A security enhancement method for a quantum noise current encryption system based on a multi-core optical fiber

Abstract

The application discloses a security enhancement method of a quantum noise stream encryption system based on a multi-core optical fiber, and shares quantum noise stream encryption keys and optical delay keys of each signal channel at a transmitting / receiving terminal; a distributed feedback laser generates a homologous local oscillator and optical carriers of each channel; a transmitting terminal uses multiple IQ modulators to modulate multiple quantum noise stream encryption optical signals, delays the signals according to the optical delay keys, and then transmits the signals to a receiving terminal through peripheral cores of a multi-core optical fiber; the homologous local oscillator light is transmitted to a receiving optical splitter through an intermediate core, and after being split, the light is subjected to optical delay matching to obtain a local oscillator of each signal channel; the local oscillator of each channel and the encryption optical signal are subjected to self-coherent detection through a coherent receiver to obtain an encryption electrical signal of each channel; and the encryption electrical signal is decrypted through the quantum noise stream encryption key to restore plaintext; the application relies on the physical structure of the multi-core optical fiber and the artificially added optical delay to interfere with illegal parties to eavesdrop, improves security, realizes expansion and simplifies a DSP.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and in particular relates to a security enhancement method for a multi-core fiber quantum noise stream encryption system. Background Technology

[0002] With the development of internet applications, a large amount of user personal information is transmitted through the network every moment. Therefore, the security of communication networks has become an important performance indicator. However, with the development of quantum computing, traditional cryptographic encryption methods based on computational complexity can no longer guarantee absolute security, and physical layer encryption technology has become an alternative. Compared with classical physical layer encryption technologies such as quantum communication, chaotic secure communication, and optical code division multiplexing, quantum noise stream encryption technology stands out due to its excellent compatibility and high-speed long-distance transmission capabilities, becoming a research hotspot in recent years.

[0003] However, unlike traditional one-time pad encryption schemes, the key for quantum noise stream encryption is typically obtained by expanding the seed key using a shift register. This makes it vulnerable to brute-force attacks, such as fast correlation attacks, making it essential to further enhance the security of quantum noise stream encryption. Currently, the main approaches to enhancing the security of quantum noise stream encryption include: First, reducing the system's signal-to-noise ratio, but this affects normal communication performance and shortens transmission distance; second, increasing the order of the quantum noise stream encryption, which places higher demands on the quantization accuracy of the transmitter's DAC and only improves the masking of the encrypted bits, leaving the information bits exposed to eavesdropping and susceptible to low-order demodulation techniques; third, artificially adding random noise, which, to avoid additional key overhead, also only masks the encrypted bits, similar to the previous approach. In short, current solutions cannot completely mask the information bits, and simply increasing the masking effect does not significantly improve the security of quantum noise stream encryption. Summary of the Invention

[0004] To address the shortcomings and improvement needs of existing technologies, this invention provides a security enhancement method based on a multi-core fiber quantum noise stream encryption system.

[0005] The multi-core fiber quantum noise stream encryption system of the present invention includes:

[0006] The multi-core fiber quantum noise stream encryption system includes:

[0007] Transmitter terminal, 1st tunable optical delay unit, 2nd tunable optical delay unit, ..., Kth tunable optical delay unit, distributed feedback laser, transmit optical splitter, fan-in, multi-core fiber, 1st IQ modulator, 2nd IQ modulator, ..., Kth IQ modulator, fan-out, receive optical splitter, 1st tunable optical delay unit, 2nd tunable optical delay unit, ..., Kth tunable optical delay unit, receiver terminal;

[0008] The transmitting terminal is connected to the receiving terminal;

[0009] The output of the transmitting terminal is connected to the input of the first tunable optical delay unit, the output of the transmitting terminal is connected to the input of the second tunable optical delay unit, ..., the output of the transmitting terminal is connected to the input of the Kth tunable optical delay unit;

[0010] The distributed feedback laser is connected to the optical transmitter splitter;

[0011] The transmitting optical splitter is connected to the fan-in unit;

[0012] The fan-in connector is connected to the middle core of the multi-core optical fiber.

[0013] The middle core of the multi-core optical fiber is connected to the fan-out.

