A phase chaos laser communication system based on time-delay dual-balanced detection structure
By adopting a time-delay dual balance detection structure in the chaotic laser communication system, the orthogonal and in-phase components of light are detected simultaneously, solving the problems of optical power waste and easy identification of delay parameters, and improving the confidentiality and complexity of the system ensures high confidential communication effect.
Patent Information
- Application Number
- CN202111483175.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-07
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2041-12-07
AI Technical Summary
The single-tube photodetector of the photoelectric delay feedback oscillator in the chaotic laser communication system can only receive the orthogonal component or in-phase component of the optical signal, resulting in waste of optical power and difficulty in oscillation and oscillation, and the delay parameters are easily identified by eavesdropping parties. Impacts the security of confidential communications.
The phase chaotic laser communication system adopts a time-delay dual balance detection structure. By setting up a chaotic encryption module and a decryption module on the transmitting and receiving ends, the dual balance detector simultaneously detects the orthogonal components and in-phase components of light, forming an optical fiber oscillation loop , and use single-mode fiber and erbium-doped fiber amplifiers in the transmission channel to achieve high complexity and low autocorrelation of chaotic signals.
It reduces the optical power loss in the oscillating loop, eliminates the chaotic dead zone phenomenon, effectively covers the delay label, and achieves high confidential communication performance.
Smart Images
Figure CN114362914B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of confidential communication and information security, and particularly relates to a phase chaos laser communication system. Background Art
[0002] Chaotic secure communication is a secure communication method based on the physical level. Chaotic secure communication is mainly based on the characteristics of chaotic signals such as ergodicity, non-periodicity, broadband spectrum continuity, and noise-like properties. Encryption is achieved by hiding the transmission message in the chaotic signal. Chaotic synchronization is the basis for achieving secure communication, which refers to the gradual development of two chaotic systems into the same orbit after being controlled by the outside world. The "master-slave" synchronization scheme is often used in the chaotic synchronization unidirectional coupling structure. The master system is called the "transmitter" and the slave system is called the "receiver". In the actual communication process, the slave system needs to completely "comply" with the master system to achieve the best synchronization effect. Due to the sensitivity of the chaotic system to the initial conditions, the control of the chaotic structure parameters as the key is crucial to achieve effective synchronization and correct decryption. The chaotic laser communication system has the advantages of high bandwidth and low attenuation, and the system dynamics is relatively complex and has extremely high sensitivity to parameters. Therefore, it has high communication confidentiality performance and is very suitable for high-speed long-distance secure communication.
[0003] At present, the photoelectric delay feedback oscillator in the chaotic laser communication system structure often uses a single-tube photodetector to realize photoelectric conversion, which can only receive the orthogonal component or the in-phase component of the optical signal. Therefore, half of the optical power is wasted, and a larger loop feedback gain is required to achieve effective oscillation of the internal oscillator of the system. In addition, the setting of the bias phase of the Mach-Zehnder interferometer in the system structure has an important influence on the chaos oscillation, and when the bias phase is set to some special phase value, the single optical component will not be able to oscillate, resulting in the inability to obtain the chaotic carrier during the actual debugging process. In addition, the delay parameter, as an important key of the chaotic security system, can be identified through the autocorrelation function or the delayed mutual information function. On the autocorrelation function graph or the mutual information function graph, there will be peaks or valleys at the time points of the delay parameter. Once the eavesdropped party obtains the delay parameter, the security of the confidential communication is difficult to guarantee. Therefore, the delay label hiding of the chaotic communication system is also the focus of the current chaotic confidential communication research. At present, the delay parameter can be concealed by increasing the system loop feedback gain. Summary of the invention
[0004] In order to solve the technical problems mentioned in the above background technology, the present invention proposes a phase chaos laser communication system based on a time-delay dual-balanced detection structure.
