CN117834110B - Chaotic secure communication method and communication system - Google Patents
Chaotic secure communication method and communication system Download PDFInfo
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Abstract
The application provides a chaotic secure communication method and a communication system, and the technical scheme comprises the following steps: the method comprises the steps that a sending end generates a modulated optical signal and a first chaotic signal, and the modulated optical signal and the first chaotic signal are subjected to beam combination and scrambling to obtain a first signal which is injected into a receiving end; the receiving end generates a second chaotic signal, and the first chaotic signal and the second chaotic signal are coherent and destructive optical signals; the first signal and the second chaotic signal can be descrambled to obtain a modulated optical signal after being combined again, and then the modulated optical signal is input to the information sink.
Description
Technical Field
The application relates to the field of chaotic communication, in particular to a chaotic secure communication method and a communication system.
Background
In recent years, due to the need for secure communication, secure communication based on chaotic synchronization has attracted great research interest, researchers have conducted a great deal of theoretical and experimental research on chaotic secure communication, and have conducted high-speed long-distance experiments in commercial optical fiber communication networks.
At present, the secret optical communication means based on the chaos mechanism is mainly divided into three types: chaos Masking (CMS), chaos modulation (Chaos Modulating, CMO), and Chaos keying (Chaos KEY SHIFTING, CKS). The CMS scheme utilizes a space beam combiner or an optical fiber beam combiner to realize encryption and hiding of chaotic carrier waves on signal light, has the advantages of simple system and low cost, and has wide application prospect.
However, the security of the CMS is the lowest of the three, because the traditional CMS scheme requires that the chaotic light and the signal light have orthogonal polarization, and generally selects an orthogonal linear polarization base or a circular polarization base, otherwise, beat frequency exists during electric domain detection to affect signal recovery, and a stealer can filter the chaotic signal in a polarization filtering manner to steal information, so that on the premise of keeping a simple system, how to raise the security problem of the CMS becomes a technical problem focused by a person skilled in the art.
Disclosure of Invention
In order to solve the technical problems, the application provides the chaotic secure communication method and the communication system, and the scheme of optical field coherence cancellation is utilized to finish decryption of an original chaotic signal through the design on an optical layer, so that electric domain processing is not needed, a complex electric system is not involved, the insertion time delay of the system is effectively shortened, and the safety of chaotic communication is ensured.
In order to achieve the technical purpose, the application adopts the following technical scheme:
in one aspect, the application provides a chaotic secure communication method, comprising the steps of,
The method comprises the steps that a sending end generates a modulated optical signal and a first chaotic signal, and the modulated optical signal and the first chaotic signal are subjected to beam combination and scrambling to obtain a first signal which is injected into a receiving end;
The receiving end generates a second chaotic signal, and the first chaotic signal and the second chaotic signal are coherent and destructive optical signals;
and after the first signal and the second chaotic signal are combined again, descrambling can be performed to obtain a modulated optical signal, and the modulated optical signal is further input to a signal sink.
In one possible implementation, the first chaotic signal and the second chaotic signal satisfy the following conditions: the first chaotic signal and the second chaotic signal have the same polarization direction, the same wavelength, the same amplitude and the phase differenceWherein/>Is a natural number.
In one possible implementation manner, the step of generating the modulated optical signal and the first chaotic signal by the transmitting end includes:
the chaotic driving source generates a driving signal, and a first slave laser is injected to generate a first chaotic signal;
the signal source emits a modulated optical signal.
In one possible implementation manner, the first chaotic signal and the modulated optical signal satisfy the following conditions: the center angular frequency of the first chaotic signal and the modulated optical signal is the same as the polarization direction.
In one possible implementation, the modulation format of the modulated optical signal includes, but is not limited to, NRZ-OOK, RZ-OOK, PAM.
In one possible implementation, the modulated optical signal is an amplitude modulated optical signal.
In one possible implementation manner, the step of generating the second chaotic signal at the receiving end includes:
the chaotic driving source is injected into the second slave laser to generate an initial chaotic signal;
the first chaotic signal and the initial chaotic signal are synchronous chaotic signals generated by adopting common external driving light injection;
the initial chaotic signal is modulated and then converted into a second chaotic signal which is coherently cancelled with the first chaotic signal, and then the second chaotic signal is combined with the first chaotic signal.
