A polarization multiplexing-based chaotic secure communication device, method and application

Abstract

The application belongs to the technical field of optical secret communication and optical signal processing, and discloses a chaotic secret communication device, method and application based on polarization multiplexing, which comprises a signal generating module for generating analog chaotic sequences and encrypted information, realizing information encryption by using the analog chaotic sequences and another digital chaotic sequence generated by a mathematical formula to perform phase position disorder on information in a digital domain, and realizing polarization multiplexing of analog chaotic signals and encrypted signals through the polarization combiner; an optical fiber transmission link for transmitting analog chaotic signals and encrypted signals and compensating dispersion damage in the transmission process; and a signal receiving module for splitting received optical signals into two beams, converting the two beams of optical signals into analog chaotic synchronization sequences and electrical signals, and offline decrypting encrypted information to obtain transmission information. The application has high integration, adopts an analog and digital chaotic hybrid encryption mode, and effectively improves security by using mutual covering between the two.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical secure communication and optical signal processing, and in particular relates to a chaotic secure communication device, method and application based on polarization multiplexing. Background Art

[0002] Currently, fiber-optic communication systems, with their advantages of low transmission loss and wide bandwidth, carry over 90% of the world's data exchange. However, the security of fiber-optic communications is threatened by fiber-optic eavesdropping techniques. Optical chaotic systems, with their unique advantages of high dynamic complexity and large bandwidth, are an effective approach to meeting physical layer security requirements and have garnered widespread attention in recent years. To meet the high-capacity demands of optical communication networks, the transmission rate of optical chaotic systems needs to be further improved.

[0003] Wavelength division multiplexing (WDM) technology is a key method for increasing the speed of chaotic secure communications. WDM enables the simultaneous transmission of two or more optical carriers of different wavelengths over the same optical fiber. Each of these optical carriers carries different information, thereby expanding the system's communication capacity. Using WDM, secure transmission of 4 × 12.5 Gb / s over 50 km of optical fiber has been achieved (see J. Lightwave Technol., Vol. 39, No. 8, p. 2288, 2021).

[0004] To further improve the secure transmission rate of a single wave, adopting higher-order modulation formats and coherent detection is an effective approach. Currently, a chaotic secure communication scheme based on a deep learning model has achieved secure transmission of a 30 Gb / s QPSK signal over 340 km of optical fiber (see Opt. Lett., Vol. 47, No. 11, P. 2650, 2022).

[0005] However, all of the above schemes employ hardware-based optical analog encryption. Limited by the physical parameter range of analog components, their key space is relatively small. Furthermore, these schemes employ a nonlinear electro-optical delay feedback loop to generate chaotic signals. The feedback loop delay, as one of the key keys, is easily obtained through statistical methods, leaving room for improvement in system security. Digital domain encryption, on the other hand, offers a larger key space. However, the computing speed of current digital signal processing equipment cannot meet the "one-time pad" requirements of high-speed fiber-optic transmission. Therefore, most digital domain encryption methods use short-period key streams, which can lead to security vulnerabilities. Therefore, combining digital and analog encryption mechanisms, leveraging mutual masking to enhance system security and achieve chaotic secure communication with high single-wavelength transmission rates, is essential.

[0006] Through the above analysis, the problems and defects of the existing technology are as follows:

[0007] (1) In order to adapt to the large capacity requirements of optical communication networks, the transmission rate of existing chaotic secure communication systems needs to be further improved.

[0008] (2) Existing hardware optical analog encryption methods are limited by the physical parameter range of analog components, resulting in a relatively small key space and latency characteristics. This leaves room for improvement in system security. On the other hand, digital domain encryption methods require the use of short-period key streams, which can lead to security vulnerabilities in the system. Summary of the Invention

[0009] In view of the problems existing in the prior art, the present invention provides a chaotic secure communication device, method and application based on polarization multiplexing.

[0010] The present invention is achieved by a polarization multiplexing-based chaotic secure communication device comprising:

[0011] A signal generation module is used to simulate the generation of chaotic sequences and encrypted information, utilize the simulated chaotic sequence and another digital chaotic sequence generated by a mathematical formula to phase-scramble information in the digital domain to achieve information encryption, and implement polarization multiplexing of the simulated chaotic signal and the encrypted signal through the polarization beam combiner;

[0012] Optical fiber transmission links are used to transmit simulated chaotic signals and encrypted signals, and to compensate for dispersion damage during transmission;

[0013] The signal receiving module is used to split the received optical signal into two beams, and convert the two optical signals into simulated chaotic synchronization sequences and electrical signals respectively, and decrypt the encrypted information offline to obtain the transmitted information.

