ROADM The Core of Agile Optical Networks - PacketLight
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Solution Overview © 2009 PacketLight Networks, All rights reserved. This document is PacketLight Public Information. www.packetlight.com ROADM – The Core of Agile Optical Networks s the bandwidth requirements grow rapidly, optical network operators face continued challenges of modifying the current optical networks to meet this growing demand. In WDM networks, this modification mainly means adding new WLs, and sometimes changing the WL distribution within the network. The WDM solutions have scaled up in recent years from typically 8-16 Wavelengths to 44-88 Wavelengths solution, with different routes per each wavelengths and mesh connectivity between sites across the ring. Network managers face the challenge to keep track of all the wavelengths, monitor their correct operation and deploy new wavelengths easily while reducing the operation cost of the network. The Reconfigurable Optical Add Drop Multiplexer (ROADM) adds the required flexibility so that adding WLs or changing the WL destination becomes easy and remotely managed process providing full control and monitoring over the entire high capacity infrastructure. Compared to a non ROADM network, if not already pre-assigned, adding new services requires redesign or major network change which takes time, resources and poses risks of traffic disruptions. This white paper explores the evolution from passive based infrastructure and its limitations compared to ROADM based solutions. Passive Based Solution In passive optical network infrastructure, the building blocks of the network are based on passive filters with fixed optical wavelength modules such as Mux/Demux, OADM or a combination of Band Pass Filters together with the Mux/Demux. This requires careful design prior to installation in order to meet estimated future network growth and connectivity matrix. Figure 1 is a drawing of simple passive Mux/DeMux based ring infrastructure. Each Node across the network is built from 2 passive Mux/DeMux's, one facing the east and one facing the west. The number of supported WL of the solution is defined by the number of channels/filters supported by the Mux/DeMux. Following are a few scenarios which illustrate the limitation and complexity of operation of such passive based networks. Scenario 1: changing distribution of the “Blue” WL. In figure 1, the "Blue" WL passes the Node-3 through the "Blue" filter of both Mux/DeMux. However, let's assume that this service is required at Node-3, this will require manual configuration of the network which can be time consuming and costly. To perform this operation, there is a need to re-patch the “Blue” WL at Node-3 which means sending a technical person to the site. In addition, the manual patches need to be documented and maintained. With too many changes, the network administrator might become disoriented with regards to the original network scheme. Also, scaling this type of solution to 88 WL is practically impossible. A
Transcript of ROADM The Core of Agile Optical Networks - PacketLight
Solution Overview
© 2009 PacketLight Networks, All rights reserved. This document is PacketLight Public Information.
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ROADM – The Core of Agile Optical Networks
s the bandwidth requirements grow rapidly, optical network operators face continued challenges of modifying the current optical networks to meet this growing demand. In WDM networks, this modification mainly means adding new WLs, and sometimes changing the WL distribution within the network. The WDM
solutions have scaled up in recent years from typically 8-16 Wavelengths to 44-88 Wavelengths solution, with different routes per each wavelengths and mesh connectivity between sites across the ring. Network managers face the challenge to keep track of all the wavelengths, monitor their correct operation and deploy new wavelengths easily while reducing the operation cost of the network. The Reconfigurable Optical Add Drop Multiplexer (ROADM) adds the required flexibility so that adding WLs or changing the WL destination becomes easy and remotely managed process providing full control and monitoring over the entire high capacity infrastructure. Compared to a non ROADM network, if not already pre-assigned, adding new services requires redesign or major network change which takes time, resources and poses risks of traffic disruptions. This white paper explores the evolution from passive based infrastructure and its limitations compared to ROADM based solutions.
Passive Based Solution
In passive optical network infrastructure, the building blocks of the network are based on passive filters with fixed optical wavelength modules such as Mux/Demux, OADM or a combination of Band Pass Filters together with the Mux/Demux. This requires careful design prior to installation in order to meet estimated future network growth and connectivity matrix. Figure 1 is a drawing of simple passive Mux/DeMux based ring infrastructure. Each Node across the network is built from 2 passive Mux/DeMux's, one facing the east and one facing the west. The number of supported WL of the solution is defined by the number of channels/filters supported by the Mux/DeMux. Following are a few scenarios which illustrate the limitation and complexity of operation of such passive based networks.
Scenario 1: changing distribution of the “Blue” WL. In figure 1, the "Blue" WL passes the Node-3 through the "Blue" filter of both Mux/DeMux. However, let's assume that this service is required at Node-3, this will require manual configuration of the network which can be time consuming and costly. To perform this operation, there is a need to re-patch the “Blue” WL at Node-3 which means sending a technical person to the site. In addition, the manual patches need to be documented and maintained. With too many changes, the network administrator might become disoriented with regards to the original network scheme. Also, scaling this type of solution to 88 WL is practically impossible.
