Photoelectric feedback phase chaotic system based on FPGA nonlinear module

Abstract

The invention provides a photoelectric feedback phase chaotic system based on an FPGA nonlinear module. The photoelectric feedback phase chaotic system comprises a driving signal generation module, a signal encryption module, an optical fiber transmission module, a signal decryption module and a signal detection module. The invention is characterized in that on the basis of a traditional photoelectric feedback phase chaotic structure, an electric domain scrambling code encryption structure realized based on the FPGA is designed, electric domain nonlinear transformation is integrated into the FPGA, and the security encryption design of a physical layer adjustable scrambling code module is realized. The design of an electric domain nonlinear scrambling module is realized based on an FPGA (Field Programmable Gate Array), including nonlinear operations such as product, convolution and the like. Through the technology, different scrambling code modules can be flexibly designed and switched according to requirements, so that the unicity of in-loop nonlinear scrambling code design is avoided, and the diversity and flexibility of the system are improved.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technology and optical fiber communication, and more specifically, to an optoelectronic feedback phase chaos system based on an FPGA nonlinear module. Background Art

[0002] In recent years, with the rapid development of emerging technologies and services such as blockchain, big data, and the Internet of Things, society's demand for network bandwidth, speed, and capacity has exploded. Optical fiber communication has gradually become the most important communication method today due to its unique advantages such as large bandwidth, high transmission rate, and low signal attenuation. Especially driven by all-optical networks and automatic switching optical network technologies, optical networks have further advantages such as transparency, grouping, and gridding.

[0003] However, with the continuous advancement of eavesdropping and sabotage technology and equipment, as well as the frequent reports of attacks on optical networks, the security of optical networks has become increasingly important. Among the existing optical security communication schemes, chaotic encryption communication has been widely favored by researchers because of its ability to effectively improve the security of optical networks. Chaotic lasers have unique advantages such as noise-like characteristics, high sensitivity to initial values, non-periodicity, and difficulty in prediction. They have shown important application potential in many fields such as confidential communication, high-speed physical random number generation, and laser ranging. As an effective physical layer information security strategy, chaotic confidential communication uses optical domain encryption technology to bury data signals in broadband noise-like signals, thereby achieving confidential transmission of information.

[0004] The traditional optoelectronic feedback structure (OEO) generates chaotic signals to transmit information confidentially. Due to its simple structure and simple nonlinearity within the loop, its time delay characteristics can be obtained using mathematical statistics methods, and then the original OEO system can be reconstructed to recover the message.

[0005] As a super-large-scale programmable logic device, the functions implemented by FPGA are custom designed by users through programming languages, and a large number of operation units required for algorithm implementation are integrated internally. Using FPGA to design digital domain nonlinear transformation circuits, realize nonlinear operations (such as product or convolution) on input electrical signals, and develop a variety of nonlinear scrambling modules, build a dynamic hardware encryption structure, and further improve the security and flexibility of the system. It is a feasible solution to increase the complexity of the photoelectric feedback chaos generation system. The present invention proposes an electric domain scrambling encryption structure based on FPGA, integrates electric domain nonlinear transformation into FPGA, and realizes the secure encryption design of the physical layer adjustable scrambling module to enhance the complexity and structural security of the chaotic system, while improving the robustness of the encryption feedback mechanism. Summary of the invention

[0006] In view of the above problems, the present invention proposes an optoelectronic feedback phase chaos system based on FPGA nonlinear module. On the basis of the traditional optoelectronic feedback phase chaos structure, nonlinear changes in the electric domain are introduced to enhance the complexity and structural security of the chaotic system, while improving the robustness of the encryption feedback mechanism.

[0007] The technical solution of the present invention is a photoelectric feedback phase chaos system based on FPGA nonlinear module, characterized in that it includes the following parts: 1-driving signal generating module, 2-signal encryption module, 3-optical fiber transmission module, 4-signal decryption module, and 5-signal detection module.

