wavelength independent. Alternatively, the directionless optical system further includes a wavelength division multiplex platform including a transponder, the splitter, and the tail-end switch, wherein the transponder connects to the client device; wherein the client device includes mesh restoration with a hold-off timer configured to allow the splitter and the tail-end switch to restore service prior to initiated mesh restoration.
In another exemplary embodiment of the present invention, a highly available directionless optical method includes providing a first path and a second path through a network between a first device and a second device, wherein the first device and the second device are each dynamically connected to the first path and the second path; upon a failure on the first path, restoring service between the first device and the second device on the second path; and reconfiguring the first path to a third path by dynamically changing a connection from the first path on each of the first device and the second device to the third path. Each of the first path and the second path includes an optical network; wherein dynamically connected includes a directionless optical switch between each of the first path and the second path and each of the first device and the second device. The highly available directionless optical method further includes performing mesh restoration at each of the first device and the second device following a hold-off time period, wherein the hold-off time period is configured to enable service restoration optically between the first device and the second device.
In yet another exemplary embodiment of the present invention, a highly available directionless optical network includes a first device including an optical connection to a first optical switch; a first optical platform connected to the first optical switch, wherein the first optical platform includes multiple degrees; a second device including an optical connection to a second optical switch; a second optical platform connected to the second optical switch, wherein the second optical platform includes multiple degrees; and a plurality of interconnected reconfigurable optical nodes between the first optical platform and the second optical platform; wherein the first optical switch and the second optical switch connect the first optical platform to the second optical platform through a first path and a second path; wherein the first path utilizes a first degree of the multiple degrees on the first optical platform and a first degree of the multiple degrees on the second optical platform; wherein the second path utilizes a second degree of the multiple degrees on the first optical platform and a second degree of the multiple degrees on the second optical platform; and wherein the first optical switch is configured to switch connections from one of the first path and the second path to a third degree of the multiple degrees on the first optical platform and a third degree of the multiple degrees on the second optical platform. Optionally, the plurality of interconnected reconfigurable optical nodes are configured in a cascaded protection ring configuration between the first optical platform and the second optical platform; and wherein the first optical platform and the second optical platform are configured to provide optical 1+1 protection. The first device and the second device can include mesh restoration with a hold-off timer operable to delay mesh restoration for a time period allowing the optical 1+1 protection to reestablish service. The highly available directionless optical network can further include one or more regenerators at one or more of the plurality of interconnected reconfigurable optical nodes; wherein each of the one or more of the plurality of interconnected reconfigurable optical nodes include an optical switch connected between the one or more regenerators and the one or more of the plurality of interconnected reconfigurable optical nodes.
In yet another exemplary embodiment of the present invention, a directionless reconfigurable optical add/drop node includes a wavelength selective switch connected to a multi-channel fixed filter, wherein the multi-channel fixed filter includes one of a band-wide and cyclic Arrayed Waveguide; an optical switch connected to the multi-channel fixed filter; and a client device connected to the optical switch; wherein the wavelength selective switch is configured to provide single channel selectivity across a plurality of wavelengths; wherein the multi-channel fixed filter receives one of the plurality of wavelengths within a multi-channel range of the multi-channel fixed filter; and wherein the optical switch routes one of the plurality of wavelengths to the client device.
The present invention is illustrated and described herein with reference to the various drawings, in which like reference numbers denote like method steps and/or system components, respectively, and in which:
In various exemplary embodiments, the present invention provides a directionless optical architecture for reconfigurable optical add/drop multiplexers (ROADMs) and wavelength selective switches (WSSs). The directionless architecture utilizes a directionless wavelength switch coupled between client devices and ROADMs/WSSs to eliminate the need to hard-wire client devices to a wavelength division multiplexed (WDM) network. Accordingly, client device connections can be automatically routed without manual intervention to provide a highly resilient network design which can recover route diversity during failure scenarios. Additionally, the present invention minimizes deployments of costly optical transceivers while providing superior resiliency. Further, the present invention couples the directionless optical architecture and associated optical protection mechanisms with existing mesh restoration schemes to provide additional resiliency. Here, the present invention provides mesh restoration, such as through SONET/SDH, across a G.709/OTN enabled sequence of rings. The G.709 rings provide high availability connectivity for the SONET/SDH connections.
Advantageously, the present invention can provide connections with high availability between switch or router ports. The present invention can also be utilized with SONET/SDH/Optical Transport Network (OTN) terminals and the like. As data rates increase to 40 Gbps, 100 Gbps, and the like, the present invention provides the potential for lower cost protection than electronic switching equipment. However, the present invention maintains carrier-grade protection requirements to offer superior resiliency.
