Patent Description:
Although nodes in a traditional CDC network may be contentionless, contentions may still occur along edges between the nodes. For example as shown in <FIG>, transponder A of Node <NUM> may be configured to transmit an optical signal of wavelength α to Node <NUM> (channel A), while transponder B of Node <NUM> may also be configured to transmit an optical signal of wavelength α to Node <NUM> (channel B). As such, optical signals from transponders A and B may need to share a same edge between Node <NUM> and Node <NUM> along their respective express paths, resulting in a contention along the shared edge. Although the optical signal for one of the contentious channels, such as channel A, can still be transmitted via a different express path using other edges (e.g., dotted lines through Node <NUM>), that express path may not be the most efficient express path in the network.

<FIG> shows an example ROADM node in a traditional CDC network. As shown, the ROADM node has three "degrees," labeled as "ROADM West," "ROADM East," and "ROADM North," each of which may receive incoming signals from and/or outgoing signals to other nodes of the network. The ROADM node may include a number of optical and/or electrical components, such as transponders, multiplexers, demultiplexers, switches, amplifiers, etc. For example, high performance data center interconnect ("DCI") transponders may be configured to perform optical to electrical conversions with relatively high spectral efficiency on the optical line. Complex add/drop structures ("MUX + DeMUX") may allow transmissions within the node to be CDC. The ROADM node may be configured to maximize optical routing (without converting to or from electrical signals), such as shown for routing signals between all degrees of the node, and to minimize optical to electrical conversions, such as shown only for local add/drop. As mentioned above, a node in the CD network may have similar components, but with different add/drop structures as those shown in <FIG>.

<FIG> shows example asymmetrical edges connecting nodes along an express path in a traditional CDC network. The asymmetry may be a result of practical constraints, such as available locations where the infrastructure can be built. As shown, some edges, such as the relatively longer edge between Node <NUM> and Node <NUM>, may require more amplifiers than other edges, such as the relatively shorter edge between Node <NUM> and Node <NUM>. Since each amplifier adds noise to the optical signals, overall optical noise along an express path is a sum of optical noise accumulated along all edges within the express path. As such, the accumulated noise lowers the spectral efficiency (bit/s/Hz) of data transmission along the express path. Or in other words, the achievable capacity (bit/s) of an optical signal in a fixed frequency or wavelength along an express path is lowered by the accumulated noise. Further, wavelength contentions along edges as described above may further reduce overall spectral efficiency and achievable capacity for data transmission along the express path between Node <NUM> and Node <NUM>.

Document <CIT> refers to methods and systems that enable placement of wavelength shifters in optical networks. The wavelength shifters may include O-E-O regenerators for a single wavelength and all optical wavelength shifters for one or more wavelengths. An auxiliary graph is used to represent various links in a provisioned optical path.

Document <CIT> refers to optical systems and devices for processing spectral groups, and optical methods for forming spectral groups, the optical system including at least one sub-network including at least one spectral group router configurable to route a plurality of optical signal channels within a spectral group, when contained within said sub-network and terminate optical channels within a spectral group, when bounding said sub-network, each optical signal channel being transmitted from one node within said sub-network to another node in said sub-network.

Document <CIT> refers to 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.

Document <CIT> refers to a directionless reconfigurable optical add/drop multiplexer (ROADM) system, providing a scalable all-optical switching element that includes a combination of 1xN wavelength selective switches (WSS), 1xN splitters/combiners, optical amplifiers, and tunable filters to provide a fully non-blocking solution which can be deployed in a scalable manner. The 1xN splitters are configured to split multiples copies of a plurality of drop wavelengths which can be amplified and sent to a tunable filter which selects out a particular wavelength for drop. The 1xN combiners are configured to combine multiple add wavelengths for egress transmission.

Document <CIT> refers to reconfigurable add/drop multiplexer (ROADM) equipment, an optical network system and a transmission method, and relates to the field of optical communication. The ROADM equipment comprises a local uplink and downlink module used for providing an uplink port and a downlink port for transmitting an optical signal; a multifunctional service board card used for processing the received optical signal transmitted by the downlink port, and sending the processed optical signal to client equipment or the uplink port, wherein the processing comprises accessing, electric regeneration and wavelength conversion.

The present disclosure provides for a network comprising a plurality of nodes connected to one another. At least one node of the plurality of nodes comprises: one or more transponders configured to: - receive optical signals having a first set of wavelengths at a first degree of a plurality of degrees in the at least one node;- convert the received optical signals into electrical signals; and - regenerate optical signals by generating, based on the electrical signals, optical signals having a second set of wavelengths; and one or more switches configured to route the regenerated optical signals to one or more of the plurality of degrees of the at least one node, wherein a first node in the network has a first edge connecting to a second node of the network and a second edge connected to a third node of the network, and wherein the first node in the network is configured to:-convert a received optical signal of a first capacity into a first electrical signal;- split the first electrical signal into a plurality of electrical signals each having a capacity smaller than the first capacity; and -regenerate optical signals by converting each of the plurality of electrical signals into a new optical signal to be transmitted through the second edge, and wherein the second node and the third node are configured to communicate with each other through optical signals of a first wavelength along the first edge and optical signals of a second wavelength along the second edge, wherein the optical signals are converted from the first wavelength to the second wavelength at the first node.

A first node in the network has a first edge connecting to a second node of the network and a second edge connected to a third node of the network, wherein the first edge has a first spectral efficiency and the second edge has a second spectral efficiency, the first spectral efficiency being higher than the second spectral efficiency.

The first node may be configured to transmit optical signals through the first edge at the second spectral efficiency.

The network may further comprise an intermediate regenerative node. The intermediate regenerative node may be configured to convert the optical signals from the first node into electrical signals; regenerate, based on the electrical signals, new optical signals; and route the new optical signals to the third node. The intermediate regenerative node may be positioned along the second edge between the first node and the third node such that a difference between the first spectral efficiency and the second spectral efficiency decreases.

