Patent Application
20120183292
In existing Reconfigurable Optical Add/Drop Multiplexer (ROADM) based optical nodes, a set of add ports and a set of drop ports are dedicated to a given output network node interface. Attached to a given add/drop port is an optical transponder. The optical transponder provides the ability to convert a “white light” non-colored optical signal to a colored optical signal (and vice versa). The ROADM then provides the ability to multiplex multiple optical signals into a single multi-wavelength wavelength division multiplexed optical signal.
Wavelength Division Multiplexing (WDM) is a method by which single-mode optical fibers are used to carry multiple light waves of different frequencies. In a WDM network, many wavelengths are combined in a single fiber, thus increasing the carrying capacity of the fiber. Signals are assigned to specific frequencies of light (wavelengths) within a frequency band. This multiplexing of optical wavelengths is analogous to the way radio stations broadcast on different wavelengths as to not interfere with each other. Because each channel is transmitted on a different wavelength, a desired channel may be selected using a tuner. WDM channels (wavelengths) are selected in a similar manner. In a WDM network, all wavelengths are transmitted through a fiber, and de-multiplexed at a receiving end. The fiber's capacity is an aggregate of the transmitted wavelengths, each wavelength having its own dedicated bandwidth.
Dense Wavelength Division Multiplexing (DWDM) is a WDM network in which wavelengths are spaced more closely than in a coarse WDM network. This provides for a greater overall capacity of the fiber.
An example embodiment of the present invention includes methods, apparatuses, and network elements for combining wavelengths of different spacings within an optical node. Such an example embodiment includes a Reconfigurable Optical Add Drop Multiplexer (ROADM) with a first express path configured or operable to be configured to pass wavelengths from an ingress side of the ROADM to an egress side of the ROADM, and further includes a second express path that restricts, or is operable to restrict, a first subset of the wavelengths and only passes the wavelengths of the remaining subset (e.g., a second subset) from the ingress side to the egress side of the ROADM.
Alternative example embodiments of the present invention include a method for trafficking an optical signal in a ROADM by passing wavelengths on a first express path from an ingress side of the ROADM to an egress side the ROADM. The method further includes restricting a first subset of the wavelengths from being trafficked on a second express path, but passing a second subset of the wavelengths on the second express path from the ingress side of the ROADM to the egress side of the ROADM.
Further alternative example embodiments of the present invention can include a multi-degree optical node, where the optical node can include or be operably interconnected to at least two ROADMs. A first ROADM can be selectably configured or is operable to be configured (or programmed) to traffic wavelengths via a first express path in the ROADM or the first ROADM can be selectably configured, or is operable to be configured (or programmed), to traffic only a subset of the wavelengths via a second path, the first ROADM being optically coupled to a second ROADM, where the second ROADM can be configured or is operable to be configured to receive the wavelengths or the subset of the wavelengths and to traffic wavelengths received via an express path.
Further example embodiments of the present invention include an optical network including at least two optical nodes being operably interconnected to each other via at least one inter-network node path. The first optical node can be selectably configured to traffic first wavelengths or a subset of the first wavelengths, and the second optical node can be configured to traffic second wavelengths. In such an example embodiment, the first optical node can be configured to traffic the first wavelengths to the second optical node if the first wavelengths correspond to the second wavelengths, and the first optical node can further be configured to traffic the subset of the first wavelengths if the subset of the wavelengths corresponds to the second wavelengths.
Further example embodiments can include a method for trafficking an optical signal in an optical network by allowing a subset of wavelengths to pass through a given hybrid ROADM toward a non-hybrid ROADM capable of handling only the subset of the wavelengths. The method may further include allowing off-grid and on-grid wavelengths to pass through the given hybrid ROADM toward another hybrid ROADM or a non-hybrid ROADM capable of handling all of the wavelengths.
The foregoing will be apparent from the following more particular description of example embodiments of the invention and as illustrated in the accompanying figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating example embodiments of the present invention.
A description of example embodiments of the invention follows.
Before describing embodiments of the present invention, a brief description of history and current developments of the art is presented.
Fiber optic links, or fibers, can be used for optical fiber communication using different techniques, such as wavelength division multiplexing (WDM). Although the entire data transmission bandwidth (capacity) of a fiber can be used as a single logical or physical channel through the fiber with a very large bandwidth and data rate, such use of the fiber is not favorable for many reasons commonly known in the art. However, WDM can be employed to maintain a high combined data rate by aggregating many channels, where each channel “exists” on a different wavelength and the transmission rates of each channel are maintained at relatively low levels (e.g., 10 gigabytes/per second (Gbps)).