[0008] The driving signal generation module generates an optical signal to be encrypted and sends the optical signal to the signal encryption module. The first phase modulator in the encryption module divides the signal into two parts, one for safe transmission, and the other part is generated by the first Mach-Zehnder interferometer to generate two low-correlated optical signals. The two optical signals are converted into electrical signals by photoelectric detectors, and then enter the first FPGA nonlinear module for complex nonlinear perturbation to generate chaotic electrical signals, which are used as the RF driving signal of the first phase modulator. Finally, at the output end of the first phase modulator, a signal with constant amplitude and chaotic phase is generated. The generated optical signal is sent to the signal decryption module through the optical fiber transmission module.

[0009] The signal decryption module decrypts the optical signal through the feedback loop phase structure, and the received signal is divided into two corresponding parts. One part is decrypted through the second phase modulator, while the other part is synchronized through the decryption structure symmetrical to the encryption branch. The parameter setting of the decryption structure is the same as that of the encryption end, so it can generate a random optical signal synchronized with the encryption end, restore chaotic synchronization, and generate a decryption signal.

[0010] Finally, the decrypted signal and the local oscillator signal are input into the coherent receiver for demodulation. The decrypted signal is received by the digital oscilloscope and the original message is restored through offline digital signal processing.

[0011] Among them, 1- the driving signal generating module is implemented by the following technical solution:

[0012] It includes: 101 - a first continuous wave semiconductor laser, 102 - an IQ modulator, and 103 - an arbitrary waveform generator.

[0013] The connection relationship between each module is as follows:

[0014] The output end of the continuous wave semiconductor laser 101 is connected to the input end of the IQ modulator 102, the output end of the arbitrary waveform generator 103 is connected to another input end of the IQ modulator 102, and the arbitrary waveform generator 103 generates a driving signal to drive the 102-IQ modulator to generate an intensity modulation signal.

[0015] 2-The signal encryption module is implemented using the following technical solutions:

[0016] It includes: 201-a first phase modulator, 202-a first optical fiber coupler, 203-a first adjustable optical fiber delay line, 204-a first Mach-Zehnder interferometer, 205-a first photodetector, 206-a first FPGA nonlinear change module, and 207-a first radio frequency amplifier.

[0017] The connection relationship between each module is as follows:

[0018] The input end of the first optical phase modulator 201 is connected to the output end of the IQ modulator 102, the output end of the first optical phase modulator 201 is connected to the input end of the first optical fiber coupler 202, an output end of the first optical fiber coupler 202 is connected to the input end of the first adjustable optical fiber delay line 203, the output end of the first adjustable optical fiber delay line 203 is connected to the input end of the first Mach-Zehnder interferometer 204, the output end of the first Mach-Zehnder interferometer 204 is connected to the input end of the first photodetector 205, the output end of the first photodetector 205 is connected to the input end of the first nonlinear change module 206, the output end of the first FPGA nonlinear change module 206 is connected to the input end of the first radio frequency amplifier 207, and the amplified output electrical signal is used as the driving signal of the first optical phase modulator 201. This module realizes the function of encrypting information.

[0019] 3- The optical fiber transmission module is implemented using the following technical solutions:

[0020] Including: 301-single mode optical fiber, 302-dispersion compensation optical fiber, 303-erbium-doped optical fiber amplifier.

[0021] The connection relationship between each module is as follows:

[0022] The other output end of the first optical fiber coupler 202 is connected to the input end of the single-mode optical fiber 301, the output end of the single-mode optical fiber 301 is connected to the input end of the dispersion-compensating optical fiber 302, and the output end of the dispersion-compensating optical fiber 302 is connected to the input end of the erbium-doped optical fiber amplifier 303.

[0023] 4-The signal decryption module is implemented using the following technical solutions:

[0024] It includes: 401-a second optical fiber coupler, 402-a second phase modulator, 403-a second adjustable optical fiber delay line, 404-a second Mach-Zehnder interferometer, 405-a second photoelectric detector, 406-a second FPGA nonlinear change module, and 407-a second radio frequency amplifier.