In one possible implementation manner, the step of performing signal modulation on the initial chaotic signal includes:
the initial chaotic signal is modulated into a second chaotic signal which is coherently cancelled with the first chaotic signal after being subjected to phase modulation, polarization modulation, optical power modulation and delay modulation in sequence.
In one possible implementation, the phase modulation includes modulating a phase of the initial chaotic signal to be different from the first chaotic signalWherein/>Is a natural number.
In one possible implementation, the polarization modulation includes modulating a polarization direction of the initial chaotic signal to be coincident with the first chaotic signal.
In one possible implementation, the optical power modulation and the time-delay modulation include modulating a time-domain amplitude, a time-domain phase of the initial chaotic signal to be consistent with the first chaotic signal.
In a second aspect, the present application also provides a chaotic communication system, the chaotic communication system comprising a transmitting module and a receiving module,
The transmitting module is used for generating a modulated optical signal and a first chaotic signal,
The receiving module is used for generating a second chaotic signal and receiving the descrambled modulated optical signal.
In one possible implementation, the sending module includes:
the chaotic driving source is used for generating a chaotic driving signal;
the chaotic driving signal generated by the chaotic driving source is divided into two paths, one path is injected into a first slave laser of the scrambling module, and the first slave laser generates a first chaotic signal; the other path is injected into the receiving module;
a signal source for generating a modulated optical signal;
and the first beam combining module is used for injecting the chaotic driving signal and the first chaotic signal into the first beam combining module to combine the first signal, and then injecting the first signal into the receiving module again.
In one possible implementation manner, the chaotic driving source comprises a vertical cavity surface emitting laser, an optical fiber coupler, a tunable optical attenuator and an optical reflector which are sequentially arranged along the emergent direction of the chaotic driving signal.
In one possible implementation, the receiving module includes:
A second slave laser for receiving the chaotic driving signal output by the scrambling module, thereby generating an initial chaotic signal,
The phase shifting module, the polarization control module, the optical power control module and the optical link delay module are sequentially arranged according to the transmission direction of the initial chaotic signal, and the initial chaotic signal is modulated into a second chaotic signal which can be coherently cancelled with the first chaotic signal after sequentially passing through the modules;
The second beam combining module is used for receiving the first signal and the second chaotic signal, outputting a modulated optical signal after beam combination,
And a sink for receiving the decrypted modulated optical signal.
In one possible implementation, the optical link delay module may be disposed before the phase shift module.
In one possible implementation, the phase shifting module is selected from one or more of a phase modulator, a phase shifter.
In one possible implementation, the polarization control module is a polarization controller.
In one possible implementation, the optical power control module is a tunable optical fiber attenuator.
In one possible implementation, the optical link delay module is a fiber delay line.
Compared with the existing chaotic hiding communication system, the application has the following technical advantages:
1. According to the technical scheme provided by the application, the information encryption and decryption process is completely realized in an optical layer, electric domain processing is not required, complicated electrical subsystems such as photoelectric detection, high-speed ADC (analog-to-digital converter) sampling, high-speed FPGA (field programmable gate array) processing and the like are not required, and the overall cost and the power consumption of the system are lower;
2. In the technical scheme provided by the application, the encryption and decryption of the signal do not need electric domain information processing, only transmission delay exists without information processing delay, the transmission delay is in the order of ten nanoseconds to hundred nanoseconds, and the information processing delay is in the order of sub-millisecond, so that the introduced delay is extremely low, the requirement of ultra-low delay safety communication can be met, and meanwhile, the insertion delay of the system is also greatly shortened;
3. The technical scheme of the application solves the problem of poor safety of the traditional chaotic hiding communication scheme, wherein the traditional chaotic hiding communication needs to require orthogonal polarization of chaotic light and signal light, otherwise, beat frequency exists during electric domain detection to influence signal recovery; the application directly realizes the removal of the chaotic hiding signal by utilizing coherent cancellation in the optical layer, bypasses the beat frequency process, thus allowing the chaotic light and the signal light to have the same polarization and solving the problem of poor safety of the traditional chaotic hiding scheme.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly explain the drawings required for the embodiments, it being understood that the following drawings illustrate only some embodiments of the present application and are therefore not to be considered limiting of the scope, and that other related drawings may be obtained according to these drawings without the inventive effort of a person skilled in the art.