[0014] The output of the transmitting optical splitter is connected to the input of the first IQ modulator, the output of the transmitting optical splitter is connected to the input of the second IQ modulator, ..., the output of the transmitting optical splitter is connected to the input of the Kth IQ modulator;

[0015] The output of the transmitting terminal is connected to the input of the first IQ modulator, the output of the transmitting terminal is connected to the input of the second IQ modulator, ..., the output of the transmitting terminal is connected to the input of the Kth IQ modulator;

[0016] The output of the k-th IQ modulator is sequentially connected to the input of the k-th transmitter tunable optical delay unit, where k∈[1,K].

[0017] The output of the first adjustable optical delay unit is connected to the input of the fan-in unit; the output of the second adjustable optical delay unit is connected to the input of the fan-in unit; ..., the output of the Kth adjustable optical delay unit is connected to the input of the fan-in unit.

[0018] The fan-in device is sequentially connected to the multiple outer cores of the multi-core optical fiber.

[0019] The multiple outer cores of the multi-core optical fiber are connected to the fan-out in sequence.

[0020] The fan-out is connected to the receiving optical splitter;

[0021] The output of the receiving optical splitter is connected to the input of the first adjustable optical delay unit at the receiving end; the output of the receiving optical splitter is connected to the input of the second adjustable optical delay unit at the receiving end; ..., the output of the receiving optical splitter is connected to the input of the Kth adjustable optical delay unit at the receiving end;

[0022] The output of the first adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver; the output of the second adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver; ..., the output of the Kth adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver.

[0023] The fan-out is connected to the coherent receiver;

[0024] The coherent receiver is connected to the receiving terminal;

[0025] The number of tunable optical delay units at the transmitting end, the outer cores of the multi-core optical fiber, the IQ modulator, and the tunable optical delay units at the receiving end are all the same.

[0026] The security enhancement method specifically includes the following steps:

[0027] Step 1: The transmitting terminal and the receiving terminal share the quantum noise stream encryption key and the optical delay key for each signal channel, and transmit the optical delay key for each signal channel to each tunable optical delay unit at the transmitting end;

[0028] Step 2: The distributed feedback laser generates a local oscillator signal from the same source and transmits it to the fan-out, generating an optical carrier for each signal channel and transmitting it to each IQ modulator;

[0029] Step 3: The transmitting terminal generates a high-order encrypted analog signal, which is further modulated to obtain the quantum noise stream encrypted optical signal for each signal channel;

[0030] Step 4: Generate a delayed quantum noise stream encrypted optical signal for each signal channel and transmit it to the fan-out;

[0031] Step 5: Couple the local oscillator optical signal from the same source to the receiving optical splitter, and couple the delayed quantum noise stream encrypted optical signal of each signal channel to the coherent receiver;

[0032] Step 6: Generate the local oscillator optical signal of the signal channel and transmit it to the adjustable optical delay unit at the receiving end;

[0033] Step 7: Generate the local oscillator optical signal for each signal channel by using the adjustable optical delay unit at each receiver, and transmit it to the coherent receiver for self-coherent detection to obtain the quantum noise stream encrypted electrical signal for each signal channel, and output it to the receiver terminal;

[0034] Step 8: The receiving terminal combines the quantum noise stream encrypted electrical signal of each signal channel with the quantum noise stream encryption key and decrypts it using the quantum noise stream decryption method to obtain the decrypted plaintext signal.

[0035] Preferably, step 1 is as follows:

[0036] The transmitting terminal generates a plaintext signal and generates a quantum noise stream encryption key and an optical delay key for each signal channel through a pseudo-random number generator. The transmitting terminal transmits the quantum noise stream encryption key and the optical delay key for each signal channel to the receiving terminal for sharing. The number of bits for quantum noise stream encryption is set, and a higher-order encrypted signal is obtained by combining the noise stream encryption key with quantum noise stream encryption. The optical delay key for each signal channel is transmitted to each transmitter's adjustable optical delay unit.