[0005] In order to achieve the above technical objectives, the technical solution of the present invention is:
[0006] A phase chaos laser communication system based on a time-delay dual-balanced detection structure, characterized in that: it comprises a transmitting end, a transmission channel and a receiving end connected in sequence; the transmitting end comprises a chaos encryption module, and the receiving end comprises a chaos decryption module;
[0007] The chaotic encryption module includes a first lithium niobate modulator, a first coupler, a first optical fiber delay line, a first Mach-Zehnder interferometer, a second optical fiber delay line, a first balanced detector and a first radio frequency amplifier;
[0008] The output end of the first lithium niobate modulator is connected to the input end of the first coupler, the first output end of the first coupler is connected to the transmission channel, the second output end of the first coupler is connected to the input end of the first optical fiber delay line, the output end of the first optical fiber delay line is connected to the input end of the first Mach-Zehnder interferometer, the first output end of the first Mach-Zehnder interferometer is connected to the first input end of the first balanced detector via the second optical fiber delay line, the second output end of the first Mach-Zehnder interferometer is connected to the second input end of the first balanced detector, and the output end of the first balanced detector is connected to the electrode of the first lithium niobate modulator via the first radio frequency amplifier, so as to form an optical fiber oscillation loop;
[0009] The chaos decryption module includes a second coupler, a first tunable optical fiber delay line, a second Mach-Zehnder interferometer, a second tunable optical fiber delay line, a second balanced detector, a second radio frequency amplifier, and a second lithium niobate modulator;
[0010] The first output end of the second coupler is connected to the input end of the second lithium niobate modulator, the second output end of the second coupler is connected to the input end of the first tunable optical fiber delay line, the output end of the first tunable optical fiber delay line is connected to the input end of the second Mach-Zehnder interferometer, the first output end of the second Mach-Zehnder interferometer is connected to the first input end of the second balanced detector, the second output end of the second Mach-Zehnder interferometer is connected to the second input end of the second balanced detector via the second tunable optical fiber delay line, and the output end of the second balanced detector is connected to the electrode of the second lithium niobate modulator via the second radio frequency amplifier, forming an optical fiber oscillation circuit.
[0011] Furthermore, the transmission channel includes a single-mode optical fiber and an erbium-doped optical fiber amplifier, the single-mode optical fiber is connected to the input end of the erbium-doped optical fiber amplifier, and the output end of the erbium-doped optical fiber amplifier is connected to the chaotic decryption module.
[0012] Furthermore, the transmitting end also includes a message insertion module, which includes a first laser, a third lithium niobate modulator and a signal source; the first laser is connected to the input end of the third lithium niobate modulator, the signal source is connected to the electrode of the third lithium niobate modulator, and the output end of the third lithium niobate modulator is connected to the chaotic encryption module.
[0013] Furthermore, the first laser is a distributed feedback semiconductor laser with an output wavelength of 1550 nm.
[0014] Furthermore, the receiving end also includes a signal demodulation module, which includes a third Mach-Zehnder interferometer, a third balanced detector, a low-pass filter and a digital signal processing module; the two output ends of the third Mach-Zehnder interferometer are respectively connected to the two input ends of the third balanced detector, and the output end of the third balanced detector is connected to the digital signal processing module via the low-pass filter.
[0015] Furthermore, the message insertion module, the chaotic encryption module, the transmission channel, the chaotic decryption module and the signal demodulation module are sequentially connected via optical fibers.
[0016] Furthermore, the delay time of the first optical fiber delay line is at least ten times the characteristic time corresponding to the highest frequency of the phase chaos laser communication system.
[0017] The beneficial effects brought by adopting the above technical solution are:
[0018] (1) The present invention simultaneously detects the orthogonal component and the in-phase component of light to reduce the optical power loss in the oscillation loop, and can output a chaotic signal under the condition of half the loop feedback gain of the prior art;
[0019] (2) The present invention can simultaneously realize the oscillation of the in-phase component and the orthogonal component of light in the feedback loop, and can effectively eliminate the chaotic dead zone phenomenon;
[0020] (3) The chaotic signal output by the present invention has low autocorrelation and can effectively mask the delay label;
[0021] (4) The present invention can output highly complex chaotic signals under low loop feedback gain conditions to achieve highly secure communications. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 is a system structure diagram of the present invention;
[0023] Figure 2 It is a probability density function bifurcation diagram of the output signal of the present invention under different loop feedback gains;
[0024] Figure 3 It is a power spectrum density bifurcation diagram of the output signal of the present invention under different loop feedback gains;
[0025] Figure 4 It is a bifurcation diagram of a probability density function diagram of an output signal of the present invention at different bias phases;
[0026] Figure 5 It is a permutation entropy diagram of the output signal of the present invention under different loop feedback gains;
[0027] Figure 6 It is the peak value diagram of the autocorrelation function at the time delay moment under different loop feedback gains of the present invention;
[0028] Figure 7 This is a diagram showing the effect of implementing information encryption and decryption in the present invention (Alice: transmitting message; Bob: authorized party; Eve: eavesdropping party). DETAILED DESCRIPTION
[0029] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
[0030] This embodiment provides a phase chaos laser communication system based on a time-delay dual-balanced detection structure. Figure 1 As shown, it includes a message insertion module, a chaotic encryption module, a transmission channel, a chaotic decryption module and a signal demodulation module.