Referring to
Connections from the IP router 12 and OTN platform 34 are to the switch 52, i.e. not hard-wired to WSSs 14. The switch 52 provides connections to each WSS 14 in the ROADM 30. Based on the switch 52 configuration, the IP router 12 and OTN platform 34 can have their signals routed in different directions through the ROADM 30 without manual patching of connections.
For example, both the IP router 12 and OTN platform 34 include dual inputs/outputs to the directionless wavelength switch 52 for 1+1/1:1 or the like protection. A failure in the path or on the equipment causes the dual inputs/outputs to switch. The switch 52 can be utilized to switch the failed port to another WSS 14 to provide another route in the network ensuring resiliency during a failure.
The directionless wavelength switch 52 can include a Micro Electro-Mechanical Systems (MEMS), a liquid crystal, an inkjet, a thermal mechanism, a non-linear mechanism, an acousto-optic mechanism, and the like for the physical embodiment. As described herein, the wavelength switch 52 can be scaled to variable port sizes (i.e., depending on application size), and can also include redundancy through multiple physical devices to ensure resiliency. Generally, the directionless wavelength switch 52 is configured to receive an input including one or more wavelengths, and to switch the input to an output port based on provisioning. The directionless wavelength switch 52 can switch at a wavelength level or at a multiplexed wavelength level (i.e., groups of wavelengths). Advantageously, the scaling requirements of the directionless wavelength switch 52 are less than those required for prior art designs that require larger port counts.
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In this example, the routers 12d,12e are connected through a single optical transceiver on each router 12d,12e. For illustration purposes, a unidirectional path is shown from the router 12d to the router 12e. At the router 12d, an optical splitter 22 is configured to split an output from a transceiver on the router 12d into two identical signals with each signal separately provided to redundant switches 52 at a ROADM 64 node. The redundant switches are connected to each of three WSS 14 at the ROADM 64 node. At the router 12e, a tail end switch 24 is configured to receive outputs from redundant switches 52 connected to three different WSSs 14 at a ROADM 64 node. The switch 24 is configured to switch between the redundant switches 52 responsive to a condition, such as loss of signal.
Advantageously, introducing the directionless wavelength switch 52 functionality on top of a WSS layer provides the opportunity to achieve high availability connectivity as is illustrated in the network 70 through an exemplary fault condition 72 in
Note that, in this case, the expensive WDM interface associated with the very high speed router connections is integrated into the core router 12d,12e device and that no other costly very high speed interfaces exist in the path. For example, the core router 12d,12e can include WDM interfaces, and the core router 12d,12e can alternatively include short-reach interconnects to a WDM transceiver. Again, upon link failure, rapid ‘tail-end’ protection switching (with the switch 24) provides fast optical layer protection without the need for router 12e reconfiguration. Additionally, the network 70 can provide an alternative ‘third’ path in the network, the directionless switch 52 associated with the now failed link can reconfigure to create a new backup path.
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Not all carriers choose to implement optical layer protection between adjacent core router ports, such as in
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The ROADM node 66 receives the duplicate signals at separate WSSs 14 after transmission over the optical network 102. The outputs from the various WSSs 14 are connected to another redundant directionless switch 52 which connects to a 1×2 tail-end switch 24. The tail-end switch 24 is configured to receiver both duplicate signals and to provide one output to the optical transceiver on the router 12g. The tail-end switch 24 is configured to switch between signals based on a predetermined condition, such as loss-of-signal, alarm indication signal, signal degrade, and the like.
Advantageously, the optical 1+1 and directionless architecture provide protection and diversity despite faults while minimized transceiver costs. Note, as rates increase to 40 G, 100 G, etc., the optical transceiver costs dominate capital expense. However, the optical 1+1 does not protect against transceiver failures at the routers 12f,12g.
At the router 12f, each working and protect transceiver is connected to the switch 52 through an optical splitter 22. In the event a working transceiver fails, the protect transceiver is configured to take over transmitting the working transceiver's signal through the optical splitter 22 and the switch 52 and onto the optical network 102. Advantageously, the 1:N protection mechanism 112 minimizes transceiver costs by only using one protection transceiver for N working transceivers. For example, the 1:N protection mechanism 112 can be utilized with mesh restoration to provide similar resiliency as provided with ring configurations while providing better efficiency than rings.
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The ports 122 can each be configured to carry working traffic between the routers 12h,12i.
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The ROADM node 66 includes two redundant directionless switches 52 each includes two optical switches 142. The separate optical switches 52 provide redundancy at the ROADM node 66, i.e. a failure of one optical switch 52 is not a single point of failure. Each of the optical switches 142 are separated for receive and transmit sides (denoted as 142a for receive and 142b for transmit) of the transceiver 140. The receive side switches 142a receive inputs from demultiplexers 144. The demultiplexers 144 receive outputs from four WSS 146 devices. The WSSs 146 receive inputs external to the node 66 from optical fibers. As described herein, the WSSs 146 are configured to dynamically route one or more wavelengths to each demultiplexer. The receive side switches 142a each provide an output to the tail-end switch 24.