[0037] Preferably, step 2 is as follows:

[0038] The laser signal output by the distributed feedback laser is split into multiple original optical signals by the transmitting optical splitter. One of the original optical signals is coupled into the middle core of the multi-core optical fiber through the fan-in device as the same source local oscillator optical signal. The middle core of the multi-core optical fiber transmits the same source local oscillator optical signal to the fan-out device. The remaining original optical signals are used as the optical carriers of each signal channel. The optical carriers of each signal channel are transmitted to each IQ modulator through the optical fiber.

[0039] Preferably, step 3 is as follows:

[0040] The transmitting terminal converts the high-order encrypted signal into a high-order encrypted analog signal through digital-to-analog conversion, and then transmits it to each IQ modulator. Each IQ modulator modulates the high-order encrypted analog signal onto the optical carrier of each signal channel to obtain the quantum noise stream encrypted optical signal of each signal channel. The quantum noise stream encrypted optical signal of each signal channel is then transmitted to the tunable optical delay of each signal channel.

[0041] Preferably, step 4 is as follows:

[0042] Each transmitter's tunable optical delayer optically delays the modulated quantum noise stream encrypted optical signal of each signal channel according to the optical delay key of each signal channel, resulting in a delayed quantum noise stream encrypted optical signal for each signal channel. The delayed quantum noise stream encrypted optical signal of each signal channel is then coupled into each outer core of the multi-core optical fiber through a fan-in connector. Each outer core of the multi-core optical fiber transmits the delayed quantum noise stream encrypted optical signal of each signal channel to the fan-out connector.

[0043] Preferably, step 5 is as follows:

[0044] The fan-out coupler couples the local oscillator optical signal from the same source out of the multi-core optical fiber and transmits it to the receiving optical splitter. It couples the delayed quantum noise stream encrypted optical signal of each signal channel out of the multi-core optical fiber and transmits it to the coherent receiver.

[0045] Preferably, step 6 is as follows:

[0046] The receiving optical splitter splits the original local oscillator optical signal into multiple signal channels. The number of channels of the optical splitter is the same as the number of outer cores of the multi-core optical fiber. The local oscillator optical signal of each signal channel is transmitted to the adjustable optical delay at the receiving end.

[0047] Preferably, step 7 is as follows:

[0048] By combining the optical delay key of each signal channel, the delay corresponding to the local oscillator optical signal of each signal channel is set by the adjustable optical delayer of each receiver. The local oscillator optical signal of each signal channel is optically delayed and matched by the adjustable optical delayer of each receiver to obtain the local oscillator optical signal of each signal channel with optical delay matching. The local oscillator optical signal of each signal channel with optical delay matching and the quantum noise stream encrypted optical signal of each signal channel after delay are input to the coherent receiver for self-coherent detection to obtain the quantum noise stream encrypted electrical signal of each signal channel, and output to the receiver terminal.

[0049] The advantages of this invention are:

[0050] Using self-coherent detection simplifies the digital signal processing flow at the receiver.

[0051] Spatial division multiplexing based on multi-core optical fibers can expand transmission capacity.

[0052] By relying on the physical characteristics of multi-core optical fibers and artificially added optical delay, the range of quantum noise masking can be effectively improved, and it can mask not only encryption bits, but also signal bits.

[0053] Even if the eavesdropper obtains the quantum noise stream encryption key, they will still be unable to decrypt the plaintext. Attached Figure Description

[0054] Figure 1 : Flowchart of the method according to an embodiment of the present invention;

[0055] Figure 2 The diagram shows the transmission performance and security performance in the experiments of this invention embodiment. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] In specific implementation, the method proposed in the technical solution of this invention can be automatically executed by those skilled in the art using computer software technology. System devices for implementing the method, such as computer-readable storage media storing the corresponding computer program of the technical solution of this invention and computer equipment including the computer program running the corresponding computer program, should also be within the protection scope of this invention.

[0058] The experiments of this invention were conducted in the laboratory and can simulate high-speed fiber optic communication within or between data centers.

[0059] The following is combined with Figures 1 to 2 The present invention specifically describes a security enhancement method for a multi-core fiber quantum noise stream encryption system.