[0031] The message insertion module comprises a first laser 1-1, a first lithium niobate modulator 1-2, and a signal source 1-3. The first laser 1-1 is connected to the input end of the first lithium niobate modulator 1-2, the signal source 1-3 is connected to the electrode of the first lithium niobate modulator 1-2, and the output end of the first lithium niobate modulator 1-2 is connected to the chaotic encryption module.
[0032] The chaotic encryption module comprises a second lithium niobate modulator 2-1, a first coupler 2-2, a first optical fiber delay line 2-3, a first Mach-Zehnder interferometer 2-4, a second optical fiber delay line 2-5, a first balanced detector 2-6, and a first radio frequency amplifier 2-7. The output end of the second lithium niobate modulator 2-1 is connected to the input end of the first coupler 2-2, one output end of the first coupler 2-2 is connected to the transmission module, the other output end is connected to the input end of the first optical fiber delay line 2-3, the output end of the first delay line 2-3 is connected to the input end of the first Mach-Zehnder interferometer 2-4, one output end of the first Mach-Zehnder interferometer 2-4 is connected in sequence to the second optical fiber delay line 2-5 and one input end of the first balanced detector 2-6, the other output end of the first Mach-Zehnder interferometer 2-4 is connected to the other input end of the first balanced detector 2-6, and the output end of the first balanced detector 2-6 is connected in sequence to the first radio frequency amplifier 2-7 and the electrodes of the second lithium niobate modulator 2-1 to form an optical fiber oscillation loop.
[0033] The transmission channel comprises a single-mode optical fiber 3-1 and an erbium-doped optical fiber amplifier 3-2. The single-mode optical fiber 3-1 is connected to the input end of the erbium-doped optical fiber amplifier 3-2, and the output end of the erbium-doped optical fiber amplifier 3-2 is connected to the chaos decryption module.
[0034] The chaos decryption module comprises a second coupler 4-1, a first tunable optical fiber delay line 4-2, a second Mach-Zehnder interferometer 4-3, a second tunable optical fiber delay line 4-4, a second balanced detector 4-5, a second radio frequency amplifier 4-6, and a third lithium niobate modulator 4-7. One output end of the second coupler 4-1 is connected to the input end of the third lithium niobate modulator 4-7, and the other output end is connected to the input end of the first tunable optical fiber delay line 4-2, the output end of the first tunable optical fiber delay line 4-2 is connected to the input end of the second Mach-Zehnder interferometer 4-3, one output end of the second Mach-Zehnder interferometer 4-3 is connected to one input end of the second balanced detector 4-5, and the other output end is connected to the second tunable optical fiber delay line 4-4 and the other input end of the second balanced detector 4-5 in sequence, and the output end of the second balanced detector 4-5 is connected to the electrodes of the second radio frequency amplifier 4-6 and the third lithium niobate modulator 4-7 in sequence, forming an optical fiber oscillation loop.
[0035] The signal demodulation module comprises a third Mach-Zehnder interferometer 5-1, a third balanced detector 5-2, a low-pass filter 5-3 and a digital signal processing module 5-4. The two output ends of the third Mach-Zehnder interferometer 5-1 are respectively connected to the two input ends of the third balanced detector 5-2, and the output end of the third balanced detector 5-2 is sequentially connected to the low-pass filter 5-3 and the digital signal processing module 5-4.
