A fiber core and wavelength allocation method for coordinated transmission of optical signals and quantum signals

Abstract

This patent discloses a method for allocating fiber cores and wavelengths for the coordinated transmission of optical and quantum signals, applicable to quantum key distribution optical networks based on space-division multiplexing. This method primarily considers the major noises involved in space-division multiplexing, such as Raman scattering noise, four-wave mixing noise, and inter-core crosstalk noise, and proposes a method for allocating fiber core wavelengths for the coordinated transmission of classical and quantum signals, aiming to simultaneously improve the performance of classical optical communications and quantum key distribution. This invention provides technical support for the integrated transmission of quantum key distribution and classical optical networks, promoting the application of quantum key distribution.

Description

Technical Field

[0001] This patent relates to the field of quantum communications, specifically quantum key distribution technology for fused transmission with multi-core fiber optical networks. This method can simultaneously reduce noise interference on both classical and quantum channels in fused transmission, thereby simultaneously improving the performance of both classical optical communication and quantum key distribution, enabling coordinated transmission of both. Background Art

[0002] Quantum Key Distribution (QKD) technology, based on the fundamental principles of quantum mechanics and combined with "one-time pad" technology, can provide theoretical security for optical networks. With the development of QKD, significant progress has been made in expanding secure transmission distances and increasing secure key rates.

[0003] To promote the application of QKD, integrating transmission with classical optical networks is a key development trend. While this converged transmission approach can reduce fiber deployment costs, it also introduces new challenges. Weak quantum signals are susceptible to interference from noise generated by classical signals, such as Raman scattering and four-wave mixing. These noises are in-band noise in QKD systems and cannot be filtered out by filters. Therefore, efficient wavelength allocation schemes are required to achieve low noise and high key rates. Meanwhile, the introduction of multi-core optical fibers has increased fiber transmission capacity, but also introduces new noise, such as inter-core crosstalk. Furthermore, the noise generated by classical signals not only significantly interferes with the quantum channel but also affects it itself. In-band noise falling on the classical channel can also impair the performance of classical communication systems. However, current research on the converged transmission of classical and quantum signals has largely focused on reducing noise interference on the quantum signal while ignoring the impact of noise on the performance of the classical signal. Consequently, the noise introduced by the classical signal not only limits the improvement of the secure key rate in quantum key distribution networks but also reduces the performance of classical optical communication networks.

[0004] To sum up, the current quantum key distribution network based on multi-core optical fiber urgently needs a core and wavelength allocation method that can improve the performance of both QKD network and classical optical communication network, that is, a collaborative transmission method. Summary of the Invention

[0005] This patent addresses the application scenario of spatially multiplexed quantum key distribution (QKD) and the fusion transmission of classical optical signals. It designs a fiber core and wavelength allocation method for the coordinated transmission of optical and quantum signals. This method can both improve the security key rate of QKD and the optical signal-to-noise ratio (OSNR) of classical optical communications. The method mainly includes two technical points: 1. Proposing a wavelength allocation scheme for the coordinated transmission of classical and quantum signals; 2. Proposing a fiber core allocation scheme for the coordinated transmission of classical and quantum signals using core cycling planning.

[0006] The first technical point is described in detail as follows:

[0007] A wavelength allocation scheme for the coordinated transmission of classical and quantum signals is proposed. The proposed scheme is mainly aimed at the situation where the forward and backward classical signals and quantum signals are in different bands. That is, the available frequency range is divided into three frequency bands from low to high, which are used to transmit the forward and backward classical signals and quantum signals respectively. Figure 1 As shown. First, in order to suppress the influence of the four-wave mixing noise within the core on the classical signal, the principle of minimizing the four-wave mixing noise received by the current available band is adopted for the forward and backward classical signals respectively, and the classical channels are allocated through traversal search. Secondly, in order to avoid the influence of the inter-core crosstalk noise on the classical channel, on the basis of determining the forward and backward classical channels, the channels are shifted to the right by wavelength shift to obtain two other channels for transmitting the forward and backward classical signals respectively, for a total of four wavelength allocation schemes without crosstalk interference. Finally, the allocation of quantum channels is based on the principle of minimizing traversal noise. Ultimately, this scheme can reduce the noise on both the classical channel and the quantum channel. The specific implementation of this scheme is divided into the following steps:

[0008] S1. First, within the available channel range, determine the three classic channel numbers that have the least impact on the four-wave mixing noise generated within this range: Among them C f / b is the channel number of the maximum frequency of the optional forward or backward classical channel, and f / b indicates the forward channel or the backward channel;

[0009] S2. Find the sum of the four-wave mixing noises (FWM) generated by the remaining channels within the optional channel range to the entire available channel range. i , calculated based on:

[0010]

[0011] FWM j (i,S f / b ) represents the addition of the i-th channel, which interferes with the four-wave mixing noise on the j-th channel;

[0012] S3. The i-th selected classical channel can be determined by formula (1): i opt =arg{min[FWM i ]}, and then update the channel set: S f / b ←i opt ; min[FWM i ] is to calculate the minimum value of FWM noise on i channels, arg{min[FWM i ]} is to obtain the channel number corresponding to the minimum FWM noise;

[0013] S4, loop through steps S2-S3 to obtain the final required classical channel, and update the forward and backward classical channel sets S f / b ;

[0014] S5, set S in step S4 f / b The elements in are shifted right by Δf1 / 2 and Δf2 / 2 respectively to obtain two other types of channel sets S′ for transmitting forward and backward classical signals respectively. f / b ; Δf1 is the optional forward classical channel frequency spacing, Δf2 is the optional backward classical channel frequency spacing;

[0015] S6. By traversing the noise on the optional quantum channels, the channels least affected by the noise are selected in turn for transmitting quantum signals.