[0060] The specific implementation of the system of the present invention is a multi-core fiber quantum noise stream encryption system, as detailed below:

[0061] Transmitter terminal, 1st tunable optical delay unit, 2nd tunable optical delay unit, ..., Kth tunable optical delay unit, distributed feedback laser, transmit optical splitter, fan-in, multi-core fiber, 1st IQ modulator, 2nd IQ modulator, ..., Kth IQ modulator, fan-out, receive optical splitter, 1st tunable optical delay unit, 2nd tunable optical delay unit, ..., Kth tunable optical delay unit, receiver terminal;

[0062] The transmitting terminal is connected to the receiving terminal;

[0063] The output of the transmitting terminal is connected to the input of the first tunable optical delay unit, the output of the transmitting terminal is connected to the input of the second tunable optical delay unit, ..., the output of the transmitting terminal is connected to the input of the Kth tunable optical delay unit;

[0064] The distributed feedback laser is connected to the optical transmitter splitter;

[0065] The transmitting optical splitter is connected to the fan-in unit;

[0066] The fan-in connector is connected to the middle core of the multi-core optical fiber.

[0067] The middle core of the multi-core optical fiber is connected to the fan-out.

[0068] The output of the transmitting optical splitter is connected to the input of the first IQ modulator, the output of the transmitting optical splitter is connected to the input of the second IQ modulator, ..., the output of the transmitting optical splitter is connected to the input of the Kth IQ modulator;

[0069] The output of the transmitting terminal is connected to the input of the first IQ modulator, the output of the transmitting terminal is connected to the input of the second IQ modulator, ..., the output of the transmitting terminal is connected to the input of the Kth IQ modulator;

[0070] The output of the k-th IQ modulator is sequentially connected to the input of the k-th transmitter tunable optical delay unit, where k∈[1,K].

[0071] The output of the first adjustable optical delay unit is connected to the input of the fan-in unit; the output of the second adjustable optical delay unit is connected to the input of the fan-in unit; ..., the output of the Kth adjustable optical delay unit is connected to the input of the fan-in unit.

[0072] The fan-in device is sequentially connected to the multiple outer cores of the multi-core optical fiber.

[0073] The multiple outer cores of the multi-core optical fiber are connected to the fan-out in sequence.

[0074] The fan-out is connected to the receiving optical splitter;

[0075] The output of the receiving optical splitter is connected to the input of the first adjustable optical delay unit at the receiving end; the output of the receiving optical splitter is connected to the input of the second adjustable optical delay unit at the receiving end; ..., the output of the receiving optical splitter is connected to the input of the Kth adjustable optical delay unit at the receiving end;

[0076] The output of the first adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver; the output of the second adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver; ..., the output of the Kth adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver.

[0077] The fan-out is connected to the coherent receiver;

[0078] The coherent receiver is connected to the receiving terminal;

[0079] The number of tunable optical delay units at the transmitting end, the outer cores of the multi-core optical fiber, the IQ modulator, and the tunable optical delay units at the receiving end are all the same.

[0080] The transmitter terminal is model Keysight M8195A.

[0081] The model number of all the aforementioned transmitter-adjustable optical delay units is: MDL-002-1-35-33-SS-FC-APC

[0082] The model of the distributed feedback laser is: SWLD-1550100122-02

[0083] The model of the transmitting optical splitter is: 1:7 optical splitter.

[0084] The fan-in type is 7-core fan-in.

[0085] The multi-core optical fiber is a 10km 7-core fiber.

[0086] The model number of the multiple IQ modulators is FTM7977.

[0087] The fan-out model is 7-core fan-out.

[0088] The receiving optical splitter is a 1:7 optical splitter.

[0089] The model number of the plurality of receiver-end adjustable optical delay units is: MDL-002-1-35-33-SS-FC-APC

[0090] The model of the coherent receiver is FUJITSU-FIM24706 / 301.

[0091] The receiving terminal is model number Tektronix DPO-73304D.

[0092] The specific embodiments of the method of the present invention are as follows:

[0093] Step 1: The transmitting terminal and the receiving terminal share the quantum noise stream encryption key and the optical delay key for each signal channel, and transmit the optical delay key for each signal channel to each tunable optical delay unit at the transmitting end;

[0094] Step 1 is described in detail as follows:

[0095] The transmitting terminal generates a plaintext signal and generates a quantum noise stream encryption key and an optical delay key for each signal channel through a pseudo-random number generator. The transmitting terminal transmits the quantum noise stream encryption key and the optical delay key for each signal channel to the receiving terminal for sharing. The number of bits for quantum noise stream encryption is set, and a higher-order encrypted signal is obtained by combining the noise stream encryption key with quantum noise stream encryption. The optical delay key for each signal channel is transmitted to each transmitter's adjustable optical delay unit.

