Optical add drop multiplexer with asymmetric filtering

Abstract

This disclosure describes techniques for an optical add / drop multiplexer (OADM) that applies asymmetric filtering to allow individual channels within a channel group to be independently added / split or passed. In one example, an optical add / drop multiplexer includes a first input port configured to receive an input signal having a first wavelength channel, a second wavelength channel, and a third wavelength channel; a demultiplexer having a first filter configured to pass through the first wavelength channel and the second wavelength channel, and to filter the third wavelength channel; a multiplexer having a second filter configured to pass through a second wavelength channel and a third wavelength channel, and to filter the first wavelength channel; and a first output port configured to output an output signal of a second wavelength channel including the input signal.

Description

Technical Field

[0001] The present disclosure generally relates to optical networks and, more particularly, to optical add-drop multiplexers. Background Art

[0002] Optical interconnections within a data center or within a data center cluster provide high-speed, low-latency connectivity between computing resources. An optical add-drop multiplexer (OADM) can be used to increase the network flexibility of optical interconnection services. The OADM can add or drop wavelength channels from an existing wavelength-division multiplexing (WDM) signal. The OADM can also route the dropped channels to different network paths. This allows intermediate locations between remote sites to access the fiber segments that link them. The OADM is particularly important in metropolitan area WDM optical wave services. In these services, sites can be connected via different add-drop channels. The OADM can also enable wavelength reuse. For example, a wavelength can be dropped in one direction and then added to be transmitted in the opposite direction.

[0003] An OADM generally includes three stages: an optical demultiplexer, an optical multiplexer, and a stage for guiding wavelengths between the optical demultiplexer, the optical multiplexer, and a set of ports for inserting and dropping signals. The demultiplexer separates the wavelengths in the input fiber onto ports. Reconfiguring the OADM can be achieved by an optical patch panel or by an optical switch that guides wavelengths to the multiplexer or drop ports. The optical multiplexer multiplexes the wavelength channels to be continued from the demultiplexer ports with those wavelength channels from the insert ports onto a single output fiber. Summary of the Invention

[0004] The present disclosure describes techniques for an optical add-drop multiplexer (OADM) that applies asymmetric filtering to allow individual channels within a channel group to be added / dropped or passed independently. The OADM can implement a combination and routing configuration to combine different sets of two or more wavelength channels of a WDM signal into a channel group. This configuration effectively doubles the number of dimensions of the OADM and can be achieved by combining a color filter and a non-color filter. The color filter can include a wavelength-selective switch or an arrayed waveguide grating, while the non-color filter can include a coupler or a splitter. Within the OADM, the demultiplexer separates the wavelengths of the WDM signal, and the multiplexer combines multiple wavelengths into a new WDM signal for output on a fiber. Conventionally, in a routing and selection configuration or a combination and routing configuration, the filtering profile of the multiplexer is symmetric with the filtering profile of the demultiplexer. Thus, the channels within a group are added / dropped or passed together, and the channels within a group must be output in the same direction / dimension.

[0005] According to the technology described herein, an OADM includes a multiplexer and a demultiplexer, where the filtering profile and thus the center frequency are asymmetric. For example, the OADM can include a demultiplexer configured with a filter that passes channels 1 and 2 as group A. The OADM can be configured to add / drop channel 2 or to express or route channel 2 to a different dimension. The OADM includes a multiplexer having a filter that is configured asymmetrically with respect to the filter of the demultiplexer. For example, the filter can be offset by one channel wavelength to pass, for example, channels 2 and 3 as group B. The multiplexer filters out channel 1 and allows the OADM to independently add / drop or express, or independently route channel 2 from channel 1, even though the demultiplexer filter passes channels 1 and 2 as a group.

[0006] The techniques of the present disclosure include one or more specific technical improvements that provide at least one practical application in the field of optical network technology. As described herein, an OADM with asymmetric filters facilitates the independent add / drop or expression, or independent routing, of wavelength channels of a WDM signal. When applied in a combined and routed configuration, these techniques not only effectively double the number of ports, but they also reduce and in some cases eliminate any requirement to treat packet channels as a group within the OADM. Channels within the same group do not need to be added, dropped, or passed together, nor do they have to travel in the same direction. This increases the flexibility of routing and can expand the dimension of the OADM node. The techniques can also reduce crosstalk between adjacent channels and the need for guard bands, where crosstalk can create multipath interference if two channels are incorrectly connected. In some examples, for multiple cascaded hybrid OADMs, challenges such as compensating for dispersion and reducing the filter bandwidth are introduced. The OADM application techniques described herein can reduce dispersion and avoid reducing the filter bandwidth, allowing for more flexible routing and effectively doubling the dimension of the OADM node without requiring a doubling of the amount of hardware.

[0007] In one example, an optical add-drop multiplexer includes: a first input port configured to receive an input signal having a first wavelength channel, a second wavelength channel, and a third wavelength channel; a demultiplexer having a first filter configured to pass the first wavelength channel and the second wavelength channel and filter the third wavelength channel; a multiplexer having a second filter configured to pass the second wavelength channel and the third wavelength channel and filter the first wavelength channel; and a first output port configured to output an output signal including the second wavelength channel of the input signal.

[0008] In another example, an interconnection system includes: an optical fiber supporting the interconnection; and an optical add-drop multiplexer, including: a first input port configured to receive an input signal having a first wavelength channel, a second wavelength channel, and a third wavelength channel; a demultiplexer having a first filter, the first filter being configured to: pass the first wavelength channel and the second wavelength channel as a group, and filter the third wavelength channel; a multiplexer having a second filter configured to: pass the second wavelength channel and the third wavelength channel as a group, and filter the first wavelength channel; and a first output port configured to output, via the optical fiber, an output signal including the second wavelength channel of the input signal.

[0009] In another example, a controller includes: a processing circuit coupled to a memory, the processing circuit and the memory being configured to configure an optical add-drop multiplexer, the optical add-drop multiplexer including: a first input port configured to receive an input signal having a first wavelength channel, a second wavelength channel, and a third wavelength channel; a demultiplexer having a first filter, the first filter being configured to: pass the first wavelength channel and the second wavelength channel as a group, and filter the third wavelength channel; a multiplexer having a second filter configured to: pass the second wavelength channel and the third wavelength channel as a group, and filter the first wavelength channel; and a first output port configured to output an output signal including the second wavelength channel of the input signal.