Currently, there exist different forms of WDM, such as coarse WDM (CWDM), which employs only a small number channels (e.g., 4-10 channels), and each channel has relatively wide spacing (e.g., 20 nm). Another example of WDM is dense WDM (DWDM), which employs a larger number of channels (e.g., 44, 88, etc.), and each channel has relatively narrow wavelength spacing (e.g., 100 GHz, 50 GHz, 25 GHz, etc.). As technology is furthered, narrower wavelength spacings, higher data transmission rates, and additional aspects and components of WDM and optical transmission will continue to change.
Current systems for optical transmission can include many components (e.g., optical amplifiers, interleavers and de-interleavers, filters, optical switches, and reconfigurable optical add/drop multiplexers). One such component, namely the reconfigurable add/drop multiplexer (ROADM), can be employed in optical systems, such as a WDM network, in order to provide for flexible management of data connections, and can be used to add and drop wavelengths from respective DWDM signals at the requested or determined port, destination, network, or network component. See, e.g., International Telecommunications Union (ITU) Standard G. 694.1 (June 2002) or ITU Standard G.694.2 (December 2003).
Current standards support 44-channel ROADMs (i.e., having 44 wavelengths spaced apart by 100 GHz) and 88-channel ROADMs (i.e., having 88 wavelengths spaced apart by 50 GHz). Currently, an 88-channel ROADM cannot be optically interconnected to a 44-channel ROADM within the same system. This is because, from the incoming direction (e.g., from a line-in or line interface), the optical signal containing all wavelengths (i.e., all wavelengths on channels 1-88) is broadcast to all Wavelength Selective Switches (WSSs) on all ROADMs. In other words, if a line interface receives a signal containing 88 wavelengths, the express input on an 88-channel WSS (i.e., 100 GHz WSS) receives all 88 wavelengths. There is no mechanism to block the off-grid 44 wavelengths (i.e., wavelengths on channels 45-88) to the 100 GHz WSS other than by not connecting the express fiber containing the 88 channels to the 100 GHz based ROADM. If a 100 GHz WSS receives 50 GHz spaced wavelengths, then, because of the wide 100 GHz filters in the WSS, signal power within the two off-grid (50 GHz) wavelengths (on either side of an on-grid (100 GHz) wavelength) leaks into the on-grid channel. Such spill-over interferes with the signal within the on-grid channel, which results in an Optical Signal-to-Noise Ratio (OSNR) penalty on the on-grid channel. For example, for 10 Gbps wavelengths, the resulting OSNR penalty is over 6 decibels (dB).
Example embodiments of the present invention described herein provide for placement of any number, relative to the capability or available space of a node, of 100 GHz ROADMs and 50 GHz ROADMs in the same network element, such as a network node defined, for example, as an 8-degree node (detailed below in reference to
It should be understood that 50 GHz spacing and 100 GHz spacing are merely examples of wavelength spacing in optical networks; embodiments of the invention can also be applied to other optical channel spacing or future legacy spacing in optical networks. For example, alternative example embodiments of the present invention can be used for technologies using different wavelength patterns, for example, 25 GHz spacing (e.g., ultra dense WDM). Further alternative embodiments of the present invention can be implemented in new amplification options that can enable the extension of usable wavelengths as are currently known or hereinafter developed and discovered relating to the capacity and channels used in optical networks.
As used herein, and unless otherwise denoted, the term “hybrid ROADM” refers to a ROADM capable of handling both on-grid and off-grid wavelengths (e.g., channels 1-88), and capable of being selectably configured (or programmed) to send a subset of channels to a 100 GHz non-hybrid ROADM. The phrase “non-hybrid ROADM” refers to legacy ROADMs, those which already exist, such as 50 GHz and 100 GHz ROADMs, but not selectably (or configurably) one or the other, where either term as used herein can mean manually or automatically arrangeable to enable the hybrid ROADM to communicate operatively with legacy and non-legacy ROADMs in efficient manners. For example, a ROADM capable of handling on-grid wavelengths only (i.e., channels 1-44) is a legacy ROADM, herein referred to as a 100 GHz non-hybrid ROADM or a 100 GHz ROADM. A second such legacy ROADM is a ROADM capable of also handling off-grid wavelengths (i.e., channels 45-88), but cannot be selectably configured (or programmed) to send a subset of channels to a 100 GHz non-hybrid ROADM. This second legacy ROADM is herein referred to as a 50 GHz non-hybrid ROADM or a 50 GHz ROADM.
