Polarization multiplexed optical bidirectional link using symmetric hardware

Abstract

One embodiment includes an optical communication channel, a first network device connected to a first end of the optical communication channel, and a second network device connected to a second end of the optical communication channel. At least one of the first network device or the second network device performs polarization tracking of packets of bi-directional communications over the optical communication channel that are polarization multiplexed.

Description

[0001] Cross-reference to related applications This application claims priority to U.S. Patent Application No. 18 / 946,830, filed November 13, 2024, entitled "POLARIZATION-MULTIPLEXED OPTICAL BI-DIRECTIONAL LINKS USING SYMMETRICAL HARDWARE", which claims priority to U.S. Provisional Patent Application No. 63 / 640,818, filed April 30, 2024, entitled "POLARIZATION-MUXEDOPTICAL BI-DIRECTIONAL LINKS USING SYMMETRICAL HARDWARE". The subject matter of these related applications is incorporated herein by reference. Technical Field

[0002] The embodiments of this disclosure generally relate to computer networking and optical communication networks, and more specifically, to techniques for polarization-multiplexed optical bidirectional links using symmetrical hardware. Background Technology

[0003] Fiber optic networks provide fast and generally reliable data transmission between networked devices. In a fiber optic network, optical transceivers and waveguides (e.g., optical fibers) can be used to send and / or receive optical signals modulated using data. A transceiver is a device that can send and / or receive optical signals that are transmitted through a waveguide, for example, to or from another transceiver. A waveguide can act as a conduit through which optical signals pass. The optical signal transmitted from one transceiver to another via a waveguide may be affected by the properties of the waveguide.

[0004] One drawback of fiber optic networks is that they often employ a one-way communication paradigm. For example, a one-way communication paradigm can include a fiber optic network that transmits signals in a single direction, from the transmitting transceiver to the receiving transceiver, via waveguides. This one-way communication paradigm can limit the number of connections to network devices based on the physical size of the hardware. Furthermore, in the case of a one-way communication paradigm, the waveguides can introduce variations in all aspects of the signal passing through them, making bidirectional communication between the two devices difficult to maintain.

[0005] Some fiber optic networks use bidirectional communication where the fiber optic network transmits signals in both directions—to and from each transceiver connected to the waveguide. However, conventional bidirectional optical systems require two different optical carriers (such as two different wavelengths or colors of light), asymmetric hardware such as different hardware at each end of the waveguide (e.g., a transceiver at one end of the waveguide uses one color of light to transmit signals, while the other transceiver uses another color), and / or double the bandwidth of each communication channel. Some conventional bidirectional optical systems use different waveguides or communication paths than unidirectional systems and also require carrier collision avoidance mechanisms. For example, carrier collision avoidance mechanisms prevent simultaneous transmissions from two transceivers, ensuring that one transmission does not interfere with the other. Additionally, wavelength-based bidirectional systems can make it difficult to connect the waveguide to each transceiver because conventional receivers may not be symmetrical or identical on both sides of the link. A port or module using a specific wavelength or color cannot be connected to another module using the same color. Furthermore, the bandwidth must be evenly distributed between inbound and outbound communication. As a result, conventional bidirectional fiber optic networks are very complex to install and implement.

[0006] As explained above, what is needed in this field is a more efficient fiber optic network. Summary of the Invention

[0007] One embodiment of this disclosure illustrates a method for electro-optical implementation of polarization-multiplexed optical bidirectional communication. The method includes: sending a first message including tracking data to a second network device. The method also includes: receiving a second message including the same or different tracking data from the second network device. Furthermore, the method includes: setting a polarization tracking mode of the first network device according to a mutual polarization tracking strategy of the first and second network devices. The first polarization tracking mode and the second polarization tracking mode of the second network device are set based on the mutual polarization tracking strategy, such that at least one of the first or second network devices performs polarization tracking for bidirectional communication via a polarization-multiplexed optical communication channel.

[0008] Other embodiments of this disclosure include, but are not limited to, one or more computer-readable media including instructions for performing steps. The steps include: a first network device sending a first message including tracking data to a second network device via an optical communication channel; the first network device receiving a second message including tracking; and setting a first polarization tracking mode for the first network device. The first polarization tracking mode and a second polarization tracking mode of the second device are configured such that either the first network device or a single device in the second network device performs polarization tracking for bidirectional communication via polarization multiplexing of the optical communication channel. Further embodiments include one or more computing systems for performing one or more aspects of the disclosed technology.

[0009] Further embodiments of this disclosure illustrate a system for bidirectional communication using polarization multiplexing. The system includes an optical communication channel, a first network device connected to a first end of the optical communication channel, and a second network device connected to a second end of the optical communication channel. At least one of the first or second network devices performs polarization tracking of multiple packets for bidirectional communication using polarization multiplexing according to a mutual polarization tracking rule between the first and second network devices.

[0010] The disclosed technology offers at least one technical advantage over existing technologies in that it simplifies hardware deployment and integration while providing additional edge bandwidth density. The disclosed technology enables communication paths, such as fiber optic cables, to be connected to any type of port. The disclosed technology also achieves these benefits without sacrificing switch base, thereby reducing fiber optic costs and optical packaging. Furthermore, the disclosed technology allows for asymmetric allocation of channel capacity for inbound and outbound communications. These technical advantages represent one or more technical improvements over existing methods. Attached Figure Description

[0011] To gain a more detailed understanding of the above-described features of the invention, reference can be made to a more specific description of various embodiments having the inventive concept briefly outlined above, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only typical embodiments of the inventive concept and should therefore not be construed as limiting the scope in any way, and that other equivalent embodiments exist.

[0012] Figure 1 A block diagram of a communication system configured to implement one or more aspects of various embodiments is shown; Figure 2 This illustrates various embodiments. Figure 1 A block diagram of an exemplary network device; Figure 3 The following are illustrations of various embodiments for use. Figure 1 An exemplary recovery of polarization multiplexing in network devices; Figure 4 Various embodiments are shown. Figure 1 An exemplary visualization of matrix operations in a communication system; Figure 5 It is according to various embodiments for setting for Figure 1 A flowchart of the method steps for tracking network devices; and Figure 6 It is for configuration according to various embodiments Figure 1 A flowchart of the method steps for a communication system. Detailed Implementation

[0013] In the following description, numerous specific details are set forth to provide a more thorough understanding of the various embodiments. However, it will be apparent to those skilled in the art that the inventive concepts can be practiced without one or more of these specific details.