[0010] Details of one or more examples of the techniques of the present invention are set forth in the accompanying drawings and the following description. Other features, objects, and advantages of the technique will be apparent from the description, the drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a block diagram showing an example interconnection system incorporating an optical add-drop multiplexer with an asymmetric filter according to one or more techniques of the present disclosure.

[0012] Figure 2 is a conceptual diagram showing an example symmetric filtering profile of one or more multiplexers and demultiplexers within an OADM.

[0013] Figure 3 is a conceptual diagram showing an OADM in a combined and routed configuration of a multiplexer and a demultiplexer having Figure 2 the symmetric filtering profile shown.

[0014] Figure 4 is a conceptual diagram showing in more detail an OADM in a combined and routed configuration of two multiplexers and demultiplexers, both having symmetric filtering profiles.

[0015] Figure 5 is a conceptual diagram showing an example asymmetric filtering profile of a multiplexer filter and a demultiplexer filter in an OADM according to one or more techniques of the present disclosure.

[0016] Figure 6 is a conceptual diagram showing an OADM in a combined and routed configuration with a multiplexer and a demultiplexer, the multiplexer and the demultiplexer having Figure 5 the asymmetric filtering profile shown in

[0017] Figure 7 is a more detailed conceptual diagram showing an OADM in a combined and routed configuration with a multiplexer and a demultiplexer, the multiplexer and the demultiplexer having an asymmetric filtering profile.

[0018] Figure 8 is a conceptual diagram showing another embodiment of an OADM 80 in a combined and routed configuration with a multiplexer having the same filtering profile that is asymmetric to the filtering profile of the demultiplexer according to one or more techniques of the present disclosure.

[0019] Figure 9 is a flowchart of an example operating mode of an OADM according to one or more techniques of the present disclosure.

[0020] Figure 10 is a block diagram showing an example of a computing device operating according to one or more techniques of the present disclosure.

[0021] Figure 11A is a conceptual diagram showing an example ROADM architecture.

[0022] Figure 11B is a conceptual diagram showing an example ROADM architecture.

[0023] Figure 11C is a conceptual diagram showing an example ROADM architecture.

[0024] In all the figures and the description, like reference numerals represent like elements. DETAILED DESCRIPTION

[0025] Figure 1FIG. 0 is a block diagram showing an example interconnect system 2 in accordance with one or more techniques of the present disclosure, the interconnect system 2 including an optical add-drop multiplexer having an asymmetric filter. The interconnect system 2 depicts interconnect facilities 8A-8B (collectively "interconnect facilities 8") operated by an interconnect system provider, and the interconnect facilities 8 connected by an optical network 10 may be configured for cross-connecting customer networks 6A-6B (collectively "customer networks 6"). In some cases, each customer network 6 may be associated with a different customer of the interconnect system provider. In some cases, the customer networks 6 are all associated with a single customer of the interconnect system provider. As used herein, the term "customer" of the interconnect system provider may refer to a lessee of the interconnect facilities 8 deployed by the interconnect system provider, whereby the customer leases space within the interconnect facilities 8 in order to co-locate with other lessees to increase efficiency on a stand-alone facility, as well as to interconnect network equipment with network equipment of other lessees within the interconnect facilities or on a campus to reduce latency / jitter, as well as to increase reliability, performance, and security relative to a transport network. In some cases, the interconnect system provider may be referred to as an interconnect facilities provider since they are typically the same entity.

[0026] Each interconnect facility 8 may represent different data centers geographically located within different major metropolitan areas (e.g., New York City, Dallas, etc.) to provide a resilient and independent interconnect service exchange through which customers in one major metropolitan area and customers in different major metropolitan areas may connect to respectively receive and provide services.

[0027] Within each interconnect facility 8, space may be divided and leased to customers in flexible increments in the form of cages (areas of common floorspace enclosed by fencing or other demarcation lines), cabinets, racks, suites (enclosed rooms that are not part of the common floorspace), or other spaces in which the customers may locate their network equipment to provide and / or receive network services to / from other customers co-located within the same interconnect facility 8 and / or to other customers co-located within another interconnect facility 8.

[0028] An optical network 10 including OADMs 12A - 12B (collectively referred to as "OADM 12") represents an optical and photonic switching infrastructure configured by a programmable network platform 3 to create fiber optic cross - connects 7, which fiber optic cross - connects 7 are respectively connected to customer networks 6A and customer network 6B co - located in interconnection facilities 8A and 8B. The optical network 10 may include fiber optic cables pre - installed between at least one distribution facility (or "distribution frame") of the customer network 6 and the interconnection facility 8, and may also include fiber optic cables pre - installed between multiple distribution facilities of the interconnection facility 8. The optical network 10 may also include programmable photonic switches located within the distribution facilities of the interconnection facility 8 and / or at the demarcation points of the customer spaces within the interconnection facility 8. Although described here as dynamically configurable, many optical networks 10 may be statically configured by network operators associated with interconnection facility providers, network service providers that manage various aspects of the optical network, or other entities.

[0029] The optical network 10 may include one or more optical network devices 4, such as photonic cross - connects (PXC), optical cross - connects (OXC), opto - electronic - based switches (OEO), or other types of devices that switch optical signals. Each optical network device 4 may route optical signals (light beams or λ) between fiber optic cables coupled to the switch. Each optical network device 4 may include a large port - count switch.

[0030] Although described with respect to two interconnection facilities 8A - 8B, the system 2 in various examples may include many additional interconnection facilities connected by the optical network 10 in a manner similar to that described for the interconnection facilities 8A - 8B.

[0031] The system 2 also includes a programmable network platform (PNP) 3, which is alternatively referred to herein as an "interconnection platform". The programmable network platform 3 may expose a software interface that defines methods, fields, and / or other software primitives by which an application 15 may call the PNP 3 to dynamically provide fiber optic cross - connects 7 between customer networks 6A, 6B. In this way, the PNP 3 provides programming capabilities to customers, operators, network service providers (NSPs), and / or the interconnection system provider itself to configure the optical switching fabric 10 to interconnect customer network 6A to customer network 6B with fiber optic cross - connects 7.

[0032] The programmable network platform 3 may represent an application executed within one or more data centers of the system 2, or alternatively, for example, an application executed off - site / remotely at the back - office or branch office of the interconnection system 2 provider. The programmable network platform 3 may be distributed, in whole or in part, across the data centers. As Figure 1As shown, the programmable network platform 3 can control the service provisioning for multiple different interconnection facilities. Alternatively or additionally, multiple individual instances of the programmable network platform 3 can control the service provisioning for corresponding multiple different interconnection facilities.

