Quantum key distribution system and method capable of realizing common-fiber transmission with classical optical communication system

Abstract

The invention discloses a quantum key distribution system and method capable of realizing common-fiber transmission with a classical optical communication system. The quantum key distribution system is designed to work in the 1350nm wave band, and compared with a conventional scheme adopting the 1310nm wave band, the quantum key distribution system has the advantage that a smaller optical fiber attenuation coefficient can be obtained. Moreover, by deploying a pair of narrow-band filters at the transmitting terminal and the receiving terminal of the QKD equipment, compared with a conventional scheme, the method has the advantages that lower loss can be realized at the receiving terminal of the QKD equipment while the noise is reduced, so that higher signal receiving efficiency is realized. Therefore, when the quantum key distribution system and a classic optical communication system carry out common-fiber transmission, the light intensity of the classic optical communication system does not need to be adjusted, and compared with a conventional scheme adopting a 1310 nm wave band, the quantum key distribution system can obtain higher performance and longer transmission distance.

Description

Technical Field

[0001] The present invention relates to the field of quantum information technology, and in particular to a quantum key distribution system and method that can share fiber transmission with a classical optical communication system. Background Art

[0002] The quantum key distribution (QKD) system, based on the quantum non-cloning and uncertainty principles, can provide high-level information security protection and resist high-computing power cracking. Since the signal light in the quantum key distribution process is very weak, usually at the level of a single photon, when it is transmitted from the transmitting terminal to the receiving terminal through the link, the weak noise signal in the link has a significant impact on the signal light. For this reason, early quantum key distribution systems often need to use dedicated optical fiber links to avoid the influence of other optical signals on the signal light.

[0003] In order to save link resources, relevant technologies have been developed to transmit classical optical communication signals and quantum key distribution signals in the same link. Currently, there are mainly the following implementation methods: one is to attenuate the classical optical signal to reduce the noise it generates; the second is to increase the wavelength interval between the classical optical signal and the quantum optical signal to reduce the noise generated; the third is to add a narrowband filter at the receiving terminal to filter out some noise.

[0004] Figure 1 A device and method for multiplexing quantum signals and classical signals for optical fiber transmission in the prior art are shown, which attenuates the classical signal by arranging an adaptive light intensity adjustment device that is communicatively connected to a QKD receiving terminal between a classical signal input module and a first wavelength division multiplexer, so that the adaptive light intensity adjustment device automatically adjusts the attenuation coefficient according to noise feedback information from the QKD receiving terminal.

[0005] Figure 2 Another quantum light and classical light co-fiber transmission device and transmission method in the prior art is shown, in which a narrowband filter is designed at the receiving terminal to reduce noise; and a wavelength conversion device is designed at the transmitting terminal to convert classical light to a wavelength that is very different from the quantum light, such as 1550nm wavelength in the C band for quantum light and 1310nm or 1625nm wavelength for classical light.

[0006] Figure 3 Another method and device for classical quantum wavelength division multiplexing in the prior art is shown, which realizes co-fiber transmission of classical optical signals and quantum optical signals through a combiner and a splitter of a specific wavelength band, and reduces the influence of Raman scattering noise of the classical optical signal on the quantum optical signal by allocating the wavelength of the classical optical signal and the wavelength of the quantum optical signal.

[0007] However, the purpose of transmitting classical optical communication signals and quantum key distribution signals in the same link is to save link resources. In particular, it is hoped that quantum key distribution signals can be transmitted based on the optical fiber network already laid for classical optical communication. Therefore, the classical optical communication equipment should be modified as little as possible or even not at all.

[0008] Based on this, it can be found that the implementation scheme based on attenuating classical optical power in the existing technology is limited in many practical application scenarios due to the high requirements on the receiving sensitivity of classical optical communication equipment, and the existing optical fiber network may not be able to provide sufficient power adjustment space.

[0009] For the implementation method of reducing noise based on increasing the wavelength interval between classical light signals and quantum light signals, the classical optical communication backbone network often uses the C band, and some have also used the L band. Ultimately, as the bandwidth increases, the use of both the C band and the L band will be a trend. Therefore, in order to pursue a large wavelength interval between quantum light and classical light, the 1310nm band is currently used in many specific schemes. However, the transmission loss of the 1310nm band in optical fiber is about 0.35dB / km. For a system that can tolerate 25dB loss, the 1310nm band can only transmit 71km, which greatly reduces performance and is difficult to apply in many existing sites (whose site distance is 80km).