The present disclosure still further provides for a method in a plurality of nodes connected to one another, wherein at least one node of the plurality of nodes comprises one or more transponders, for receiving optical signals having a first set of wavelengths at a first degree of a plurality of degrees in a node of a network; converting the received optical signals into electrical signals; regenerating optical signals by generating, based on the electrical signals, optical signals having a second set of wavelengths; and routing the regenerated optical signals to one or more of the plurality of degrees of the node, wherein a first node in the network has a first edge connecting to a second node of the network and a second edge connected to a third node of the network, and wherein the first node in the network converts a received optical signal of a first capacity into a first electrical signal, splits the first electrical signal into a plurality of electrical signals each having a capacity smaller than the first capacity, and regenerates optical signals by converting each of the plurality of electrical signals into a new optical signal to be transmitted through the second edge, and wherein the second node and the third node communicate with each other through optical signals of a first wavelength along the first edge and optical signals of a second wavelength along the second edge, wherein the first node converts the optical signals from the first wavelength to the second wavelength.

The method further comprise routing the received optical signals to a plurality of ports each configured for receiving one or more wavelengths of the first set of wavelengths.

The method may further comprise routing a first portion of the received optical signals to a local termination; and routing a second portion of the received optical signals to an express transit.

The method may further comprise converting the first portion of the received optical signals in the local termination into electrical signals; and routing the electrical signals in the local termination through a router.

The optical signals having the second set of wavelengths may be regenerated using the second portion of the received optical signals in the express transit.

The technology relates generally to a regenerative optical network. As described above and illustrated by <FIG>, contentions may occur along edges of a traditional CDC network. As the number of nodes in the network increases and the required number of edges with contiguous available spectrum between two nodes increases, some of the nodes may be completely blocked from reaching each other, or at least temporarily until the optical signals traversing those edges are reconfigured for a different wavelength. Further, routing design for optical channels in a network without taking into account future channel additions may result in a fragmented network, yet it may be difficult or even impossible to predict future channel additions. A fragmented network may result in more blocked edges, which reduces maximum utilization of the network. For example, an upper limit for a traditional CDC network may be <NUM>% or lower, which is at least partially a result of blocked edges. Moreover, since noise accumulates as an optical signal propagates along each edge, as the number of required edges increases, the amount of noise in the optical signal may also increase. In addition, high performance components such as DCI transponders and complex add/drop structures shown in <FIG> may be expensive and consume a lot of energy. Still further, overall achievable spectral efficiency is lowered in a traditional CDC network since an optical signal traverses all edges along an express path without optical to electrical conversion, and thus noise along all the edges are accumulated in the routed optical signal.

To address these issues, a regenerative optical network is provided that terminates and regenerates optical signals at nodes of the regenerative optical network. For instance, an optical signal having a first wavelength may be received at a node, once received, the optical signal may first be converted into an electrical signal, and then converted back into an optical signal having a second wavelength ("regenerated"). The regenerated optical signal with the second wavelength may then be routed along an express path to another node. Thus, by regenerating optical signals at the nodes even for express transit, the optical signals can be converted into different wavelengths to avoid contentions along edges of the regenerative optical network. As such, contiguous spectrum along multiple edges is not required in the regenerative optical network to transmit optical signals of a particular channel along an express path.

Each node of the regenerative optical network includes one or more transponders configured for optical to electrical and electrical to optical conversions. For example, the transponders may be low cost and low energy transponders, such as 400ZR or ZR+ type transponders. Optical signals received at the node may be transmitted to one or more transponders, such as two transponders coupled to each other. The first transponder may convert the received optical signals into electrical signals, then the second transponder may convert the electrical signals back into optical signals.

The regenerative optical network may also include one or more switches. For example, a switching array, such as a wavelength selective switch ("WSS") array or an arrayed waveguide grating ("AWG"), may be configured to route optical signals received from different channels through a line port to different express paths. The switching may be frequency or wavelength selective, where different wavelengths in the received optical signals may be routed from the line port to multiple local ports. As another example, one or more switches may be configured to route the received optical signals to either local add/drop or express transit. Optical signals in local add/drop may then be converted into electrical signals and transmitted to servers and/or client devices, for example via a router. In contrast, optical signals in express transit may be routed further, such as to another node of the regenerative optical network. The regenerative optical network may also include other switches configured to direct the regenerated optical signals between various degrees within the node.

In the regenerative optical network, each node may have a similar or different configuration. For example, one node in the regenerative optical network may not include any DCI or similar transponders, while another node may include a DCI or similar transponder in one or more degrees of the node. The DCI transponder may be configured to convert optical signals into electrical signals for local add/drop.

Nodes in the regenerative optical network may further include any of a number of additional components. For example, the nodes may additionally include one or more amplifiers. As another example, the local add/drop section in a node may include multiple ports such that electrical signals may first be received at a common port, and then divided into multiple ports potentially having different speeds, before being connected to a router.

In another aspect, the regenerative optical network may further include features that mitigate the effects of noise asymmetry on transmission efficiency and capacity. In one example, nodes in the regenerative optical network may be configured to transmit optical signals at a capacity that is a lowest denominator among achievable capacities of different edges along an express path. In another example, an edge with a higher achievable capacity in an express path may be split into multiple edges by one or more additional regenerative nodes. In the claimed embodiments, an optical signal along an edge carrying higher data volume are re-groomed into multiple optical signals each carrying a lower data volume, so that remaining capacity along that edge can be used for transmitting other optical signals.