[0033] Application 15 represents at least one application that communicates with the PNP 3 to request and dynamically provide an interconnection between the interconnection facilities 8 of the customer networks 6A, 6B. Application 15 represents the client-side software for interfacing with the PNP 3 and can include a customer portal, a web browser, a customer application, an application of the interconnection system 2 provider that is only accessible to the operator of the interconnection facility 8, and a console such as a command-line interface or a graphical user interface. The users or clients of Application 15 can include, for example, enterprise customers, cloud service and content providers, carriers, network service providers (NSPs), and / or the interconnection system provider itself.

[0034] The application in Application 15 issues an interconnection request 11 to the PNP 3, and the interconnection request 11 specifies the parameters for the interconnection between the interconnection facilities 8 of the customer networks 6A and 6B. In response to receiving the interconnection request 11, the PNP 3 determines a path for the interconnection, such as an optical path through the optical network 10, and dynamically specifies a path for interconnection with the fiber cross-connect 7 in the optical network 10 to provide a fiber-based interconnection between the customer networks 6A, 6B, thereby satisfying the interconnection request 11.

[0035] The PNP 3 configures the devices of the optical network 10 by directly issuing configuration commands to the optical devices within the optical network 10 via the configuration interfaces of the elements, or indirectly issuing configuration commands to these elements via a software-defined networking (SDN) controller (such as an SDN controller) or other configuration elements that manage the optical devices on behalf of the PNP 3. For example, the OADM 12A with the asymmetric filter 13 can provide a configuration interface through which it receives configuration data from the PNP 3 or another controller to configure the add / drop of the OADM ports, configure the routing between the OADM 12As in multiple dimensions, configure the filter 13, and so on. Various configuration protocols can be used. In some cases, the PNP 3 can alternatively be referred to as an orchestrator because the PNP 3 orchestrates one or more SDN controllers to configure the OADM 12, the optical network device 4 (e.g., a photonic switch), and / or other elements of the optical network 10 to establish the fiber cross-connect 7.

[0036] The programmable network platform 3 configures the optical network device 4 to switch optical signals along optical paths, each optical path starting at an optical transmitter and terminating at an optical receiver, and each of the optical transmitter and the optical receiver being associated with one of the customer networks 6. In this way, the customer networks 6 can exchange frames and packets of services through dynamically provided fiber cross-connections. Alternatively, the optical path can be referred to as an optical route, λ, or optical transport network wavelength, or a composite DWDM optical signal. Example bandwidths of the optical paths for cross-connections can include, for example, 2.5 Gbps, 10 Gbps, 40 Gbps, 100 Gbps, 400 Gbps, or even multi-bit DWDM optical signals. The optical fiber can include multiple optical paths, that is, the optical fiber can transmit optical signals for multiple optical paths of different λs, for example. The optoelectronic-based switch can limit the switch applications according to the data rate, protocol, and format supported by the electronic components of the switch.

[0037] The fiber cross-connection 7 can represent a layer 0 (“L0”) connection, where the fiber cross-connection is the basis for the Open Systems Interconnection (OSI) model or the TCP / IP model for packet networking. In particular, the fiber cross-connection 7 can be located below the optical transport network (OTN) layer, which (usually in combination with the SONET / SDH layer) provides layer 1 (“L1”) connectivity between optical network devices 4 (such as wavelength division multiplexing (WDM) devices). For example, the fiber cross-connection 7 can represent one or more wavelengths (or “λs”) switched photonically by elements of an optical switching fabric to provide an optical path (or “optical route”) for optical signals exchanged between customer networks 6A, 6B associated with different customers / tenants of the interconnection system 2 provider. In this way, the optical network 10 is configured to provide non-blocking switching for the customers of the interconnection system 2 provider through high-speed fiber connections between the corresponding customer networks 6A, 6B, and in doing so, can provide reliable and low-latency communication between the customer networks 6A, 6B.

[0038] The customer networks 6A, 6B use the respective access links 9A, 9B to access the fiber cross-connection 7 to exchange data. In some cases, the access links 9A, 9B can represent gray links / optics, where the routers or switches of the customer networks 6A, 6B exchange gray (colorless) optical signals with coherent optics, and the coherent optics convert between the gray optical signals and optical signals of a specific wavelength (color) exchanged with the optical network devices of the optical network 10. In some examples, the pluggable coherent optics can be directly integrated into the optical network device (for example, the panel of the optical network device), which eliminates the need for short-range optical pluggable modules.

[0039] In some cases, the fiber optic cross-connect 7 can be located below the layer 2 ("L2") or layer 3 ("L3") services provided by the interconnect system 2 provider to interconnect customer networks 6A, 6B according to the L2 or L3 services. For example, the interconnect facility 8 can operate network service switches such as Ethernet switching, Internet switching, and / or cloud switching, and each of these can utilize the dynamically provided fiber optic cross-connect 7 to transmit L2 / L3 packet data between customer networks 6A, 6B.

[0040] The OADM 12 can be used to increase the network routing flexibility of the optical interconnect service. The OADM 12 will be described below with reference to OADM 12A. The OADM 12A includes a demultiplexer for separating the wavelengths of one or more input signals and a multiplexer for combining the wavelengths of the output signals. In some examples, the input signal of the OADM 12A can include the wavelengths of a WDM signal for implementing the wavelengths of the fiber optic cross-connect 7. Examples of the OADM 12A include, but are not limited to, configurations of reconfigurable optical add-drop multiplexers (ROADMs), such as Broadcast-and-Select, Route-and-select, and Combine-and-Route. One or more of these configurations can use the filter 13 to implement the multiplexer and demultiplexer of the OADM, or in combination with the multiplexer and demultiplexer of the OADM. Example components of the OADM using the filter 13 include, but are not limited to, wavelength selective switches, arrayed waveguide gratings, couplers, and splitters. Thus, the term "OADM" as used herein can refer to any of the foregoing architectures or any other configuration suitable for implementing the techniques described herein.