[0014] Furthermore, the signal generating device includes: a laser for providing a stable DC optical signal; a polarization beam splitter for splitting the DC optical signal into two optical signals with different polarization states, namely, X-polarized light and Y-polarized light; a first IQ modulator for applying a certain nonlinear modulation to the X-polarized light, and its bias point needs to be set at a nonlinear point; a second IQ modulator for loading information onto the Y-polarized light, and its bias point needs to be set at a linear point; a polarization beam combiner for realizing polarization multiplexing of simulated chaotic signals and encrypted signals; a first optical amplifier for adjusting the fiber input power of the signal; a first optical coupler for splitting the polarization multiplexed signal into three beams, one for forming a nonlinear feedback loop to generate simulated chaos, one for forming an encryption feedback loop, and one for transmitting to a receiving end; a first optically adjustable delay line for adjusting the delay time of the encryption feedback loop; a first photodetector for converting the simulated chaotic optical signal into a simulated chaotic electrical signal; a first analog-to-digital converter for converting the simulated chaotic electrical signal into a simulated chaotic sequence; a second photodetector for converting the nonlinearly modulated X-polarized light into an electrical signal; a power divider for splitting the electrical signal into two; and a dual-channel radio frequency amplifier for simultaneously amplifying the split electrical signal and loading it onto the first IQ modulator.

[0015] Furthermore, the optical fiber transmission link includes: a single-mode optical fiber for transmitting simulated chaotic signals and encrypted signals; a dispersive medium for compensating for dispersion damage during signal transmission; and a second optical amplifier for compensating for power damage during signal transmission.

[0016] Furthermore, the signal receiving device includes: a second optical coupler, used to split the transmitted polarization multiplexing signal into two, one beam is output to a coherent receiver, and the other beam is output to a second optical adjustable delay line; a coherent receiver, used to convert the polarization multiplexing signal into an electrical signal with polarization, phase, and amplitude information; a second optical adjustable delay line, used to control the delay time so that the delay time at the receiving end is consistent with the delay time of the encryption feedback loop at the transmitting end; a third photodetector, used to convert the chaotic synchronization optical signal into a chaotic synchronization electrical signal; and a second analog-to-digital converter, used to convert the chaotic synchronization electrical signal into a chaotic synchronization sequence.

[0017] Another object of the present invention is to provide a chaotic secure communication method based on polarization multiplexing, the chaotic secure communication method based on polarization multiplexing comprising:

[0018] Step 1: Generate an analog chaotic signal, which is converted into an analog chaotic sequence in sequence through a first optical adjustable delay line, a first photodetector, and a first analog-to-digital converter. The analog chaotic sequence and another digital chaotic sequence generated by a digital formula encrypt information offline. The encrypted information is loaded onto Y-polarized light through a second IQ modulator. The X-polarized light and the Y-polarized light carrying the encrypted information are polarization-multiplexed through the polarization combiner.

[0019] Step 2: After the polarization multiplexed signal passes through the first amplifier and the first optical coupler in sequence, it is input into the single-mode optical fiber, output into the dispersive medium after transmission to compensate for the dispersion damage during the transmission process, and then input into the second optical amplifier;

[0020] In step three, the optical signal output by the second optical amplifier is divided into two beams of light through the second optical coupler, one of which is converted into an analog chaotic synchronization sequence through the second optical adjustable delay line, the third photodetector and the second analog-to-digital converter in sequence, and the other optical signal is input into the coherent detector and converted into an electrical signal. The polarization demultiplexing of the electrical signal is performed in the digital domain using an algorithm to obtain the encrypted information loaded on the Y-polarized light. The encrypted information is decrypted offline using the analog chaotic synchronization sequence and the digital chaotic sequence generated by the same digital formula to obtain the transmitted information.

[0021] Furthermore, the step of generating a simulated chaotic signal in step 1 includes:

[0022] The light emitted by the laser is split into two beams of light with different polarization states after passing through a polarization beam splitter, namely X-polarized light and Y-polarized light. The X-polarized light passes through the first IQ modulator, the polarization beam combiner, the first optical amplifier, and the first optical coupler in sequence, is detected by the second photodetector and converted into an electrical signal, which is then input into the power divider. The power divider splits the input electrical signal into two beams of electrical signals, which are amplified by a dual-channel RF amplifier and respectively input into the I and Q ports of the first IQ modulator, completing a closed feedback loop and causing it to oscillate and generate a simulated chaotic signal.