For illustrative purposes, example embodiments presented herein are described in reference to 100 GHz spaced and 50 GHz spaced wavelengths. However, it should be understood that the example embodiments are applicable to other spacings of wavelengths, such as 50 and 25 GHz spacings, non-multiple spacings, etc. More generally, the example embodiments apply to wavelengths and a subset of the wavelengths, where, for example, the term “wavelength” can mean wavelengths corresponding to channels 1-88, which includes 50 GHz spaced channels (i.e., all channels) and the term “subset of the wavelengths” can mean wavelengths corresponding to channels 1-44, which includes 100 GHz spaced channels. The term “subset” can alternatively refer to other channels, consecutive or non-consecutive, among the “wavelengths.” It should be understood that channels 1-88 and 1-44 are used here as a convenient example; other channels at different corresponding wavelength spacings are also possible.
In the example embodiment of the optical network 100, the optical nodes 105a-d are interconnected via at least one inter-network node path (INNP) 121, which can be any suitable optical connection, such as a fiber optic cable, and include multiple optical network components. The example optical nodes 105a-d can include optical interfaces 111a-n, which can interface with the INNP 121 at specified positions, such as the available ports (not shown) to which to attach a fiber optic cable. In alternative example embodiments of the present invention, each node 105a-d may have different numbers of optical interfaces 111a-n available to be interfaced with the optical connection. Additionally, optical connections may be changed, updated, or modified to different capacity fibers as may be deemed necessary or beneficial. Each node 105a-d can be operably interconnected and maintain at least one reconfigurable optical add/drop multiplexer (ROADM), which can be configured to transmit and receive optical wavelengths, such as wavelength division multiplexed (WDM) signals. An example embodiment of the present invention illustrates optical node 105c configured with four interconnected ROADMs, where two of the ROADMs are hybrid-ROADMs 160a-b and two of the ROADMs are non-hybrid ROADMS. Specifically, in the case of a network with 100 GHz ROADMs and 50 GHz ROADMs, one of the non-hybrid ROADMs is a non-hybrid 50 GHz ROADM 150 and the other is a non-hybrid 100 GHz ROADM 140. Each of the ROADMs 160a-b, 150, and 140 are interconnected via an intra-node network path 131.
In an example embodiment, the wavelengths 202 can include both on-grid and off-grid wavelengths (not shown), where the on-grid wavelengths are wavelengths that are spaced apart by 100 GHz and the off-grid wavelengths are wavelengths that are spaced apart by 100 GHz and offset from the on-grid wavelengths by 50 GHz. On-grid wavelengths are those wavelengths that are on the 100 GHz ITU grid, while off-grid wavelengths are those wavelengths that are not on the 100 GHz ITU grid, but instead offset from that grid by 50 GHz. In further example embodiments of the present invention, a first subset of wavelengths can include off-grid wavelengths but no on-grid wavelengths, and a second subset of the wavelengths, such as the wavelengths 292, can include on-grid wavelengths but no off-grid wavelengths. In example embodiments of the present invention, the ROADM 260 can be optically interconnected with at least a first egress path 222a and a second egress path 222b, where the first and second egress paths are different paths. Further example embodiments of the hybrid ROADM 260 can further be configured to receive optical signals via ingress paths, such as a first ingress path 223a of the first express path 270 and a second ingress path 223b of the second express path 280.
Alternative example embodiments of the present invention can include the egress side of the ROADM having the first and second egress paths coupled to a common egress port via a switch (not shown), or other such component. In further alternative example embodiments of the present invention, the first and second ingress paths 223a-b can be coupled to a common ingress port via a beam splitter or switch, or other optical component, or may be split or otherwise separated prior to entering the hybrid ROADM.
Alternative example embodiments of the present invention can include the interleaver 365 configured or operable to be configured to direct the off-grid wavelengths to a first drop path of the ROADM and direct the on-grid wavelengths to a second drop path of the ROADM. The ROADM can further include any number of drop paths as may be required. The drop paths, which can be coupled to an ingress path or line-in 368 of the ROADM, can be configured to carry the wavelengths to at least one drop port coupled to the ROADM.