The technology is advantageous because it provides an energy and cost efficient mesh optical network. As described above, the regenerative optical network prevents network fragmentation and blocking to increase edge utilization, which in some instances may reach up to <NUM>%. Since optical signals are regenerated at each node along an express path, noise is not accumulated along multiple edges of the express path. The regenerative optical network also provides for features that increase transmission efficiency and capacity along an express path with edges that are asymmetric with respect to noise. Further, compared to a traditional CDC network using high performance transponders, the regenerative optical network may use low energy and low cost transponders to reduce the overall power usage and infrastructure cost. For instance, even where the low cost and low power transponders may have lower performance, the lower performance may be more than compensated by reduction/elimination of edge to edge noise accumulation.

<FIG> shows an example regenerative optical network <NUM>. The regenerative optical network <NUM> includes a plurality of nodes, such as nodes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The nodes of the regenerative optical network <NUM> are connected to one another through edges. For example, node <NUM> is connected to node <NUM> through edge <NUM>, to node <NUM> through edge <NUM>, and to node <NUM> through edge <NUM>. The nodes of the regenerative optical network <NUM> may transmit optical signals to one another through express paths including one or more edges. For example, node <NUM> may transmit optical signals to node <NUM> through express path <NUM>, which includes only edge <NUM>, and node <NUM> may transmit optical signals to node <NUM> through express path <NUM>, which includes edge <NUM> and edge <NUM>. Thus, express path <NUM> and express path <NUM> share the edge <NUM>.

The regenerative optical network <NUM> may be configured to terminate and regenerate optical signals at each node, or at least at some of the nodes. For instance, optical signals may be received at node <NUM>, the received optical signals may be converted into electrical signals, and then converted back into optical signals before being transmitted to node <NUM> of the regenerative optical network <NUM>. Thus, instead of directly routing optical signals in express transit from one node to another, the optical signals are terminated at each node by conversion into electrical signals, and then "regenerated" as optical signals at the node for further routing.

In such a regenerative optical network, contentions along edges may be reduced or eliminated. For example, a first optical signal may be added at node <NUM>, for instance by local add/drop <NUM> to be transmitted along express path <NUM> including edge <NUM> and terminated at node <NUM>. The first optical signal may be assigned a first wavelength α along edge <NUM> between the nodes <NUM> and <NUM>, for example by configuring a first transponder A at node <NUM>. Later, a second optical signal may be added at node <NUM> by local add/drop <NUM> to be transmitted along express path <NUM> including edges <NUM> and <NUM> and terminated at node <NUM>. This second optical signal may be assigned a second wavelength β along edge <NUM>, for example by configuring a second transponder B at node <NUM>, since wavelength α is already occupied along edge <NUM> by the first optical signal. This way, a potential contention along shared edge <NUM> is eliminated.

Further as shown, once node <NUM> receives the second optical signal having the second wavelength β, node <NUM> will need to transmit the second optical signal to node <NUM>. However, edge <NUM> may already be configured to transmit another optical signal with the second wavelength β (for example this other optical signal might have been added at another node, not shown). As such, the second optical signal need to be reconfigured to another wavelength. In this regard, the second node <NUM> may terminate the second optical signal with a second wavelength β, and regenerate optical signal in a third, available, wavelength, by transponder C. For example, the regenerated optical signal at node <NUM> may have a third, available, wavelength γ as shown, or revert back to the first wavelength α (if it is available along edge <NUM>).

As such, the shared edge <NUM> of <FIG>, unlike the shared edge of <FIG>, is not blocked for transmitting optical signals from two transponders configured for the same wavelength. Thus, as compared to the traditional CDC network of <FIG>, higher edge utilization is possible in the regenerative optical network <NUM>, in some instances up to <NUM>% (all edges are usable for transmission between any pair of transponders). In addition, transmission for a single channel along express path <NUM> may include transmission of optical signals having different wavelengths - second wavelength β along edge <NUM> and third wavelength γ along edge <NUM>. Thus, another consequence is that contiguous spectrum along multiple edges is not required for transmission for a single channel along an express path in the regenerative optical network <NUM>.

Also as mentioned above, by terminating the optical signal at each node, the regenerative optical network <NUM> prevents noise from accumulating along multiple edges along an express path. For example, an optical signal traversing through express path <NUM> may accumulate a certain amount of noise along edge <NUM>, but when the optical signal and the noise is received at a node, the received optical signal is terminated and regenerated from scratch (from electrical signals), which does not include the optical noise from edge <NUM>. The regenerated optical signal therefore does not carry the noise from edge <NUM> while traversing through edge <NUM>. Thus, noise accumulation from edge to edge may be fully prevented by the regeneration.

Although only a few nodes are depicted in <FIG>, it should be appreciated that a typical regenerative optical network can include a large number of connected nodes. Likewise, although the nodes in <FIG> are depicted to have a few connections, it should be appreciated that a typical node in a regenerative optical network can include a large number of connections. Further, <FIG> does not depict relative geographical positioning of the nodes.

To terminate and regenerate optical signals, nodes in the regenerative optical network <NUM> may include a number of components. <FIG> shows an example node <NUM> in a regenerative optical network, such as the node <NUM> in the regenerative optical network <NUM>. As shown, node <NUM> has three degrees, ROADM West <NUM>, ROADM North <NUM>, and ROADM East <NUM>, each of which may receive incoming signals from and/or transmit outgoing optical signals to other nodes of the regenerative optical network <NUM>. For example, ROADM West <NUM> may be receiving optical signals from and/or transmitting optical signals to node <NUM>, ROADM North <NUM> may be receiving optical signals from and/or transmitting optical signals to node <NUM>, and ROADM East <NUM> may be receiving optical signals from and/or transmitting optical signals to node <NUM>.