[0014] General Overview Embodiments of this disclosure provide techniques for implementing polarization-multiplexed optical bidirectional links using symmetric hardware. Some embodiments of this disclosure include a system for polarization-multiplexed bidirectional communication, the system including an optical communication channel, a first network device connected to a first end of the optical communication channel, and a second network device connected to a second end of the optical communication channel. The first network device and / or the second network device perform polarization tracking of packets in polarization-multiplexed bidirectional communication via the optical communication channel.

[0015] In some embodiments, network devices exchange identifiers using techniques that facilitate polarization tracking based on a mutual polarization tracking strategy or rule set. Whether polarization tracking is performed using two network devices or a single network device, the system enables the use of symmetric hardware. In some embodiments, the symmetric hardware includes two network devices communicating via a communication path such as an optical fiber. The network devices exchange identifiers using techniques that facilitate polarization tracking and negotiate which network device maintains polarization tracking. Tracking data enables the network devices to perform polarization tracking, and the identifier prevents the tracking of reflected signals. The identifier can also be used as part of a mutual polarization tracking strategy. More specifically, a first network device sends a first message to a second network device, the first message including the first network device's tracking data and a first identifier or other data. The first network device receives a second message from the second network device, the second message including the same or different tracking data and a second identifier of the second network device. In some examples, the first network device sets or configures a polarization tracking mode to a leader mode where polarization tracking is relaxed or disabled, or a follower mode where polarization tracking is enabled. In various embodiments, the polarization tracking mode is selected based on the relationship between the first and second identifiers, or through random or pseudo-random selection. In another embodiment, a mutual polarization tracking strategy enables two network devices to perform polarization tracking.

[0016] The mechanisms disclosed in this paper have many real-world applications. For example, polarization-multiplexed optical bidirectional links or network devices can be used for communication within a single device, between components in a data center, and over a wide area network. Polarization-multiplexed optical bidirectional network devices can be deployed alongside new fiber optic installations. As another example, polarization-multiplexed optical bidirectional network devices can be used to improve or upgrade existing optical networks.

[0017] The examples above are by no means intended to be limiting. As those skilled in the art will understand, in general, polarization-multiplexed optical bidirectional network devices can be implemented in any suitable system.

[0018] System Overview Figure 1 A block diagram of a symmetrical bidirectional polarization multiplexing communication system 100 configured to implement one or more aspects of at least one embodiment is shown. As illustrated, the polarization multiplexing communication system 100 includes, but is not limited to, one or more network devices 104a and 104b (network device 104) and a communication network 108. Network device 104a includes, but is not limited to, a polarization tracking component 110a, an identifier 112a, and tracking data 114. Network device 104b includes, but is not limited to, a polarization tracking component 110b, an identifier 112b, and tracking data 114. Network device 104 uses the communication network 108 to transmit one or more packets 120 and other data. Packets 120 include, but are not limited to, an identifier 112, payload data 122, and tracking data 114.

[0019] Each of network devices 104 refers to a device such as a network switch (e.g., an Ethernet switch), a network interface controller (NIC), or any other suitable device for controlling the flow of data between devices connected to the bidirectional communication network 108. Each of network devices 104 can be connected to one or more personal computers (PCs), laptops, tablets, smartphones, servers, server clusters, etc. In a specific but non-limiting example, network device 104 includes multiple network devices, such as a group of switches in a fixed configuration or a modular configuration. Network device 104 may include sub-components of switches, NICs, or any other suitable devices.

[0020] Examples of communication networks 108 used for connecting network devices 104 include, but are not limited to, Internet Protocol (IP) networks, Ethernet networks, InfiniBand (IB) networks, Fibre Channel networks, the Internet, cellular communication networks, wireless communication networks, combinations thereof (e.g., Fibre Channel over Ethernet), variations thereof, etc. In a specific but non-limiting example, at least a portion of the communication network 108 uses optical communication paths or optical signals in waveguides to enable communication between network devices 104. The communication network 108 may include single-mode fiber or another type of communication path that imparts random birefringence to signals such as optical signals. As a result, digital communication through the communication network 108 can be associated with a transfer matrix that affects the digital communication. Network devices 104 may identify the transfer matrix of the communication network 108. In some embodiments, network devices 104 use bits corresponding to beacons to identify the transfer matrix of the communication network 108.

[0021] Although not explicitly shown, network devices 104a and / or 104b may include storage devices and / or processing circuitry for performing computational tasks, such as tasks related to controlling data flow within each of network devices 104, data flow on communication network 108, and / or communication with other devices (not shown). Such processing circuitry may include software, hardware, or a combination thereof. For example, the processing circuitry may include a memory containing executable instructions and a processor (e.g., a microprocessor) that executes the instructions in the memory. The memory may correspond to any suitable type of memory device or collection of memory devices configured to store instructions. Non-limiting examples of suitable memory devices that may be used include flash memory, random access memory (RAM), read-only memory (ROM), variations thereof, combinations thereof, etc. In some embodiments, the memory and processor may be integrated into a common device (e.g., a microprocessor may include integrated memory). Additionally or alternatively, the processing circuitry may include hardware such as application-specific integrated circuits (ASICs). Other non-limiting examples of processing circuitry systems include integrated circuit (IC) chips, central processing units (CPUs), general-purpose processing units (GPUs), microprocessors, field-programmable gate arrays (FPGAs), logic gates or collections of transistors, resistors, capacitors, inductors, diodes, etc. Some or all of the processing circuitry system may be located on a printed circuit board (PCB) or an assembly of PCBs.

[0022] It should be understood that any suitable type of electronic component or collection of electronic components may be suitably included in the processing circuitry system. Furthermore, although not explicitly shown, it should be understood that network device 104 includes one or more communication interfaces for facilitating wired and / or wireless communication between itself and with other components of system 100 (not shown). Although not explicitly shown, each of network devices 104 may include one or more transmitters that transmit optical signals through communication network 108, and one or more receivers that receive optical signals through communication network 108. Although not explicitly shown, it should be understood that network devices 104a and 104b may include other processing devices, storage devices, and / or communication interfaces typically associated with computing tasks such as sending and receiving data.