The array of two-to-one optical switches 362a-b, allow each express port 312a-b to be selectively configured to pass either all 88 wavelengths (i.e., both the on-grid and off-grid wavelengths) or 44 wavelengths (i.e., just the on-grid wavelengths). This can be accomplished by selectively configuring (or programming) each two-to-one optical switch 362a-b to select either the first express pass or the second express path. In alternative example embodiments, the optical switches can be removed, and the two sets of express paths can both be connected to output ports on the ROADM 360.
The optional optical amplifier 363, which may be implemented using an Erbium Doped Fiber Amplifier (EDFA) is used to boost the amplitude of the on-grid wavelengths exiting the express ports 312a-b from the second express path 380, in order to compensate for the insertion losses of the second express path 3. Alternatively, the optional optical amplifier 363 can be placed prior to the interleaver 365, such that both the on-grid and off-grid wavelengths traversing the second express path are amplified.
Key to the architecture of the ROADM 360 is the fact that wavelengths passing through the first express path do not traverse through the interleaver, and therefore do not suffer any filter narrowing effects associated with traversing through the interleaver filter. Therefore, wavelengths will only experience filter narrowing effects when traversing from an 88-channel portion of a given network to a 44 channel portion of the given network. Due to typical network topologies, the number of times a given wavelength traverses from an 88-channel portion of a given network to a 44 channel portion of the given network will be quite limited.
Whenever a wavelength passes through an optical amplifier (such as an EDFA), amplified spontaneous emission (ASE) noise is added to the wavelength. Since the optical amplifier 363 is placed only in the second express path, when a wavelength passes from the Line In port 368 to the express port 312a-b on the ROADM, the wavelength will only have ASE noise added to it when traversing from an 88-channel portion of a given network to a 44 channel portion of the given network.
Further example embodiments of the present invention can include the ROADM's multiple optical devices, such as amplifiers, optical couplers 361a-g, optical switches 362a-b, at least one wavelength selective switch (WSS) 315, array wavelength gratings (AWGs) 364a-d, add paths 367a-d, or other such optical devices currently used or hereinafter developed for use associated with reconfigurable add/drop multiplexing in optical networks.
Alternative example embodiments of the hybrid ROADM allow for an 88-channel ROADM that can contain configurable wavelength band-blocking capabilities on its express output ports. Alternative example embodiments of the hybrid ROADM can allow for software programs to allow all eighty-eight channels (on-grid and off-grid channels) or only the first forty-four channels (on-grid channels) to be passed to each express output port. Such example embodiments allow for individual express output ports on the hybrid ROADM to be independently programmed to allow the combination of 88-channel and 44-channel ROADMs to work together within a given optical node.
Further still, the example hybrid ROADM can employ an interleaver (“INT” in
Additional example embodiments of the block diagram 500 can include a multi-degree optical node 505, where the first ROADM 560a can be selectably or fixedly configured to traffic the wavelengths or the subset of the wavelengths as a function of wavelength capacity of the second ROADM 560b. Further, the multi-degree optical node 505 can include additional ROADMs, such additional ROADMs being operably interconnected at open slots 516a-h, where each “slot” is considered a “degree.” In other words, in the example optical node 505, the node can be an eight-degree (8D) node, where the “degrees” represent connection points in different actual (i.e., or physical) directions located on the optical node 505. For example, the node key 555 illustrates the cardinal points and ordinal points as would be the directions of the 8D node slots. Alternative example embodiments can include a third ROADM that can be operatively interconnected to an empty slot 516g, which would correspond to the cardinal point “West.” As many intra-node network paths 531 as needed to interconnect the ROADMs may be employed within the optical node 505.
In such embodiments, the first ROADM, for example, can further be configured or is operable to be configured to traffic the wavelengths or subset of the wavelengths to the second and third ROADMs as a function of their respective wavelength capacities. In other example embodiments of the present invention, additional ROADMs (hybrid or non-hybrid) may be operatively interconnected as needed, limited only as a function of available space on the node. Further still, example embodiments of the present invention can include a multi-degree optical node, where the second ROADM can include a Wavelength Selective Switch (WSS) configured to receive the wavelengths or the subset of the wavelengths, and further be configured to provide wavelengths received or a further subset of the wavelengths received to an express path of the second ROADM.
In alternative example embodiments of the optical network 600, the first optical node 605a can be further configured to serve as a gateway node, which can operably interconnect an on-grid and off-grid portion of the network (not shown) and/or an on-grid-only portion of the network (not shown). Such an example optical network can be, for example, an interconnected dense wavelength division multiplexing optical network.