[0023] Furthermore, the simulated chaotic sequence in step 1 is denoted as {C i}, its encryption depth is denoted as d1; the digital chaotic sequence is denoted as {X i}, its encryption depth is recorded as d2, and the loading information is recorded as {T i}, the encrypted information is recorded as {T i '},satisfy

[0024] Furthermore, the simulated chaotic synchronization sequence in step 3 is recorded as {C i '}, the encrypted information is recorded as {R i '}, the transmission information is recorded as {R i}, {R i}satisfy

[0025] Furthermore, the polarization demultiplexing in step three adopts a blind source separation algorithm that is independent of the modulation format.

[0026] Another object of the present invention is to provide an optical fiber communication system, which adopts the chaotic secure communication device based on polarization multiplexing.

[0027] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0028] The present invention proposes a coherent secure communication transmission scheme based on polarization multiplexing, in which the transmitting end can simultaneously realize information loading and chaotic signal generation. The system structure has a high degree of integration.

[0029] Compared to traditional hardware optical analog encryption schemes, this invention uses a hybrid encryption method of analog and digital chaos. This method effectively improves system security by masking the periodicity of digital chaos with analog chaos and the delay characteristics of analog chaos with digital chaos, while also increasing the key space.

[0030] The transmitter of this invention requires only a commercial IQ modulator to simultaneously generate chaotic signals and load information signals. Polarization multiplexing allows both chaotic and information signals to be transmitted over the same optical fiber link, resulting in a highly integrated structure. The mutual masking effect of analog and digital chaos effectively enhances system security, and the encryption depth of both analog and digital chaos can be flexibly adjusted to accommodate different scenarios.

[0031] The expected benefits and commercial value of the technical solution of the present invention after transformation are as follows: after transformation, its highly integrated structure can be perfectly compatible with the existing polarization multiplexing communication system, and its analog-digital hybrid encryption method can effectively ensure the security of transmitted information, and has great commercial value.

[0032] The technical solution of this invention fills a technological gap in the industry, both domestically and internationally. For the first time, this solution simultaneously achieves information loading and chaotic signal generation using a single commercial dual-bias IQ modulator, resulting in a highly integrated structure. Previous solutions require two or more modulators on the transmitter side, resulting in a complex structure. Furthermore, this solution utilizes a hybrid analog-digital encryption method, significantly improving system security compared to traditional hardware-based optical encryption solutions.

[0033] Does the technical solution of the present invention solve a technical problem that has long been sought but has eluded its solution? The technical solution of the present invention utilizes polarization multiplexing technology to simultaneously achieve signal loading and chaotic signal generation, resulting in a highly integrated structure. Previous chaotic secure communication schemes often required additional modulators to generate chaotic signals, resulting in a complex structure. The present invention solves this problem. Furthermore, the present invention utilizes a hybrid analog-digital encryption method, effectively improving system security and further increasing the single-wave transmission rate. Previous hardware optical analog encryption schemes and digital domain encryption schemes both have their own security vulnerabilities, which the present invention addresses. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a structural block diagram of a chaotic secure communication device based on polarization multiplexing provided by an embodiment of the present invention;

[0035] Figure 2 These are the constellation diagrams of the sender, the constellation diagram of the legal receiver, and the constellation diagram of the illegal attacker provided by the embodiments of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an explanatory embodiment that expands on the technical solutions of the claims.

[0038] like Figure 1 As shown, the device of the present invention includes a laser 11, a polarization beam splitter 12, a first IQ modulator 13, a second IQ modulator 14, a polarization beam combiner 15, a first optical amplifier 16, a first optical coupler 17, a first optical adjustable delay line 18, a first photodetector 19, a first analog-to-digital converter 110, a second photodetector 111, a power divider 112, a dual-channel RF amplifier 113, a single-mode optical fiber 21, a dispersive medium 22, a second optical amplifier 23, a second optical coupler 31, a coherent receiver 32, a second optical adjustable delay line 33, a third photodetector 34, and a second analog-to-digital converter 35.

[0039] The light emitted by the laser 11 passes through the polarization beam splitter 12 and is split into two beams of light with different polarization states, namely, X-polarized light and Y-polarized light.