[0023] Identifier 112a includes a set of bits defining unique or device-specific data stored by network device 104a. Identifier 112a identifies network device 104a from another network device 104, polarization tracking component 110a from another tracking component, manufacturing date and time, or another type of data. Similarly, identifier 112b includes a set of bits defining a unique identifier stored by network device 104b. Identifier 112 may include or represent bits of numerical or other comparable data instructing network device 104 (e.g., using polarization tracking component 110) to evaluate or compare it to determine which of a pair of network devices 104 operates in leader mode and which operates in follower mode (discussed in more detail below).

[0024] Tracking data 114 can be identical for all network devices 104, such that the tracking data 114 stored in network device 104a is the same as the tracking data 114 stored in network device 104b. In some embodiments, tracking data 114 includes pseudo-random binary sequence (PRBS) bits, or another type of bit pattern or number sequence. In some embodiments, tracking data 114 may include a beacon tracking pattern or an acknowledgment tracking pattern as a different pattern from the beacon tracking pattern. As a result, polarization tracking component 110 is able to identify beacons using the beacon tracking pattern and acknowledgments using the acknowledgment tracking pattern. In some other embodiments, a single tracking pattern may be used, and payload data 122 includes an indication of whether the data is a beacon or an acknowledgment. Payload data 122 may also include any messages or data transmitted by network device 104 in packet 120.

[0025] In operation, network devices 104a and 104b cooperate to enable polarization-multiplexed symmetrical bidirectional communication over communication network 108. Network devices 104a and 104b perform an auto-negotiation technique that uses polarization tracking component 110, including polarization tracking components 110a and 110b, to identify the leader and follower devices. In the auto-negotiation technique, each of the polarization tracking components 110 sends a beacon and responds with an acknowledgment. The beacon includes tracking data 114, such as a sequence of bits identifiable by all network devices 104. The beacon also includes an identifier bit corresponding to an identifier 112. In some embodiments, the beacon also includes message bits of a message transmitted between network devices 104a and 104b. The auto-negotiation technique also includes each of the polarization tracking components 110a and 110b sending an acknowledgment in response to detecting a beacon. The acknowledgment may also include tracking data 114. In some embodiments, the acknowledgment also includes the identifier 112 of the responding network device 104.

[0026] In one example, polarization tracking component 110a sends a packet 120 corresponding to a first beacon, including at least tracking data 114 and an identifier 112a of network device 104a. Polarization tracking component 110b detects the first beacon and responds by sending a first acknowledgment including the acknowledgment of tracking data 114 and the identifier 112b of network device 104b. Polarization tracking component 110a establishes that tracking is correctly configured and / or successful based on the acknowledgment. Polarization tracking component 110a identifies the acknowledgment based on tracking data 114 and / or payload data 122 indicating that the message is acknowledged. Polarization tracking component 110a detects the first acknowledgment and sets a polarization tracking configuration for operation in bootstrap mode based on a comparison or relationship between (e.g., local) identifier 112a and (e.g., remote) identifier 112b. For example, in some embodiments, the local network device operates in bootstrap mode if the local identifier 112a is greater than (or, in an alternative example, less than) the remote identifier 112b. Conversely, if the local identifier 112a is less than the remote identifier 112b, then network device 104a operates in follower mode. Network device 104a can use any predetermined relationship between identifiers 112a and 112b to determine which device operates in leader mode and which device operates in follower mode.

[0027] In this example, network device 104a can be a leader device operating in leader mode. In leader mode, network device 104a stops polarization tracking and sets the local transformation matrix of polarization tracking component 110a to an identity matrix (or another fixed matrix). In the case of an identity matrix, the matrix does not affect the signals and / or data received through communication network 108. In leader mode, network device 104a does not modify the local transformation matrix and does not detect or identify the transition matrix. As a result, network device 104a and the entire polarization multiplexing communication system 100 use less energy than prior art. Two network devices 104 (e.g., polarization tracking component 110) may perform polarization tracking and adjustment. However, system 100 saves energy by negotiating the leader and follower so that only the follower network device 104 tracks and adjusts the local transformation matrix.

[0028] The polarization multiplexing communication system 100 is a symmetric system using symmetric hardware and symmetric programming (e.g., executable code) for each network device 104. Identifier 112 and / or tracking data 114 can be different. As a result, the polarization tracking component 110b of network device 104b operates similarly to the polarization tracking component 110a of network device 104a. Continuing this example, polarization tracking component 110b sends a packet 120 corresponding to a second beacon, including at least beacon tracking data 114 and the identifier 112b of network device 104b. Polarization tracking component 110a detects the second beacon and responds by sending a second acknowledgment including the acknowledgment tracking data 114 and the identifier 112a of network device 104a. Polarization tracking component 110b detects the second acknowledgment and sets the polarization tracking configuration to follower (or leader) based on a comparison or relationship between the local identifier 112b and the remote identifier 112a.

[0029] In this example, network device 104b can be a follower device operating in follower mode. In follower mode, network device 104b uses polarization tracking component 110b to maintain active polarization tracking. Network device 104b changes or updates its local transformation matrix until the tracking data 114 identified in the received packet 120 matches a local copy of the tracking data 114. Network device 104b also establishes that the tracking data 114 identified in packet 120 originates from remote network device 104 based on identifier 112. For example, if identifier 112 in packet 120 is different from local identifier 112, then network device 104b identifies packet 120 as originating from remote network device 104. Otherwise, if identifier 112 in packet 120 is the same as local identifier 112, then packet 120 is a reflection originating from local network device 104. Establishing that packet 120 originates from remote network device 104 ensures that network device 104b is performing polarization tracking on remote network device 104a, rather than a reflection. In practice, polarization tracking causes network device 104b to set its local transformation matrix as a matrix that corrects the transfer matrix of communication network 108 and / or the remote transformation matrix of network device 104a. In the example where the remote transformation matrix of network device 104a is an identity matrix, the local transformation matrix of network device 104b is the inverse of the transfer matrix of communication network 108. As a result, network device 104b and / or network device 104a can recognize the transfer matrix of communication network 108. The transfer matrix of communication network 108 may change over time based on temperature and other factors. Network device 104b maintains active polarization tracking and updates its local transformation matrix to correct changes to the transfer matrix of communication network 108.