In alternative example embodiments of the block diagram 700a, a core 88-channel network may be combined with a 44-channel network on the peripheral. Furthermore, example embodiments of the diagram 700a illustrate that only channels 1-44 (i.e., on-grid wavelengths in this network illustration) may be used between 100 GHz nodes and that channels 1-88 (i.e., on-grid and off-grid wavelengths in this network illustration) may be used between 50 GHz interconnected nodes. In an example embodiment, 100 GHz spaced wavelengths transmitted or received via 50 GHz nodes may, to some extent, follow optical rules of the 50 GHz system.
Alternative example embodiments of the present invention can include a single component type that can be utilized as both an interleaver, to interleave two streams, and a de-interleaver, to de-interleave two streams.
Alternative example embodiments of the procedure of
Further alternative example embodiments of the procedure of
In alternative example embodiments of the block diagram 1000, the second ROADM 1060b can traffic wavelengths or subsets of wavelengths to the first ROADM 1060a. In further example embodiments of the present invention, both the first and second ROADMs may exchange collateral information, as may be common in the art; additionally, the ROADMs can be individually programmed to perform or send and receive information as per coded instructions. In alternative example embodiments of the present invention, the network apparatus 1005 of block diagram 1000 can be a multi-degree optical node, such as the optical node 505 in
Alternative example embodiments of the present invention allow for an optical network based on a 44-channel network to be upgraded to an 88-channel network by upgrading at least one ROADM at a time. In one such alternative example, only the on-grid wavelengths, channels 1-44, can be used while the entire network, portion of the network, or a network element is being upgraded. Further, the original 44-channel network may be designed or implemented using optical rules associated with an 88-channel optical network. In further alternative example embodiments of the present invention, a network operating with channels 1-88, which mixes 50 GHz ROADMs and 100 GHz ROADMs in the same network element, such as a network node, may cause failure. Network nodes containing only 100 GHz ROADMs can be interconnected to nodes containing 50 GHz ROADMs, but the 50 GHz ROADMs will transmit channels 1-44 to the 100 GHz ROADMs. In such alternative example embodiments, a network having both 50 GHz nodes (i.e., nodes comprised of 50 GHz ROADMs) interconnected to 100 GHz nodes (i.e., nodes comprised of 100 GHz ROADMs), channels 45-88 may be first be assigned to the connections between the 50 GHz nodes, which allows for a maximum number of wavelengths for transmission between 100 GHz nodes across a 50 GHz core network.
In alternative example embodiments of the present invention, a hybrid ROADM can fully interoperate with existing 100 GHz spaced ROADMs while also providing 50 GHz spaced ROADM capability. Such an embodiment can allow 100 GHz spaced wavelengths to pass (e.g., transmitted and received) between the hybrid ROADM and an existing 100 GHz spaced ROADM. In addition, such an example embodiment can allow 50 GHz spaced wavelengths to pass between the hybrid ROADM and other hybrid ROADMs, and other 50 GHz spaced ROADMs. In further alternative example embodiments of the present invention, a hybrid ROADM can provide two wavelength paths in at least one direction, where the first path is configured or is operable to be configured to carry 50 GHz spaced wavelengths and the second path is configured or is operable to be configured to carry only 100 GHz spaced wavelengths. In such an example embodiment of a hybrid ROADM with 50 GHz spaced wavelengths being transmitted or received on a path, the 50 GHz spaced wavelength path does not pass through any optical filters prior to being emitted on an interconnected express output port; as such, the 50 GHz spaced wavelengths do not suffer effects of filter narrowing. Such example embodiments of express output ports can be configured to be independently programmable to transmit or pass 50 GHz spaced wavelengths or only 100 GHz spaced wavelengths.
In further alternative example embodiments, an optical interleaver can be employed to separate the on-grid wavelengths from the off-grid wavelengths. Such an example interleaver can be used to separate (i.e., de-interleave) the on-grid and off-grid wavelengths for both on- and off-grid drop ports and express ports. Further example embodiments may maintain an optical interleaver attached directly to a ROADM, or operatively interconnected thereto, but such interleaver can be programmed or reprogrammed not to separate the on- and off-grid wavelengths that can be dropped via the drop ports.