[0040] The first IQ modulator 13, polarization beam combiner 15, first optical amplifier 16, first optical coupler 17, second photodetector 111, power divider 112, and dual-channel RF amplifier 113 form a nonlinear electro-optical delay feedback loop to generate an analog chaotic signal. This analog chaotic signal is sequentially converted into an analog chaotic sequence through the first optical adjustable delay line 18, the first photodetector 19, and the first analog-to-digital converter 110. This analog chaotic sequence and another digital chaotic sequence generated by a mathematical formula are used to phase-scramble the information to obtain encrypted information. This encrypted information is loaded onto Y-polarized light through the second IQ modulator 14 and is referred to as the encrypted signal.

[0041] Furthermore, the simulated chaotic signal and the encrypted signal are polarization-multiplexed by the polarization combiner 15, and then sequentially pass through the first optical amplifier 16 and the first optical coupler 17 and are input into the single-mode optical fiber 21. After being transmitted through the same single-mode optical fiber, the polarization-multiplexed signal sequentially passes through the dispersive medium 22 and the second optical amplifier 23 and is input into the second optical coupler 31.

[0042] The second optical coupler 31 splits the polarization-multiplexed signal into two beams. One beam passes through the second optical adjustable delay line 33, the third photodetector 34, and the second analog-to-digital converter 35, converting it into an analog chaotic synchronization sequence. The other beam is output to the coherent receiver 32. The coherent receiver 32 detects the encrypted signal and, after algorithmic processing, obtains the encrypted information. The transmitted information is then decrypted using the analog chaotic synchronization sequence and the digital chaotic sequence.

[0043] The working principle of the embodiment of the present invention is as follows:

[0044] 1) Generation of chaotic sequences

[0045] The first IQ modulator 13, polarization beam combiner 15, first optical amplifier 16, first optical coupler 17, second photodetector 111, power divider 112, and dual-channel RF amplifier 113 form a delay feedback loop. Nonlinear modulation is achieved by controlling the bias voltage of the first IQ modulator 13 to generate an analog chaotic signal. This analog chaotic signal is converted into an analog chaotic sequence {C i}.

[0046] Furthermore, the digital chaotic sequence {X i The present invention provides a preferred implementation method, which is to use Logistic chaos.

[0047] 2) Information encryption

[0048] Using the simulated chaotic sequence {C i} and digital chaotic sequence {X i Information encryption is achieved by scrambling the information in the digital domain.

[0049] The simulated chaotic sequence {C i The encryption depth of the digital chaotic sequence {X i The encryption depth of} is recorded as d2. The loading information is recorded as {T i}, the encrypted information is recorded as {T i '}, should satisfy

[0050]

[0051] Furthermore, the second IQ modulator 14, polarization beam combiner 15, first optical amplifier 16, first optical coupler 17, first optical adjustable delay line 18, first photodetector 19, first analog-to-digital converter 110, and digital link form another feedback loop. The delay time of the first optical adjustable delay line 18 and the digital link serves as a communication key.

[0052] 3) Fiber optic transmission

[0053] The simulated chaotic signal and the encrypted signal are polarization multiplexed by the polarization combiner 15 and then transmitted in the same single-mode optical fiber. The dispersion medium 22 is used to compensate for the dispersion damage during transmission and can be implemented by dispersion compensating optical fiber, fiber Bragg grating, etc.

[0054] 4) Information demodulation

[0055] The second optical coupler 31 divides the transmission signal into two beams. One of the beams passes through the second optical adjustable delay line 33 to match the delay time, thereby achieving synchronization of the simulated chaotic signal. This simulated chaotic synchronization signal is converted into a simulated chaotic synchronization sequence {C i The other beam of light is input into the coherent receiver 32 and converted into an electrical signal, which is then demultiplexed by an algorithm to obtain encrypted information {R i '}.

[0056] Furthermore, the same mathematical formula as that of the transmitter is used to generate the same digital chaotic sequence {X i Then, the chaotic synchronization sequence and the digital chaotic sequence are used to decrypt in the digital domain to obtain the transmission information {R i}, {R i}satisfy

[0057] Furthermore, the polarization demultiplexing algorithm needs to adopt a blind source separation algorithm that is independent of the modulation format. The present invention provides a preferred implementation, namely a fast independent component analysis algorithm.

[0058] In order to prove the creativity and technical value of the technical solution of the present invention, this section provides application examples of the claimed technical solution on specific products or related technologies.

