CDC-ROADM design method for multi-dimensional multiplexing quantum optical network

Abstract

The invention provides an innovative architecture design method of a low-loss, color-less, directionless and contention-less reconfigurable optical add drop multiplexer (CDC-ROADM) oriented to a multi-dimensional multiplexing quantum optical network, and the scheme is specially used for optimizing the quantum optical network with large capacity, low blocking and high reliability in the future. Based on special requirements of quantum signal transmission, a quantum signal switching module with high flexibility is designed by innovatively using a low-loss wavelength selective switch (WSS). The classical signal switching module adopts a hierarchical cascade architecture: a space cross connection (SXC) layer realizes fiber core level switching, a wavelength cross connection (WXC) layer supports wavelength / wave group level flexible scheduling, and the use of expensive devices and the construction cost and loss of the system are reduced while the switching flexibility is ensured through a double-level coordination mechanism. The design method provided by the invention has the advantages of low loss, large capacity, efficient transmission, low blocking rate and the like, and can provide key technical support for large-scale deployment of the quantum optical network.

Description

Technical Field

[0001] This patent relates to the field of quantum communication, and more particularly to an architectural design for switching nodes in a multidimensional multiplexed quantum optical network suitable for information exchange among large-scale quantum users. The patent provides an innovative architectural design method for a low-loss, colorless, directionless, and concentrationless reconfigurable optical add-drop multiplexer (CDC-ROADM) for multidimensional multiplexed quantum optical networks. The proposed architecture features low loss, large capacity, high-efficiency transmission, and low blocking rate, providing key technical support for the large-scale deployment of quantum optical networks. Background Technology

[0002] Quantum key distribution (QKD) technology relies on the Heisenberg uncertainty principle, measurement collapse principle, and no-cloning principle of quantum states from quantum mechanics, combined with the "one-time pad" encryption method, to significantly improve the security of information transmission. To reduce the deployment cost of QKD, switching technology can be used to expand point-to-point QKD systems into QKD networks, thereby achieving network capacity expansion and improving network flexibility and reliability. Quantum optical switching nodes are the main interconnecting devices for future quantum-switched optical networks and a key technology for scaling up QKD networks. Because quantum signals are extremely weak and possess the characteristics of being unclonable and unamable, the switching node structure in classical optical networks is not suitable for quantum communication. Therefore, one of the core tasks in the future integration of classical optical networks and quantum key distribution networks is the design of switching nodes.

[0003] With the ever-increasing demand for network traffic, the transmission capacity of traditional single-core single-mode fiber (SSMF) is approaching the Shannon limit. Multi-core fiber (MCF), as a space-division multiplexing (SDM) technology, combined with wavelength-division multiplexing (WDM) technology, can break through the capacity bottleneck and significantly improve transmission capacity. For QKD, it is developing towards a technology that integrates quantum and classical optical transmission by combining SDM and WDM. Therefore, for switching technology, corresponding to QKD, its future development trend is a switching technology that integrates multi-dimensional multiplexed QKD with classical optical networks. Therefore, in co-fiber transmission scenarios based on multi-dimensional multiplexing of quantum and classical signals, it is necessary to study switching node architectures that are suitable for both classical and quantum signals.

[0004] ROADM is a widely used and flexible scalable switching architecture in network construction. It allows for dynamic configuration of uplink or downlink service wavelengths via remote control, enabling flexible service scheduling. To achieve non-blocking switching, next-generation ROADM switching nodes are required to possess the characteristics of colorlessness, directionlessness, and contention-free (CDC). "Colorlessness" means wavelength independence, indicating that signals of any wavelength can be uplinked or downlinked from any port of the switching node; "directionlessness" means direction independence, indicating that any local service can be routed to any direction of the switching node, or services from any direction can be routed downlink locally; and "contention-free" means contention-free, meaning that multiple services with the same wavelength can be uplinked or downlinked on the same local node.