[0010] For example, in the implementation scheme disclosed in the document "Ultra-high bandwidth quantum secured data transmission", a 25GHz narrowband filter is used, and both quantum light and classical light are selected in the C band (with an interval of about 20nm), which requires lowering the power of classical light. In this implementation scheme, it is proposed to adjust the power of a single channel to -25.5dBm, and the total power is about -15.5dBm when 10 channels are used. At present, the optical communication backbone network equipment often reaches 80 waves, 110 waves or even more, and the fiber-input optical power reaches +21dBm or even higher. When adopting the implementation scheme proposed in this document, the power of conventional optical communication equipment needs to be lowered by about 36.5dB (corresponding to about 4000 times), which is almost difficult to achieve in actual engineering applications.

[0011] In the implementation scheme disclosed in the document "Integrating quantum key distribution with classical communications in backbone fiber network", a 20GHz narrowband filter is used and there is no need to lower the classical light power. The quantum light and classical light are configured in bands far apart to reduce noise (quantum light is in the 1310nm band, classical light is in the C band, and the wavelength interval is about 240nm). Ultimately, only a common fiber transmission distance of 66km can be achieved.

[0012] In the implementation scheme disclosed in the document "Co-propagation of 6 Tb / s (60*100Gb / s) DWDM&QKD channels with~17dBm aggregated WDM power over 50km Standard Single Mode Fiber", quantum optical signals use the 1310nm band, classical optical communication uses the 1550nm band, and the light intensity is attenuated to 16dBm, ultimately only achieving a co-fiber transmission distance of 70km.

[0013] In general, in the currently disclosed classical-quantum signal co-fiber transmission scheme, it is often necessary to lower the classical signal power or set the quantum light wavelength to the 1310nm band. Lowering the classical signal power means that more requirements are placed on classical equipment, which hinders the practical application of classical-quantum signal co-fiber transmission technology. Setting the quantum light wavelength to the 1310nm band results in large transmission losses in the optical fiber, which greatly reduces the performance of the quantum key distribution system. Summary of the invention

[0014] In order to solve the deficiencies existing in the above-mentioned existing implementation schemes, the present invention discloses a quantum key distribution system and method that can be used for co-fiber transmission with a classical optical communication system. Among them, by designing the quantum key distribution system to work in the 1350nm band, a smaller optical fiber attenuation coefficient can be obtained compared with the conventional scheme using the 1310nm band. In addition, by deploying a pair of narrowband filters at the sending and receiving terminals of the QKD device, compared with the conventional scheme, it is possible to reduce noise while achieving smaller losses at the receiving terminal of the QKD device, thereby achieving higher signal reception efficiency. Therefore, when the quantum key distribution system of the present invention is co-fiber transmitted with the classical optical communication system, there is no need to adjust the light intensity of the classical optical communication system, and higher performance and longer transmission distance can be obtained compared with the conventional scheme using the 1310nm band.

[0015] Specifically, the first aspect of the present invention relates to a quantum key distribution system that can be used for co-fiber transmission with a classical optical communication system, which includes a QKD device transmitting terminal and a QKD device receiving terminal, and a classical quantum wave division component and a classical quantum demultiplexing component connected through an optical fiber channel;

[0016] The QKD device transmitting terminal is configured to modulate and generate a quantum light signal having a first wavelength;

[0017] The classical quantum wavelength division component is configured to perform wavelength division multiplexing on the quantum optical signal and the classical optical signal to form a combined light beam for input into the optical fiber channel;

[0018] The classical quantum demultiplexing component is configured to demultiplex the combined light beam from the optical fiber channel to obtain the quantum light signal and the classical light signal;

[0019] The QKD device receiving terminal is configured to demodulate and detect single photons of the quantum optical signal obtained by demultiplexing;

[0020] Wherein, the first wavelength is set between 1345nm and 1355nm.

[0021] Preferably, the first wavelength is 1350 nm.

[0022] Furthermore, the QKD device transmitting terminal includes a light source having a first wavelength and a quantum state modulation module; and the QKD device receiving terminal includes a quantum state demodulation module and a single photon detection module.

[0023] Preferably, the QKD device transmitting terminal further comprises a first narrowband filtering module, which is configured to filter the optical signal output by the light source or the quantum state modulation module;

[0024] The QKD device receiving terminal also includes a second narrowband filtering module, which is configured to filter the quantum light signal.