[0025] The connection relationship between each module is as follows:

[0026] The output end of the erbium-doped fiber amplifier 303 is connected to the input end of the second fiber coupler 401, one output end of the second fiber coupler 401 is connected to the input end of the second adjustable fiber delay line 403, the output end of the second adjustable fiber delay line 403 is connected to the input end of the second Mach-Zehnder interferometer 404, the output end of the second Mach-Zehnder interferometer 404 is connected to the input end of the second photodetector 405, the output end of the second photodetector 405 is connected to the input end of the second nonlinear change module 406, the output end of the second FPGA nonlinear change module 406 is connected to the input end of the second radio frequency amplifier 407, and the amplified output electrical signal is used as the driving signal of the second optical phase modulator 402. This module realizes the function of decrypting information.

[0027] 5-The signal detection module is implemented using the following technical solutions:

[0028] It includes: 501 - coherent receiver, 502 - second continuous wave semiconductor laser, 503 - digital oscilloscope, 504 - offline processing module.

[0029] The connection relationship between each module is as follows:

[0030] The output end of the second optical phase modulator 402 is connected to one input end of the coherent receiver 501, the output end of the second continuous wave semiconductor laser 502 is connected to another input end of the coherent receiver 501, the output end of the coherent receiver 501 is connected to the input end of the digital oscilloscope 503, and the output end of the digital oscilloscope 503 is connected to the input end of the offline processing module 504.

[0031] In this technical solution, the original message is first sent through an arbitrary waveform generator and modulated to the optical carrier output by the continuous wave laser through an IQ modulator. The optical carrier with information then enters the designed optoelectronic feedback electrical domain nonlinear transformation encryption part, disturbs the phase, and finally outputs the encrypted signal through the phase modulator. The encrypted signal is transmitted to the receiving end through the transmission link, and first phase decryption is performed through a decryption optoelectronic feedback loop that matches the hardware parameters of the encryption end. Then, it is input into the coherent receiver together with the local oscillator signal for demodulation. The decrypted signal is received by the data oscilloscope, and the original message is restored through offline digital signal processing. Based on the verification of the introduction of electrical domain analog multiplication nonlinear changes in the loop, the solution designs a scrambling module based on FPGA to implement the electrical domain nonlinear transformation circuit. The FPGA module performs complex nonlinear perturbations on the input electrical signal, which not only ensures the security of the system structure, but also enhances the complexity of the chaotic signal, thereby improving the robustness of the entire chaotic security system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of an optoelectronic feedback phase chaos system based on FPGA nonlinear module;

[0033] In the figure, 1-driving signal generating module: 101-first continuous wave semiconductor laser, 102-IQ modulator, 103-arbitrary waveform generator;

[0034] 2-Signal encryption module: 201-first phase modulator, 202-first fiber coupler, 203-first adjustable fiber delay line, 204-first Mach-Zehnder interferometer, 205-first photodetector, 206-first FPGA nonlinear change module, 207-first radio frequency amplifier;

[0035] 3-Fiber transmission module: 301-single mode fiber, 302-dispersion compensation fiber, 303-erbium-doped fiber amplifier;

[0036] 4-Signal decryption module: 401-second optical fiber coupler, 402-second phase modulator, 403-second adjustable optical fiber delay line, 404-second Mach-Zehnder interferometer, 405-second photodetector, 406-second FPGA nonlinear change module, 407-second radio frequency amplifier;

[0037] 5-Signal detection module: 501-coherent receiver, 502-second continuous wave semiconductor laser, 503-digital oscilloscope, 504-offline processing module; DETAILED DESCRIPTION

[0038] In order to clearly illustrate the photoelectric feedback phase chaos system based on FPGA nonlinear module of the present invention, the present invention is further described in combination with the embodiments and drawings, but this should not limit the protection scope of the present invention.