[0036] During operation, first, the transmission information is differentially encoded and converted into a BDPSK signal. The constant power laser sent by the first laser is modulated in the first lithium niobate modulator to generate an additional phase When the differential encoding signal sent is "1", the additional phase When the differential encoding signal sent is "0", the additional phase is "0", in the second lithium niobate modulator, the signal light is modulated again and superimposed with phase chaos Φ. In the first coupler, the additional phase is The light beam is divided into two paths, one path is transmitted to the chaotic decryption module through the single-mode optical fiber and the erbium-doped fiber amplifier in sequence, and the other path is transmitted to the first Mach-Zehnder interferometer through the first optical fiber delay line, and an unbalanced interference phenomenon occurs in the first Mach-Zehnder interferometer. The first Mach-Zehnder interferometer outputs two paths of light, one path is directly connected to one input end of the first balanced detector, and the other path enters the other input end of the first balanced detector through the second optical fiber delay line. The output photocurrent of the first balanced detector is converted into a driving voltage after transimpedance amplification and radio frequency amplification, and applied to the electrode of the second lithium niobate modulator. The dynamic equation of the chaotic carrier output by the chaotic encryption module of the present invention can be written as
[0037]
[0038]
[0039]
[0040] Among them, τ and θ are the high cutoff characteristic response time and low cutoff characteristic response time of the system respectively, τ is 25ps, θ is 5μs, β is the loop feedback gain, Φ0 is the bias phase of the Mach-Zehnder interferometer, T1 and T2 are the delay time of the delay line, which are 30ns and 13ns respectively, t is the system operation time, t0 is the system operation start time, δT is the delay time in the Mach-Zehnder interferometer, which is 400ps.
[0041] In the chaos decryption module, the light beam is divided into two paths through the second coupler. One path enters the third lithium niobate modulator, and the other path passes through the first tunable fiber delay line in turn and is transmitted to the second Mach-Zehnder interferometer. Unbalanced interference occurs in the second Mach-Zehnder interferometer. The interferometer outputs two paths of light. One path is directly input into one input end of the second balanced detector, and the other path enters the other input end of the second balanced detector through the second tunable fiber delay line. The output photocurrent of the second balanced detector is converted into a driving voltage after transimpedance amplification and radio frequency amplification, and applied to the electrode of the third lithium niobate modulator. In the third lithium niobate modulator, the light beam is modulated again to obtain an additional phase Φ', so the output signal light phase of the third lithium niobate modulator is In order to eliminate phase chaos, Φ=-Φ' must be satisfied. Specifically, this can be achieved by exchanging the light components at the input end of the second balanced detector, or by adjusting the interference bias phase of the second Mach-Zehnder interferometer to make it differ from the bias phase of the first Mach-Zehnder interferometer by π / 2. Similarly, the dynamic equation of the chaos decryption module of the present invention can be written as
[0042]
[0043] The symbol “′” in the equation represents parameters and functions similar to those involved in the transmitting device.
[0044] The chaotic encryption module and chaotic decryption module of the communication system proposed by the present invention have symmetrical structures. Theoretically, as long as all the components and working points of the chaotic decryption module match the chaotic encryption module, the nonlinear transmission process of the signal in the chaotic encryption module will be inverted in the chaotic decryption module, and the encrypted signal will be compensated and decrypted. Finally, the demodulation, low-pass filtering and digital signal processing of the decrypted signal are implemented in the signal demodulation module, thereby restoring the original signal.
[0045] According to the simulation results of the embodiment, Figure 2 and Figure 3As shown in , when the loop gain is greater than 1, the probability density function and power spectrum density of the output signal present a uniform distribution state, that is, the system output enters a chaotic state; Figure 4 As shown in FIG. 1 , when the bias phase of the Mach-Zehnder interferometer is set to different values in the range of 0 to π, the system of the present invention can output a chaotic signal without the phenomenon of being unable to oscillate, that is, the chaotic dead zone problem is effectively solved; Figure 5 As shown in the figure, the complexity of the output signal is measured by the permutation entropy value. When the loop gain is greater than 2.5, the permutation entropy value of the output chaotic signal is greater than 0.8, that is, the output signal has a good complexity. Figure 6 The function value of the autocorrelation function when the delay parameter T = 30ns is shown. In the illustration, no peak or valley value is observed when the loop gain is 4, that is, the output chaotic signal has a good delay label hiding ability at this time; the effect diagram of the encryption and decryption communication realized by the present invention is shown in FIG. Figure 7 It shows that when the loop gain value is set to 3, the transmitted picture information is effectively masked.