[0025] More preferably, the first narrowband filtering module and / or the second narrowband filtering module has a bandwidth of 5-10 GHz.

[0026] Preferably, the light source is a semiconductor laser; and / or the narrowband filtering module includes an FP cavity filter or a fiber grating.

[0027] The second aspect of the present invention relates to a quantum key distribution method that can be used for co-fiber transmission with a classical optical communication system, which includes a quantum optical signal generation step, a wavelength division multiplexing step, a wavelength demultiplexing step, and a quantum optical signal detection step;

[0028] The quantum light signal generating step is used to modulate and generate a quantum light signal having a first wavelength, wherein the first wavelength is between 1345 nm and 1355 nm;

[0029] The wavelength division multiplexing step is used to wavelength division multiplex the quantum light signal and the classical light signal to form a combined light beam;

[0030] The wavelength division multiplexing step is used to demultiplex the combined light beam into wavelength division multiplexing to obtain the quantum light signal and the classical light signal;

[0031] The quantum light signal detection step is used to demodulate and detect single photons of the quantum light signal obtained by de-wavelength division multiplexing.

[0032] Preferably, the quantum light signal generating step further comprises the step of performing narrowband filtering on the light signal within a first bandwidth, and the quantum light signal detecting step further comprises the step of performing narrowband filtering on the quantum light signal within a second bandwidth.

[0033] More preferably, the first bandwidth is less than or equal to the second bandwidth.

[0034] Preferably, the quantum key distribution method of the present invention is implemented with the aid of the above-mentioned quantum key distribution system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. It is obvious that the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1-3 Several classical-quantum wavelength division multiplexing schemes in the prior art are shown respectively;

[0038] Figure 4 A preferred example of a quantum key distribution system that can be used for co-fiber transmission with a classical optical communication system according to the present invention is shown;

[0039] Figure 5 A graph showing the actual attenuation coefficient of a quantum light signal in a fiber channel in a quantum key distribution system according to the present invention is shown. DETAILED DESCRIPTION

[0040] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so as to fully convey the spirit of the present invention to those skilled in the art to which the present invention belongs. Therefore, the present invention is not limited to the embodiments disclosed herein.

[0041] Figure 4 A preferred example of a quantum key distribution system according to the present invention that can be used for co-fiber transmission with a classical optical communication system is shown.

[0042] As shown in the figure, the quantum key distribution system of the present invention includes a QKD device sending terminal, a classical quantum wave division component, a classical quantum wave decomposition component and a QKD device receiving terminal, wherein the classical quantum wave division component and the classical quantum wave decomposition component are connected through an optical fiber channel.

[0043] On the transmitting side, the QKD device transmitting terminal performs quantum state modulated on the optical signal to generate a quantum optical signal. The classical quantum wavelength division multiplexing component combines the quantum optical signal generated by the QKD device transmitting terminal with the classical optical signal generated by the classical optical communication device through wavelength division multiplexing, and outputs the combined light to the optical fiber channel for transmission to the receiving side.

[0044] On the receiving side, the combined light beam reaches the classical quantum wavelength division multiplexing component through the optical fiber channel, and the quantum light signal and the classical light signal are obtained through wavelength division multiplexing. The classical light signal and the quantum light signal are then transmitted to the classical optical communication equipment and the QKD equipment receiving terminal respectively.

[0045] In the QKD device receiving terminal, the quantum light signal is demodulated and then detected by the single-photon detection module.

[0046] The inventors have broken through the inherent thinking in this field and conducted research and found that by selecting the wavelength of the quantum light signal (i.e., the first wavelength) within a specific wavelength range, i.e., between 1345nm and 1355nm, especially in the 1350nm band, it is possible to further improve the performance and working distance of the QKD system while meeting the requirements of wavelength division multiplexing co-fiber transmission.

[0047] Figure 5 The actual attenuation coefficient curve of the quantum light signal in the optical fiber channel in the quantum key distribution system according to the present invention is shown, from which it can be seen that in the 1350nm band, the attenuation of the quantum light signal in the optical fiber channel is reduced by about 15% or more compared with the attenuation coefficient in the conventional 1310nm band. For example, in the G652.D optical fiber widely used in the current network, the link attenuation coefficient in the 1350nm band is about 0.3dB / km, while the link attenuation coefficient in the 1310nm band is 0.35dB / km, and the link attenuation coefficient is reduced by about 15%.