[0030] Figure 2 This is a block diagram illustrating an exemplary network device 104 according to various embodiments. Network device 104 may include any type of device, including but not limited to one or more of a switch, router, network hub, modem, repeater, controller system, server, server platform, desktop machine, laptop machine, handheld / mobile device, digital kiosk, in-vehicle infotainment system, and / or distributed computing system. In some embodiments, network device 104 is an optical networking machine operating in a data center or cloud computing environment that provides scalable computing resources as a service. Network device 104 includes, but is not limited to, a processor 202, a network interface 204, and memory 206. Network interface 204 includes a polarization tracking component 110, an identifier 112, and tracking data 114.

[0031] Processor 202 includes any technically feasible processing device configured to process data and execute program instructions. For example, processor 202 may include an application-specific integrated circuit (ASIC). Other non-limiting examples of processing circuitry systems include integrated circuit (IC) chips, central processing units (CPUs), general-purpose processing units (GPUs), microprocessors, field-programmable gate arrays (FPGAs), logic gates or collections of transistors, resistors, capacitors, inductors, diodes, etc. Some or all of the processing circuitry system may be disposed on a printed circuit board (PCB) or an assembly of PCBs.

[0032] Memory 206 may correspond to any suitable type of memory device or collection of memory devices configured to store instructions. Non-limiting examples of suitable memory devices that may be used include flash memory, random access memory (RAM), read-only memory (ROM), variations thereof, combinations thereof, etc. In some embodiments, the memory and processor may be integrated into a common device (e.g., a microprocessor may include integrated memory). Additionally or alternatively, the processing circuitry may include hardware such as application-specific integrated circuits (ASICs). Other non-limiting examples of processing circuitry include integrated circuit (IC) chips, central processing units (CPUs), general-purpose processing units (GPUs), microprocessors, field-programmable gate arrays (FPGAs), logic gates or collections of transistors, resistors, capacitors, inductors, diodes, etc. Some or all of the processing circuitry may be disposed on a printed circuit board (PCB) or an assembly of PCBs.

[0033] Network interface 204 may correspond to any suitable type of networking component that facilitates wired and / or wireless communication between itself and other components of the polarization multiplexing communication system 100 (not shown). Network interface 204 may include one or more transmitters that transmit optical signals through communication network 108, and one or more receivers that receive optical signals through communication network 108. It should be understood that network device 104 may include any processor 202, memory 206, and / or network interface 204 typically associated with computational tasks such as sending and receiving data.

[0034] It should be understood that the network device 104 shown herein is illustrative, and variations and modifications are possible. The connection topology can be modified as needed. In some embodiments, Figure 2 One or more components shown may be absent. Finally, in some embodiments, Figure 2 One or more components shown can be implemented as virtualized resources in a virtual computing environment, such as a cloud computing environment.

[0035] Bidirectional communication using polarization multiplexing Figure 3 The following are illustrations of various embodiments for use. Figure 1 An exemplary restoration of polarization multiplexing in network device 104. Restoration device 300 communicatively connects components of network device 104 to communication network 108. Restoration device 300 includes a bidirectional communication port 306 or other connections to communication network 108. Restoration device 300 includes, but is not limited to, a sub-component including a feedback photodetector.

[0036] The recovery device 300 uses a randomly polarized optical signal to achieve bidirectional communication via a communication network 108. This randomly polarized optical signal comprises two components with two different polarizations (e.g., transverse electric (TE) and transverse magnetic (TM) polarization). Polarization can include two degrees of freedom: relative phase and relative power. The polarized optical signal can include two signal components, and each signal component can include a different phase and / or different power relative to the other signal component, resulting in two orthogonal polarizations or otherwise different polarizations.

[0037] Recovery device 300 identifies an optical signal at bidirectional communication port 306, divides the optical signal into two components (e.g., a local signal component and a remote signal component), and provides the received signal component or the remote signal component with the same polarization (e.g., TE) as the local signal component to be transmitted. Recovery device 300 may include a polarization rotator beamsplitter assembly for dividing and rotating the optical signal.

[0038] Example embodiments are shown and described regarding TE and TM polarization states; however, these example embodiments are not limited thereto and can be applied to other polarization states (e.g., right-hand circular polarization, left-hand circular polarization, linear +45° polarization, linear -45° polarization, etc.). On the network device 104 side of recovery device 300, recovery device 300 identifies the transmitted signal (e.g., corresponding to the local component of the optical signal) at the transmit port and provides the received signal (e.g., corresponding to the remote component of the optical signal) at the receive port. An optical fiber of communication network 108 is connected to bidirectional communication port 306.

[0039] Recovery device 300 and / or polarization tracking component 110 perform polarization tracking to maximize the output power from recovery device 300 and / or minimize the feedback power to the feedback photodetector (PD) of recovery device 300. Recovery device 300 may include polarization tracking component 110, or may be a standalone device cooperating with polarization tracking component 110. Output power from recovery device 300 may include the power of signals supplied to receiving components and / or other components of network device 104. In some embodiments, network device 104 (e.g., tracking component 110 and / or recovery device 300) uses a gradient descent algorithm or operation to minimize feedback power and / or maximize output power.

[0040] Another aspect of polarization restoration is described in U.S. Patent No. 11,588,549. The subject matter of U.S. Patent No. 11,588,549 is incorporated herein by reference in its entirety.

[0041] Figure 4 Various embodiments are shown. Figure 1 An exemplary visualization of matrix operations in the communication system 100 is provided. As shown, the polarization multiplexing communication system 100 includes, but is not limited to, network device 104a, network device 104b, and communication network 108. Network device 104a includes, but is not limited to, polarization tracking component 110a, identifier 112a, and tracking data 114. Network device 104b includes, but is not limited to, polarization tracking component 110b, identifier 112b, and tracking data 114.