[0016] The second technical point is described in detail as follows:

[0017] A core allocation scheme for the coordinated transmission of classical and quantum signals with core cyclic planning is proposed. This scheme is mainly applied to multi-core optical fibers with any number of cores. The core resources are allocated based on the principle of maximizing the distance between the classical core and the quantum core. By cyclically allocating the four wavelength allocation schemes obtained in the first technical point, crosstalk between adjacent cores is avoided, so as to achieve the purpose of simultaneously improving the performance of classical optical communications and the security key rate of the quantum key distribution system. This scheme can be used in two scenarios with different classical core requirements: one is that the core resources of the multi-core optical fiber are sufficient to meet the classical core requirements, and the other is that the core resources of the multi-core optical fiber are insufficient to meet the classical core requirements. For the first scenario, that is, the core resources are sufficient, the classical signal and the quantum signal are transmitted on different cores, that is, independent core transmission; for the second scenario, the core resources are tight, then the classical signal and the quantum signal are transmitted on the same core, and this type of core is a hybrid core. The specific implementation steps for the second technical point are as follows:

[0018] S1. Select any vertex of the multi-core optical fiber and number it as 1. Draw a tangent line along the outermost edge of core 1 and move downward, passing through the centers of the other cores in turn. Number the corresponding cores on each line in the order of left > right > middle until all the cores are numbered.

[0019] S2. Allocate quantum cores according to the principle of core numbering from large to small;

[0020] S3, plan the fiber cores in the order of tangent downward translation, which are the unshifted forward classic wavelength S f , shift the forward classical wavelength S′ f , unshifted backward classical wavelength S b , shifted back to the classical wavelength S′ b The fiber core is planned in a cycle of 4;

[0021] S4. Based on the core planning in S3, allocate classic cores in ascending order of core numbers.

[0022] S5. When the number of classical fiber cores is met, the allocation is completed; otherwise, continue to cover the quantum fiber core with a mixed transmission core of classical and quantum signals according to the steps of S4 until the classical fiber core allocation is completed.

[0023] The method described in this patent can be applied to quantum key distribution transmission networks based on multi-core optical fibers, improving both the optical signal-to-noise ratio (OSNR) of classical communications and the secure key rate of QKD, thereby extending the secure transmission distance. The implementation of this method can lay the foundation for the integration of QKD and classical optical networks, playing a positive role in improving QKD performance and ensuring the transmission performance of classical signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Attachment Figure 1 Schematic diagram of the classical and quantum wavelength resource allocation scheme. The frequency range for the optional forward classical signal is [F1, F2]; the frequency range for the optional backward classical signal is [F2, F3]; and the frequency range for the optional quantum signal is [F3, F4]. Δf1: Optional forward classical channel frequency spacing; Δf2: Optional backward classical channel frequency spacing; Δf3: Optional quantum channel frequency spacing.

[0025] Attachment Figure 2 Diagram showing implementation examples of classical and quantum wavelength resource allocation schemes.

[0026] Attachment Figure 3 This is a diagram showing the implementation of the classical and quantum fiber core resource allocation scheme. 1F is the unshifted forward classical channel, i.e., S f ; 2F is the shifted forward classical channel, i.e. S′ f 1B is the unshifted backward classical channel, i.e. S b ; 2B is the shifted backward classical channel, i.e. S′ b . DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] The following example illustrates a coordinated wavelength allocation scheme using four forward classical channels, four backward classical channels, and four quantum channels. The spacing between the optional forward classical channels, optional backward classical channels, and optional quantum channels is 200 GHz, i.e., Δf1 = 200 GHz, Δf2 = 200 GHz, and Δf3 = 200 GHz. From step 2 of the classical and quantum wavelength resource allocation scheme, the frequencies of the unshifted forward classical channels, i.e., 1F, are 194.0THz, 194.2THz, 194.5THz, and 194.9THz, respectively. The frequencies of the forward classical channels after shift, i.e., 2F, are 194.1THz, 194.3THz, 194.6THz, and 195.0THz, respectively. Similarly, the frequencies of the backward classical signals, i.e., 1B, are 195.2THz, 195.4THz, 195.7THz, and 196.1THz, respectively. The frequencies of the backward classical signals, i.e., 2B, are 195.3THz, 195.5THz, 195.8THz, and 196.2THz, respectively. The frequencies of the quantum channels are 196.4THz, 196.6THz, 196.8THz, and 197.0THz, respectively. Figure 2 shown.