Fig. 1 is a schematic flow chart of a chaotic secure communication method according to an embodiment of the present application;
FIG. 2 (a) is a first chaotic signal optical field mode value;
FIG. 2 (b) is a first chaotic signal optical field phase;
FIG. 2 (c) is a real part of the optical field of the first chaotic signal;
FIG. 2 (d) is a second chaotic signal optical field mode value;
FIG. 2 (e) is a second chaotic signal light field phase;
FIG. 2 (f) is a real part of the optical field of the second chaotic signal;
FIG. 2 (g) is a light field model of a combined signal obtained after combining the first chaotic signal and the second chaotic signal;
FIG. 2 (h) is the optical field phase of the combined signal;
FIG. 2 (i) is the real part of the combined light field;
fig. 3 is a block diagram of a chaotic secure communication system according to an embodiment of the present application;
fig. 4 (a) is an intensity time domain waveform of a first chaotic signal;
fig. 4 (b) is a time domain phase variation of the first chaotic signal;
fig. 4 (c) is an intensity time domain waveform of an initial chaotic signal;
Fig. 4 (d) is a time domain phase variation of the initial chaotic signal;
fig. 4 (e) is a plot of intensity correlation of the first chaotic signal and the initial chaotic signal;
FIG. 5 (a) is an intensity time domain waveform of a modulated optical signal;
Fig. 5 (b) is an eye diagram of a modulated optical signal;
FIG. 5 (c) is an intensity time domain waveform of the first signal;
FIG. 5 (d) is an eye diagram of the first signal;
FIG. 5 (e) is a waveform of the intensity time domain of the decrypted optical signal;
fig. 5 (f) is an eye diagram of the decrypted optical signal.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present application, it should be noted that, the azimuth or positional relationship indicated by the terms "upper", "lower", etc. are based on the azimuth or positional relationship shown in the drawings, or the azimuth or positional relationship that is commonly put in use of the product of the application, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and therefore should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
Furthermore, the terms "horizontal," "vertical," "overhang," and the like do not denote a requirement that the component be absolutely horizontal or overhang, but rather may be slightly inclined. As "horizontal" merely means that its direction is more horizontal than "vertical", and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the present application, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.
It should be noted that, in the case of no conflict, different features in the embodiments of the present application may be combined with each other.
The following describes specific embodiments of the present application in detail with reference to the drawings.
Referring to fig. 1, the chaotic secure communication method of the present application includes the steps of,
The method comprises the steps that a sending end generates a modulated optical signal and a first chaotic signal, and the modulated optical signal and the first chaotic signal are subjected to beam combination and scrambling to obtain a first signal which is injected into a receiving end;
The transmitting end is defined as a transmitting end which is universal in the communication field, namely a source end of information, the transmitting end can convert the information to be transmitted into signals suitable for transmission, such as optical signals and electric signals, and transmits the signals into channels, wherein the channels can be wired or wireless cables, optical fibers and the like, and the channels adopted in the application are optical fibers and the transmission is modulated optical signals.
The chaotic signal in the application, including but not limited to a first chaotic signal and a second chaotic signal hereinafter, is generated in a nonlinear system, shows random-like motion behaviors with characteristics of non-periodicity, sensitivity to initial values and the like, and can not only effectively mask real information but also realize synchronous control compared with real noise, so that the chaotic signal has important application in various fields.
In one embodiment of the present application, the generation of the chaotic signal may employ the following method: under the condition of external disturbance, for example, the semiconductor laser can show nonlinearity under the action of external disturbance such as external light feedback, external light injection, photoelectric feedback and the like, and the output of the semiconductor laser can be transited from a constant state to a chaotic state by setting certain disturbance conditions, so that chaotic signals are generated. The laser signal has the advantages of high bandwidth, randomness and the like, and can be used as an optical carrier to provide physical layer security assurance for an optical fiber communication system.
The modulated optical signal emitted by the transmitting end comprises information to be transmitted, is signal light, and is loaded on the signal light signal after being combined with the first chaotic signal, so that the modulated optical signal is encrypted and hidden.
The receiving end generates a second chaotic signal, and the first chaotic signal and the second chaotic signal are coherent and destructive optical signals;
The second chaotic signal generating method is the same as the first chaotic signal and is generated under the condition of external disturbance of the semiconductor laser.
The coherence of optical signals means that two optical signals simultaneously satisfy the following 3 conditions in the transmission process: 1. the frequencies (wavelengths) are the same; 2. the vibration directions are the same; 3. the optical signals satisfying the above conditions have constant phase difference and can generate stable interference between each other during transmission, and the interference can be coherent enhancement or coherent cancellation, which depends on the phase difference between the two optical signals, when the phase difference between the two optical signals at the spatial point isWhen the two optical signals are relevant reinforcement; when the phase difference of two optical signals at a spatial point is/>When the two optical signals are coherently cancelled.