The transmit side switches 142b each receive an output from the splitter 22, and connect to multiple multiplexers 148 which are configured to multiplex one or more outputs from the switches 142b. Outputs from the multiplexers 148 can be combined with pass-through signals 150 from the WSSs 146 for output from the node 66. For example, the multiplexer 148 outputs and pass-through signals 150 can be combined with a multiplexer 152. Additionally, those of ordinary skill in the art will recognize that this degree four configuration can also be extended to different degree configurations as are known in the art.
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The WSS 146 is configured to reconfigurably drop different wavelengths from the input 188 to a channel demultiplexer 192. The demultiplexer 192 is configured to separate one or more channels. In this exemplary embodiment, outputs from the various demultiplexers 192 are connected to the switch 182. The switch 182 provides a directionless architecture similar to the switch 52 described herein. The switch 182 can route outputs from any of the demulitplexers 192 to any receiver 194. This avoids the need to hard-wire receivers 194 to the demultiplexers 192 allowing path changes as described herein. Note, the switch 182 requires full capacity up from for all receiver 194 connections. This could require a lot of demultiplexers 192 and significant wiring upon initial deployment.
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Advantageously, the multi-channel (either band-wide or cyclic AWG) fixed filters under the WSS layer provide the WSS 146 single channel selectivity. The ROADM configuration 200 still preserves some channel wavelength tunability, but with the cost of fixed filters. The ROADM configuration 200 also allows a more scalable growth in the switch size that gets used in the directionless architecture. The ROADM configuration 200 provides a balance between tunability and cost. Tunability is available within the ranges of the filters 202 allowing wavelength assignments to be dynamically changed to re-optimize a network and reduce wavelength blocking probability.
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In this exemplary embodiment, receivers 194a,194b can be either directional or directionless. For example, receiver 194a can be initially connected directly to the filter 202 for a directional configuration. However, the node 220 can evolve to a directionless configuration through the addition of the switch 220 and connecting the receiver 194b directly to the switch 222 instead of the filter 202. Additionally, extra switches 222 can be added to provide efficient growth and added redundancy.
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The cross-connects 306 are configured to provide mesh restoration, such as using ITU-T Automatically Switched Optical Network (ASON), IETF Generalized Multi-Protocol Label Switching (G-MPLS) also known as Automatic Switched Transport Network (ASTN), or the like. The DWDM platforms 308 are configured to provide optical 1+1 protection such as described herein with the splitter 22 and tail-end switch 24.
Advantageously, the present invention combines the use of mesh restoration and optical ring protection (i.e., not SONET/SDH) to achieve super high availability performance. The optical ring protection can utilized G.709/OTN to encapsulate SONET/SDH signals while maintaining the mesh restoration on the underlying SONET/SDH signals. Additionally, G.709/OTN provides a header with operations, administration, maintenance, and provisioning (OAM&P) capabilities on the optical ring, such as determining fault conditions. The G.709/OTN optical rings provide high availability connectivity for the mesh SONET/SDH connections.
The cross-connect nodes 306 that participate in mesh restoration are connected together using cascaded protection rings 312,314 based on the DWDM platform 308. The use of cascaded protection rings 312,314 provides protection against a single fiber failure within the context of a small geographical domain. Thus, multiple fiber failures may exist simultaneously (on different rings 312,314) between a pair of mesh restoration nodes without the need to implement mesh restoration.
The present invention utilizes a protected transparent ring solution between mesh restoration nodes, such as cross-connects 306. These transparent rings 312,314 can include simple optical 1+1/tail-end protection of optical signals over fiber or WDM or, if a managed solution is preferred, then the rings can be defined using OTN/G.709 framing. For example, DWDM platforms 308 can be configured to frame incoming signals from the cross-connect 306 using G.709. This provides complete transparency while providing OAM&P at the DWDM layer. The G.709 framing can be utilized to indicate a protection switch at the DWDM layer.
In this scenario, the connection between a pair of cross-connect nodes 306 simply looks like a highly available SDH or SONET connection. The cross-connect nodes 306 communicate as if each is an adjacent SONET or SDH line or multiplex section terminating piece of equipment. Signaling and routing protocols for mesh restoration can communicate unimpeded across the chosen Data Communications Channel (DCC). The present invention cascades multiple optical protection rings 312,314 and combines the protection attributes of these rings 312,314 with mesh restoration to achieve a higher availability solution.
For the present invention to work, a hold-off timer is required at each cross-connect node 306. In the event of a failure, the cross-connect node 306 detects the failure and attempt to recover service. In this scenario, the cross-connect node 306 must wait to confirm that the intermediate 1+1 optical layer protection has not recovered the service before implementing its own recovery efforts. Because the proposed 1+1 optical protection is based on tail-end protection, it is expected to be rapid so the cross-connect node 306 hold off timer can be quite short, i.e. to ensure sub-50 ms restoration.
