A non-uniformly spaced wavelength allocation method for improving key rate in multi-core optical fiber quantum key distribution

Abstract

This patent discloses a non-equally spaced wavelength allocation method for improving the key rate in multi-core optical fiber quantum key distribution. This method is applicable to quantum key distribution optical networks based on space division multiplexing. This method mainly considers the main noises involved in the space division multiplexing system, such as Raman scattering noise, four-wave mixing noise, and inter-core crosstalk noise, and proposes a quantum channel non-equal frequency interval allocation scheme, aiming to improve the security key rate of quantum key distribution and extend the secure transmission distance. The present invention provides technical support for the fusion transmission of quantum key distribution and classical optical networks, and promotes the application process of quantum key distribution.

Description

Technical Field

[0001] This patent relates to the field of quantum communication, and in particular to a quantum key distribution system that integrates transmission with a multi-core optical fiber network. This method can mainly reduce the noise interference of quantum signals in the co-fiber transmission system of classical signals and quantum signals, thereby improving the security key rate of the quantum key distribution system and extending the secure transmission distance. Background Art

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

[0003] In order to promote the practical application of QKD, integrated transmission with classical optical networks is an important development trend. Integrated transmission can reduce the cost of optical fiber deployment but will introduce new challenges, namely, weak quantum signals are susceptible to noise interference generated by classical signals, such as Raman scattering noise and four-wave mixing noise. These noises are in-band noises for QKD systems and cannot be filtered out by filters. Therefore, an efficient wavelength allocation scheme is required to achieve the goal of low noise and high key rate. At the same time, the introduction of multi-core optical fibers increases the transmission capacity, but also introduces new noises, such as core-to-core crosstalk noise. At present, in order to reduce the noise interference on quantum signals, many methods are adopted, such as allocating quantum signals and classical signals to different bands or reducing the power of classical signals. Although these methods can reduce noise, they sacrifice resource utilization or classical signal performance, which is not conducive to widespread promotion. Therefore, severe noise interference further restricts the improvement of the security key rate in quantum key distribution systems.

[0004] In summary, the current quantum key distribution transmission system based on multi-core optical fiber urgently needs a wavelength allocation method that can both improve the security key rate and improve resource utilization. Summary of the invention

[0005] This patent aims at the application scenario of space-division multiplexing quantum key distribution and classical optical signal fusion transmission, and designs a non-equally spaced wavelength allocation method to improve the key rate in multi-core optical fiber quantum key distribution. It can reduce the noise interference in the common fiber transmission system and improve the security key rate of the QKD system on the basis of improving the utilization rate of wavelength resources. The technical key points of this method are: the steps of the quantum channel non-equal frequency interval allocation scheme.

[0006] The proposed scheme is mainly aimed at the case where the classical channels are equally spaced, that is, the frequency intervals between the classical channels are equal. In order to improve channel utilization and suppress the crosstalk noise between cores and four-wave mixing noise, the quantum channel and the classical channel are arranged alternately. At the same time, the quantum channel is preferentially arranged on the low-wavelength side of the classical channel to reduce the interference of Raman scattering noise on the quantum signal, and ultimately improve the security key rate of the QKD system.

[0007] As attached Figure 1 As shown, the classical channel is divided into M forward classical channels and N backward classical channels The Q quantum channels are

[0008] The technical points are described in detail as follows:

[0009] In the quantum channel unequal frequency interval allocation scheme, the frequency intervals between quantum channels are not equal, and the optimal quantum channel is selected, which is divided into the following steps:

[0010] S1. Determine the number of optional quantum channels in a multi-core optical fiber. First, determine the frequency range of the optional quantum channels in the multi-core optical fiber [F 1 ,F 2 ], where F 1 is the lowest frequency of the selectable quantum channel, F 2 is the highest frequency of the selectable quantum channel; secondly, determine the number of selectable quantum channels in the multi-core fiber Where g is the minimum frequency interval of the selectable quantum channels, M and N are the number of forward classical channels and backward classical channels respectively;

[0011] S2, calculate the noise power on the optional quantum channel in the multi-core optical fiber; calculate the noise power set P of M forward classical signals and N backward classical signals on K optional quantum channels in the classical fiber core, P = [P 1 ,P 2 ,…P K ], where P K For all classical channels, the kth (k = 1, 2 ... K)

[0012] Select the noise of the quantum channel, as shown in formula (1):

[0013]

[0014] In formula (1), P dark represents the power of the dark count noise, represents the forward in-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel, represents the forward inter-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel,

[0015] represents the backward in-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel, represents the backward inter-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel, represents the forward in-core four-wave mixing noise power generated by the jth group of classical signals on the kth quantum channel, represents the forward inter-core four-wave mixing noise power generated by the j-th group of classical signals on the k-th quantum channel, represents the backward in-core four-wave mixing noise power generated by the j-th group of classical signals on the k-th quantum channel, represents the backward inter-core four-wave mixing noise power generated by the j-th group of classical signals on the k-th quantum channel; the j-th group of classical signals is mainly used to illustrate that the combination of multiple classical signals generates four-wave mixing noise; in the method described in this patent, since the classical channel and the quantum channel are staggered, the quantum channel will not be affected by the four-wave mixing noise generated by the classical signal, so and All are 0;

[0016] S3. Calculate the security key rate of the optional quantum channel, that is, R = [R 1 ,R 2 ,...R K ];

[0017] S4. Remove the channels that cannot generate security keys from the optional quantum channels. The remaining channels are called candidate quantum channels. Update the candidate quantum channel set in descending order of security key rate, that is, R′=[R′ 1 ,R′ 2 ...R′ K ];

[0018] S5. Allocate quantum channels. ch(.) represents the function of obtaining the quantum channel.