[0005] In summary, the main challenge in co-fiber transmission scenarios involving two-dimensional multiplexing of quantum and classical signals is designing a low-loss CDC-ROADM architecture based on a quantum key distribution network that also features multi-granularity switching capabilities. Summary of the Invention

[0006] This patent targets multidimensional multiplexed quantum optical networks, designing a multi-granularity CDC-ROADM architecture characterized by low loss, high capacity, high efficiency, and low blocking rate. The main considerations are how to reduce quantum signal loss, efficiently handle large-scale user requests, and effectively reduce uplink and downlink classical service blocking rates. It includes three key technical points:

[0007] 1. A CDC-ROADM architecture for multidimensional quantum optical networks is proposed;

[0008] 2. A classic signal uplink and downlink module capable of achieving "contention-free" functionality was designed;

[0009] 3. A signal packet switching method that can achieve high-efficiency signal exchange is proposed.

[0010] The first technical point is explained in detail below:

[0011] A CDC-ROADM architecture for multidimensional quantum optical networks is proposed, such as... Figure 1As shown, this architecture has ports in M ​​directions (the number of ports can be increased or decreased as needed), and the optical fibers at the ports use multi-core fibers. In a QKD system, each user can transmit three types of signals: quantum signals, synchronization signals, and classical signals. Synchronization signals provide the clock signal during quantum key distribution and are crucial for quantum signal detection. To ensure that the quantum signal at the receiving end remains synchronized with the synchronization signal of the same user, the quantum signal and synchronization signal should always travel through the same path during the exchange; therefore, the quantum signal and synchronization signal are transmitted in the same fiber core. To reduce interference from classical signals to quantum signals, classical signals are transmitted in different fiber cores than quantum signals and synchronization signals.

[0012] At the port, the multi-core optical fiber undergoes fan-in / fan-out (FIFO) multiplexing and demultiplexing. Depending on the type of signal transmitted, the fiber cores are divided into cores for transmitting quantum and synchronization signals (leading to the quantum switching module) and cores for transmitting classical signals (leading to the classical switching module). The classical switching module consists of an SXC layer and a WXC layer, such as... Figure 2 As shown. For a switching node with degree M and the number of classic signal fiber cores N (N is a multiple of 2), there is a total of 1 SXC layer and N / 2 WXC layers. Each WXC layer has two uplink modules and two downlink modules.

[0013] The SXC layer consists of an L×L MEMS optical switch (OS), where L=M×N. Classical signal fiber cores, demultiplexed via FIFO, are connected to one side of the OS (cores 1 to N / 2) and to the other side (cores N / 2+1 to N). Each fiber core has a portion of its channels used for forward transmission (in the same direction as the quantum signal) and a portion for backward transmission (in the opposite direction). A signal from any input fiber core (1 to N / 2) can be switched to any output fiber core (N / 2+1 to N), and vice versa. This design allows for flexible switching of the classical signal fiber cores, improving the flexibility of the switching node.

[0014] The SXC layer enables core-level switching. If all inputs to a fiber core are destined for the same direction (i.e., the input signals do not need to be local uplink or downlink), the input signals do not need to pass through the WXC layer; all signals are directly connected to the FIFO in the output direction for multiplexing. If the input signals of the fiber core are destined for different directions, or if some / all of the input signals need to be local uplink or downlink, the input signals need to be transmitted to the WXC layer after passing through the SXC layer, requiring wavelength / wavegroup-level switching. The WXC layer consists of 2×M WSSs, which can handle local uplink and downlink signals, returning to the SXC layer before being switched to the destination output port.

[0015] The quantum switching module enables wavelength / band granularity switching and consists of low-loss WSSs specifically designed for quantum signals. The insertion loss of a single WSS can be as low as 1 dB. For a switching node with degree M and the number of quantum signal cores P, each core is equipped with one WSS, for a total of M×P low-loss WSSs. The WSSs can be dynamically configured for input signal pass-through, partial / full uplink / downlink, etc. This design not only enables high-quality transmission of quantum signals but also offers high flexibility.