Although only a few degrees are depicted in <FIG>, it should be appreciated that a typical node in a regenerative optical network can include a large number of degrees, such as <NUM> degrees. Further, although the degrees of node <NUM> are labeled as "West," "East," and "North," the degrees do not necessarily correspond to compass directions. The degrees may not even correspond to their relative positioning. Rather, these labels simply correspond to how the components are depicted in <FIG>.

Referring to <FIG>, incoming optical signals <NUM> may be received from node <NUM> at one or more incoming ports at ROADM West <NUM>. The incoming optical signals <NUM> may be received at ROADM West <NUM> from a line port or a common port (not shown) and may be dispersed in wavelengths. For example, the incoming optical signals <NUM> may come from multiple channels of node <NUM>, such as from a first channel of the first transponder A of node <NUM> and a second channel from the second transponder B of node <NUM> as shown in <FIG>. As such, the incoming optical signals <NUM> may include an optical signal from the first channel having wavelength α and an optical signal from the second channel having wavelength β.

Thus, one or more switches or switching arrays, such as a wavelength selective switch ("WSS") array <NUM>, may be configured to route optical signals from different channels in the incoming optical signals <NUM> to their respective express paths. In this regard, the switching may be frequency or wavelength selective, where the received incoming optical signals <NUM> may be routed from the common port to multiple local ports or channels (not shown) based on what wavelength(s) each local port is configured to receive. For example, WSS <NUM> may be configured to select two optical signals in the received incoming optical signals <NUM> based on wavelength, and route the two selected optical signals respectively to two local ports (two lines coming out of WSS <NUM>), where each of the two local ports may be configured to receive one wavelength. Practically, WSS <NUM> may select optical signals and route the selected optical signals to many ports (e.g. <NUM>) within the node <NUM>, each of which may be configured to receive one or more wavelengths. This wavelength switching (routing) process may be dynamically changed through an electronic communication control interface on the WSS <NUM>.

Once the incoming optical signals <NUM> are routed to different ports for different channels, one or more switches may be configured to route the optical signals to either local add/drop or express transit. For example, one or more 1x2 switches <NUM> may be configured to route optical signals to either local add/drop (dashed lines) or express transit (solid lines). For instance, based on traffic distribution across different geographical locations and/or datacenters, some portions of the incoming optical signals <NUM> may be routed to local add/drop for local traffic, while other portions of the incoming optical signals <NUM> may be routed to express transit. Optical signals routed to local add/drop may then be routed directly to servers and/or client machines. For example, the optical signals may be converted into electrical signals by a transponder (not shown), such as a ZR transponder, and then routed through a router <NUM>. In contrast, optical signals routed to express transit may be routed further, such as to another degree of the node <NUM> to be transmitted to another node. In some instances such as where traffic in the regenerative optical network is highly asymmetric in terms of volume, broadcast and/or multicast may be implemented with 1xN or MxN switches, and optical transponders capable of multi-cast and/or broadcast.

Referring to the optical signals routed for express transit (solid lines from 1x2 switches <NUM>), one or more transponders may be configured to terminate these optical signals and regenerate them. For example as shown, transponders <NUM>, <NUM>, <NUM>, <NUM> may be configured to make the optical to electrical conversions for incoming optical signals <NUM> received at ROADM West <NUM>. Further as shown, the transponders may be coupled in pairs. For instance, a first transponder <NUM> may convert the optical signal from the first channel into one or more electrical signals (bold line). Then, a second transponder <NUM> coupled to the first transponder <NUM> may convert the one or more electrical signals back or regenerated into an optical signal (solid line). Likewise, the pair of transponders <NUM> and <NUM> may perform the optical to electrical, and electrical to optical conversions for the optical signals from the second channel.

In this regard, the transponders may be any of a number of transponders. The transponders may be low cost and low energy transponders. For example as shown, the transponders may conform to a standard, such as 400ZR or ZR+ type transponders. ZR or ZR+ type transponders are transponders specifically designed to have a much smaller footprint both in terms of power consumption and physical size than DCI transponders. For instance, digital signal processing logic may be simplified to a bare minimum in ZR transponders as compared to DCI transponders. In this regard, if a traditional CDC network requires N number of DCI transponders, to achieve the same efficiency or capacity, the regenerative optical network <NUM> described herein may require N x (number of edges per node) x (capacity_,ZR/capacity_DCI) number of ZR transponders. Thus, although in some instances more ZR transponders may be required in the regenerative optical network <NUM> to operate at a comparable performance level as the CDC network with DCI transponders, the low energy and low cost of the ZR transponders may still reduce the overall power usage and infrastructure cost.

Once electrical signals are regenerated as optical signals in express transit, one or more switches <NUM> may be configured to direct the regenerated optical signals to one or more outgoing ports at one or more degrees of the node. For example as shown in <FIG>, a 1xD switch (where D is the number of degrees of the node, which in this case is <NUM>) may be configured to direct the regenerated optical signal from the first channel to degrees ROADM North <NUM>, ROADM East <NUM>, or back to ROADM West <NUM>. As another example, a 1xD-<NUM> switch may be configured to direct the regenerated optical signal from the second channel to degree ROADM North <NUM> or ROADM East <NUM>.

Since the outgoing optical signals may also come from more than one channel, one or more switches, such as WSS <NUM>, may be provided on the outgoing side of a degree to combine the optical signals to be sent through an outgoing line port or common port. Subsequently, the regenerated optical signals may be transmitted to another node, for example via one or more edges in an express path as described above. For instance, an edge may be made of one or more fiber spans, where each fiber span is an optical fiber followed by an optical amplifier.

