A method for allocating equally spaced wavelengths to suppress noise in a multi-core optical fiber quantum key distribution system

Abstract

The present invention discloses an equally spaced wavelength allocation method for suppressing noise in a multi-core optical fiber quantum key distribution system, and the method is applicable to a space-division multiplexing quantum key distribution optical network. The method mainly considers the main noises involved in the space-division multiplexing system, such as the intra-core noise, inter-core noise, forward noise, and backward noise, and aims to minimize the noise on the quantum channel and maximize the security key rate. A quantum channel equal frequency interval wavelength allocation scheme is proposed, which can ensure that while improving the utilization rate of channel resources, the security key rate is improved, the secure transmission distance is extended, etc. The present invention lays a technical foundation 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 light-sharing transmission system integrated with a multi-core optical fiber classical optical network. This method mainly provides a low-noise wavelength allocation scheme for a classical signal and quantum signal co-fiber transmission system based on space division multiplexing and wavelength division multiplexing, which can reduce the interference of inter-core noise and intra-core noise. Background Art

[0002] Quantum Key Distribution (QKD) technology has made significant progress since it was first proposed in 1984, such as the improvement of safe transmission distance. At present, the safe transmission distance of the dual-field protocol exceeds 600km, and it has moved from laboratory optical fiber verification to field verification, indicating that QKD technology has great development potential. Establishing a quantum network for QKD alone requires huge optical fiber costs, which is not conducive to the large-scale deployment and application of QKD. Therefore, integrating QKD with existing optical networks is an important development direction of QKD.

[0003] Combining QKD with classical optical network transmission can save deployment costs and increase transmission capacity, but it will also bring new problems. The power of quantum signals is extremely low, and the noise generated by classical signals has a serious impact on the performance of QKD systems, such as spontaneous Raman scattering noise and four-wave mixing noise. At the same time, as single-core single-mode optical fibers approach their capacity limit, research on space-division multiplexing technology has gradually been put on the agenda. Multicore fiber (MCF) based on space-division multiplexing technology brings hope for the improvement of optical fiber capacity, and can also increase the transmission rate of classical and quantum signals. However, this will also bring new noise, such as inter-core crosstalk noise, inter-core Raman noise, and inter-core four-wave mixing noise. Therefore, the noise interference problem is still the main problem faced by space-division multiplexing quantum key light transmission systems.

[0004] At present, some wavelength allocation schemes have been proposed for quantum key distribution networks, such as the joint suppression scheme for suppressing Raman scattering and four-wave mixing noise in the core, and the channel allocation scheme of classical channel-quantum channel interleaving to suppress crosstalk noise between cores. However, these channel allocation schemes can only suppress one type or part of the noise, and cannot suppress all the noise of the space-division multiplexing quantum key distribution network at the same time. At the same time, there are also some schemes that place quantum signals and classical signals in different bands. Although this reduces noise interference, it will cause a waste of wavelength resources, which is not conducive to promoting the application of space-division multiplexing quantum key distribution networks.

[0005] In summary, the current space-division multiplexing quantum key light-sharing transmission system urgently needs a wavelength allocation method that can both suppress the main noise of the system and improve resource utilization. Summary of the invention

[0006] This patent is aimed at the application scenario of quantum key distribution based on multi-core optical fiber and co-fiber transmission of classical optical communication. It designs a wavelength allocation method that simultaneously suppresses the noise within the core and the noise between the cores. It can reduce the noise interference in the co-fiber transmission system and improve the performance of the QKD system on the basis of improving the utilization rate of wavelength resources. The technical points included in this method are: the process and steps of the frequency interval allocation scheme of quantum channels.

[0007] In the proposed method, the classical channels are distributed at equal frequency intervals. In order to avoid the influence of inter-core crosstalk noise, intra-core four-wave mixing noise and inter-core four-wave mixing, the quantum channels are arranged in an interlaced manner with the classical channels. Furthermore, the quantum channels are distributed on the high-frequency side of the classical channels as much as possible to reduce the interference of Raman scattering noise. 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] The premise for the application of this patent is that the forward classical channel and the backward classical channel are distributed in different bands and the bands cannot overlap. Figure 1 As shown, two cases are considered:

[0010] 1) The forward classical channel frequency band is lower than the backward classical channel frequency band, that is, Where t0 is the number of optional quantum channel intervals g within the classical channel interval G. The frequency of the first allocated quantum channel is lower than that of the Nth backward classical channel by (t0-t)*g(t∈[1,t0-1]), and the frequency of the second allocated quantum channel is lower than that of the N-1th backward classical channel by (t0-t)*g. The interval between the allocated quantum channels is G. Therefore, the frequencies of the Q allocated quantum channels are:

[0011]

[0012] 2) The backward classical channel frequency band is lower than the forward classical channel frequency band, that is, The frequency of the first allocated quantum channel is lower than that of the Mth forward classical channel by (t0-t)*g, and the frequency of the second allocated quantum channel is lower than that of the M-1th forward classical channel by (t0-t)*g. The interval between the allocated quantum channels is G. Therefore, the frequencies of the Q allocated quantum channels are:

[0013]

[0014] In the quantum channel equal frequency interval allocation scheme, the channel intervals between quantum channels are equal. In engineering, it is convenient to control the management layer to control the channels and is easy to implement.