[0096] Step 2: The distributed feedback laser generates a local oscillator signal from the same source and transmits it to the fan-out, generating an optical carrier for each signal channel and transmitting it to each IQ modulator;

[0097] Step 2 is described in detail below:

[0098] The laser signal output by the distributed feedback laser is split into multiple original optical signals by the transmitting optical splitter. One of the original optical signals is coupled into the middle core of the multi-core optical fiber through the fan-in device as the same source local oscillator optical signal. The middle core of the multi-core optical fiber transmits the same source local oscillator optical signal to the fan-out device. The remaining original optical signals are used as the optical carriers of each signal channel. The optical carriers of each signal channel are transmitted to each IQ modulator through the optical fiber.

[0099] Step 3: The transmitting terminal generates a high-order encrypted analog signal, which is further modulated to obtain the quantum noise stream encrypted optical signal for each signal channel;

[0100] Step 3 is described in detail below:

[0101] The transmitting terminal converts the high-order encrypted signal into a high-order encrypted analog signal through digital-to-analog conversion, and then transmits it to each IQ modulator. Each IQ modulator modulates the high-order encrypted analog signal onto the optical carrier of each signal channel to obtain the quantum noise stream encrypted optical signal of each signal channel. The quantum noise stream encrypted optical signal of each signal channel is then transmitted to the tunable optical delay of each signal channel.

[0102] Step 4: Generate a delayed quantum noise stream encrypted optical signal for each signal channel and transmit it to the fan-out;

[0103] Step 4 is described in detail below:

[0104] Each transmitter's tunable optical delayer optically delays the modulated quantum noise stream encrypted optical signal of each signal channel according to the optical delay key of each signal channel, resulting in a delayed quantum noise stream encrypted optical signal for each signal channel. The delayed quantum noise stream encrypted optical signal of each signal channel is then coupled into each outer core of the multi-core optical fiber through a fan-in connector. Each outer core of the multi-core optical fiber transmits the delayed quantum noise stream encrypted optical signal of each signal channel to the fan-out connector.

[0105] Step 5: Couple the local oscillator optical signal from the same source to the receiving optical splitter, and couple the delayed quantum noise stream encrypted optical signal of each signal channel to the coherent receiver;

[0106] Step 5 is described in detail below:

[0107] The fan-out coupler couples the local oscillator optical signal from the same source out of the multi-core optical fiber and transmits it to the receiving optical splitter. It couples the delayed quantum noise stream encrypted optical signal of each signal channel out of the multi-core optical fiber and transmits it to the coherent receiver.

[0108] Step 6: Generate the local oscillator optical signal of the signal channel and transmit it to the adjustable optical delay unit at the receiving end;

[0109] Step 6 is as follows:

[0110] The receiving optical splitter splits the original local oscillator optical signal into multiple signal channels. The number of channels of the optical splitter is the same as the number of outer cores of the multi-core optical fiber. The local oscillator optical signal of each signal channel is transmitted to the adjustable optical delay at the receiving end.

[0111] Step 7: Generate the local oscillator optical signal for each signal channel by using the adjustable optical delay unit at each receiver, and transmit it to the coherent receiver for self-coherent detection to obtain the quantum noise stream encrypted electrical signal for each signal channel, and output it to the receiver terminal;

[0112] Step 7 is as follows:

[0113] By combining the optical delay key of each signal channel, the delay corresponding to the local oscillator optical signal of each signal channel is set by the adjustable optical delayer of each receiver. The local oscillator optical signal of each signal channel is optically delayed and matched by the adjustable optical delayer of each receiver to obtain the local oscillator optical signal of each signal channel with optical delay matching. The local oscillator optical signal of each signal channel with optical delay matching and the quantum noise stream encrypted optical signal of each signal channel after delay are input to the coherent receiver for self-coherent detection to obtain the quantum noise stream encrypted electrical signal of each signal channel, and output to the receiver terminal.