Each degree in the node may be configured similarly or differently. For example, ROADM North <NUM> in <FIG> is shown similar to ROADM West <NUM> in that incoming optical signals received at ROADM North <NUM> are routed to multiple ports by a WSS, the optical signals are then directed to either local add/drop (dashed lines) or express transit (solid lines), where the optical signals in express transit are converted into electrical signals and regenerated as optical signals by ZR transponders. Note that for ease of illustration, various components and lines are omitted from ROADM North <NUM>. For example, transponders for express transit of one of the optical signals (for one of the lines out of incoming WSS) is omitted. As another example, lines representing regenerated optical signals are omitted, which would otherwise come out of switch 1xD-<NUM> to reach various degrees in the node <NUM>.

ROADM North <NUM> is shown configured differently from ROADM West <NUM> with respect to the local add/drop section. As shown, a DCI transponder <NUM> is provided for connection to a router. The DCI transponder <NUM> may terminate the optical signal, and convert the optical signal to one or more electrical signal(s) for transmission through the router. Connection (not shown) between the DCI transponder <NUM> and the router in ROADM North <NUM> may be implemented by one or more copper connections or low cost short reach optical modules, which are different from ROADM West <NUM>. For example as mentioned above, the router <NUM> in ROADM West <NUM> may be provided with ZR based transponders (not shown) for optical to electrical conversion for local add/drop, the ZR based transponders are coherent, and therefore can be directly connected to the router <NUM>.

Since the number of DCI transponders are reduced as compared to the traditional CDC network shown in <FIG>, cost and energy consumption of the node and therefore the regenerative optical network may be reduced. On the other hand, since DCI transponders can potentially provide higher spectral efficiency, a hybrid network with both ZR and DCI transponders, such as shown in <FIG>, may further increase spectral efficiency of the regenerative optical network. Further as shown, the switches of <FIG> (such as 1x2 switches <NUM> and 1xD and 1xD-<NUM> switches <NUM>) replaced the add/drop structures of <FIG>, which include complex MUX and DeMUX structures.

ROADM East <NUM> may also be configured similarly as ROADM West <NUM>. Note that for ease of illustration, most components are omitted from ROADM East <NUM>, including transponders, local add/drop, router, switches, etc. ROADM East <NUM> is intended to illustrate that, instead of a WSS, one or more switching arrays can be other types of switching arrays, such as an arrayed waveguide grating ("AWG"). Since AWG <NUM> is a passive element that does not allow reconfigurable selections of wavelengths as a WSS does, cost may be saved by using AWGs instead of WSSs in the node <NUM>. Node <NUM> may further include any of a number of additional components. For example as shown, the node <NUM> may additionally include one or more amplifiers, such as amplifier <NUM>.

<FIG>, <FIG> and <FIG> show other alternative configurations of example nodes in a regenerative optical network, such as regenerative optical network <NUM>. Example nodes <NUM>, 700A, and 700B each includes many of the features of example node <NUM>, but with differences as discussed further below.

For instance, referring to example node <NUM> of <FIG>, for ROADM West <NUM>, the local add/drop section has a different configuration as ROADM West <NUM> of <FIG>. As shown, transponders <NUM>, <NUM>, <NUM>, <NUM> configured for optical to electrical conversions for express transit may also be used for local transit. For example, transponder <NUM> may convert an incoming optical signal into one or more electrical signal(s) and direct the electrical signal(s) to a common port <NUM>. The common port <NUM> may in turn be connected to multiple ports <NUM> potentially having different speeds. For example, a router <NUM> may have a port with a speed matching one of the multiple ports <NUM>. Alternatively, if the router <NUM> does not have a port with a speed matching any of the multiple ports <NUM>, the port with the higher speed may be throttled. Further, an AWG is shown in ROADM North <NUM> of <FIG>, instead of ROADM East <NUM> in <FIG>.

Referring to example node 700A of <FIG>, ROADM West 710A is shown configured the same way as ROADM West <NUM>, but ROADM North 780A is shown with a different configuration as ROADM North <NUM> of <FIG>. For example, no DCI transponder is used in ROADM North 780A. Rather, ROADM North 780A is shown with identical configuration as ROADM West 710A (and ROADM West <NUM>), using ZR transponders. By not using any DCI transponders, node 700A may further reduce energy consumption.

Referring to <FIG>, node 700B is shown as a hybrid node that includes both regenerative and traditional CDC network components. For example, ROADM West 710B and ROADM North 780B are each shown connected to traditional CDC add/drop structures similar to those shown in <FIG>. In contrast, ROADM East 790B is shown with similar components as ROADM West <NUM> of <FIG>, including ZR transponders for regenerating optical signals for express transit. Note that the signals for local add/drop for ROADM East 790B may also be connected to traditional CDC add/drop structures. By combining traditional CDC degrees and add/drop structures with degrees similar to those described by <FIG>, the hybrid node 700B of <FIG> may simplify transition from one system to another. Further, such hybrid nodes may provide capability to optimize for different routes/paths in the regenerative optical network.

Although <FIG>, <FIG>, <FIG>, <FIG> illustrate some example configurations of nodes in the regenerative optical network <NUM>, other configurations are possible. Nodes in the regenerative optical network <NUM> may be configured similarly or differently from one another. For example, some nodes in the regenerative optical network may be configured similarly as shown in <FIG>, while other nodes in the regenerative optical network may be configured similarly as shown in <FIG>, making the overall network a hybrid of different types of nodes including traditional CDC nodes, regenerative nodes, and/or hybrid nodes. As other examples, some nodes of the regenerative optical network <NUM> may include one or more degrees that only include local termination or express transit, but not both. Likewise, some nodes of the regenerative optical network <NUM> may be configured for only local termination or express transit, but not both.

In another aspect, the regenerative optical network may be configured with features that mitigate the effects of noise asymmetry on transmission efficiency and capacity. As mentioned above with respect to <FIG>, in the traditional CDC network, an overall capacity bottleneck may be introduced by the total accumulated noise along all edges along an express path. Although such noise accumulation does not occur along an express path in a regenerative optical network, such as express path <NUM>, inefficiencies may be introduced by noise asymmetry along different edges in an express path.