[0016] The second technical point is explained in detail below:

[0017] A classical signal uplink / downlink module with "contention-free" functionality is designed. In the proposed architecture, the classical switching module, quantum switching module, and synchronous switching module are each equipped with local uplink / downlink modules. For quantum and synchronous signals, the WSS at the port is equipped with the transmitter and receiver for quantum and synchronous signals; for classical signals, its uplink module consists of... Figure 3 As shown, it includes n 1×M operating systems (OS) and M n×1 couplers. The n OSs are responsible for connecting n local signals to the ROADM system, and the N n×1 couplers are responsible for routing the coupled signals to M directions, where M is the degree of the switching node architecture. The N WSSs are responsible for routing the N local signals to the coupler modules, and the M couplers are responsible for routing the coupled signals to the M directions of the switching node. The downlink module is as follows... Figure 4 As shown, it comprises M 1×n power dividers and n M×1 operating systems (OS). The M 1×n power dividers split optical signals from N directions into n paths, and the n M×1 OS selects one output path from the output signals of the N power dividers. The uplink and downlink modules designed above can avoid wavelength conflicts in the uplink and downlink signals, thus achieving the goal of "no contention". Therefore, the designed architecture has the functions of colorless, directionless, and contention-free (CDC).

[0018] The third technical point is explained in detail below:

[0019] A signal packet switching method is proposed to achieve high-efficiency signal switching. When services from different directions arrive at the switching node simultaneously, grouping the services in different fiber cores allows for simultaneous wavelength allocation for multiple services, thereby improving switching efficiency. All classic signal fiber cores of an MCF port can be represented as follows: The core of quantum and synchronous signals can be represented as Assuming that in a fiber optic core transmitting classic services at any port, the first... A classic business can be represented as: Then the j-th MCF port's th The first classic fiber core Each business is represented as Similarly, in the fiber core for transmitting quantum services at any port, the first... A quantum business can be represented as Then the first The first MCF port The first quantum fiber core Each business is represented as ,in For the first in the fiber core The wavelength of the classic signal for a classic business. and The first in the fiber core The wavelengths of quantum signals and synchronization signals in a quantum business. This indicates that the first [unit / item] in the fiber core The first classic business or the first The target output fiber core for quantum services. That is, for any fiber core, the services in the fiber core transmitting classical signals or quantum and synchronous signals are respectively represented as follows: and .

[0020] To meet wavelength consistency requirements, for classical signals, when there are two classical fiber cores from different multi-core fiber ports... and If the conditions are met The target output fiber core for all services is and simultaneously satisfy The target output fiber core for all services is At that time, by controlling the L×L optical switch to make and Fiber core-level switching is performed; in other cases, such as when at least one service in any fiber core is different from the target output fiber core of other services, or when at least one service needs to be downlinked at the local node, wavelength or wavegroup-level switching is performed by controlling the WSS and optical switches.

[0021] For quantum signals, wavelength or wavegroup granularity can be exchanged by controlling the WSS. This applies to two quantum fiber cores from different multi-core fiber ports. and If satisfied The target output fiber core for all services is and simultaneously satisfy The target output fiber core for all services is When necessary, the service can be bypassed by controlling the WSS; otherwise, local partial / full uplink and downlink can be performed by controlling the WSS.

[0022] The architecture described in this patent is geared towards multidimensional multiplexed quantum optical networks, and has the advantages of low loss, large capacity, high efficiency transmission and low blocking rate. It helps to promote the integration of quantum key distribution networks and classical optical networks, and lays a key foundation for building a quantum-classical optical integrated high-efficiency switching network. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a multi-granularity quantum CDC-ROADM architecture based on multi-core optical fiber. TX: Signal transmitter; RX: Signal receiver; MCF: Multi-core optical fiber; WSS: Wavelength selective switch; OS: Optical switch; FIFO: Fan-in / Fan-out; Cl: Classical signal.