[0015] The method described in this patent can be applied to the space-division multiplexing quantum key distribution and classical optical signal fusion transmission system, and can effectively suppress the main noise in the system under the premise of ensuring low channel resource utilization. Through the implementation of this method, the safe transmission distance of the space-division multiplexing quantum key distribution optical network can be extended, the safe key rate can be improved, and the foundation for the fusion transmission of quantum key distribution and classical optical network can be laid, which can accelerate the application process of quantum key distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attached Figure 1 The wavelength allocation diagram is a diagram in which the frequency band of the forward classical channel is lower than the frequency band of the backward classical channel. F1: the lowest frequency of the optional quantum channel; F2: the highest frequency of the optional quantum channel; f1 f : The frequency of the first forward classical channel; The frequency of the Mth forward classical channel; f1 b : 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.

[0017] Attached Figure 2 This is a diagram showing an implementation example of the equal frequency spacing allocation scheme for quantum channels. DETAILED DESCRIPTION

[0018] 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.

[0019] The following is an example of 4 forward classical channels and 4 backward classical channels, i.e., M=4, N=4. The interval between classical channels is 200GHz, i.e., G=200GHz. The number of quantum channels is 4, and the channel interval between quantum channels is 50GHz, i.e., Q=4, t=4. The frequencies of the forward classical channels are 194.2THz, 194.4THz, 194.6THz, 194.8THz, and the frequencies of the backward classical channels are 195.0THz, 195.2THz, 195.4THz, 195.6THz, respectively. According to the rules of the quantum channel equal frequency interval allocation scheme, the channels between the classical channels are first selected as optional quantum channels, and are allocated from the high frequency band to the low frequency band. Select t0 = 1. According to formula (1), the frequency of the first quantum channel is 195.55 THz. Similarly, the frequencies of the remaining three quantum channels are 195.35 THz, 195.15 THz, and 194.95 THz respectively. Figure 2 shown.

[0020] It can be seen from the above embodiments that in the quantum key distribution and classical optical signal co-fiber transmission system based on multi-core optical fiber, the channel allocation scheme proposed by this method can, on the one hand, effectively suppress the noise interference of the QKD system and improve the security key rate; on the other hand, it can save channel resources and improve resource utilization, thus providing technical support for the application of co-fiber transmission of quantum signals and classical signals.

Claims

1. A method for allocating equally spaced wavelengths to suppress noise in a multi-core optical fiber quantum key distribution system, the purpose of which is to reduce the interference of intra-core noise and inter-core noise on the quantum channel, the quantum channel and the classical channel are interleaved, the classical channels are equally spaced, the quantum channels are equally spaced, the forward classical channel and the backward classical channel are distributed in different bands and the bands cannot overlap, characterized in that: There are two main categories: A. The frequency band of the forward classical channel is lower than that of the backward classical channel; the frequency bands of M forward classical channels are lower than those of N backward classical channels, that is, is the frequency of the Mth forward classical channel, is the frequency of the first backward classical channel; for quantum channels, the frequency of the first allocated quantum channel is (t0-t)*g(t∈[1,t0-1]) lower than that of the Nth backward classical channel, where t0 is the number of optional quantum channel intervals g contained in the classical channel interval G, and the relationship between G and g satisfies G=t0*g; the frequency of the second allocated quantum channel is (t0-t)*g lower than that of the N-1th backward classical channel, and the interval between the allocated quantum channels is G, and so on, until the allocation of Q quantum channels is completed, and the frequencies of the allocated Q quantum channels are as follows: B. The frequency band of the backward classical channel is lower than the frequency band of the forward classical channel; the frequency bands of N backward classical channels are lower than the frequency bands of M forward classical channels, that is, is the frequency of the Nth backward classical channel, f1 f is the frequency of the first forward classical channel; for quantum channels, the frequency of the first allocated quantum channel is lower than that of the Mth forward classical channel by (t0-t)*g, and the frequency of the second allocated quantum channel is lower than that of the M-1th forward classical channel by (t0-t)*g. The interval between the allocated quantum channels is G, and so on, until the allocation of Q quantum channels is completed. The frequencies of the allocated Q quantum channels are as follows:

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