For instance, <FIG> shows an example configuration <NUM> for mitigating effects of asymmetric edges. As shown, an express path, such as express path <NUM> connecting nodes <NUM>, <NUM>, and <NUM> of regenerative optical network <NUM> may include edges <NUM> and <NUM>. Further as shown, the edges <NUM> and <NUM> may be asymmetric, for example as a result of practical constraints, such as available locations where the infrastructure can be built. As such, the relative longer edge <NUM> may require more amplifiers, shown with amplifiers <NUM>, <NUM>, <NUM>, and <NUM>, than the relative shorter edge <NUM>, shown with amplifiers <NUM> and <NUM>. Since each amplifier adds noise to the optical signals, the edges <NUM> and <NUM> may be asymmetric in terms of accumulated optical noise. As such, data transmission along edge <NUM> of express path <NUM> may occur at a lower spectral efficiency (bit/s/Hz) than data transmission along edge <NUM>. For example, achievable capacity (bit/s) of an optical signal in wavelength β may be higher along edge <NUM>, shown as <NUM>/s, than along edge <NUM>, shown as <NUM>/s.

Thus, in the example shown in <FIG>, nodes connected by asymmetric edges may be configured to transmit optical signals at a capacity that is a lowest denominator of achievable capacities along the express path. For example as shown, nodes <NUM>, <NUM>, and <NUM> connected by asymmetric edges <NUM> and <NUM> may be configured to transmit optical signals at a capacity that is a lowest denominator <NUM>/s of achievable capacities along the express path <NUM>. This may be accomplished by changing a setting at the nodes <NUM>, <NUM>, and/or <NUM>. This way, instead of having an overall, less than full capacity utilization of the <NUM>/s-<NUM>/s, for example <NUM>% or less due to wavelength contentions along edges, full utilization <NUM>% may be made of the overall capacity of <NUM>/s.

<FIG> shows another example configuration <NUM> for mitigating effects of asymmetric edges using an intermediate regenerative node. Example configuration <NUM> includes many of the features of example configuration <NUM>, but with differences as discussed further below. For instance, an intermediate regenerative node, such as intermediate regenerative node <NUM>, may split the relatively longer edge <NUM> into two edges <NUM> and <NUM>. The intermediate regenerative node <NUM> may be configured to terminate and regenerate optical signals similarly as the nodes shown in <FIG>. The intermediate regenerative node <NUM> may be positioned between the nodes <NUM> and <NUM>, for example halfway between the nodes <NUM> and <NUM> or some other available location. As shown, the newly created two edges <NUM> and <NUM> each have fewer amplifiers than the original longer edge <NUM>, and thus each contribute less noise than the original longer edge <NUM>. Since terminating and regenerating optical nodes prevent optical noise to accumulate over multiple edges, the overall noise along edges <NUM> and <NUM> is lower than noise accumulated over the original longer edge <NUM>.

In the particular example shown in <FIG>, the intermediate regenerative node <NUM> may be positioned such that <NUM>/s can be achieved along both the edges <NUM> and <NUM> (e.g., <NUM>/s along edge <NUM> and <NUM>/s along edge <NUM>). As such, node <NUM> and the shorter edge <NUM> may be re-configured to transmit optical signals that is the lowest denominator <NUM>/s achievable along the express path <NUM> (for example by changing a setting at the node <NUM>). As another example, when the intermediate regenerative node <NUM> is positioned somewhere else between nodes <NUM> and <NUM>, different capacities may be achievable along edge <NUM> and edge <NUM> (e.g., <NUM>/s at both), based on which the node <NUM> and the shorter edge <NUM> may be configured (e.g., <NUM>/s).

<FIG> shows an example intermediate regenerative node, such as the intermediate regenerative node <NUM> of <FIG>. Intermediate regenerative node <NUM> includes many of the features of example node <NUM>. For instance, the intermediate regenerative node <NUM> may include wavelength selective arrays, such as AWG <NUM>, which may be designed similarly as AWG <NUM>. For example, AWG <NUM> may route optical signals of dispersed wavelengths from multiple channels received at a common port to multiple local ports (here shown as two ports). The intermediate regenerative node <NUM> may include one or more transponders, such as transponders <NUM>, <NUM>, <NUM>, <NUM> configured to make the optical to electrical conversions. The transponders <NUM>, <NUM>, <NUM>, <NUM> may be configured the same way as transponders <NUM>, <NUM>, <NUM>, <NUM> of <FIG>. For example, the transponders may be coupled in pairs. The first transponder <NUM> may convert the optical signal from a channel into one or more electrical signals (bold line). Then, a second transponder <NUM> coupled to the first transponder <NUM> may convert the one or more electrical signals back or regenerated into an optical signal (solid line).

The intermediate regenerative node <NUM> may be configured differently from other regenerative nodes of the regenerative optical network. For instance, the intermediate regenerative node <NUM> may include only degrees leading to the nodes whose connecting edge is being split. As such, in this example the intermediate regenerative node <NUM> is shown with two degrees, degree <NUM> leading to node <NUM>, and degree <NUM> leading to node <NUM>. Further, since the intermediate regenerative node <NUM> is configured to split along only one direction, there is no need for switches. The intermediate regenerative node <NUM> also may not include any features for local add/drop, since the intermediate regenerative node <NUM> is designed to split an edge in express transit between two nodes. As with <FIG>, for ease of illustration, various components and lines are omitted from degree <NUM>, which may be configured similarly as degree <NUM>.