[0029] The following describes the coordinated fiber core allocation scheme using independent core transmission scenarios and hybrid core transmission scenarios as examples. In the independent core transmission scenario, six quantum cores are required, while 31 classical cores are required. In the hybrid core transmission scenario, six quantum cores are required, while 37 classical cores are required.

[0030] In the independent core transmission scenario, first number the cores, according to the core allocation step S1, that is, number 1-37, and then allocate quantum cores from large to small, that is, number 32-37 cores are allocated as quantum cores, as shown in the attached figure. Figure 3 Finally, 31 classic fiber cores are allocated according to the core planning and the order of the core numbers from small to large, that is, the cores numbered 1-31 are allocated as classic fiber cores, as shown in the attached figure. Figure 3 (b) shown.

[0031] In the hybrid core transmission scenario, according to the allocation scheme of independent core transmission, the remaining 6 classical fiber cores are allocated in descending order according to the core planning and core numbering, that is, the cores numbered 32-37 are allocated as classical quantum signal hybrid transmission cores, as shown in the attached figure. Figure 3 (c) shown.

[0032] It can be seen from the above embodiments that in the fusion transmission of quantum key distribution and classical optical signals, the fiber core and wavelength allocation scheme for classical and quantum cooperative transmission proposed in this patent can simultaneously improve the performance of classical communication networks and quantum key distribution networks, such as improving the optical signal-to-noise ratio of classical signals, extending the secure transmission distance, and increasing the secure key rate, providing technical support for the application of fusion transmission of quantum signals and classical signals.

Claims

1. A fiber core and wavelength allocation method for the coordinated transmission of optical signals and quantum signals, the purpose of which is to simultaneously improve the performance of classical optical communication and quantum key distribution, that is, to achieve the coordinated transmission of classical signals and quantum signals, characterized in that: There are two main categories: A. A wavelength allocation scheme for the coordinated transmission of classical and quantum signals is proposed. The frequencies are divided into three bands from low to high, used to transmit forward and backward classical signals and quantum signals respectively. An ergodic search method is used within the frequency band to suppress four-wave mixing interference in the classical channel. A wavelength shift method is used to generate four wavelength allocation schemes with no crosstalk, following the rule that forward and backward classical signals use independent fiber cores for transmission. The quantum channel selects the channel with the lowest noise within the frequency band. B. A core allocation scheme for the coordinated transmission of classical and quantum signals based on core cyclic planning is proposed. By cyclically using four wavelength allocation schemes, crosstalk between adjacent cores is avoided. This scheme is applicable to multi-core optical fibers with any number of cores.

2. The method according to claim 1 proposes a wavelength allocation scheme for the coordinated transmission of classical signals and quantum signals, characterized in that: The following steps are involved: S1. First, within the available channel range, determine the three classic channel numbers that have the least impact on the four-wave mixing noise generated within this range: Among them C f / b is the channel number with the highest frequency among the optional forward and backward classical channels, and f / b indicates the forward channel or the backward channel; S2. Find the sum of the four-wave mixing noises (FWM) generated by the remaining channels within the optional channel range to the entire available channel range. i , calculated based on: in FWM j (i,S f / b ) represents the addition of the i-th channel, which interferes with the four-wave mixing noise on the j-th channel; S3. The i-th selected classical channel can be determined by formula (1): i opt =arg{min[FWM i ]}, and then update the channel set: S f / b ←i opt ; min[FWM i ] is to calculate the minimum value of FWM noise on i channels, arg{min[FWM i ]} is to obtain the channel corresponding to the minimum FWM noise; S4, loop through steps S2-S3 to obtain the final required classical channel, and update the forward and backward classical channel sets S f / b ; S5, set S in step S4 f / b The elements in the channel set in are shifted right by Δf1 / 2 and Δf2 / 2 respectively to obtain two other types of channel sets S′ for transmitting forward and backward classical signals respectively. f / b ; Δf1 is the optional forward classical channel frequency spacing, Δf2 is the optional backward classical channel frequency spacing; S6. By traversing the noise on the optional quantum channels, the channels least affected by the noise are selected in turn for transmitting quantum signals.

3. The method according to claim 1 proposes a core allocation scheme for the coordinated transmission of classical and quantum signals using core cycle planning, characterized in that: The following steps are involved: S1. Select any vertex of the multi-core optical fiber and number it as 1. Draw a tangent line along the outermost edge of core 1 and move downward, passing through the centers of the other cores in turn. Number the corresponding cores on each line in the order of left > right > middle until all the cores are numbered. S2. Allocate quantum cores according to the principle of core numbering from large to small; S3, plan the fiber cores in the order of tangent downward translation, which are the unshifted forward classic wavelength S f , shift the forward classical wavelength S′ f , unshifted backward classical wavelength S b , shifted back to the classical wavelength S′ b The fiber core is planned in a cycle of 4; S4. Based on the core planning in S3, allocate classic cores in ascending order of core numbers. S5. When the number of classical fiber cores is met, the allocation is completed; otherwise, continue to cover the quantum fiber core with a mixed transmission core of classical and quantum signals according to the steps of S4 until the classical fiber core allocation is completed.

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