And after the first signal and the second chaotic signal are combined again, descrambling can be performed to obtain a modulated optical signal, and the modulated optical signal is further input to a signal sink.
In the application, after the first chaotic signal and the second chaotic signal are combined, the first chaotic signal and the second chaotic signal are coherent and destructive optical signals, after the first chaotic signal and the second chaotic signal are combined again, the first chaotic signal and the second chaotic signal are offset from the optical angle, the signals after the combination are descrambled, the output is the modulated optical signal generated by the transmitting end, the modulated optical signal is input into the information sink again, and the encrypted signal can be decrypted to recover the plaintext, thereby achieving the aim of secret communication.
In one possible embodiment of the present application, the first chaotic signal and the second chaotic signal satisfy the following conditions: the first chaotic signal and the second chaotic signal have the same polarization direction, the same wavelength, the same amplitude and the phase differenceWherein/>Is a natural number.
The related art principle is explained as follows for the present embodiment:
in this embodiment, the modulated optical signal emitted from the transmitting end is set as Then/>Can be expressed as formula 1:
（1）
Wherein the method comprises the steps of Represents the center angular frequency of the modulated optical signal,/>Representing the initial phase of the modulated optical signal,/>Representing the polarization direction of the modulated optical signal,/>Is a baseband signal modulated on a modulated optical signal.
At the transmitting end, the semiconductor laser can be injected by external light, so as to drive the first slave laser to generate a first chaotic signalThen/>Can be expressed as formula 2:
（2）
Wherein the method comprises the steps of Represents the center angular frequency of the first chaotic signal,/>Represents the time domain phase of the first chaotic signal,Representing the polarization direction of the first chaotic signal,/>Is the time domain amplitude modulus value of the first chaotic signal,/>As a function of complex amplitude form.
The modulated optical signalAnd the first chaotic signal/>After beam combination scrambling, a first signal can be obtainedThen
（3）
At this time, the optical signal is modulatedHas been hidden in the first chaotic signal/>In the method, the transmission link can be effectively prevented from being illegally eavesdropped.
At the receiving end, the second slave laser is injected by the chaos driving signal in a common driving way, so that a second chaos signal can be generatedThen/>Can be expressed as formula 4:
（4）
Wherein the method comprises the steps of Represents the center angular frequency of the second chaotic signal,/>Representing the initial phase of the second chaotic signal,/>Representing the polarization direction of the second chaotic signal,/>Is the time domain amplitude modulus value of the second chaotic signal,/>As a function of complex amplitude form.
The first signal and the second chaotic signal are combined again to obtain a signalThen:
(5)
illustratively, when the first chaotic signal and the second chaotic signal satisfy the following conditions, And/>Can coherently cancel:
，/>，/>，/>。
wherein, The method can be realized through polarization modulation, and the polarization direction of the chaotic signal is modulated;
the method can be realized by adjusting parameters of the first slave laser and the second slave laser, and the output chaotic signals are adjusted to have the same wavelength; /(I) This can be achieved by controlling the time delay and the optical power,Phase shifting adjustment may be utilized.
At this time, the liquid crystal display device,Equation (5) can be reduced to:
(6)
i.e. the receiving end can descramble the complete modulated optical signal loaded with transmission information The chaotic decryption of the receiving end is completed.
For example, please see the simulation results shown in fig. 2 (a) -2 (i), and fig. 2 (a) -2 (i) are examples of the coherent cancellation effect of the optical field of two signals, when the two signals satisfy: 1. the frequencies (wavelengths) are the same, and the two signals need to have the same frequency in order to have a stable phase difference, and when the frequencies of the two signals are different, the phase difference will change with time; 2. the polarization directions (polarization states) are the same, and the interference nature of the light field is superposition of electric field components with the same polarization state, so that the signal polarization states are required to be the same; 3. the amplitudes (modulus values) are the same, and if the signal amplitudes are different, the two signals cannot be cancelled to 0; 4. phase difference ofAt this time, the optical field mode value obtained after the two signals are combined is 0, namely, the coherent cancellation is realized.