A
Solution Overview
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Scenario 2: Connecting “Yellow” WL between Nodes-1 to Node-4. In order to drop the "Yellow" wavelength (service) from Node 1 to Node 4, it must pass through Node-2 and Node-3 and be manually patched in the Mux/DeMux. However since the “Yellow” wavelength is not available in the Mux/DeMux, it cannot be passed through. This problem is due to a prior design with fixed passive infrastructure; there are not enough wavelengths to pass this new service between the Node-1-Node-4. Therefore, in order to add WL, the network designer needs to replace the Mux/DeMux in Node-2 and Node-3 to support higher number of wavelengths which is not only costly but will most likely also cause traffic disruption. This issue will not occur in ROADM based infrastructure since the ROADM based network supports full C-band expansion (50/100GHz) from day-1.
Figure 1: Adding new WL
Power Balancing
Another major issue that usually requires manual handling in non-ROADM networks is the power balancing of the bypass wavelengths as opposed to locally added wavelengths on any particular node ( see figure 2). It is necessary to balance the optical power of these WLs at the input point to an EDFA (Erbium-Doped Fiber Amplifier). Otherwise in a link with many EDFAs and multiple channels; some channels might be lost due to a lack of optical power if not balanced along the path. In non-ROADM networks, this is done by reducing the optical power of the added services at the local node and installing fixed attenuators right after the transceiver. This manual operation involves test equipment and calibration of each new service independently which can be cumbersome and time consuming. Since the distances between sites differ from site to site, the power levels of the pass through channels change as well, resulting in the need to place different attenuators at each node and documenting them accordingly.
Solution Overview
© 2009 PacketLight Networks, All rights reserved. This document is PacketLight Public Information.
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Figure 2: Power balancing with fixed attenuators
In a dynamic network that constantly changes, inserting a new node (Node 4 in figure 3) adds additional IL (Insertion Loss) to the "Blue" WL, resulting in sending a technician to Node 2 to replace fix attenuators (increase attenuation) for the "Red" WL . Of course, one might choose to place VOA's and Photo Detectors (PD) or Variable Mux (VMUX) with PD (Photo Detector), but, this would consume space and increase expenses especially due to management complexity requiring constant monitoring and adjustment of the optical power accordingly.
Figure 3: New attenuator with new Node
ROADM Based Solution
The basic element of the ROADM is the Wavelength Selective Switch (WSS). The WSS is an active component that performs the actual WL switching and monitoring. Together with OCM (Optical Channel Monitoring), it monitors and balances power across all channels using VOAs array.
Solution Overview
© 2009 PacketLight Networks, All rights reserved. This document is PacketLight Public Information.
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Figure 4: WSS based ROADM
Figure 4 describes one particular node in the ring network with East and West facing ROADMs. The WSS can select any color to be routed towards the drop side of the local Node or bypass to the next Node. The input port can receive the whole C band and the drop (or add) ports can drop, bypass or block any channel as chosen. Combined with the Tunable Transceivers, the ROADM becomes the most flexible and easily scalable solution for optical networks. Figure 5 illustrates WL provisioning for two Nodes. The management SW determines the WL for the two Transceivers and the relevant configuration for the ROADMs in the ring. Power balancing is performed automatically by the WSS. The whole process is done from a remote site via a network management system.
Figure 5: WSS and Tunable Transceivers
Multi-degree Node A multi degree node is a node with more complex network architecture as in full mesh or ring with spur. This requires a few WSS and PS (Power Splitters) as shown in Figure 6. This adds additional level of flexibility, letting WL to route from any line to any line or be dropped anywhere. In an event of failure of any of the service, the protecting WL routes its path through the network to overcome or bypass the failure. The number of
Solution Overview
© 2009 PacketLight Networks, All rights reserved. This document is PacketLight Public Information.
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node degrees depends on the number of the WSS components present on the node. WSS normally is the building block that is chained together to form a multi degree node.