[0059] Application Example 1:

[0060] At the transmitting end, a laser 11 emits direct current light with a wavelength of 1550nm and a linewidth of approximately 100kHz. After passing through a polarization beam splitter 12, it is split into two beams of light with different polarization states: X-polarized light and Y-polarized light. The X-polarized light sequentially passes through a first IQ modulator 13, a polarization beam combiner 15, a first optical amplifier 16, a first optical coupler 17, a second photodetector 111, a power divider 112, and a dual-channel RF amplifier 113, forming a nonlinear electro-optical delay feedback loop that generates a simulated chaotic signal. In this embodiment, the I, Q, and P points of the first IQ modulator are biased to π, π, and 0, respectively, and the modulation depth is approximately 1 times the half-wave voltage. This simulated chaotic signal sequentially passes through a first optical adjustable delay line 18, a first photodetector 19, and a first analog-to-digital converter 110, where it is converted into a simulated chaotic sequence. This simulated chaotic sequence, along with another logistic chaotic sequence generated by a mathematical formula, is used to phase-scramble the 60Gbit / s QPSK signal, achieving chaotic encryption. This encrypted information is loaded onto the Y polarized light through the second IQ modulator 14 and is called an encrypted signal. In this application embodiment, the encryption depth of both simulated chaos and logistic chaos is set to π / 2.

[0061] After polarization multiplexing, the simulated chaotic signal and the encrypted signal are polarization-multiplexed by polarization combiner 15 and then sequentially passed through first optical amplifier 16 and first optical coupler 17 into single-mode optical fiber 21. After 100 kilometers of transmission along the same single-mode optical fiber, the polarization-multiplexed signal passes through dispersive medium 22 and second optical amplifier 23 before being input into second optical coupler 31. In this application example, dispersive medium 22 is a fiber Bragg grating, and its dispersion value is set to -1700 ps / nm.

[0062] At the receiving end, a second optical coupler 31 is used to split the polarization-multiplexed signal into two beams of light. One beam of light passes through a second optical adjustable delay line 33, a third photodetector 34, and a second analog-to-digital converter 35, and is converted into an analog chaotic synchronization sequence. The other beam of light is output to a coherent receiver 32. The coherent receiver 32 detects the encrypted signal and obtains an electrical signal containing phase, amplitude, and polarization information. Polarization demultiplexing is then performed on this electrical signal using a fast independent component analysis algorithm to obtain an encrypted signal loaded on the Y polarization. The algorithm then performs IQ orthogonalization and normalization, chaos decryption, polarization equalization, and carrier phase recovery on this encrypted signal to recover the transmitted information.

[0063] The embodiments of the present invention have achieved some positive effects during the development or use process, and indeed have great advantages compared with the existing technology. The following content describes them in conjunction with data, charts, etc. of the experimental process.

[0064] During the test of the embodiment of the present invention, 2 15 The transmission information is generated using a -1 pseudo-random bit sequence and mapped into a QPSK format with a transmission rate of 60 Gbit / s. The 60 Gbit / s QPSK signal is then phase-scrambled in the digital domain using both simulated chaotic sequences and logistic chaotic sequences, with the encryption depth of both sequences set to π / 2.

[0065] Figure 2 The embodiment of the present invention provides a constellation diagram of the sender, a constellation diagram of the legitimate receiver after 100 kilometers of transmission, and a constellation diagram of the illegal attacker;

[0066] from Figure 2 As can be seen, only the legitimate receiver can correctly recover the constellation diagram and obtain the transmitted information. However, the constellation diagram obtained by the unauthorized attacker is disrupted by the chaotic signal and cannot be correctly recovered. This shows that the embodiment of the present invention can achieve secure transmission of a 60 Gbit / s single-wave QPSK signal over a distance of 100 kilometers.