[0019] The method described in this patent can be applied to quantum key distribution transmission systems based on multi-core optical fibers. While improving the utilization rate of wavelength resources, it can also improve the security key rate of the quantum key distribution system and extend the safe transmission distance. The implementation of this method can lay the foundation for the integration of quantum key distribution and classical optical networks, and play a positive role in improving the performance of quantum key distribution systems and resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1The wavelength allocation diagram is a diagram showing that the frequency band of the forward classical channel is lower than the frequency band of the backward classical channel. 1 : The lowest frequency of the selectable quantum channel; F 2 : The highest frequency of the selectable quantum channel; The frequency of the first forward classical channel; The frequency of the Mth forward classical channel; The frequency of the first backward classical channel; The frequency of the Nth backward classical channel; the frequency spacing between classical channels is G; the spacing between optional quantum channels is g, and the spacing between the classical channel and the nearest optional quantum channel is also g.

[0021] Attached Figure 2 This is a diagram showing an implementation example of the unequally spaced wavelength allocation scheme for quantum channels. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The following is an example of 4 forward classical channels and 4 backward classical channels, i.e., M=4, N=4. The interval between the classical channels is 200 GHz, i.e., G=200 GHz. The number of quantum channels is 4, and the channel interval between the quantum channels is 50 GHz, i.e., Q=4, t=4. The frequencies of the forward classical channels are 194.2 THz, 194.4 THz, 194.6 THz, and 194.8 THz, respectively, and the frequencies of the backward classical channels are 195.0 THz, 195.2 THz, 195.4 THz, and 195.6 THz, respectively.

[0024] For the quantum channel unequal frequency interval allocation scheme, it is necessary to calculate the noise power of each quantum channel according to formula (1), and then calculate the security key rate. According to S1 to S5 in the invention content, four quantum channels are selected based on the principle of maximum security key rate. When the frequencies of the forward classical channels are 194.2THz, 194.4THz, 194.6THz, and 194.8THz, and the frequencies of the backward classical channels are 195.0THz, 195.2THz, 195.4THz, and 195.6THz, the selected quantum channel frequencies are 195.55THz, 195.05THz, 194.95THz, and 194.9THz, respectively. Figure 2 shown.

[0025] It can be seen from the above embodiments that in the fusion transmission of quantum key distribution and classical optical signals, the quantum channel unequal frequency interval allocation scheme proposed in this patent can improve the performance of the quantum key distribution system, such as extending the secure transmission distance, improving the secure key rate, etc. At the same time, the interleaved distribution of classical channels and quantum channels can improve the utilization rate of channel resources and provide technical support for the application of co-fiber transmission of quantum signals and classical signals.

Claims

1. A non-equally spaced wavelength allocation method for improving the key rate in multi-core optical fiber quantum key distribution, the purpose is to reduce the four-wave mixing noise and Raman scattering noise on the quantum channel, and improve the performance of the quantum key distribution system; the frequency between the classical channel and the quantum channel is staggered to completely avoid the four-wave mixing noise generated by the classical signal falling on the quantum channel; the classical channels are equally spaced, including forward classical channels and backward classical channels; the quantum channels are non-equally spaced; the Raman scattering noise on the quantum channel cannot be completely avoided, and the channel with less interference is determined as the quantum channel, characterized in that The following steps are involved: S1. Determine the number of optional quantum channels in the multi-core optical fiber. First, determine the frequency range of the optional quantum channels in the multi-core optical fiber [F1, F2], where F1 is the lowest frequency of the optional quantum channel and F2 is the highest frequency of the optional quantum channel. Second, determine the number of optional quantum channels in the multi-core optical fiber. Where g is the minimum frequency interval of the selectable quantum channels, M and N are the number of forward classical channels and backward classical channels respectively; S2, calculate the noise power on the optional quantum channel in the multi-core optical fiber; calculate the noise power set P of M forward classical signals and N backward classical signals on K optional quantum channels in the classical fiber core, P = [P1, P2, ... P K ], where P k is the noise of all classical channels on the kth (k=1,2…K) optional quantum channel, as shown in formula (1): In formula (1), P dark represents the power of the dark count noise, represents the forward in-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel, represents the forward inter-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel, represents the backward in-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel, represents the backward inter-core Raman scattering noise power generated by the i-th classical signal on the k-th quantum channel, represents the forward in-core four-wave mixing noise power generated by the jth group of classical signals on the kth quantum channel, represents the forward inter-core four-wave mixing noise power generated by the j-th group of classical signals on the k-th quantum channel, represents the backward in-core four-wave mixing noise power generated by the j-th group of classical signals on the k-th quantum channel, represents the backward inter-core four-wave mixing noise power generated by the j-th group of classical signals on the k-th quantum channel; the j-th group of classical signals is mainly used to illustrate that the combination of multiple classical signals generates four-wave mixing noise; in the method described in this patent, since the classical channel and the quantum channel are staggered, the quantum channel will not be affected by the four-wave mixing noise generated by the classical signal, so and All are 0; S3. Calculate the security key rate of the optional quantum channel, that is, R = [R1, R2, ... R K ]; S4. Remove the channels that cannot generate security keys from the optional quantum channels. The remaining channels are called candidate quantum channels. Update the candidate quantum channel set in descending order of security key rate, that is, R′=[R′1,R′ ′ ...R′ k ]; S5. Allocate quantum channels. represents the first quantum channel, represents the second quantum channel, and ch(.) represents the function of obtaining the quantum channel.

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