[0039] Implementation Examples

[0040] Figure 1 It is a structural diagram based on. It should be noted that the dotted line in the structural diagram is the electrical signal transmission line, and the solid line is the optical signal transmission line; 1-The signal emitted by the driving signal generating module can be an optical signal of any modulation format, such as four-level pulse modulation PAM4 signal, eight-level pulse amplitude modulation PAM8, orthogonal phase shift keying QPSK, hexadecimal orthogonal amplitude modulation 16QAM, etc.

[0041] from Figure 1 It can be seen that in the 1-driving signal generating module, the laser output by the 101-first continuous wave semiconductor laser acts as an optical carrier and carries a high-order modulated signal. The high-order electrical modulation signal generated by the 103-arbitrary waveform generator is modulated onto the optical carrier through the 102-IQ modulator. The modulated optical signal is sent to the 2-signal encryption module as a signal to be encrypted. In the 2-signal encryption module, the signal output by the 1-driving signal generating module first passes through the 201-first phase modulator to phase encrypt the high-speed optical modulation signal to achieve signal disruption. The output end of the 201-first phase modulator is connected to the input end of the 202-first optical fiber coupler, and the output signal at one end of the 202-first optical coupler is connected to the 203-first adjustable optical fiber delay line to adjust the signal delay. The delayed signal is transmitted to the input end of the 204-first Mach-Zehnder interferometer to convert the signal from phase to intensity to achieve the second signal disruption. Next, the signal is sequentially input from the output end of the first Mach-Zehnder interferometer 204 to the first photodetector 205 to complete the conversion of the electrical signal. The converted electrical signal enters the first FPGA nonlinear change module 206 for complex nonlinear disturbance to generate a chaotic electrical signal, thus achieving the third disturbance of the signal. The electrical signal is adjusted by the first RF amplifier 207 and finally serves as the driving signal of the first phase modulator 201, forming a closed-loop feedback loop of phase encryption.

[0042] In the 3-fiber transmission module, the encrypted signal enters a transmission link composed of a 301-single-mode optical fiber and a 302-dispersion compensation optical fiber matching its dispersion value for transmission, and then a 303-erbium-doped fiber amplifier is used to amplify the power of the transmitted optical signal.

[0043] In the 4-signal decryption module, the decryption function of the encrypted signal is realized. This module adopts a symmetrical structure and consistent device parameters that match the signal encryption module to generate a random-like optical signal synchronized with the encryption end, restore chaotic synchronization, and generate a decryption signal. In this process, an output port of the 401-second optical fiber coupler is connected to the input port of the 403-first adjustable optical fiber delay line to adjust the signal delay. Then the delayed signal enters the 404-second Mach-Zehnder interferometer to convert the signal from phase to intensity. Then it enters the 405-second photodetector to complete the conversion of the electrical signal, and the converted electrical signal enters the 406-second FPGA nonlinear change module input end, and the 406-second FPGA nonlinear change module output end is connected to the 407-second RF amplifier input end. The amplified output electrical signal is used as the driving signal of the 402-second optical phase modulator, and finally the synchronization is restored to generate a decryption signal.

[0044] In 5-signal detection module, the decrypted signal and 502-local oscillator signal generated by the second continuous wave semiconductor laser are input into 501-coherent receiver for demodulation, the decrypted signal is received by 503-digital oscilloscope, and the original message is restored through 504-offline digital signal processing.

[0045] As can be seen from the specific examples, the present invention proposes an optoelectronic feedback phase chaos system based on an FPGA nonlinear module. The technology first uses a phase modulator to perform phase-level encryption processing on high-speed optical signals to achieve a disrupting effect. Furthermore, the technology uses a Mach-Zehnder interferometer and an FPGA nonlinear module through the architecture of a feedback loop to perform nonlinear conversion processing on the signal, thereby completing further disruption. Signal decryption requires the use of a symmetric decryption module. The decryption process not only requires the construction of a structure that matches the encryption module at the transmitting end, but also requires the correct setting of the corresponding phase modulation depth, delay time, nonlinear converter hardware parameters, active device hardware parameters and other key keys. Different key parameter combinations greatly improve the security of the system. At the same time, the system can use existing commercial equipment and fiber channels to maintain compatibility with the current fiber optic network architecture.