[0024] Figure 2 This is a hierarchical diagram of a classic switching module. SXC: Spatial Cross-Connect; WXC: Wavelength Cross-Connect; Add: Classic Uplink Module; Drop: Classic Downlink Module

[0025] Figure 3 This is a schematic diagram of a classic signal uplink module that can achieve "contention-free" functionality. OS: Optical switch; TX: Signal transmitter; Cl: Classic signal.

[0026] Figure 4 This is a schematic diagram of a classic signal downlink module that can achieve "contention-free" functionality. OS: Optical switch; RX: Signal receiver; Cl: Classic signal. Detailed Implementation

[0027] To make the objectives, technical methods, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] In a specific embodiment of the CDC-ROADM architecture for multidimensional multiplexed quantum optical networks proposed in this patent, the optical fiber at the port is a multi-core optical fiber, which can accommodate more services compared to SSMF.

[0029] like Figure 1 As shown, the proposed architecture leverages the characteristics of quantum signals, employing a WSS (Wavelength Separator) specifically designed for quantum signals with a loss as low as 1dB, to achieve quantum signal wavegroup granularity exchange, enabling quantum signals to pass through or move uplink / downlink. When the quantum signal passes through, it needs to pass through two WSSs; when the signal moves uplink / downlink, it only needs to pass through one WSS, offering both high flexibility and low loss. Figure 1 and Figure 2The classic switching module is divided into SXC layer and WXC layer. The SXC layer supports fiber core granularity switching, and the WXC layer supports wavelength / wavegroup granularity switching. All classic signal fiber cores demultiplexed by FIFO are connected in half to the left side of the L×L optical switch (OS) and half to the right side of the OS. This design can realize flexible switching of classic signal fiber cores with different numbers, improve the flexibility of the switching node, improve the utilization rate of the equipment, and reduce costs.

[0030] The classic signal uplink module of the proposed architecture is as follows: Figure 3 As shown, the classic signal downlink module is as follows: Figure 4 As shown. For uplink signals, assume there are 4 services with the same wavelength that need to go uplink to 4 different directions, and the wavelengths of the 4 services are... = = = =1550 nm (193.40 THz), these four services can be input to four operating systems (OS) through four classical signal transmitters, and then the OS routes these four services to four couplers respectively, thus enabling unblocked routing of four services with the same wavelength to four different directions; for downlink signals, assuming there are four services with the same wavelength from different directions that need to be downlinked locally at the switching node, the wavelengths of the four services are the same. = = = =1550 nm (193.40 THz), these four services pass through four power dividers respectively. The power dividers divide the services into several equal parts to the OS module. The OS can select one of the signals from all the power beam splitters and output it to the corresponding classical signal receiver, so that the four services of the same wavelength from different directions can be downlinked to the local receiver without obstruction.

[0031] As can be seen from the above embodiments, the CDC-ROADM architecture for multidimensional multiplexed quantum optical networks proposed in this patent has advantages such as low loss, large capacity, high efficiency transmission and low blocking rate.

Claims

1. A novel architecture design method for a low-loss, colorless, directionless, and attentionless reconfigurable optical add-drop multiplexer (CDC-ROADM) for multidimensional multiplexed quantum optical networks, characterized in that... The CDC-ROADM comprises multiple modules, each implementing a specific switching function, including a port fan-in / fan-out (FIFO) module, a quantum switching module, a classical switching module, and a classical uplink / downlink module, wherein: The FIFO module is used to multiplex and demultiplex the multi-core optical fiber at the port, dividing the multi-core optical fiber into a core for transmitting classical signals and a core for transmitting quantum signals and synchronization signals. The quantum exchange module uses a wavelength selective switch (WSS) designed specifically for quantum communication for cross-connection, which enables the exchange of quantum signals and synchronization signals at the wavelength / wavegroup granularity, and flexibly controls the quantum signal to pass through or go up or down. The classic switching module is divided into a spatial cross-connect (SXC) layer and a wavelength cross-connect (WXC) layer. An L×L optical switch (OS) in the SXC layer is used to realize the switching of classic signal fiber core granularity, and the WSS cross-connect in the WXC layer is used to realize the switching of wavelength / wavegroup granularity. The classic uplink / downlink module uses an OS and a beam splitter / coupler cross-connected to implement the CDC function for classic signal uplink / downlink.