Figure 6: Multi degree Node
PacketLight PL-1000RO
PacketLight ROADM solution follows the conceptual planning and design of the rest of PacketLight's product line which is based on 1U architecture. PacketLight’s PL-1000RO not only saves space, power consumption and provides easy scalability, but also provides high level of integrated optical elements such as EDFAs and Mux/DeMuxes enclosed within a single 1U enclosure. This economical solution contains 1x2 WSS on the add ports and a PS (Power Splitter) on the drop ports. Together with the internal OCM and VOA per each WL, PL-1000RO handles the switching of the WL, as well as the power balancing. This compact solution also contains the Booster and the Pre Amplifier and two PSU for redundancy. The passive Mux/Dmux are FRUs (Field Replaceable Units) giving the user the ability to economically design the network according to network manager's needs. Figure 7 illustrates the PL-1000RO as a part of a ring with West unit, East unit and the passive unit. With PacketLight’s solution, it is simple, easy and cost effective to build highly flexible optical backbone network which can be scaled with the required transponders at any stage according to the customer's requirements and capacity of each node. No pre-designing is needed and the solution is ready from day-1 for the full C-Band 44/88 WL capacity. PacketLight’s ROADM solution reduces the CAPEX and OPEX of managing and maintenance of the network as well as reducing the time and simplifying the assigning or removing services on the fly without traffic disruption.
Solution Overview
© 2009 PacketLight Networks, All rights reserved. This document is PacketLight Public Information.
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Figure 7: PacketLight PL-1000RO
PacketLight's Management Software
To take a full advantage of ROADM solution, management SW becomes crucial. It configures WSS along the network; monitors, blocks and passes bypass WLs; monitors the optical power at each node as well as facilitates power balancing. As the network becomes more flexible, the management SW becomes more sophisticated. E.g. Tunable transceiver with ROADM allows the SW not only to provision the WL but also to determine the actual WL based on the available wavelengths across the path. Figure-8 illustrates the remote management of PacketLight's ROADM with the ability to control the path of each wavelength at each of the Nodes and the readouts of the power balancing of each channel at each of the Nodes.
Figure 8: ROADM management SW
Solution Overview
© 2009 PacketLight Networks, All rights reserved. This document is PacketLight Public Information.
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Easy Upgrade Path
1x4 WSS is a basic building block in ROADM that allows users to easily and seamlessly add additional nodes in the Network, by simply adding the node and connecting it to the upgrade ports of the existing ROADM. This will let the Network designer to add a spur or create a multi degree node See figure 9.
Figure 9: ROADM with upgrade ports
PL-1000RO and PL-2000
PL-1000RO easily integrates with the rest of PacketLight's Optical Transport Layer (OTN ) products such as PL-1000TN and PL-2000 thus forming a fully flexible optical network for a variety and mix of services. PacketLight's PL-2000 is an MSPP (Multi Service Provisioning Platform) that packs multiple sub 10Gb/s services onto OTU2 10G OTN uplinks. PL-1000TN on the other hand is an 8G/10G OTN based multiprotocol transponder; both can be equipped with tunable DWDM transceivers. Combining the PL-1000RO with the PL-2000 and PL1000TN gives administrators full flexibility down from the service side), through the common optical transport layer, Tunable WL selection and up to the flexible WL termination point somewhere in the Network of each service.
Summary ROADM becomes the best solution for dynamic as well for new networks. It solves most of the challenges facing network administrators. The combination of 100G and 10G services in the network makes ROADM networks even more appealing and cost effective. Combining the advantages of ROADM with PackeLight's other solutions makes it ideal solution for cost, space and power savings. Service and WL changing have never been so easy. The advantages of using ROADM are clear.
1) No need to patch WLs on the pass through Nodes
2) No need for manual power balancing;
Solution Overview
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3) ROADM minimizes time and effort involved in network maintenance, as well as
eliminates the need for constantly documenting the patch panels and
attenuators.
4) Visibility and performance monitoring on all wavelengths at all sites
5) Moreover, ROADM enables routing of any WL between any nodes, thereby easing
the management process and giving the network administrators the ability to
manage the WLs in the network merely with a click of a mouse allowing them to
block, pass or add WLs as needed. Moreover, actual distribution of the WLs in
the network can be viewed at any time while allowing the ROADM to perform
automatic power balancing.
About PacketLight Networks, Ltd. PacketLight Networks offers a suite of Leading 1U Metro CWDM and DWDM solutions, for transport of data, storage, voice and video applications, over dark fiber and WDM networks, featuring high quality, reliability and performance at affordable prices. Our products are distinguished with low power consumption ideal for CLE (Customer Located Equipment) allowing maximum flexibility as well as ease of maintenance and operation and providing real Pay-as-you-grow architecture. PacketLight customers are carriers, service providers, data centers, IT integrators and enterprises who are active in meeting the demands for metro Ethernet, business continuity, Triple Play solutions and enterprise data sharing applications. For product and reseller information, Please contact [email protected]