[0046] In addition, unlike the traditional intra-loop optical domain scrambling method, the present invention introduces nonlinear transformation in the electric domain, which significantly enhances the robustness of the optoelectronic feedback encryption structure. The electric domain nonlinear scrambling function is integrated into the digital circuit, and the FPGA is used to implement complex electric domain nonlinear transformations on the input electrical signal. The digital domain nonlinear scrambling module design based on FPGA further improves the system security. At the same time, the photoelectric feedback loop encryption and decryption structure avoids the need for additional channels to transmit driving signals, ensuring the security of the hardware parameter space. And thanks to the programmable flexibility of FPGA, the electric domain scrambling module can be updated and replaced according to user needs, which increases the scalability and adaptability of the system, allowing chaotic secure communication to be combined with different modulation formats, with higher flexibility, and is expected to increase the rate in high-speed and long-distance communications.

[0047] Although the above describes the specific embodiments of the present invention, it is for the convenience of those skilled in the art to understand the present invention. It should also be noted that the present invention is not limited to the specific details in the above embodiments, and various simplifications and modifications within the scope of the principle and method of the present invention are included in the protection scope of the claims of the present invention.

Claims

1. An optoelectronic feedback phase chaos system based on FPGA nonlinear module, characterized in that: It includes the following parts: drive signal generation module, signal encryption module, optical fiber transmission module, signal decryption module, and signal detection module: The output end of the driving signal generating module is connected to the input end of the signal encryption module. The signal encryption module encrypts the optical signal generated by the driving signal generating module. The output end of the signal encryption module is connected to the input end of the optical fiber transmission module to transmit the encrypted signal to the receiving end. The output end of the optical fiber transmission module is connected to the input end of the signal decryption module. The output end of the signal decryption module is connected to the signal detection module, and the signal detection module outputs the original signal.

2. The photoelectric feedback phase chaos system based on FPGA nonlinear module according to claim 1 is characterized in that: The driving signal generating module includes a continuous wave semiconductor laser, an IQ modulator, and an arbitrary waveform generator. The output end of the continuous wave semiconductor laser is connected to the input end of the IQ modulator, the arbitrary waveform generator outputs the original message electrical signal, the output electrical signal is used as the driving signal of the IQ modulator, the driving signal is modulated onto the optical carrier output by the continuous wave laser, the output end of the IQ modulator is connected to the input end of the signal encryption module, and the optical carrier with information then enters the designed optoelectronic feedback electrical domain nonlinear transformation encryption part.

3. The photoelectric feedback phase chaos system based on FPGA nonlinear module according to claim 2 is characterized in that: The signal encryption module includes a first phase modulator, a first fiber coupler, a first adjustable fiber delay line, a first Mach-Zehnder interferometer, a first photodetector, a first FPGA nonlinear change module, and a first radio frequency amplifier, wherein: The input end of the first optical phase modulator is connected to the output end of the IQ modulator of the driving signal generating module, the output end of the first optical phase modulator is connected to the input end of the first optical fiber coupler, one output end of the first optical fiber coupler is connected to the input end of the first adjustable optical fiber delay line, the output end of the first adjustable optical fiber delay line is connected to the input end of the first Mach-Zehnder interferometer, the output end of the first Mach-Zehnder interferometer is connected to the input end of the first photodetector, the output end of the first photodetector is connected to the input end of the first nonlinear change module, and the output end of the first FPGA nonlinear change module is connected to the input end of the first RF amplifier.