[0041] In some examples, the OADM 12A can be configured in a combined and routed configuration to combine different sets of two or more wavelength channels of one or more WDM signals into channel groups. Conventionally, in the combined and routed configuration, the filtering profile of the multiplexer is symmetric with the filtering profile of the demultiplexer. The filter of the multiplexer passes the wavelength channels within the group in a manner similar to the filter of the demultiplexer. With this symmetric filtering profile, the wavelength channels within the group must be added / dropped or routed together in the same direction / dimension. A single channel cannot be processed independently without the other channels in its group, thus limiting the routing flexibility. Additionally, the conventional use of the combined and routed configuration may result in crosstalk between adjacent channels and the need for guard bands. Furthermore, when an optical channel passes through an OADM node, only one optical path connection is required. If two paths with the same optical channel are incorrectly connected, multipath interference (MPI) may occur. Similarly, in some examples with multiple cascaded OADMs, challenges such as dispersion compensation and bandwidth filter narrowing are introduced. Therefore, it may be desirable for the OADM to be configured with independent channel processing for flexible routing while reducing: crosstalk, multipath interference, dispersion, and bandwidth narrowing.

[0042] According to the techniques described in the present invention, the OADM 12A includes a multiplexer and a demultiplexer, where the filtering profile of filter 13 and thus the center frequency is asymmetric. For example, the OADM 12A includes a demultiplexer having a filter that passes wavelength channels 1 and 2 as group A and filters wavelength channel 3. Channel 2 can be added / dropped, ejected, or routed by the OADM to a different dimension. The multiplexer of the OADM 12A has a filter that is asymmetrically configured with respect to the filter of the demultiplexer and applies the filter to the signal of channel 2. The filter of the multiplexer can be offset by one channel wavelength to, for example, pass channels 2 and 3 as group B. This multiplexer filters out channel 1, which allows the OADM 12A to be configured to add / drop, eject, or route channel 2 independently from channels 1 and 3. Additionally, the use of the asymmetric filter can reduce the impairment of bandwidth narrowing, thus allowing more OADMs to be deployed, reducing the need for guard bands, reducing chromatic dispersion (CD) ripple, ensuring tolerance to frequency errors, and removing multipath interference. Furthermore, the techniques of the present disclosure can effectively double the dimension of the OADM node without doubling the amount of hardware.

[0043] Figure 2It is a conceptual diagram showing an example symmetric filtering profile 20 of one or more multiplexers and demultiplexers within an OADM. In this example, the center frequencies and passbands of the multiplexer and demultiplexer filters are symmetric and include four filters configured with respective passbands, each passband passing two channels as a group. For example, an input signal entering the multiplexer or demultiplexer may contain 8 channels c1 - c8; the first passband p1 may pass channels c1 and c2 and filter channels c3 - c8. The number of channels is not limited to 8 and may be increased or decreased according to the allowed width of the spectrum. In some examples, the filtering center and bandwidth of the filters may be dynamically configured for additional network flexibility.

[0044] Figure 3 It is a conceptual diagram showing an OADM 32 in a combined and routed configuration of a multiplexer 36 and a demultiplexer 34 having Figure 2 the shown symmetric filtering profile. The demultiplexer 34 and the multiplexer 36 may be associated with the OADM 32 in a specific dimension.

[0045] The combined and routed configuration can be achieved by combining a color filter implemented as a multiplexer / demultiplexer with a colorless filter. In some examples, the color filter may include a wavelength selective switch (WSS) and / or an arrayed waveguide grating (AWG) 30, while the colorless filter may include a splitter 38 and / or a coupler 39. Each of the demultiplexer 34 and the multiplexer 36 may be implemented with a different WSS. The demultiplexer 34 may be a color filter having Figure 2 the shown four passbands p1 - p4. When receiving an input signal with 8 wavelength channels, the demultiplexer 34 may pass four groups of channels c1 / c2, c3 / c4, c5 / c6, and c7 / c8 to the corresponding splitters 38. Then, the splitter 38 may divide the channel groups into two identical channels (e.g., c1 / c2 is divided into c1 / c2 and c1 / c2 - shown by the upper and lower arms formed on the right side of each splitter 38). The splitter 38 doubles the number of ports of the OADM (e.g., from 4 to 8). The coupler 39 associated with the multiplexer 36 combines groups of two channels (i.e., combines the upper and lower arms) to be passed or filtered by one or more multiplexers 36 of the OADM 32. However, if the coupler 39 combines two channels among these channels having the same wavelength, multipath interference may occur. This limitation, along with other limitations (refer to Figure 4 discussed in further detail), results in the number of ports for the combined and routed configuration with symmetric filters not truly doubling.

[0046] Figure 4FIG. 0 is a conceptual diagram that more particularly illustrates an OADM in a combined and routed configuration having two multiplexers 36A and 36B and a demultiplexer 34, where the two multiplexers 36A and 36B and the demultiplexer 34 all have symmetric filtering profiles.

[0047] In Figure 4 the example, in addition to the first dimension associated with multiplexer 36A, multiplexer 36B is also associated with a second dimension of the OADM (i.e., a second direction of any channel to be routed). In this example, the limitations of a combined and routed configuration with symmetric filters are shown. For example, channels within a group must be added / dropped or pass through together, channels within a group must go in the same direction, and if two paths including channels within the same group are connected, multipath interference will occur.

[0048] For example, it may be desirable to route channel c5 in output group c5 / c6 to the first dimension (e.g., multiplexer 36A) and route channel c6 in output group c5 / c6 to the second dimension (e.g., multiplexer 36B), but this is not allowed for the symmetric filters of demultiplexer 34 / multiplexer 36 due to the limitation that channels within a group must go in the same direction (i.e., the same dimension). As another example, it may be desired to route channel c1 in output group c1 / c2 to multiplexer 36A, and “drop” channel c2 in output group c1 / c2, and then “add” channel c2 from the input line to the OADM and route it back to multiplexer 36A. This is not allowed due to the limitation that channels within a group must be added / dropped or pass through together. As another example, the paths of channels c3 and c4 in output group c3 / c4 may be wrongly connected. For example, an optical splitter creates two paths containing the same signal, the upper arm path contains channels c3 and c4, and the lower arm path contains channels c3 and c4. If both the upper arm and the lower arm are connected to multiplexer 36A, multipath interference may occur because the upper arm and the lower arm each have the same optical signal but different phases. In addition, in this case, depending on the phase, constructive interference or destructive interference may occur, and fluctuations may also occur due to unstable phases. Therefore, it is necessary to implement certain active procedures to prevent this problem from occurring. For example, a photodiode can be placed within the input port, and when a wrong connection occurs, an alert can be sent to the end user. In another example, a variable optical attenuator (VOA) can be placed in the optical path, and the VOA can be set to high attenuation to block the wrong connection. At least due to these limitations, the number of ports cannot be truly doubled (e.g., the lack of the ability to route channels separately in different dimensions may only allow the actual use of 4 ports instead of all 8). The techniques of the present invention can overcome these limitations.