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Although the present invention has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present invention and are intended to be covered by the following claims.
Claims
1. A directionless reconfigurable optical add/drop multiplexer (ROADM) node for high availability between switch or router ports, the node communicatively coupled to an optical network via at least two links, the node comprising:
- a directionless switch, including one or more switches, connected to each of the at least two links and configured to selectively route a lightpath from a client device to any of the at least two links for protection thereof;
- wherein the directionless switch is located between the at least two links and the client device, and wherein the client device is not hard-wired to any of the at least two links; and
- wherein the directionless switch is configured with a single input/output for the client device and the protection is 1:1 optical protection.
2. The node of claim 1, wherein the client device has one protection transceiver for up to N working transceivers, and wherein each of the N working transceivers and the one protection transceiver are connected to the directionless switch.
3. The node of claim 1, wherein the directionless switch includes a receive side and a transmit side, and wherein the at least two links each comprise a wavelength selective switch connected to the receive side and a multiplexer connected to the transmit side.
4. The node of claim 1, wherein the directionless switch is a combination of switches added based on bandwidth at the node.
5. A directionless switch method for high availability between switch or router ports, the method comprising:
- receiving at least two lightpaths from a client device; and
- selectively routing the at least two lightpaths to separate degrees of a reconfigurable optical add/drop multiplexer (ROADM) node, wherein each of the separate degrees provides a link to an optical network;
- wherein the client device is not hard-wired to any of the separate degrees; and
- wherein the receiving is from one of (i) a single input/output for the client device and the protection is 1:1 optical protection and (ii) dual inputs/outputs for the client device and the protection is 1+1 or 1:1.
6. The method of claim 5, wherein the receiving is from the dual inputs/outputs for the client device with each of the dual inputs/outputs configured for a maximum fill rate of around 50%, and
- wherein responsive to a failure affecting one of the dual inputs/outputs, the other of the dual inputs/outputs is set to 100% using a reroute, and the method further comprises
- switching the one of the dual inputs/outputs for restoration, and responsive to the restoration, the dual inputs/outputs are configured for the maximum fill rate of around 50%.
7. The method of claim 5, wherein the client device has one protection transceiver for up to N working transceivers, and wherein each of the N working transceivers and the one protection transceiver are connected to a directionless switch, including one or more switches.
8. A directionless reconfigurable optical add/drop multiplexer (ROADM) node for high availability between switch or router ports, the node communicatively coupled to an optical network via at least two links, the node comprising:
- a directionless switch, including one or more switches, connected to each of the at least two links and configured to selectively route a lightpath from a client device to any of the at least two links for protection thereof;
- wherein the directionless switch is located between the at least two links and the client device, and wherein the client device is not hard-wired to any of the at least two links; and
- wherein the directionless switch is configured with dual inputs/outputs for the client device and the protection is 1+1 or 1:1.
9. The node of claim 8, wherein each of the dual inputs/outputs is configured for a maximum fill rate of around 50% of traffic, and
- wherein, responsive to a failure affecting one of the dual inputs/outputs, the other of the dual inputs/outputs is set to 100% of the traffic using a reroute, and the directionless switch is configured to switch the one of the dual inputs/outputs for restoration, and responsive to the restoration, the dual inputs/outputs are configured for the maximum fill rate of around 50% of the traffic.
10. The node of claim 8, wherein the client device has one protection transceiver for up to N working transceivers, and wherein each of the N working transceivers and the one protection transceiver are connected to the directionless switch.
11. The node of claim 8, wherein the directionless switch includes a receive side and a transmit side, and wherein the at least two links each comprise a wavelength selective switch connected to the receive side and a multiplexer connected to the transmit side.
12. The node of claim 8, further comprising:
- a second directionless switch connected to each of the at least two links, wherein the second directionless switch provides redundancy to the directionless switch,
- wherein the client device has dual inputs/outputs each provided to one of the directionless switch and the second directionless switch, and
- wherein the directionless switch and the second directionless switch are configured to selectively route lightpaths from the dual inputs/outputs to any of the at least two links for protection thereof.
13. The node of claim 8, wherein the directionless switch is a combination of switches added based on bandwidth at the node.
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Type: Grant
Filed: Aug 12, 2014
Date of Patent: Feb 23, 2016
Patent Publication Number: 20140348504
Assignee: Ciena Corporation (Hanover, MD)
Inventors: Loudon T. Blair (Severna Park, MD), Michael Y. Frankel (Baltimore, MD)
Primary Examiner: Nathan Curs
Application Number: 14/457,201
International Classification: H04J 14/02 (20060101); H04Q 11/00 (20060101);