4. The photoelectric feedback phase chaos system based on FPGA nonlinear module according to claim 3 is characterized in that: The optical fiber transmission module includes a single-mode optical fiber, a dispersion-compensating optical fiber, and an erbium-doped optical fiber amplifier, wherein: The second output port of the first optical fiber coupler is connected to the input end of the single-mode optical fiber, the output end of the single-mode optical fiber is connected to the input end of the dispersion compensating optical fiber, the output end of the dispersion compensating optical fiber is connected to the input end of the erbium-doped fiber amplifier, and the output end of the erbium-doped fiber amplifier is connected to the input end of the signal decryption module.

5. The photoelectric feedback phase chaos system based on FPGA nonlinear module according to claim 4 is characterized in that: The signal decryption module includes a second optical fiber coupler, a second phase modulator, a second adjustable optical fiber delay line, a second Mach-Zehnder interferometer, a second photodetector, a second FPGA nonlinear change module, and a second radio frequency amplifier, wherein: The output end of the erbium-doped fiber amplifier is connected to the input end of the second fiber coupler, one output end of the second fiber coupler is connected to the input end of the second adjustable fiber delay line, the output end of the second adjustable fiber delay line is connected to the input end of the second Mach-Zehnder interferometer, the output end of the second Mach-Zehnder interferometer is connected to the input end of the second photodetector, the output end of the second photodetector is connected to the input end of the second nonlinear change module, and the output end of the second FPGA nonlinear change module is connected to the input end of the second RF amplifier.

6. The photoelectric feedback phase chaos system based on FPGA nonlinear module according to claim 5, characterized in that: The signal detection module includes a coherent receiver, a second continuous wave semiconductor laser, a digital oscilloscope, and an offline processing module, wherein: The output end of the second optical phase modulator is connected to one input end of the coherent receiver, the output end of the second continuous wave semiconductor laser is connected to another input end of the coherent receiver, the output end of the coherent receiver is connected to the input end of the digital oscilloscope, and the output end of the digital oscilloscope is connected to the input end of the offline processing module.

7. An optoelectronic feedback phase chaos system based on FPGA nonlinear module, comprising the following steps: In the 1-driving signal generation module, the continuous semiconductor laser outputs continuous light as an optical carrier signal, the arbitrary waveform generator generates a signal, which is modulated onto the optical carrier through the IQ modulator, and the modulated optical carrier signal is transmitted to the 2-signal encryption module as the signal to be encrypted. In the 2-signal encryption module, the first phase modulator in the encryption module divides the signal into two parts, one part is used for safe transmission, and the other part is generated by the first Mach-Zehnder interferometer to generate two low-correlated optical signals. The two optical signals are converted into electrical signals by the photoelectric detector respectively, and then enter the first FPGA nonlinear module for complex nonlinear perturbation to generate chaotic electrical signals, which are used as the RF driving signal of the first phase modulator. Finally, at the output end of the first phase modulator, a signal with constant amplitude and chaotic phase is generated. The generated optical signal enters the optical fiber transmission module. In the 3-optical fiber transmission module, the encrypted signal enters the transmission link composed of a single-mode optical fiber and a dispersion compensation optical fiber matching its dispersion value for transmission, and then the optical power of the transmission signal is amplified by an erbium-doped fiber amplifier, and the amplified signal enters the signal decryption module. In the 4-signal decryption module, the encrypted signal is decrypted. The signal decryption module performs phase decryption on the optical signal through the feedback loop phase structure, and the received signal is divided into two corresponding parts. One part is decrypted by the second phase modulator, while the other part is synchronized by the decryption structure symmetrical to the encryption branch. The parameter setting of the decryption structure is the same as that of the encryption end, so it can generate a random-like optical signal synchronized with the encryption end, restore chaotic synchronization, and generate a decrypted signal. In the 5-signal detection module, the decrypted signal is input into the coherent receiver together with the local oscillator signal for demodulation. The decrypted signal is received by the digital oscilloscope, and the original message is restored through offline digital signal processing.

Images