[0049] In some examples, the only routing allowed for this configuration is when only one channel in a channel group is added / dropped or routed. For example, in the case where channel c3 in output group c3 / c4 is routed to multiplexer 36A, channel c4 of output group c3 / c4 must be routed to multiplexer 36A using the same connection. Channel c4 of output group c3 / c4 cannot be added / dropped or routed anywhere.

[0050] Figure 5 is a conceptual diagram showing an example asymmetric filtering profile of a multiplexer filter 52 and a demultiplexer filter 50 within an OADM in accordance with one or more techniques of the present disclosure. The multiplexer filter 52 may represent Figure 1 any filter 13 or the filter for multiplexer 66 described herein. The demultiplexer filter 50 may represent Figure 1 any filter 13 or the filter for demultiplexer 64 described herein. Figure 5 It is shown that the center frequencies and passbands pm1 - pm5 of the multiplexer filter 52 and the demultiplexer filter 50 are asymmetric. According to the techniques of the present disclosure, the term "asymmetric" in the present disclosure means that the configurations of the corresponding filters of the multiplexer and the demultiplexer are not mirror images of each other and do not have symmetry. Instead, the asymmetric filtering profiles of the multiplexer and the demultiplexer are offset from each other by at least one channel spacing (i.e., the wavelength range between channels).

[0051] For example, the center frequencies between the multiplexer filter 52 and the demultiplexer filter 50 are offset by one channel spacing, so the passbands pm1 - pm5 of the multiplexer 52 group different channels compared to the passbands pd1 - pd4 of the demultiplexer filter 50. In the illustrated example, the demultiplexer filter 50 includes four filters, and the respective passbands pd1 - pd4 thereof are configured such that two channels of each passband pass through as a group, and the multiplexer filter 52 includes five filters, and the respective passbands pm1 - pm5 thereof are configured such that one or two channels of each passband pass through as a group. Here, the input signal input to the multiplexer filter 52 or the demultiplexer filter 50 may include eight channels c1 - c8. The first passband pd1 of the demultiplexer may pass through channels c1 and c2 and filter channels c3 - c8; however, the first passband pm1 of the multiplexer filter 52 may only pass through channel c1 and filter channels c2 - c8. By combining the asymmetric filters 50 and 52 within the OADM, individual channels are allowed to be processed. The number of channels is not limited to eight and may be increased or decreased depending on how wide a spectrum is allowed and the number of channels supported by the OADM. In some examples, the filtering center and bandwidth of the filters may be dynamically configured for additional network flexibility. In addition, the number of channels grouped by the passbands and the channel spacing offset between the multiplexer filter 52 and the demultiplexer filter 50 may be increased or decreased.

[0052] Figure 6 is a conceptual diagram showing an OADM 60 in a combined and routed configuration with a multiplexer 66 and a demultiplexer 64 according to one or more techniques of the present disclosure, the multiplexer 66 and the demultiplexer 64 having Figure 5 the asymmetric filtering profile shown in. For example, the OADM 60 can represent a planar lightwave circuit (PLC) ROADM, a wavelength selective switch (WSS), or a wavelength cross-connect. The configuration can be implemented by combining a color filter implemented as a multiplexer / demultiplexer with a colorless filter. In some examples, the color filter can include a WSS and / or an AWG 62, while the colorless filter can include a splitter 68 and / or a coupler 69. For example, the demultiplexer 64 can be a color filter having Figure 5 the four passbands shown, and when receiving an input signal having 8 wavelength channels, can pass four groups of channels c1 / c2, c3 / c4, c5 / c6, and c7 / c8 to their respective splitters 68. In some examples, the splitter 68 can then split the channel groups into two identical channels (e.g., c1 / c2 can be split into c1 / c2 upper arm and c1 / c2 lower arm). The splitter 68 can double the number of ports (e.g., from 4 to 8). Additionally, in some examples, the coupler 69 can combine two channels to be passed or filtered by the multiplexer 66. However, different from the Figure 3 example shown, due to the characteristics of the asymmetric filter, multipath interference will not occur, and the OADM can process the channels within any group separately and independently, as further discussed in detail with reference to Figure 7 and Figure 8 below.

[0053] In some examples, the color filters can be cascaded and configured to filter specific frequency bands. These color filters can also include an asymmetric filtering profile to facilitate independent channel routing. For example, a color filter can be added after the demultiplexer 64 but before each splitter 68, and a color filter can be added after each coupler 69 but before the multiplexer 66. These filters can be configured to filter the wavelength range into specific bands. Adding color filters will further double the number of ports (e.g., from 8 to 16). In some examples, cascaded color filters having an asymmetric filtering profile can be added after the demultiplexer 64 but before each splitter 68, and cascaded color filters can be added after each coupler 69 but before the multiplexer 66. Adding each color filter in a cascaded configuration can also double the number of ports.

[0054] In some examples of the OADM 60, an optical switch can be placed before the splitter 68. This allows for the selection to configure the OADM 60 in a traditional OADM configuration or in theFigure 6 Configure the OADM 60 in the combined and routed configuration shown.

[0055] Figure 7 FIG. is a conceptual diagram more particularly showing the OADM 60 in a combined and routed configuration with a multiplexer 66 and a demultiplexer 64 according to one or more techniques of the present disclosure, the multiplexer 66 and the demultiplexer 64 having an asymmetric filtering profile. The OADM 60 in the combined and routed configuration of the present disclosure may include a drop output port referring to the output of the dropped signal from the OADM and an output port referring to the output of the signal after the multiplexer of the OADM.