[0048] Based on this study, a light source having the above-mentioned first wavelength may be provided in the transmitting terminal of the QKD device of the present invention to provide an optical signal having the first wavelength.

[0049] As a preferred example, the light source may be a semiconductor laser.

[0050] In the QKD device transmitting terminal, the quantum state modulation module can operate in a first wavelength band and perform quantum state modulation on the optical signal generated by the light source to generate a quantum optical signal having a first wavelength.

[0051] In the present invention, a first narrowband filtering module may also be provided in the QKD device transmitting terminal for performing narrowband filtering on the optical signal output by the light source or the quantum state modulation module, thereby further reducing the system noise.

[0052] In a preferred example, the bandwidth of the first narrowband filter module may be 5-10 GHz.

[0053] In a preferred example, the first narrowband filtering module may be an FP cavity filter or a fiber Bragg grating.

[0054] According to the present invention, a second narrowband filtering module may be provided in the QKD device receiving terminal to perform narrowband filtering on the received quantum light signal.

[0055] In a preferred example, the bandwidth of the second narrowband filtering module may be 5-10 GHz.

[0056] In a preferred example, the second narrowband filtering module may be an FP cavity filter or a fiber Bragg grating.

[0057] According to the present invention, the bandwidth of the first narrowband filter module can be set to be less than or equal to the bandwidth of the second narrowband filter module, ensuring that the quantum light signal can pass through the second narrowband filter module better, thereby further reducing the loss of the quantum light signal in the QKD device receiving terminal and achieving overall lower loss.

[0058] Continue to see Figure 4 In the receiving terminal of the QKD device, the quantum state demodulation module can operate in the first wavelength band to demodulate the quantum light signal that has been narrowband filtered, for example. The demodulated quantum light signal finally enters the single-photon detection module (for example, a single-photon detector) for single-photon detection.

[0059] Based on the quantum key distribution system described above, the present invention also proposes a quantum key distribution method that can be used for co-fiber transmission with a classical optical communication system, which includes a quantum light signal generation step, a wavelength division multiplexing step, a wavelength decomposition multiplexing step and a quantum light signal detection step.

[0060] In the quantum light signal generation step, a light signal may be generated by means of a light source, and a quantum state modulation module may be used to perform quantum state modulation on the light signal to generate a quantum light signal, wherein the quantum light signal may have a first wavelength between 1345 nm and 1355 nm, preferably 1350 nm.

[0061] According to the present invention, in the step of generating the quantum optical signal, a first narrowband filtering module can be used to perform narrowband filtering on the optical signal with a first bandwidth, wherein the first bandwidth can be 5-10 GHz.

[0062] In the wavelength division multiplexing step, the quantum light signal generated by the QKD device sending terminal and the classical light signal generated by the classical optical communication device can be wavelength-division multiplexed to form a combined light beam with the help of classical quantum wavelength division components, so as to co-transmit the quantum light signal and the classical light signal in the optical fiber channel.

[0063] In the wavelength division demultiplexing step, the combined light beam can be demultiplexed by means of a classical quantum wavelength division demultiplexing component to obtain a quantum light signal and a classical light signal.

[0064] In the quantum light signal detection step, the quantum light signal obtained by de-wavelength division multiplexing can be demodulated by a quantum state demodulation module, and single photon detection can be performed on the optical signal obtained by demodulation by a single photon detection module.

[0065] According to the present invention, in the quantum light signal detection step, a second narrowband filtering module can be used to perform narrowband filtering on the quantum light signal with a second bandwidth, wherein the second bandwidth can be 5-10 GHz.

[0066] Among them, by setting the first bandwidth to be less than or equal to the second bandwidth, it is ensured that the quantum light signal can better pass through the second narrowband filtering module, effectively ensuring that the quantum light signal has a smaller loss in the QKD device receiving terminal.