2. The CDC-ROADM node as described in claim 1, characterized in that, The quantum switching module uses a low-loss WSS designed specifically for quantum signals. For a switching node with degree M and number of quantum signal cores P, each quantum fiber core is equipped with one WSS, for a total of M×P low-loss WSSs. The WSS can be dynamically configured to allow input signals to pass through or partially / fully uplink and downlink, enabling flexible and high-quality transmission of quantum signals.

3. The CDC-ROADM node as described in claim 1, characterized in that, The classic switching module is divided into an SXC layer and a WXC layer. The L×L OS of the SXC layer is used to realize the switching of signal fiber core granularity, and the WSS of the WXC layer is used to realize the switching of signal wavelength / wavegroup granularity. All classic signal fiber cores demultiplexed by FIFO are connected in half to the left side of OS (L=M×N) and half to the right side of OS, which is used to realize the flexible switching of some classic signal fiber cores with different numbers.

4. The CDC-ROADM node as described in claim 1, characterized in that, The classic uplink module includes n 1×M operating systems (OS) and M n×1 couplers. The n OS connects n local signals to the ROADM system, and the N n×1 couplers route the coupled signals to M directions, where M is the degree of the switching node architecture. The downlink module includes M 1×n beam splitters and n M×1 OS. The M 1×n beam splitters split the optical signals from the N directions into n paths, and the n M×1 OS select one output path from the output signals of the N beam splitters.

5. The CDC-ROADM node as described in claims 3 and 4, characterized in that, A signal grouping and switching method is used to achieve high-efficiency signal switching between the classical and quantum switching modules; firstly, all classical signal cores can be represented as A. jk (j=1,2,…,M;k=1,2,…,N), the core of the quantum and synchronization signals can be represented as B. jk (j = 1, 2, ..., M; k = 1, 2, ..., P), where M is the degree of the switching node, N is the number of fiber cores for classical signals, and P is the number of quantum and synchronization signal fiber cores for MCF; assuming that the i-th classical service in the fiber core transmitting classical services at any port can be represented as {C i ,OUT i }, then the i-th service of the k-th classic fiber core of the j-th MCF port is represented as A. jk {C i ,OUT i Similarly, the i-th quantum service in a fiber core transmitting quantum services at any port can be represented as {Q}. i ,S i ,OUT i }, then the i-th service of the k-th quantum fiber core of the j-th MCF port is represented as B. jk {Q i ,S i ,OUT i }, where C i Let Q be the wavelength of the classical signal of the i-th classical service in the fiber core. i and S i OUT represents the wavelengths of the quantum signal and synchronization signal for the i-th quantum service in the fiber core, respectively. i This indicates the target output fiber core for the i-th classical service or the i-th quantum service in the fiber core; to satisfy wavelength consistency, for classical signals, when there are two classical fiber cores A from different multi-core fiber ports... xk and A yt (x,y∈{1,2,…,M}; If A is satisfied xk The target output fiber core for all services is A. yt And A yt The target output fiber core for all services is A. xk The condition is then met by controlling L×L OS to make A xk and A yt For services within the fiber, core-level granularity is exchanged; if the above conditions are not met, wavelength / wavegroup granularity is exchanged; for quantum signals, wavelength or wavegroup granularity is exchanged by controlling the WSS; for two quantum fiber cores B from different multi-core fiber ports... xk and B yt (x,y∈{1,2,…,M};k,t∈{1,2,…,P},k=t), if B xk The target output fiber core for all services is B. yt And simultaneously satisfy B yt The target output fiber core for all services is B. xk When necessary, the service can be bypassed by controlling the WSS; otherwise, local partial or full uplink and downlink can be controlled by controlling the WSS.

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