[0042] The polarization tracking component 110a of network device 104a will transform the matrix A 1 This is applied to digital communication transmitted (and / or received) via communication network 108. Network device 104a may include a transformation matrix. A 2 A component applied to digital communications transmitted and / or received via a communication network 108. The communication network 108 itself may be connected to an optical fiber transfer matrix that influences digital communications transmitted via the communication network 108. F Relatedly, each of network devices 104a and 104 can modify its local transformation matrix using data in packets 120 transmitted via communication network 108 to take into account the fiber transfer matrix F and / or the remote transformation matrix of another network device 104. Polarization tracking in this context involves modifying the local transformation matrix over time to account for changes in conditional aspects, as illustrated by the effective transfer matrix F of communication network 108 and / or the remote transformation matrix of another network device 104.

[0043] In an ideal or target scenario, the transition matrix of communication network 108 F It is a permutation matrix as shown in equation (1) (e.g., row inverse matrix, column inverse matrix, inverse matrix, backward identity matrix or standard involutional permutation matrix).

[0044] (1) A 1 and A 2 It is the identity matrix shown in equations (2) and (3) (e.g., I Alternatively, in some embodiments, A 1 and A 2It can be a constant instead of an identity matrix.

[0045] (2) (3) Therefore, in the target scenario, equation (4) represents the communication system 100.

[0046] (4) And because of the identity matrix I Any matrix multiplied is the original matrix, so regardless of the order of multiplication, equation (5) can represent the target for communication system 100.

[0047] (5) However, in real-world scenarios, a single-mode fiber or another single-mode fiber introduces a variation into the communication network 108, making the transfer matrix F unknown. In an example where network device 104a operates in follower mode, polarization tracking component 110a uses a transfer matrix that is specific to any fiber. F set up A 1 To maintain polarization tracking. Within this, network device 104b is locked or set. A 2 As an example of an identity matrix, the polarization tracking component 110a is set according to equation (6). A 1 .

[0048] (6) However, because the polarization tracking component 110a uses a modified A 1 The feedback-based method dynamically sets the local transformation matrix. A 1 Until the tracking data 114 identified in the received packet 120 matches a local copy of the tracking data 114, the polarization tracking component 110a is able to concurrently correct any arbitrary fiber transfer matrix F and any arbitrary transformation matrix locked to a set of static values ​​by the network device 104b, as indicated by equation (7).

[0049] (7) Equations (6) and (7) are in which the polarization tracking component 110a of the network device 104a is configured by... A 1 This is to maintain the expression in the scenario of polarization tracking. Equations (6) and (7) are solved for... A 1Equation (5) is used to show the local transformation matrix set by the polarization tracking component 110a. However, in which the polarization tracking component 110b of the network device 104b sets... A 2 To maintain polarization tracking and A 1 In scenarios where a set of values ​​is locked to a static value (e.g., the identity matrix or any other matrix), equation (5) can be applied to... A 2 Solve for the local transformation matrix dynamically set by the polarization tracking component 110b. A 2 .

[0050] Polarization tracking (e.g., using equations (6) and / or (7) to set) A 1 This may include operations that maximize the output power from the recovery device 300 and / or minimize the power to the feedback photodetector of the recovery device 300. In some embodiments, the network device 104 (e.g., tracking component 110 and / or recovery device 300) uses a gradient descent algorithm or operation to minimize the feedback power and / or maximize the output power and sets... A 1 Minimizing feedback power and / or maximizing output power at one network device 104 ensures that signal components are correctly oriented for recovery at both network devices 104. Polarization tracking in some examples may include maximizing the signal component associated with a first polarization (e.g., TE, TM, etc.) relative to communication in the communication network 108 and / or minimizing the signal component associated with a second polarization relative to communication in the communication network 108. Tracking polarization at a single network device 104 while the other network device remains static (e.g., frozen or locked) allows the output power for the two polarized signal components to be correctly oriented for bidirectional communication at both network devices 104. However, in other examples, the two network devices 104 may perform tracking concurrently. The symmetric hardware of each of the network devices 104 is configured to execute a predefined mutual polarization tracking strategy. In various embodiments, the mutual polarization tracking strategy causes either a single network device 104 to perform polarization tracking, or both network devices 104 to perform polarization tracking.

[0051] Figure 5 It is according to various embodiments for setting for Figure 1 A flowchart of the method steps for tracking network devices. Although combined with... Figures 1 to 4 The components and systems described herein represent method steps, but those skilled in the art will understand that any system configured to perform method steps in any order falls within the scope of embodiments of this disclosure.

[0052] As shown in the figure, method 500 begins at step 502, where local network device 104 sends and / or receives a first message (e.g., packet 120). The first message may include a beacon message. However, the described techniques can also be performed using any type of message including tracking data 114 and a first identifier 112. The first message may also include payload data 122. In some embodiments, the first message includes an indication that the first message is a beacon message. The first identifier 112 or other identifying data is specific to the originating or transmitting device. As a result, if the first message is sent from local network device 104, the first identifier 112 identifies local network device 104. However, if the first message is received from remote network device 104, the first identifier 112 identifies remote network device 104.

[0053] In the case where local network device 104 receives a first message from remote network device 104, local network device 104 performs polarization tracking or tuning techniques using a feedback-based approach to dynamically set or update the local transformation matrix using tracking data 114. Local network device 104 performs polarization tracking by modifying the local transformation matrix until the tracking data 114 identified in the (received) first message matches a local copy of the tracking data 114. In some embodiments, both network devices 104 may perform polarization tracking based on the received message (e.g., including an identifier 112 different from the local identifier 112) until local network device 104 and / or remote network device 104 negotiate which device operates in leader mode and which device operates in follower mode. As a result, if local network device 104 sends the first message, remote network device 104 performs polarization tracking or tuning techniques by dynamically updating the remote transformation matrix by modifying the remote transformation matrix until the tracking data 114 identified in the (sent) first message matches a copy of the tracking data 114 stored on remote network device 104.

[0054] In step 504, local network device 104 receives and / or sends a second message. The second message may include an acknowledgment message. However, the described techniques can also be performed using any type of message including tracking data 114 and a second identifier 112. The second message may also include payload data 122. In some embodiments, the second message includes an indication that the second message is an acknowledgment message. Like the first identifier 112, the second identifier 112 is specific to the originating or transmitting device. As a result, if the second message is sent from local network device 104, the second identifier 112 identifies local network device 104. However, if the second message is received from a remote or remote network device 104, the second identifier 112 identifies remote network device 104.