[0056] The asymmetric filtering profile for the demultiplexer 64 and the multiplexer 66 addresses the limitations of combined and routed configurations with symmetric filters, as shown in reference Figure 4 FIG. The demultiplexer 64 filters the input channels into groups for replication and routing to the upper and lower arms by an optical splitter. Depending on the configuration of the OADM 60, the channels output by the optical splitter may be individually added, dropped, or routed to the multiplexer 66. In one example, all odd channels (c1, c3, c5, and c7) are individually routed directly to the multiplexer 66, and all even channels (c2, c4, c6, and c8) are dropped / added before being routed to the multiplexer 66. For example, channel c2 of the output group c1 / c2 is dropped, and then a new channel c2 signal from the input port is added to combine with channel c3 of the input group c2 / c3. After being combined by a coupler, the multiplexer 66 passes channels c2 and c3 of the group, but filters channels c1 and c4, thereby allowing the individual channels within the output group c1 / c2 to be added, dropped, or routed to the multiplexer 66. In some examples, when certain requirements of the free spectral range are met, the periodic characteristics of optical diffraction may be used such that channel c8 of the output group c7 / c8 can be dropped, and then channel c0 is added to combine with channel c1 of the output group c1 / c2, thereby forming the input c0 / c1. The multiplexer 66 passes the added channels c0 / c8 and channel c1, but filters channels c2 and c7. For example, if the free spectral range (FSR) is equal to n*(channel spacing), then channel n (n = 8 in the example of Figure 7 but not limited to n = 8) can be connected to the port 0 input of the OADM 60, where mλ0 = d(sinα + sinβ) = (m - 1)λ8, and λ iis the i-th channel. Here, m is the diffraction order, d is the grating period, α is the input angle, and β is the output angle. As shown, when their input angles are aligned, the output angles of λ0 and λ8 are the same. The difference between λ0 and λ8 is defined as the FSR. Again, this uses the periodic characteristics of light diffraction. The color filter utilizes light diffraction to demultiplex or multiplex signals with different frequencies. By using this property, the signal at λ8 can be routed to port 0 without loss.

[0057] Figure 8 is a conceptual diagram showing another embodiment of the OADM 80 in a combined and routed configuration with multiplexers 66A and 66B according to one or more techniques of the present disclosure, the multiplexers 66A and 66B having the same filtering profile that is asymmetric to the filtering profile of the demultiplexer 64.

[0058] Figure 8 An example of can be similar to Figure 4 an example, where the OADM 80 has a second dimension associated with the multiplexer 66B in this case, and a first dimension is associated with the multiplexer 66A. However, in reference Figure 8 the example, the asymmetric filter implemented solves the limitations of the symmetric filter configuration described in reference Figure 4 For example, Figure 8 shows that the channels within a group can be added / dropped or routed independently, the channels within a group can be routed to different dimensions, and this configuration can reduce and in some cases eliminate multipath interference.

[0059] For example, the OADM 80 can be configured to route channel c5 of the output group c5 / c6 to the first dimension 82 (e.g., multiplexer 66A) and route channel c6 of the output group c5 / c6 to the second dimension 84 (e.g., multiplexer 66B). Utilizing the asymmetric profiles of the demultiplexer 64 and the multiplexers 66A - 66B, channels within the same group can be routed to different dimensions (i.e., directions). In this example, the OADM 80 routes channel c5 of the output group c5 / c6 to the first dimension 82, where the multiplexer 66A passes channel c5 but filters channel c6 (for the c4 / c5 group at the multiplexer 66A). Additionally, the OADM 80 routes channel c6 of the output group c5 / c6 to the second dimension 84, where the multiplexer 66B passes channel c6 but filters channel c5 (for the c6 / c7 group at the multiplexer 66B). In some examples, the signal of channel c6 may be output through the output port of the second dimension.

[0060] The OADM 80 can be configured to route channel c1 of output group c1 / c2 to multiplexer 66A, demultiplex channel c2 of output group c1 / c2, and then add the new input signal of channel c2 as part of input group c2 / c3 to multiplexer 66A. Using the asymmetric profile of demultiplexer 64 and multiplexers 66A - 66B, channels within the same group can be added / demultiplexed or routed individually. As Figure 8 shown, the OADM 80 routes channel c1 of output group c1 / c2 to multiplexer 66A. Multiplexer 66A passes through channel c1 but filters channel c2 as part of input group c0 / c1. Additionally, after adding the new input signal, channel c2 of output group c1 / c2 is routed to multiplexer 66A. Multiplexer 66A passes through channel c2 but filters channel c1 as part of input group c2 / c3. In some examples, channel c2 of output group c1 / c2 can be added from a second input signal that passes through a second demultiplexer and is routed to multiplexer 66A.

[0061] The OADM 80 can be configured to route both c3 and c4 of output group c3 / c4 to multiplexer 66A. Using the asymmetric profile of demultiplexer 64 and multiplexers 66A - 66B, two channels within the same group from the demultiplexer can be routed in the same direction without any active process to prevent multipath interference because interfering channels will be filtered out. In this example, the OADM 80 routes channel c3 of output group c3 / c4 to multiplexer 66A. Multiplexer 66A passes through channel c3 but filters channel c4 as part of input group c2 / c3. Channel c4 of output group c3 / c4 is also routed to multiplexer 66A. Multiplexer 66A passes through channel c4 but filters channel c3 as part of input group c4 / c5.

[0062] By processing the channels of the group individually, this further reduces interference downstream, allowing each of the 8 ports to be utilized in practice. Thus, the OADM combination and routing configuration with asymmetric filters can provide a practical doubling of the number of ports.

[0063] The asymmetric filtering technique of the present disclosure can be applied to other scenarios. For example, the technique can be applied to superchannels and carrier groups. A superchannel is a group of individual channels combined with a minimum guard band and can be regarded as one channel. A carrier group is a group of individual channels with equal channel spacing. For example, 64 channels of 400GE - ZR (with a 75GHz channel spacing) can fit into the C band. The 64 channels can be divided into 8 carrier groups. Each carrier group contains 8 channels. The channel spacing is 600GHz, and the carrier group can be routed as one channel.

[0064] Figure 9is a flowchart of an example operating mode of an OADM according to one or more techniques of the present disclosure. Figure 9 The asymmetric multiplexer and demultiplexer filters 52 and 50 within the OADM 60 have been described respectively. However, Figure 9 the example techniques of

[0065] The OADM 60 receives configuration data to configure the demultiplexer 50 such that the demultiplexer includes a filter configured to pass the first and second channels as a group (92) but filter the third channel. The OADM 60 also receives configuration data to configure the multiplexer 52 of the OADM 60 such that the multiplexer 52 includes a filter configured to pass the second and third channels as a group (94) but filter the first channel.

[0066] The OADM 60 may receive an input signal including three wavelength channels (channel 1, channel 2, and channel 3). By applying the asymmetric filter, the OADM 60 outputs a signal including the second wavelength channel 2 of the input signal. The second wavelength channel 2 may be coupled as a group with the added channel 3 or the channel 3 received from a different dimension of the OADM 60 and filtered by the multiplexer 52.