[0114] Step 8: The receiving terminal combines the quantum noise stream encrypted electrical signal of each signal channel with the quantum noise stream encryption key and decrypts it using the quantum noise stream decryption method to obtain the decrypted plaintext signal.

[0115] The output of the transmitting laser is split by an optical splitter. A portion of the split beam serves as a self-coherent optical carrier at the receiving end, transmitted through the central fiber core. The remaining portion is used to modulate the quantum noise stream encryption signal. The outer cores of the multi-core fiber are used to transmit the ciphertext signal, while the middle cores are used to transmit the local oscillator.

[0116] For each signal channel, an optical delay is artificially added to introduce a mismatch length. This prevents the eavesdropper from achieving ideal self-coherent detection after successfully intercepting the co-originating optical carrier in the middle fiber core.

[0117] At the receiver, the received optical carrier from the middle fiber core is divided into n parts, where n is the number of outer fiber cores. Then, the split optical carriers from the same source are subjected to the same optical delay as the corresponding channel at the transmitter. Afterwards, the optically delayed carriers and the quantum noise stream encryption signal transmitted through the channel are input to a coherent optical transmitter for coherent detection. Assuming the initial phase of the laser is 0, the signal light before entering the coherent receiver can be represented as:

[0118] ,

[0119] in, t For a certain moment of the defined signal transmission, s ( t )for t Encrypting signals with quantum noise stream at any given moment. and φ For the frequency and phase noise of the laser, τ A The optical delay added by the transmitter in the signal path. t-τ A This indicates the time after the transmitter delay. Similarly, a local oscillator from the same source can be represented as:

[0120] ,

[0121] in τ B The optical delay added to the optical carrier path at the receiving end. and φ For the frequency and phase noise of the laser, t-τ B This represents the time after the receiver's delay. For a legitimate receiver, the phase noise carried by the signal can be expressed as:

[0122] .

[0123] Since the two parties involved in the initial operation have already shared the optical delay key, therefore τ A = τ B Therefore, the phase noise is 0. The receiver does not need to perform phase noise compensation.

[0124] For the eavesdropper, firstly, it is difficult to intercept the optical carrier located in the middle fiber core. Secondly, even if they successfully intercept it, they cannot perform optical path matching because they do not know the optical delay artificially added by the transmitter, and the signal they receive still carries phase noise.

[0125] This invention provides a preferred embodiment. The transmitter first maps the 35GBaud signal to be transmitted into a 16QAM modulation format, then encrypts the 16QAM signal using QNSC according to key A. After upsampling and roll-off filtering, the signal is input to an arbitrary waveform generator. The transmitter uses a DFB laser as the light source, splitting its output in two: one as the local oscillator and the other as the carrier of the modulation signal. The output signal of the arbitrary waveform generator is modulated onto the optical carrier by a dual-polarization IQ modulator, and then input into the outer core of a seven-core optical fiber for transmission. The local oscillator light is coupled into the middle core for transmission. After transmission through the optical fiber, the receiver performs self-coherent detection on the signal, and then inputs it to an oscilloscope for offline signal processing. During signal processing, roll-off filtering and downsampling are performed first, followed by channel equalization using an RDE equalizer, and then transceiver non-ideal characteristics compensation using a 4x2 MIMO equalizer. Finally, QNSC decryption is performed according to key A to obtain the 16QAM plaintext signal.

[0126] Figure 2 The diagram shows the performance of transmission through different channels. It can be seen that the signal quality of each peripheral fiber core is not significantly different. By using multi-core optical fibers for spatial multiplexing, the transmission capacity can be effectively improved.

[0127] Figure 2 b shows the noise masking number and bit error rate performance at different mismatch lengths. The noise masking number (NMS) is commonly used to quantitatively measure the security of quantum noisy stream encryption systems, and it is defined as:

[0128] .

[0129] in, NMS I Represents the quantum noise masking number of the I-path. NMS Q σ represents the quantum noise masking number of the Q-path. I and σ Q Δ represents the noise standard deviation of the I-path and Q-path respectively, and Δ represents the adjacent level difference of the quantum noise stream encryption signal.