[0055] In the case where local network device 104 receives a second message from remote network device 104, local network device 104 performs polarization tracking or tuning techniques by dynamically updating the local transformation matrix using a feedback-based method that modifies the local transformation matrix until the tracking data 114 identified in the (received) second message matches a local copy of the tracking data 114. However, if local network device 104 sends a second message, remote network device 104 performs polarization tracking by modifying the remote transformation matrix until the tracking data 114 identified in the (sent) second message matches a copy of the tracking data 114 stored on remote network device 104.

[0056] In step 506, the local network device 104 identifies a mutual polarization tracking policy. The mutual polarization tracking policy may be a shared set of rules or instructions that allow network devices 104 to agree on how to perform polarization tracking using the local network device 104, a remote network device 104, or both. The symmetric hardware of network device 104 performs polarization tracking according to a pre-configured mutual polarization tracking policy for each of the network devices 104. Network device 104 may include symmetric hardware and programming. However, network device 104 may include different identification data, such as identifier 112. For example, based on identifier 112 or another policy, a shared or mutual polarization tracking policy may instruct the use of a single network device 104 to perform polarization tracking. Alternatively, a mutual polarization tracking policy may configure two network devices 104 to perform polarization tracking. In some embodiments, the local network device 104 may identify a relationship between a first identifier 112 in a first message and a second identifier 112 in a second message. For example, the first identifier 112 may be greater than, less than, or otherwise distinguished from the second identifier 112. In some embodiments, all network devices 104 may store the same one or more rules to evaluate the relationships between identifiers 112 to determine which network device 104 performs polarization tracking for the system. Network devices 104 may use any predetermined rules to evaluate the relationships between identifiers 112, such as a rule instructing the network device 104 with the largest identifier 112 to perform polarization tracking. Other rules may instruct the network device 104 with the smallest, most recent, oldest, etc., identifiers 112 to perform polarization tracking.

[0057] Alternatively, the local network device 104 identifies a single network device 104 to perform polarization tracking based on a random or pseudo-random decision. In the example of random or pseudo-random decision, the local network device 104 sends payload data 122 including an indication of which network device 104 should perform polarization tracking. As a result, both network devices 104 operate according to the same decision. In some embodiments, each of the network devices 104 is configured to select itself to perform polarization tracking, such that the network device 104 that first receives and successfully modifies its transformation matrix becomes the follower.

[0058] In step 508, local network device 104 performs polarization tracking according to a mutual polarization tracking strategy. For example, local network device 104 sets its polarization tracking mode to either leader mode or follower mode based on the decision identified in step 506. For example, local network device 104 may set its polarization tracking mode to leader mode and lock its local transformation matrix. The local transformation matrix may be locked to its current set of values, locked to an identity matrix, or another static set of values. In this example, remote network device 104 performs polarization tracking. Alternatively, local network device 104 sets its polarization tracking mode to follower mode and dynamically updates its local transformation matrix to perform polarization tracking. Network device 104 can bidirectionally transmit data packets 120 for any purpose, thereby using a single network device within network device 104 to maintain polarization tracking. Compared to other techniques, using a single network device within network device 104 for polarization tracking can reduce power and energy consumption.

[0059] In step 510, local network device 104 determines whether signal tracking has been lost. For example, if local network device 104 fails to recover packet 120 (e.g., data including tracking data 114, payload data 122, and identifier 112), signal tracking is lost. If signal tracking is lost, local network device 104 may proceed to step 502 to repeat the autonegotiation indicated in steps 502 through 508. Otherwise, local network device 104 continues to transmit data with remote network device 104.

[0060] Figure 6 It is for configuration according to various embodiments Figure 1 A flowchart of the method steps for a communication system. Although combined with... Figures 1 to 4 The components and systems described herein represent method steps, but those skilled in the art will understand that any system configured to perform method steps in any order falls within the scope of embodiments of this disclosure.

[0061] As shown in the figure, method 600 begins at step 602, wherein a first network device 104 is connected to a communication network 108. The first network device 104 can identify a port on the fiber optic cable or other communication network 108 connected to the first network device 104. The port may be a bidirectional communication port 306 of the PRS 300 of the first network device 104.

[0062] In step 604, the second network device 104 connects to the communication network 108. The first network device 104 can identify the port of the fiber optic or other communication network 108 connected to the second network device 104. The port can be the bidirectional communication port 306 of the PRS 300 of the second network device 104. Initially, both the first network device 104 and the second network device 104 perform polarization tracking concurrently.

[0063] In step 606, the first network device 104 and the second network device 104 perform auto-negotiation, which identifies that the tracking modes for the first network device 104 and the second network device 104 are not symmetrically set. As a result, one of the network devices 104 is set to leader mode, and the other of the network devices 104 is set to follower mode. This can be achieved, for example, by combining the above. Figure 5 The described method 500 is used to perform automatic negotiation. For example, the first network device 104 and the second network device 104 can execute instructions to implement a pre-configured mutual polarization tracking strategy for each of the network devices 104.

[0064] In step 608, the communication system 100, including the first network device 104, the second network device 104, and the communication network 108, uses one or more of the first network device 104 and the second network device 104 to maintain polarization tracking. The first network device 104 and the second network device 104 have symmetrical hardware and programming. However, auto-negotiation techniques enable the communication system 100 to use one (or both) of the network devices 104 for polarization tracking. The network devices 104 may include symmetrical hardware and programming. However, the network devices 104 may include different identification data, such as identifier 112. For example, based on identifier 112 or another strategy, a shared or mutual polarization tracking strategy can instruct the use of a single network device 104 to perform polarization tracking. Alternatively, a mutual polarization tracking strategy can configure two network devices 104 to perform polarization tracking.