<FIG> shows yet another example configuration <NUM> for mitigating effects of asymmetric edges by re-grooming optical signals. Example configuration <NUM> includes many of the features of example configuration <NUM>, but with differences as discussed further below. For instance, nodes <NUM> and/or <NUM> of <FIG> may be re-configured with features configured to re-groom optical signals, shown as re-grooming nodes <NUM> and <NUM> in <FIG>. Thus as shown, re-grooming node <NUM> may re-groom an optical signal carrying <NUM>/s of data to be transmitted over shorter edge <NUM> into two re-groomed optical signals <NUM> and <NUM> each carrying <NUM>/s of data. This way, at a given time or time period, one of the re-groomed optical signals <NUM> or <NUM> may be transmitted through edge <NUM>. As such, the extra <NUM>/s capacity along the shorter edge <NUM> may be used for transmission of other optical signals. Although re-grooming by splitting in two optical signals of equal capacity is shown, in other examples an optical signal may be re-groomed into more than two signals, and/or each with same or different capacities.

<FIG> shows an an embodiment of the claimed invention with a node configured to re-groom optical signals, such as re-grooming node <NUM> of <FIG>. As shown, re-grooming node <NUM> may include many of the features of example node <NUM>, such as switching arrays, switches, amplifiers, etc. As with <FIG>, for ease of illustration, various components and lines are omitted from degrees ROADM North <NUM> and ROADM East <NUM>. Further, only one port is shown at the incoming WSS of ROADM West <NUM>. As shown in <FIG>, once the incoming optical signals are converted into electrical signals by a transponder <NUM>, the electrical signals may be re-groomed by a gear box <NUM> into two electrical signals of smaller capacities. The two electrical signals may then each be regenerated into optical signals by transponders, such as transponders <NUM>, <NUM>, and further routed. The transponders <NUM>, <NUM>, and <NUM> may be configured similarly as transponders <NUM>, <NUM>, <NUM>, <NUM> of <FIG>, for example the transponders <NUM>, <NUM>, <NUM> may each be a ZR type transponder. Alternatively, packet processors such as a switch or router may be used to re-groom the electrical signals.

<FIG> illustrates an example block diagram of some components in a node in a regenerative optical network, such as node <NUM> in the regenerative optical network <NUM>. It should not be considered as limiting the scope of the disclosure or usefulness of the features described herein. In this example, the node <NUM> is shown with one or more computing devices <NUM>. The computing devices <NUM> contains one or more processors <NUM>, memory <NUM> and other components typically present in general purpose computing devices. Memory <NUM> of the computing devices <NUM> can store information accessible by the one or more processors <NUM>, including instructions <NUM> that can be executed by the one or more processors <NUM>. For instance, configuration and re-configuration of a regenerative optical network as discussed above with respect to the examples shown in <FIG> may be performed by the one or more processors <NUM> according to instructions <NUM> and data <NUM> in memory <NUM>.

Memory <NUM> can also include data <NUM> that can be retrieved, manipulated or stored by the processor. The memory can be of any non-transitory type capable of storing information accessible by the processor, such as a hard-drive, memory card, ROM, RAM, DVD, CD-ROM, write-capable, and read-only memories.

Data <NUM> may be retrieved, stored, or modified by the one or more processors <NUM> in accordance with the instructions <NUM>. For instance, although the subject matter described herein is not limited by any particular data structure, the data can be stored in computer registers, in a relational database as a table having many different fields and records, or XML documents. The data can also be formatted in any computing device-readable format such as, but not limited to, binary values, ASCII or Unicode. Moreover, the data can comprise any information sufficient to identify the relevant information, such as numbers, descriptive text, propriety codes, pointers, references to data stored in other memories such as at other network locations, or information that is used by a function to calculate the relevant data. As shown, the data <NUM> may include data on various components of the node <NUM> and of the regenerative optical network <NUM>.

The instructions <NUM> can be any set of instructions to be executed directly, such as machine code, or indirectly, such as scripts, by the one or more processors. In that regard, the terms "instructions," "application," "steps," and "programs" can be used interchangeably herein. The instructions can be stored in object code format for direct processing by a processor, or in any other computing device language including scripts or collections of independent source code modules that are interpreted on demand or compiled in advance. As shown, the instructions <NUM> may include functions or methods for controlling various components of the node <NUM> to perform routing, conversion, etc..

The one or more processors <NUM> can be any conventional processors, such as a commercially available CPU. Alternatively, the processors can be dedicated components such as an application specific integrated circuit ("ASIC") or other hardware-based processor. Although not necessary, one or more of the computing devices <NUM> may include specialized hardware components to perform specific computing processes.

Although <FIG> functionally illustrates the processor, memory, and other elements of computing devices <NUM> as being within the same block, the processor, computer, computing device, or memory can actually comprise multiple processors, computers, computing devices, or memories that may or may not be stored within the same physical housing. For example, the memory can be a hard drive or other storage media located in housings different from that of the computing devices <NUM>. Accordingly, references to a processor, computer, computing device, or memory will be understood to include references to a collection of processors, computers, computing devices, or memories that may or may not operate in parallel. For example, the computing devices <NUM> may include server computing devices operating as a load-balanced server farm, distributed system, etc. Yet further, although some functions described below are indicated as taking place on a single computing device having a single processor, various aspects of the subject matter described herein can be implemented by a plurality of computing devices, for example, communicating information over a network.

The computing devices <NUM> may be capable of directly and indirectly communicating with other nodes of the regenerative optical network <NUM>. Computing devices in the regenerative optical network <NUM>, such as computing devices <NUM>, may be interconnected using various protocols and systems, such that computing devices in the regenerative optical network <NUM> can be part of the Internet, World Wide Web, specific intranets, wide area networks, or local networks. Computing devices in the network can utilize standard communication protocols, such as Ethernet, WiFi and HTTP, protocols that are proprietary to one or more companies, and various combinations of the foregoing. Although certain advantages are obtained when information is transmitted or received as noted above, other aspects of the subject matter described herein are not limited to any particular manner of transmission of information.