[0046] The embodiments are only for illustrating the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.
Claims
1. A phase chaos laser communication system based on a time-delay dual-balanced detection structure, characterized in that: It includes a transmitting end, a transmission channel and a receiving end connected in sequence; the transmitting end includes a chaotic encryption module, and the receiving end includes a chaotic decryption module; The chaotic encryption module includes a first lithium niobate modulator, a first coupler, a first optical fiber delay line, a first Mach-Zehnder interferometer, a second optical fiber delay line, a first balanced detector and a first radio frequency amplifier; The output end of the first lithium niobate modulator is connected to the input end of the first coupler, the first output end of the first coupler is connected to the transmission channel, the second output end of the first coupler is connected to the input end of the first optical fiber delay line, the output end of the first optical fiber delay line is connected to the input end of the first Mach-Zehnder interferometer, the first output end of the first Mach-Zehnder interferometer is connected to the first input end of the first balanced detector via the second optical fiber delay line, the second output end of the first Mach-Zehnder interferometer is connected to the second input end of the first balanced detector, and the output end of the first balanced detector is connected to the electrode of the first lithium niobate modulator via the first radio frequency amplifier, so as to form an optical fiber oscillation loop; The chaos decryption module includes a second coupler, a first tunable optical fiber delay line, a second Mach-Zehnder interferometer, a second tunable optical fiber delay line, a second balanced detector, a second radio frequency amplifier, and a second lithium niobate modulator; The first output end of the second coupler is connected to the input end of the second lithium niobate modulator, the second output end of the second coupler is connected to the input end of the first tunable optical fiber delay line, the output end of the first tunable optical fiber delay line is connected to the input end of the second Mach-Zehnder interferometer, the first output end of the second Mach-Zehnder interferometer is connected to the first input end of the second balanced detector, the second output end of the second Mach-Zehnder interferometer is connected to the second input end of the second balanced detector via the second tunable optical fiber delay line, and the output end of the second balanced detector is connected to the electrode of the second lithium niobate modulator via the second radio frequency amplifier, forming an optical fiber oscillation circuit.
2. According to claim 1, the phase chaos laser communication system based on the time-delay dual-balanced detection structure is characterized in that: The transmission channel comprises a single-mode optical fiber and an erbium-doped optical fiber amplifier. The single-mode optical fiber is connected to the input end of the erbium-doped optical fiber amplifier, and the output end of the erbium-doped optical fiber amplifier is connected to the chaos decryption module.
3. According to claim 1, the phase chaos laser communication system based on the time-delay dual-balanced detection structure is characterized in that: The transmitting end also includes a message insertion module, which includes a first laser, a third lithium niobate modulator and a signal source; the first laser is connected to the input end of the third lithium niobate modulator, the signal source is connected to the electrode of the third lithium niobate modulator, and the output end of the third lithium niobate modulator is connected to the chaotic encryption module.
4. According to claim 3, the phase chaos laser communication system based on the time-delay dual-balanced detection structure is characterized in that: The first laser is a distributed feedback semiconductor laser with an output wavelength of 1550 nm.
5. According to claim 3, the phase chaos laser communication system based on the time-delay dual-balanced detection structure is characterized in that: The receiving end also includes a signal demodulation module, which includes a third Mach-Zehnder interferometer, a third balanced detector, a low-pass filter and a digital signal processing module; the two output ends of the third Mach-Zehnder interferometer are respectively connected to the two input ends of the third balanced detector, and the output end of the third balanced detector is connected to the digital signal processing module via the low-pass filter.
6. The phase chaos laser communication system based on the time-delay dual-balanced detection structure according to claim 5 is characterized in that: The message inserting module, the chaotic encryption module, the transmission channel, the chaotic decryption module and the signal demodulation module are sequentially connected through optical fibers.
7. The phase chaos laser communication system based on the time-delay dual-balanced detection structure according to any one of claims 1 to 6, characterized in that: The delay time of the first optical fiber delay line is at least ten times the characteristic time corresponding to the highest frequency of the phase chaos laser communication system.