[0065] In summary, techniques for implementing polarization-multiplexed optical bidirectional links using symmetric hardware are disclosed. In some embodiments, the symmetric hardware includes two network devices communicating via a communication path such as optical fiber. The network devices exchange identifiers using techniques that facilitate polarization tracking performed by one or more of the network devices. More specifically, a first network device sends a first message including tracking data to a second network device. The first network device receives a second message from the second network device including the same or different tracking data. The first network device sets or configures a polarization tracking mode based on a mutual polarization tracking strategy of the first and second network devices. The first polarization tracking mode and the second polarization tracking mode of the second network device are set based on the mutual polarization tracking strategy, such that at least one of the first or second network devices performs polarization tracking for bidirectional communication via polarization multiplexing through an optical communication channel. In various embodiments, the polarization tracking mode is selected based on the relationship between the first and second identifiers or through random or pseudo-random selection.

[0066] Another embodiment includes a system for bidirectional communication with polarization multiplexing, the system comprising an optical communication channel, a first network device connected to a first end of the optical communication channel, and a second network device connected to a second end of the optical communication channel. A single device in either the first or second network device performs polarization tracking of packets for bidirectional communication with polarization multiplexing via the optical communication channel.

[0067] The disclosed technology offers at least one technical advantage over existing technologies in that it simplifies hardware deployment and integration while providing additional edge bandwidth density. The disclosed technology enables communication paths, such as fiber optic cables, to be connected to any type of port. The disclosed technology also achieves these benefits without sacrificing switch base, thereby reducing fiber optic costs and optical packaging. Furthermore, the disclosed technology allows for asymmetric allocation of channel capacity for inbound and outbound communications. These technical advantages represent one or more technical improvements over existing methods.

[0068] The following clauses describe some embodiments of this disclosure. 1. In some embodiments, a method for electro-optical implementation of polarization-multiplexed optical bidirectional communication includes: a first network device sending a first message including tracking data to a second network device via an optical communication channel; the first network device receiving a second message including the tracking data; and setting a first polarization tracking mode of the first network device according to a mutual polarization tracking strategy of the first network device and the second network device, wherein the first polarization tracking mode and the second polarization tracking mode of the second network device are set based on the mutual polarization tracking strategy, such that at least one of the first network device or the second network device performs polarization tracking for polarization-multiplexed bidirectional communication via the optical communication channel.

[0069] 2. The electro-optical implementation method as described in Clause 1, wherein the first message further includes first data of the first network device, the second message further includes second data of the second network device, and the first polarization tracking mode is set based on the relationship between the first data and the second data.

[0070] 3. The electro-optical implementation method as described in Clause 1 or 2, wherein the first polarization tracking mode is set to a leader mode, the leader mode configuring the first network device to stop polarization tracking by setting the transformation matrix of the first network device to a static set of values.

[0071] 4. The electro-optical implementation method as described in any one of clauses 1 to 3, wherein the first polarization tracking mode is set to a follower mode, the follower mode configuring the first network device to perform polarization tracking by dynamically updating a set of values ​​of the transformation matrix of the first network device.

[0072] 5. The electro-optical implementation method as described in any one of Clauses 1 to 4, wherein the second message further includes second data of the second network device, and the first network device uses the second data to determine that the second message is not a message reflected from the first network device.

[0073] 6. The electro-optical implementation method as described in any one of clauses 1 to 5, wherein the first message is a beacon message, and the second message is an acknowledgment message received based on the beacon message.

[0074] 7. The electro-optical implementation method as described in any one of clauses 1 to 6, wherein the first message further includes payload data.

[0075] 8. The electro-optical implementation method as described in any one of Clauses 1 to 7, wherein the first network device includes hardware and programming that are symmetrical with respect to the second network device.

[0076] 9. The electro-optical implementation method as described in any one of Clauses 1 to 8 further includes sending an instruction from the first network device to the second network device that the first network device or a single device in the second network device performs polarization tracking.

[0077] 10. The electro-optical implementation method as described in any one of clauses 1 to 9, wherein the tracking data includes a predetermined sequence for polarization tracking.

[0078] 11. In some embodiments, one or more non-transitory computer-readable media store instructions that, when executed by at least one processor, cause the at least one processor to perform the following steps: sending a first message including tracking data from a first network device to a second network device via an optical communication channel; receiving a second message including the tracking data from the first network device; and setting a first polarization tracking mode of the first network device according to a mutual polarization tracking strategy of the first network device and the second network device, wherein the first polarization tracking mode and the second polarization tracking mode of the second device are configured to cause one or more of the first network device or the second network device to perform polarization tracking of bidirectional communication via polarization multiplexing through the optical communication channel.

[0079] 12. One or more non-transitory computer-readable media as described in Clause 11, wherein the first message further includes first data of the first network device, the second message further includes second data of the second network device, and the first polarization tracking mode is set based on the relationship between the first data and the second data.

[0080] 13. One or more non-transitory computer-readable media as described in Clause 11 or 12, wherein the first polarization tracking mode is configured to maintain polarization tracking based on a random or pseudo-random selection of a single device among the first network device or the second network device.

[0081] 14. One or more non-transitory computer-readable media as described in any one of clauses 11 to 13, wherein the first message includes an identifier of the first network device, and the first network device prevents reflection of tracking of the first message based on the identifier.

[0082] 15. One or more non-transitory computer-readable media as described in any one of clauses 11 to 14, wherein the polarization-multiplexed bidirectional communication is transmitted via the optical communication channel via at least two different polarizations.

[0083] 16. In some embodiments, a system for polarization-multiplexed bidirectional communication includes an optical communication channel, a first network device connected to a first end of the optical communication channel, and a second network device connected to a second end of the optical communication channel, wherein at least one of the first network device or the second network device performs polarization tracking of a plurality of packets of the polarization-multiplexed bidirectional communication according to a mutual polarization tracking rule of the first network device and the second network device.

[0084] 17. The system as described in Clause 16, wherein the first network device includes hardware and programming that are symmetrical with respect to the second network device.

[0085] 18. The system as described in Clause 16 or 17, wherein polarization tracking includes dynamically updating a first transformation matrix of a single device in the first network device or the second network device, and wherein a second transformation matrix of the other device in the first network device or the second network device is statically set.

[0086] 19. The system of any one of Clauses 16 to 18, wherein the optical communication channel comprises a single-mode optical fiber.