[0130] As can be seen, when the mismatch length reaches 3m, NMS improves to 6 times that of the case without a mismatch length. Meanwhile, the bit error rates at different mismatch lengths indicate that even if the eavesdropper obtains the key for quantum noise stream encryption, they are completely unable to decrypt the correct plaintext when the mismatch length is greater than 6m.

[0131] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0132] It should be understood that the above description of the embodiments is quite detailed, but it should not be considered as a limitation on the scope of protection of this invention. Those skilled in the art can make substitutions or modifications under the guidance of this invention without departing from the scope of protection of the claims of this invention, and all such substitutions or modifications fall within the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims.

Claims

1. A security enhancement method for a multi-core fiber quantum noise stream encryption system, characterized in that: The multi-core fiber quantum noise stream encryption system includes: Transmitter terminal, 1st tunable optical delay unit, 2nd tunable optical delay unit, ..., Kth tunable optical delay unit, distributed feedback laser, transmit optical splitter, fan-in, multi-core fiber, 1st IQ modulator, 2nd IQ modulator, ..., Kth IQ modulator, fan-out, receive optical splitter, 1st tunable optical delay unit, 2nd tunable optical delay unit, ..., Kth tunable optical delay unit, receiver terminal, coherent receiver; The transmitting terminal is connected to the receiving terminal; The output of the transmitting terminal is connected to the input of the first IQ modulator, the output of the transmitting terminal is connected to the input of the second IQ modulator, ..., the output of the transmitting terminal is connected to the input of the Kth IQ modulator; The output of the first IQ modulator is connected to the input of the first tunable optical delay unit at the transmitter; the output of the second IQ modulator is connected to the input of the second tunable optical delay unit at the transmitter; ..., the output of the Kth IQ modulator is connected to the input of the Kth tunable optical delay unit at the transmitter; The distributed feedback laser is connected to the optical transmitter splitter; The transmitting optical splitter is connected to the fan-in unit; The fan-in device is connected to the multi-core optical fiber; The multi-core optical fiber is connected to the fan-out; The output of the transmitting optical splitter is connected to the input of the first IQ modulator, the output of the transmitting optical splitter is connected to the input of the second IQ modulator, ..., the output of the transmitting optical splitter is connected to the input of the Kth IQ modulator; The output of the first tunable optical delay unit is connected to the input of the fan-in unit; the output of the second tunable optical delay unit is connected to the input of the fan-in unit; ..., the output of the Kth tunable optical delay unit is connected to the input of the fan-in unit. The fan-out is connected to the receiving optical splitter; The output of the receiving optical splitter is connected to the input of the first adjustable optical delay unit at the receiving end; the output of the receiving optical splitter is connected to the input of the second adjustable optical delay unit at the receiving end; ..., the output of the receiving optical splitter is connected to the input of the Kth adjustable optical delay unit at the receiving end; The output of the first adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver; the output of the second adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver; ..., the output of the Kth adjustable optical delay unit at the receiving end is connected to the input of the coherent receiver. The fan-out is connected to the coherent receiver; The coherent receiver is connected to the receiving terminal; The number of tunable optical delay units at the transmitting end, the outer cores of the multi-core optical fiber, the IQ modulator, and the tunable optical delay units at the receiving end are all the same. The security enhancement method specifically includes the following steps: Step 1: The transmitting terminal and the receiving terminal share the quantum noise stream encryption key and the optical delay key for each signal channel, and transmit the optical delay key for each signal channel to each tunable optical delay unit at the transmitting end; Step 2: The distributed feedback laser generates a local oscillator signal from the same source and transmits it to the fan-out, generating an optical carrier for each signal channel and transmitting it to each IQ modulator; Step 3: The transmitting terminal generates a high-order encrypted analog signal, which is further modulated to obtain the quantum noise stream encrypted optical signal for each signal channel; Step 4: Generate a delayed quantum noise stream encrypted optical signal for each signal channel and transmit it to the fan-out; Step 5: Couple the local oscillator optical signal from the same source to the receiving optical splitter through the middle core of the multi-core optical fiber, and couple the delayed quantum noise stream encrypted optical signal of each signal channel to the coherent