[0067] Based on the above, it can be seen that for the conventional implementation schemes that currently need to attenuate the power of classical optical communication equipment or configure the wavelength of QKD equipment in the 1310nm band, in practical applications, it is faced with the need to transform classical optical communication equipment or quantum key distribution equipment because the 1310nm optical signal has a large loss in the optical fiber, the performance is reduced, and the actual engineering application is hindered. The present invention designs the quantum key distribution system to work in the 1350nm band, which has a smaller attenuation coefficient in the optical fiber than the conventional 1310nm band; and by designing a pair of narrowband filters, compared with conventional schemes, it can reduce noise while achieving smaller losses at the QKD device receiving terminal, and achieve higher signal receiving efficiency. Therefore, the quantum key distribution system of the present invention does not need to adjust the light intensity of the classical optical communication system when it is transmitted on the same fiber as the classical optical communication system, and can obtain higher performance and longer transmission distance than the conventional 1310nm scheme. More importantly, with the increase in the shared fiber transmission distance (which can reach more than 80km with the help of the solution of the present invention), it will be able to meet the distances of most existing network sites, allowing quantum key distribution equipment to directly use existing network optical fiber resources, greatly reducing the deployment cost of quantum key distribution equipment, promoting the application of quantum key distribution equipment, and providing information security protection for more users.

[0068] Although the present invention has been described above through specific embodiments in conjunction with the accompanying drawings, those skilled in the art will readily recognize that the above embodiments are merely exemplary and are used to illustrate the principles of the present invention, and do not limit the scope of the present invention. Those skilled in the art may make various combinations, modifications and equivalent substitutions to the above embodiments without departing from the spirit and scope of the present invention.

Claims

1. A quantum key distribution system that can be used for co-fiber transmission with a classical optical communication system, comprising a QKD device transmitting terminal and a QKD device receiving terminal, as well as a classical quantum wave division component and a classical quantum wave decomposition component connected via an optical fiber channel; The QKD device transmitting terminal is configured to modulate and generate a quantum light signal having a first wavelength; The classical quantum wavelength division component is configured to perform wavelength division multiplexing on the quantum optical signal and the classical optical signal to form a combined light beam for input into the optical fiber channel; The classical quantum demultiplexing component is configured to demultiplex the combined light beam from the optical fiber channel to obtain the quantum light signal and the classical light signal; The QKD device receiving terminal is configured to demodulate and detect single photons of the quantum optical signal obtained by demultiplexing; in, The first wavelength is set between 1345nm and 1355nm.

2. The quantum key distribution system according to claim 1, wherein: The first wavelength is 1350 nm.

3. The quantum key distribution system according to claim 1, wherein: The QKD device transmitting terminal includes a light source having a first wavelength, and a quantum state modulation module; The QKD device receiving terminal includes a quantum state demodulation module and a single photon detection module.

4. The quantum key distribution system according to claim 3, wherein: The QKD device transmitting terminal also includes a first narrowband filtering module, which is configured to filter the optical signal output by the light source or the quantum state modulation module; The QKD device receiving terminal also includes a second narrowband filtering module, which is configured to filter the quantum light signal.

5. The quantum key distribution system according to claim 4, wherein: The first narrowband filtering module and / or the second narrowband filtering module has a bandwidth of 5-10 GHz.

6. The quantum key distribution system according to claim 4, wherein: The light source is a semiconductor laser; and / or the narrowband filtering module includes an FP cavity filter or a fiber grating.

7. A quantum key distribution method that can be used for co-fiber transmission with a classical optical communication system, comprising a quantum optical signal generation step, a wavelength division multiplexing step, a wavelength demultiplexing step, and a quantum optical signal detection step; The quantum light signal generation step is used to modulate and generate a quantum light signal having a first wavelength, wherein: The first wavelength is between 1345nm and 1355nm; The wavelength division multiplexing step is used to wavelength division multiplex the quantum light signal and the classical light signal to form a combined light beam; The wavelength division multiplexing step is used to demultiplex the combined light beam into wavelength division multiplexing to obtain the quantum light signal and the classical light signal; The quantum light signal detection step is used to demodulate and detect single photons of the quantum light signal obtained by de-wavelength division multiplexing.

8. The quantum key distribution method according to claim 7, wherein: The quantum light signal generation step further includes a step of performing narrowband filtering on the light signal within a first bandwidth, and the quantum light signal detection step further includes a step of performing narrowband filtering on the quantum light signal within a second bandwidth.

9. The quantum key distribution method according to claim 8, wherein: The first bandwidth is less than or equal to the second bandwidth.

10. The quantum key distribution method according to any one of claims 7 to 9, which is implemented by means of the quantum key distribution system according to any one of claims 1 to 6.

Images