Further example embodiments of the present invention allow a ROADM with at least two express paths to receive all wavelengths (e.g., channels 1-88) via a line-in interface and can simultaneously drop the received wavelengths via at least one drop port to be sent to all express output ports. In further example embodiments, only the on-grid wavelengths on the 100 GHz express output path and the on-grid wavelengths being dropped via the at least one drop port may be amplified. Alternatively, the on-grid wavelengths on the 100 GHz express output path and both the on-grid and off-grid wavelengths being dropped via at least one drop path are amplified. Further still, the on-grid wavelengths, off-grid wavelengths, or both may be dropped via a single array wavelength grating (AWG) or via multiple AWGs.
An alternative example embodiment of the present invention can include a hybrid ROADM that allows for any mixture of 44-channel and 88-channel ROADMs within the same system, while providing a complete interconnection between all ROADMs in the system. In one such example embodiment, in regard to the add and drop ports, array wavelength gratings (AWGs) with 100 GHz spacing and 50 GHz shape (i.e., bandwidth) can be used. For an example embodiment employing AWGs for use with add and drop ports, the interleavers used in alternative example embodiments of the present invention for the adding and dropping of optical signals, wavelengths, or subsets thereof, can be replaced with a simple optical coupler (e.g., a 1:2 optical coupler). In an example embodiment, one set of AWGs can be offset in frequency by 50 GHz, such that the AWGs can filter the off-grid wavelengths. In further alternative example embodiments, in regard to add and drop ports, 88-channel AWGs with 50 GHz spacing and 50 GHz shape (i.e., bandwidth) can be employed. In one such example embodiment, no interleavers or couplers are necessary for the adding and dropping of optical signals, wavelengths, or subsets thereof.
Further alternative example embodiments of the present invention can include a method and apparatus for adding additional wavelengths to an optical node, where such a process can include replacing at least one 100 GHz ROADM with at least one hybrid ROADM. Such an example embodiment or alternative example embodiments, as detailed herein, may include a method and apparatus for adding wavelengths in a dense wavelength division multiplexed (DWDM) network.
It is further contemplated that alternative example embodiments of the present invention may include multiple express paths, such as three or more express paths, optically interconnected to a hybrid ROADM as the future need for additional transport differently-spaced wavelengths may require. For example, one embodiment of a hybrid ROADM may include a 25 GHz spacing express path, a 50 GHz spacing express path, and a 100 GHz spacing express path, where the 50 and 100 GHz spacing express paths may employ interleavers or other optical elements as described herein to effectuate separation of the 50 GHz and 100 GHz spaced wavelength subsets from the full set of wavelengths (i.e., the 25, 50 and 100 GHz spaced wavelengths). Furthermore, a three-to-one switch (or two two-to-one switches configured so as to enable a three-to-one switching function) may be utilized to switch one of three types of express paths (i.e., 25 GHz, 50 GHz, and 100 GHz) to a common express port.
Further example embodiments may include mixtures of hybrid and non-hybrid ROADMs in network nodes greater than eight degrees.
Further example embodiments of the present invention may be configured using a computer program product; for example, controls may be programmed in software for implementing example embodiments of the present invention. Further example embodiments of the present invention may include a non-transitory computer readable medium containing instruction that may be executed by a processor, and, when executed, cause the processor to traffic wavelengths of different spacings within an optical node or optical network. It should be understood that elements of the block and flow diagrams described herein may be implemented in software, hardware, firmware, or other similar implementation determined in the future. In addition, the elements of the block and flow diagrams described herein may be combined or divided in any manner in software, hardware, or firmware. If implemented in software, the software may be written in any language that can support the example embodiments disclosed herein. The software may be stored in any form of computer readable medium, such as random access memory (RAM), read only memory (ROM), compact disk read only memory (CD-ROM), and so forth. In operation, a general purpose or application specific processor loads and executes software in a manner well understood in the art. It should be understood further that the block and flow diagrams may include more or fewer elements, be arranged or oriented differently, or be represented differently. It should be understood that implementation may dictate the block, flow, and/or network diagrams and the number of block and flow diagrams illustrating the execution of embodiments of the invention.
While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
This application claims the benefit of U.S. Provisional Application No. 61/450,444, filed on Mar. 8, 2011, which is related to U.S. Provisional Application No. 61/433,155, filed on Jan. 14, 2011, entitled, “A Method and Apparatus for Mixing Wavelengths of Different Spacings within an Optical Node,” the entire teachings of both being incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61450444 | Mar 2011 | US | |
| 61433155 | Jan 2011 | US |