receiver. Step 6: Generate the local oscillator optical signal of the signal channel and transmit it to the adjustable optical delay unit at the receiving end; Step 7: Generate the local oscillator optical signal for each signal channel by using the adjustable optical delay unit at each receiver, and transmit it to the coherent receiver for self-coherent detection to obtain the quantum noise stream encrypted electrical signal for each signal channel, and output it to the receiver terminal; Step 8: The receiving terminal combines the quantum noise stream encrypted electrical signal of each signal channel with the quantum noise stream encryption key and decrypts it using the quantum noise stream decryption method to obtain the decrypted plaintext signal; Step 3 is described in detail below: The transmitting terminal converts the high-order encrypted signal obtained through the quantum noise stream encryption key into a high-order encrypted analog signal through digital-to-analog conversion, and then transmits it to each IQ modulator. Each IQ modulator modulates the high-order encrypted analog signal onto the optical carrier of each signal channel to obtain the quantum noise stream encrypted optical signal of each signal channel. The quantum noise stream encrypted optical signal of each signal channel is then transmitted to the transmitting adjustable optical delay unit of each signal channel. Step 4 is described in detail below: Each transmitter's adjustable optical delay unit optically delays the quantum noise stream encrypted optical signal of each signal channel according to the optical delay key of each signal channel, resulting in a delayed quantum noise stream encrypted optical signal for each signal channel. The delayed quantum noise stream encrypted optical signal of each signal channel is then coupled into each outer core of the multi-core optical fiber through a fan-in connector. Each outer core of the multi-core optical fiber transmits the delayed quantum noise stream encrypted optical signal of each signal channel to the fan-out connector. Step 5 is described in detail below: The fan-out coupler couples the same source local oscillator optical signal out of the multi-core optical fiber and transmits it to the receiving optical splitter. It couples the delayed quantum noise stream encrypted optical signal of each signal channel out of the multi-core optical fiber and transmits it to the coherent receiver. Step 6 is as follows: The receiving optical splitter splits the same source local oscillator optical signal into multiple signal channels of local oscillator optical signal. The number of channels of the optical splitter is the same as the number of outer cores of the multi-core optical fiber. The local oscillator optical signal of each signal channel is transmitted to the adjustable optical delay at the receiving end. Step 7 is as follows: By combining the optical delay key of each signal channel, the delay corresponding to the local oscillator optical signal of each signal channel is set by the adjustable optical delayer of each receiver. The local oscillator optical signal of each signal channel is optically delayed and matched by the adjustable optical delayer of each receiver to obtain the local oscillator optical signal of each signal channel with optical delay matching. The local oscillator optical signal of each signal channel with optical delay matching and the quantum noise stream encrypted optical signal of each signal channel after delay are input to the coherent receiver for self-coherent detection to obtain the quantum noise stream encrypted electrical signal of each signal channel, and output to the receiver terminal.

2. The security enhancement method for a multi-core fiber quantum noise stream encryption system according to claim 1, characterized in that: Step 1 is described in detail as follows: The transmitting terminal generates a plaintext signal and generates a quantum noise stream encryption key and an optical delay key for each signal channel through a pseudo-random number generator. The transmitting terminal then transmits the quantum noise stream encryption key and the optical delay key for each signal channel to the receiving terminal for sharing. Set the number of bits for quantum noise stream encryption, combine the noise stream encryption key with quantum noise stream encryption to obtain a high-order encrypted signal, and transmit the optical delay key of each signal channel to each transmitter's tunable optical delay unit.

3. The security enhancement method for a multi-core fiber quantum noise stream encryption system according to claim 2, characterized in that: Step 2 is as follows: The laser signal output by the distributed feedback laser is split into multiple original optical signals by the transmitting optical splitter. One of the original optical signals is coupled into the middle core of the multi-core optical fiber through the fan-in device as the same source local oscillator optical signal. The middle core of the multi-core optical fiber transmits the same source local oscillator optical signal to the fan-out device. The remaining original optical signals are used as the optical carriers of each signal channel. The optical carriers of each signal channel are transmitted to each IQ modulator through the optical fiber.

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