[0067] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A chaotic secure communication device based on polarization multiplexing, characterized in that: The chaotic secure communication device based on polarization multiplexing includes: A signal generation module includes a laser, a polarization beam splitter, a first IQ modulator, a second IQ modulator, a polarization beam combiner, a first optical amplifier, a first optical coupler, a first optical adjustable delay line, a first photodetector, a first analog-to-digital converter, a second photodetector, a power divider, and a dual-channel radio frequency amplifier. The module generates an analog chaotic signal, which is converted into an analog chaotic sequence through the first optical adjustable delay line, the first photodetector, and the first analog-to-digital converter in sequence. The analog chaotic sequence and another digital chaotic sequence generated by a mathematical formula perform phase scrambling on the information to achieve encryption. The encrypted information is loaded onto Y-polarized light through the second IQ modulator, which is called an encrypted signal. The analog chaotic signal and the encrypted signal are polarization-multiplexed through the polarization beam combiner. The polarization-multiplexed signal passes through the first optical amplifier and the first optical coupler in sequence and is input into the single-mode optical fiber of the optical fiber transmission link. The optical fiber transmission link includes a single-mode optical fiber, a dispersive medium, and a second optical amplifier. After being transmitted through the single-mode optical fiber, the polarization multiplexed signal is output to the dispersive medium to compensate for dispersion damage during transmission, and then input to the second optical amplifier. The signal receiving module includes a second optical coupler, a coherent receiver, a second optically adjustable delay line, a third photodetector, and a second analog-to-digital converter. The optical signal output by the second optical amplifier is divided into two beams of light through the second optical coupler. One beam of light signal is converted into an analog chaotic synchronization sequence through the second optically adjustable delay line, the third photodetector, and the second analog-to-digital converter in sequence. The other beam of light signal is input into the coherent receiver and converted into an electrical signal. The electrical signal is polarization demultiplexed in the digital domain using an algorithm to obtain encrypted information loaded on the Y-polarized light. The encrypted information is decrypted offline using the analog chaotic synchronization sequence and the digital chaotic sequence generated by the same mathematical formula to obtain the transmitted information.

2. A polarization multiplexing-based chaotic secure communication method for implementing the polarization multiplexing-based chaotic secure communication device according to claim 1, characterized in that: The chaotic secure communication method based on polarization multiplexing includes: Step 1: Generate an analog chaotic signal. The analog chaotic signal is converted into an analog chaotic sequence through a first optical tunable delay line, a first photodetector, and a first analog-to-digital converter. The analog chaotic sequence and another digital chaotic sequence generated by a mathematical formula scramble the phase of the information to achieve encryption. The encrypted information is loaded onto Y-polarized light through a second IQ modulator, which is called an encrypted signal. The analog chaotic signal and the encrypted signal are polarization-multiplexed through a polarization beam combiner. Step 2: After the polarization multiplexed signal passes through the first optical amplifier and the first optical coupler in sequence, it is input into the single-mode optical fiber, output into the dispersive medium after transmission to compensate for the dispersion damage during the transmission process, and then input into the second optical amplifier; In step three, the optical signal output by the second optical amplifier is divided into two beams of light through the second optical coupler, one of which is converted into an analog chaotic synchronization sequence through the second optical adjustable delay line, the third photodetector and the second analog-to-digital converter in sequence, and the other optical signal is input into the coherent receiver and converted into an electrical signal. The electrical signal is polarization demultiplexed in the digital domain using an algorithm to obtain the encrypted information loaded on the Y-polarized light, and the encrypted information is decrypted offline using the analog chaotic synchronization sequence and the digital chaotic sequence generated by the same mathematical formula to obtain the transmission information.

3. The chaotic secure communication method based on polarization multiplexing according to claim 2, wherein: The step of generating a simulated chaotic signal in step 1 includes: The light emitted by the laser is split into two beams of light with different polarization states after passing through the polarization beam splitter, namely X-polarized light and Y-polarized light. The X-polarized light passes through the first IQ modulator, the polarization beam combiner, the first optical amplifier, and the first optical coupler in sequence, is detected by the second photodetector and converted into an electrical signal, which is then input into the power divider. The power divider splits the input electrical signal into two beams of electrical signals. The two beams of electrical signals are amplified by a dual-channel RF amplifier and respectively input into the I and Q ports of the first IQ modulator, completing a closed feedback loop and causing it to oscillate and generate a simulated chaotic signal.

4. The chaotic secure communication method based on polarization multiplexing according to claim 2, wherein: The simulated chaotic sequence in step 1 is denoted as {C i }, its encryption depth is denoted as d1; The digital chaotic sequence is denoted as {X i }, the encryption depth is recorded as d2, and the loaded information is recorded as {T i }, the encrypted information is recorded as {T i ’ },satisfy 5. The chaotic secure communication method based on polarization multiplexing according to claim 2, wherein: The simulated chaotic synchronization sequence in step 3 is denoted as {C i ’ }, the encrypted information is recorded as {R i ’ }, the transmission information is recorded as {R i }, {R i }satisfy d1 is the encryption depth of the simulated chaotic sequence; the digital chaotic sequence is denoted as {X i }, and its encryption depth is denoted as d2.

6. The chaotic secure communication method based on polarization multiplexing according to claim 2, wherein: The polarization demultiplexing in step three adopts a blind source separation algorithm that is independent of the modulation format.

7. An optical fiber communication system, characterized in that: The optical fiber communication system adopts the chaotic secure communication device based on polarization multiplexing according to claim 1.

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