[0067] Figure 10 is a block diagram of an example of a computing device operating according to one or more techniques of the present disclosure. Figure 10 A specific example of a server or other computing system 100 including one or more processors 102 for performing PNP 3 may be shown. Other examples of the computing system 100 may be used in other instances. Although shown as a stand-alone computing system 100 for purposes of example in Figure 10 the computing system may be any component or system including one or more processors or other suitable computing environment for executing software instructions and, for example, need not include Figure 10 one or more of the elements shown in

[0068] As in Figure 10As shown in the specific example, the computing system 100 includes one or more processors 102, one or more input devices 104, one or more communication units 106, one or more output devices 112, one or more storage devices 108, and a user interface (UI) device 110 and a communication unit 106. In one example, the computing system 100 also includes one or more application programs 122, a programmable network platform application program 124, and an operating system 116 that can be executed by the computing system 100. Each of the components 102, 104, 106, 108, 110, and 112 is coupled (physically, communicatively, and / or operably) for inter-component communication. In some examples, the communication channel 114 can include a system bus, a network connection, an inter-process communication data structure, or any other method for transferring data. As an example, the components 102, 104, 106, 108, 110, and 112 can be coupled through one or more communication channels 114.

[0069] In one example, the processor 102 is configured to implement functions and / or process instructions for execution within the computing system 100. For example, the processor 102 is capable of processing instructions stored in the storage device 108. Examples of the processor 102 can include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or equivalent discrete or integrated logic circuits.

[0070] One or more storage devices 108 can be configured to store information within the computing system 100 during operation. In some examples, the storage device 108 is described as a computer-readable storage medium. In some examples, the storage device 108 is temporary memory, which means that the primary purpose of the storage device 108 is not long-term storage. In some examples, the storage device 108 is described as volatile memory, which means that when the computer is turned off, the storage device 108 does not maintain the stored content. Examples of volatile memory include random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), and other forms of volatile memory known in the art. In some examples, the storage device 108 is used to store program instructions executed by the processor 102. In one example, the storage device 108 is used by software or an application program running on the computing system 100 to temporarily store information during program execution.

[0071] In some examples, the storage device 108 also includes one or more computer-readable storage media. The storage device 108 can be configured to store a larger amount of information than volatile memory. The storage device 108 can also be configured for long-term storage of information. In some examples, the storage device 108 includes non-volatile storage elements. Examples of such non-volatile storage elements include magnetic hard disks, optical disks, floppy disks, flash memory, or forms of electrically programmable memory (EPROM) or electrically erasable programmable (EEPROM) memory.

[0072] In some examples, the computing system 100 also includes one or more communication units 106. In one example, the computing system 100 utilizes the communication unit 106 to communicate with external devices via one or more networks such as one or more wired / wireless / mobile networks. The communication unit 106 can include network interface cards such as Ethernet cards, optical transceivers, radio frequency transceivers, or any other type of device capable of sending and receiving information. Other examples of such network interfaces can include 3G and WiFi radios. In some examples, the computing system 100 uses one or more communication units 106 to communicate with external devices.

[0073] In one example, the computing system 100 also includes one or more user interface devices 110. In some examples, the user interface device 110 is configured to receive input from the user via tactile, audio, or visual feedback. Examples of the user interface device 110 include presence-sensitive displays, mice, keyboards, voice response systems, cameras, microphones, or any other type of device for detecting commands from the user. In some examples, the presence-sensitive display includes a touch-sensitive screen.

[0074] The computing system 100 may also include one or more output devices 112. In some examples, the output device 112 is configured to provide output to the user using tactile, audio, or visual stimuli. In one example, the output device 112 includes a presence-sensitive display, a sound card, a video graphics adapter card, or any other type of device for converting signals into a suitable form understandable by humans or machines. Additional examples of the output device 112 include speakers, cathode ray tube (CRT) monitors, liquid crystal displays (LCDs), or any other type of device capable of generating an understandable output to the user.

[0075] The computing system 100 may include an operating system 116. In some examples, the operating system 116 controls the operation of the components of the computing system 100. For example, in one example, the operating system 116 facilitates communication between one or more application programs 122 and the programmable network platform application program 124 with the processor 102, the communication unit 106, the storage device 108, the input device 104, the user interface device 110, and the output device 112 to (e.g.) implement Figure 1 PNP 3 of

[0076] The application programs 122 and the programmable network platform application program 124 may also include program instructions and / or data executable by the computing system 100. Example programmable network platform application programs 124 executable by the computing system 100 may include any one or more of an orchestration engine module, an API gateway module, and a subsystem. The programmable network platform application program 124 includes an OADM configuration module 154.

[0077] The OADM configuration module 154 may include instructions for causing the computing system 100 to perform one or more operations and actions described in this disclosure regarding communicating with any one of the OADMs 60 or 80, such as configuring the asymmetric filters and routing within the OADM. The OADM configuration module 154 may communicate with the OADM using a device configuration protocol. Although described as a programmable network platform application, the OADM configuration module 154 may be a stand-alone application, service, library, or other software module.

[0078] Figure 11A is a conceptual diagram showing an example ROADM architecture. In this example, which is commonly referred to as broadcast and select, a broadcast passive 1×N optical splitter 160 is followed by a select N×1 WSS 162. The signal is broadcast (i.e., replicated) onto all of the optical splitter 160 output ports and then selectively passed or blocked at each of the select N×1 WSS 162 input ports.

[0079] Figure 11B is a conceptual diagram showing another example ROADM architecture. In this example, which is commonly referred to as route and select, a route 1×N WSS 164 is followed by a select N×1 WSS 166. The signal is selectively routed or blocked to the route 1×N WSS 164 output ports and then selectively passed or blocked at each of the select N×1 WSS 166 input ports.

[0080] Figure 11C is a conceptual diagram showing another example ROADM architecture. In this example, which is commonly referred to as drop and waste, an erbium-doped fiber amplifier (EDFA) 168 is applied to the optical mode of an add / drop ROADM module for coherent client signals.

[0081] The techniques described herein may be implemented in hardware, software, firmware, or any combination thereof. Various features described as modules, units, or components may be implemented together in an integrated logic device or separately as discrete but interoperable logic devices or other hardware devices. In some cases, the various features of an electronic circuit may be implemented as one or more integrated circuit devices, such as an integrated circuit chip or chipset.

[0082] If implemented in hardware, the present disclosure may relate to devices such as a processor or an integrated circuit device (e.g., an integrated circuit chip or chipset). Alternatively or additionally, if implemented in software or firmware, the techniques may be at least partially implemented by a computer-readable data storage medium comprising instructions that, when executed, cause a processor to perform one or more of the methods described above. For example, the computer-readable data storage medium may store such instructions for execution by the processor.