[0087] 20. The system of any one of Clauses 16 to 19, wherein the first network device or an individual device of the second network device is selected based on a relationship between a first identifier of the first network device and a second identifier of the second network device.

[0088] 21. The system of any one of Clauses 16 to 20, wherein an individual device in the first network device or the second network device is identified based on a random or pseudo-random selection.

[0089] Any and all combinations of any element listed in any of the claims and / or any element described in this application fall within the scope of this disclosure and protection in any way.

[0090] For illustrative purposes, various embodiments have been described, but these descriptions are not intended to be exhaustive or limiting to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0091] Various aspects of this embodiment can be embodied as a system, a method, or a computer program product. Therefore, aspects of this disclosure can take the form of a completely hardware embodiment, a completely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects generally referred to herein as "modules" or "systems." Additionally, aspects of this disclosure can take the form of a computer program product embodied in one or more computer-readable media, on which computer-readable program code is embodied.

[0092] Any combination of one or more computer-readable media may be used. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any suitable combination of the foregoing. More specific examples (not an exhaustive list) of computer-readable storage media will include the following: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium can be any tangible medium capable of containing or storing a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0093] The foregoing description of aspects of this disclosure refers to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine. When executed via a processor of a computer or other programmable data processing apparatus, the instructions are capable of implementing the functions / actions specified in one or more flowchart illustration and / or block diagram blocks. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, an application-specific processor, or a field-programmable gate array (FPGA).

[0094] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, code segment, or code portion comprising one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may not appear in the order indicated in the figures. For example, two blocks shown consecutively may actually be executed substantially concurrently, or these blocks may sometimes be executed in reverse order, depending on the functionality involved. It will also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a system based on dedicated hardware or a combination of dedicated hardware and computer instructions that performs the specified function or action.

[0095] While the foregoing description pertains to embodiments of this disclosure, other and additional embodiments of this disclosure may be devised without departing from the basic scope of this disclosure, the scope of which is defined by the appended claims.

Claims

1. A method for electro-optical realization of polarization-multiplexed optical bidirectional communication, the method comprising: The first network device sends a first message, including tracking data, to the second network device via an optical communication channel; The first network device receives a second message including the tracking data; as well as The first polarization tracking mode of the first network device is set according to the mutual polarization tracking strategy of the first network device and the second network device. The first polarization tracking mode and the second polarization tracking mode of the second network device are set based on the mutual polarization tracking strategy, such that at least one of the first network device or the second network device performs polarization tracking for bidirectional communication via polarization multiplexing through the optical communication channel.

2. The electro-optical realization method as described in claim 1, wherein, The first message also includes first data from the first network device, the second message also includes second data from the second network device, and the first polarization tracking mode is set based on the relationship between the first data and the second data.

3. The electro-optical realization method as described in claim 1, wherein, The first polarization tracking mode is set to a guide mode, which configures the first network device to stop polarization tracking by setting the transformation matrix of the first network device to a static set of values.

4. The electro-optical realization method as described in claim 1, wherein, The first polarization tracking mode is set to follower mode, which configures the first network device to perform polarization tracking by dynamically updating a set of values ​​of the transformation matrix of the first network device.

5. The electro-optical realization method as described in claim 1, wherein, The second message also includes second data from the second network device, and the first network device uses the second data to determine that the second message is not a reflected message originating from the first network device.

6. The electro-optical realization method as described in claim 1, wherein, The first message is a beacon message, and the second message is an acknowledgment message received based on the beacon message.

7. The electro-optical realization method as described in claim 1, wherein, The first message also includes payload data.

8. The electro-optical realization method as described in claim 1, wherein, The first network device includes hardware and programming that are symmetrical with respect to the second network device.

9. The electro-optical realization method as described in claim 8, further comprising: The first network device sends an instruction to the second network device that either the first network device or a single device within the second network device perform polarization tracking.

10. The electro-optical realization method as described in claim 1, wherein, The tracking data includes a predetermined sequence for polarization tracking.

11. One or more non-transitory computer-readable media storing instructions, which, when executed by at least one processor, cause the at least one processor to perform the following steps: The first network device sends a first message, including tracking data, to the second network device via an optical communication channel; The first network device receives a second message including the tracking data; as well as The first polarization tracking mode of the first network device is set according to the mutual polarization tracking strategy of the first network device and the second network device. The first polarization tracking mode and the second polarization tracking mode of the second device are configured such that one or more of the first network device or the second network device perform polarization tracking for bidirectional communication via polarization multiplexing through the optical communication channel.

12. One or more non-transitory computer-readable media as claimed in claim 11, wherein, The first message also includes first data from the first network device, the second message also includes second data from the second network device, and the first polarization tracking mode is set based on the relationship between the first data and the second data.

13. One or more non-transitory computer-readable media as claimed in claim 11, wherein, The first polarization tracking mode is set based on randomly or pseudo-randomly selecting a single device from the first network device or the second network device to maintain polarization tracking.

14. One or more non-transitory computer-readable media as claimed in claim 11, wherein, The first message includes an identifier of the first network device, and the first network device uses the identifier to prevent the tracking of reflections of the first message.

15. One or more non-transitory computer-readable media as claimed in claim 11, wherein, The polarization-multiplexed bidirectional communication is transmitted via the optical communication channel through at least two different polarizations.

16. A system for bidirectional communication using polarization multiplexing, the system comprising: Optical communication channel; A first network device connected to the first end of the optical communication channel; as well as A second network device connected to the second end of the optical communication channel. At least one of the first network device or the second network device performs polarization tracking of multiple packets of the polarization-multiplexed bidirectional communication according to the mutual polarization tracking rules of the first network device and the second network device.

17. The system of claim 16, wherein, The polarization tracking includes dynamically updating a first transformation matrix of a single device in the first network device or the second network device, wherein a second transformation matrix of the other device in the first network device or the second network device is statically set.

18. The system of claim 16, wherein, The optical communication channel includes single-mode optical fiber.

19. The system of claim 16, wherein, The first network device or a single device in the second network device is selected based on the relationship between the first identifier of the first network device and the second identifier of the second network device.

20. The system of claim 16, wherein, The first network device or a single device in the second network device is identified based on random or pseudo-random selection.

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