Further to example systems described above, example methods are now described. Such methods may be performed using the systems described above, modifications thereof, or any of a variety of systems having different configurations. It should be understood that the operations involved in the following methods need not be performed in the precise order described. Rather, various operations may be handled in a different order or simultaneously, and operations may be added or omitted.

For instance, <FIG> shows an example flow diagram that may be performed by a regenerative optical network, such as the regenerative optical network <NUM>. For example, a node in the regenerative optical network <NUM>, such as node <NUM>, <NUM>, 700A, or 700B may receive optical signals, and route the optical signals to other nodes in the regenerative optical network <NUM>. In some instances, the flow diagram may at least partially be performed by computing devices in the regenerative optical network <NUM>, such as computing devices <NUM> shown in <FIG>.

Referring to <FIG>, in block <NUM>, optical signals having a first set of wavelengths are received at a first degree of a plurality of degrees in a node of a network. For example as shown in <FIG>, incoming optical signals <NUM> may be received at degree ROADM West <NUM>.

In block <NUM>, the received optical signals are converted into electrical signals. In this regard, one or more transponders may convert the received optical signals into electrical signals. For example as shown in <FIG>, transponders <NUM> and <NUM> are shown as coupled, where transponder <NUM> may be configured to convert incoming optical signal <NUM> into electrical signals.

In block <NUM>, optical signals having a second set of wavelength are generated based on the electrical signals, resulting in "regenerated" optical signals. For example as shown in <FIG>, transponders <NUM> and <NUM> are shown as coupled, where transponder <NUM> may be configured to convert the electrical signals from transponder <NUM> back into optical signals. The regenerated signals may have any wavelength, including having the same wavelength as the incoming optical signals, or different wavelength as the incoming optical signals.

In block <NUM>, the regenerated optical signals are routed to one or more of the plurality of degrees of the node. In this regard, one or more switches may be configured to route the regenerated optical signals. For example as shown in <FIG>, one or more switches <NUM> may be configured to route the regenerated optical signals to one or more of degrees ROADM North <NUM>, ROADM East <NUM> and/or ROADM West <NUM>.

In some instances, the received optical signals may be routed to a plurality of ports each configured for receiving one or more wavelengths of the first set of wavelengths. One or more switches may be configured to perform the routing. For example as shown in <FIG>, switch arrays such as WSS <NUM> and AWG <NUM> may route the incoming optical signals <NUM> to different ports within the node <NUM>.

In addition, a first portion of the received optical signals may be routed to a local termination, while a second portion of the received optical signals to an express transit. One or more switches may be configured to perform the routing. For example as shown in <FIG>, switches <NUM> may be configured to route the incoming optical signal <NUM> to a local termination, for example converting to electrical signals to be transmitted to a router <NUM>. Alternatively or additionally, as shown in <FIG>, once converted into electrical signals, the electrical signals may be divided into different ports <NUM>, <NUM> having different speeds, before connecting to a router. Also as shown in <FIG>, switches <NUM> may be configured to route the incoming optical signal <NUM> to an express transit, for example, converted and regenerated by transponders <NUM>-<NUM>, and further routed by switches <NUM> to ROADM North <NUM>, ROADM East <NUM>, etc..

In another aspect as described above with respect to <FIG>, additional methods may be used to mitigate the effects of noise asymmetry on transmission efficiency and capacity. In the example shown in <FIG>, optical signals may be transmitted at a capacity that is a lowest denominator among achievable capacities of different edges along an express path. In the examples shown in <FIG>, an edge with a higher achievable capacity in an express path may be split into multiple edges by one or more additional regenerative nodes. Alternatively, in the example shown in <FIG>, an optical signal along an edge carrying higher data volume may be re-groomed into multiple optical signals each carrying a lower data volume, so that remaining capacity along that edge can be used for transmitting other optical signals.

The technology is advantageous because it provides an energy and cost efficient mesh optical network. As described above, the regenerative optical network prevents network fragmentation and blocking to increase edge utilization, which in some instances may reach up to <NUM>%. Since the optical signals are regenerated at each node along an express path, noise is not accumulated along multiple edges of the express path. The regenerative optical network also provides for features that increase transmission efficiency and capacity along an express path with edges that are asymmetric with respect to noise. Further, compared to a traditional CDC network using high performance transponders, the regenerative optical network may use low energy and low cost transponders to reduce the overall power usage and infrastructure cost.

Claim 1:
A network (<NUM>), comprising:
a plurality of nodes (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) connected to one another, wherein at least one first node (<NUM>) of the plurality of nodes comprises:
one or more transponders (<NUM>, <NUM>, <NUM>, <NUM>) configured to:
receive (<NUM>) optical signals (<NUM>) having a first set of wavelengths at a first degree of a plurality of degrees in the at least one first node;
convert (<NUM>) the received optical signals into electrical signals; and
regenerate (<NUM>) optical signals by generating, based on the electrical signals, optical signals having a second set of wavelengths; and
one or more switches (<NUM>) configured to route (<NUM>) the regenerated optical signals to one or more of the plurality of degrees of the at least one first node,
wherein the first node (<NUM>) in the network has a first edge connecting to a second node of the network and a second edge connected to a third node of the network, and wherein the first node (<NUM>) in the network is configured to:
convert a received optical signal of a first capacity into a first electrical signal;
split the first electrical signal into a plurality of electrical signals each having a capacity smaller than the first capacity; and
regenerate optical signals by converting each of the plurality of electrical signals into a new optical signal to be transmitted through the second edge, and wherein the second node and the third node are configured to communicate with each other through optical signals of a first wavelength along the first edge and optical signals of a second wavelength along the second edge, wherein the optical signals are converted from the first wavelength to the second wavelength at the first node.