[0083] The computer-readable medium may form part of a computer program product, which may include packaging material. The computer-readable medium may include a computer data storage medium, such as random access memory (RAM), read only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read only memory (EEPROM), flash memory, magnetic or optical data storage media, and the like. In some examples, an article of manufacture may include one or more computer-readable storage media.

[0084] In some examples, the computer-readable storage medium may include a non-transitory medium. The term “non-transitory” may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In certain examples, the non-transitory storage medium may store data that can change over time (e.g., in RAM or a cache).

[0085] The code or instructions may be software and / or firmware executed by a processing circuit, which includes one or more processors, such as one or more digital signal processors (DSPs), general microprocessors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Thus, as used herein, the term “processor” may refer to any of the foregoing structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within software modules or hardware modules.

Claims

1. An optical add-drop multiplexer, comprising: A first input port configured to receive an input signal having a first wavelength channel, a second wavelength channel, and a third wavelength channel; A demultiplexer having a first filter, the first filter being configured to: Pass the first wavelength channel and the second wavelength channel, and Filter the third wavelength channel; A multiplexer having a second filter, the second filter being configured to: Pass the second wavelength channel and the third wavelength channel, and Filter the first wavelength channel; and A first output port configured to output an output signal including the second wavelength channel of the input signal.

2. The optical add-drop multiplexer according to claim 1, wherein the input signal includes a first input signal, and the optical add-drop multiplexer further includes: A second input port configured to receive a second input signal having a second wavelength channel.

3. The optical add-drop multiplexer according to claim 2, Wherein the demultiplexer has a third filter configured to pass the third wavelength channel, Wherein the optical add-drop multiplexer is configured to direct the second wavelength channel of the second input signal through the second filter of the multiplexer, and Wherein the output signal output by the first output port includes the second wavelength channel of the second input signal and the third wavelength channel of the first input signal.

4. The optical add-drop multiplexer according to claim 1, further includes: A second output port configured to output a second output signal, Wherein the output signal includes a first output signal, and Wherein the output signal output by the second output port includes the second wavelength channel of the input signal.

5. The optical add-drop multiplexer according to claim 4, Wherein the multiplexer includes a first multiplexer, and Wherein the second multiplexer has a wavelength filter configured to pass the second wavelength channel and the third wavelength channel.

6. The optical add-drop multiplexer according to claim 4, wherein the optical add-drop multiplexer is configured to direct the second wavelength channel of the first input signal to the second multiplexer.

7. The optical add-drop multiplexer according to claim 1, Wherein the input signal has a fourth wavelength channel, and Wherein the demultiplexer has a third filter configured to: Pass the third wavelength channel and the fourth wavelength channel, and Filter the first wavelength channel and the second wavelength channel.

8. The optical add-drop multiplexer according to any one of claims 1 to 7, wherein the filter channel center of the first filter of the demultiplexer and the multiplexer filter channel center of the second filter of the multiplexer are offset by one channel interval.

9. The optical add-drop multiplexer according to any one of claims 1 to 7, Wherein both the demultiplexer and the multiplexer are configured with filters to pass wavelength channel groups from multiple wavelength channels, and the wavelength channels within each group are from their respective bands.

10. The optical add-drop multiplexer according to any one of claims 1 to 7, wherein the demultiplexer is cascaded with one or more additional filters, and / or wherein the multiplexer is cascaded with one or more additional filters.

11. The optical add-drop multiplexer according to any one of claims 1 to 7, wherein the input signal has a third wavelength channel and a fourth wavelength channel; a demultiplexer having a third filter, the third filter being configured to: pass the third wavelength channel and the fourth wavelength channel, and a multiplexer having a fourth filter, the fourth filter being configured to: pass the second wavelength channel and the third wavelength channel as a group, and wherein the first output port is configured to output the output signal including the third wavelength channel of the input signal.

12. The optical add-drop multiplexer according to any one of claims 1 to 7, wherein the free spectral range is satisfied, and wherein channel n is connected to port 0.

13. The optical add-drop multiplexer according to any one of claims 1 to 7, wherein the demultiplexer includes a wavelength selection switch configured to receive configuration data to: dynamically adjust the channel center of the first filter, and dynamically adjust the channel bandwidth of the first filter.

14. The optical add-drop multiplexer according to any one of claims 1 to 7, further comprising: a wave selection switch and an arrayed waveguide grating implementing at least one of the first filter or the second filter.

15. An interconnection system, comprising: an optical fiber supporting interconnection; and an optical add-drop multiplexer, comprising: a first input port configured to receive an input signal having a first wavelength channel, a second wavelength channel, and a third wavelength channel; a demultiplexer having a first filter, the first filter being configured to: pass the first wavelength channel and the second wavelength channel as a group, and filter the third wavelength channel; a multiplexer having a second filter, the second filter being configured to: pass the second wavelength channel and the third wavelength channel as a group, and filter the first wavelength channel; and a first output port configured to output, via the optical fiber, an output signal including the second wavelength channel of the input signal.

16. The interconnection system according to claim 15, wherein the first input port is connected to a customer network located in a data center.

17. The interconnection system according to any one of claims 15 to 16, further comprising: a controller including processing circuitry and configured to output configuration data to configure the first filter of the demultiplexer and the second filter of the multiplexer.

18. A controller, comprising: processing circuitry coupled to a memory, the processing circuitry and the memory being configured to configure an optical add-drop multiplexer, the optical add-drop multiplexer including: a first input port configured to receive an input signal having a first wavelength channel, a second wavelength channel, and a third wavelength channel; a demultiplexer having a first filter, the first filter being configured to: pass the first wavelength channel and the second wavelength channel as a group, and filter the third wavelength channel; A multiplexer with a second filter, the second filter being configured to: pass the second wavelength channel and the third wavelength channel as a group, and filter the first wavelength channel; and a first output port configured to output an output signal including the second wavelength channel of the input signal.

19. The controller according to claim 18, wherein the processing circuit and the memory are configured to output configuration data to configure the first filter of the demultiplexer and the second filter of the multiplexer.

20. The controller according to any one of claims 18 to 19, wherein the processing circuit and the memory are configured to output configuration data to configure the optical add-drop multiplexer to direct the second wavelength channel of the first input signal to the second multiplexer of the optical add-drop multiplexer.

21. A method, comprising: configuring an optical add-drop multiplexer as the optical add-drop multiplexer according to any one of claims 1 to 14.

22. A computer-readable storage medium encoded with instructions for causing one or more processors to be configured to configure an optical add-drop multiplexer as the optical add-drop multiplexer according to any one of claims 1 to 14.

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