Illustratively, fig. 2 (a) is a first chaotic signal optical field model; FIG. 2 (b) is a first chaotic signal optical field phase; for the convenience of observation, the phase value is limited to be between (-pi, pi) by performing periodic translation of 2n pi on the phase value; FIG. 2 (c) is a real part of the optical field of the first chaotic signal; fig. 2 (d) shows a second chaotic signal optical field mode value, and the value at any time is the same as the optical field mode value at the corresponding time of the first chaotic signal.
FIG. 2 (e) shows the optical field phase of the second chaotic signal, the value at any time of which differs from the optical field phase at the corresponding time of the first chaotic signalFor the convenience of observation, the phase value is limited to be between (-pi, pi) by performing periodic translation of 2n pi on the phase value; FIG. 2 (f) is a real part of the optical field of the second chaotic signal; FIG. 2 (g) is a light field model of a combined signal obtained after combining the first chaotic signal and the second chaotic signal; FIG. 2 (h) is the optical field phase of the combined signal; for the convenience of observation, the phase value is limited to be between (-pi, pi) by performing periodic translation of 2n pi on the phase value; fig. 2 (i) is the real part of the combined light field.
As can be seen from fig. 2 (g) and fig. 2 (h), the optical field mode value is 0 after the beam combination in fig. 2 (g), and the optical field intensity is 0 after the beam combination in fig. 2 (i). Therefore, after the first chaotic signal and the second chaotic signal are combined, coherent cancellation is realized.
In one embodiment of the present application, the step of generating the modulated optical signal and the first chaotic signal at the transmitting end includes:
the chaotic driving source generates a driving signal, and a first slave laser is injected to generate a first chaotic signal;
the signal source emits a modulated optical signal.
In this embodiment, the chaotic driving source refers to a component that generates a chaotic driving signal, and when the chaotic driving signal is injected into the slave laser, the chaotic signal can be generated.
The signal source in this embodiment is generally referred to as an optoelectronic component that can generate an optical signal.
In one embodiment of the present application, the first chaotic signal and the modulated optical signal satisfy the following conditions: the center angular frequency of the first chaotic signal and the modulated optical signal is the same as the polarization direction. When the first chaotic signal and the modulated optical signal have central angular frequenciesAnd/>When the same, can prevent the stealer from filtering out the effective information, such as modulating the optical signal, through the wavelength filtering means effectively; when the polarization direction of the first chaotic signal and the modulated optical signal/>And/>And when the two types of information are the same, the effective information can be effectively prevented from being filtered out by a stealer through a polarization filtering means.
In one embodiment of the present application, the modulation format of the modulated optical signal includes, but is not limited to, NRZ-OOK, RZ-OOK, PAM, PSK, QAM. The chaotic shelter can achieve encryption effect on the signals, and the chaotic signals are directly coherently cancelled during decryption, so that demodulation of a back-end signal sink DSP is not affected. Illustratively, as a preferred scheme, NRZ-OOK (non-return-to-zero on-off keying modulation) mode, RZ-OOK (return-to-zero on-off keying modulation) mode may be adopted in this embodiment, and on/off keying (OOK) is the most basic modulation format, and modulation signal is achieved by adjusting amplitude. PAM (pulse amplitude modulation) may also be used, i.e. a continuous-time baseband time domain signal is used to modulate the amplitude of a rectangular pulse carrier signal, i.e. a variation of the amplitude of the rectangular pulse carrier signal, to deliver the amplitude of the continuous-time lacing time domain signal.
In one embodiment of the application, the modulated optical signal is an amplitude modulated optical signal.
In one embodiment of the present application, the step of generating the second chaotic signal at the receiving end includes:
the chaotic driving source is injected into the second slave laser to generate an initial chaotic signal;
the first chaotic signal and the initial chaotic signal are synchronous chaotic signals generated by adopting common external driving light injection;
the initial chaotic signal is modulated and then converted into a second chaotic signal which is coherently cancelled with the first chaotic signal, and then the second chaotic signal is combined with the first chaotic signal.
In this embodiment, the process of injecting the first chaotic signal into the first slave laser by the chaotic driving source is the same as the process of generating the second slave laser;
in this embodiment, the initial chaotic signal and the first chaotic signal are synchronizable chaotic signals generated by co-driving injection, the co-driving injection is a common technology in the field of chaotic lasers, and the technology for generating the synchronizable chaotic signals is used for externally driving a light injection synchronization system together.
The chaotic driving source works in a chaotic state under the action of certain feedback intensity, chaotic laser emitted by the chaotic driving source is divided into two identical paths of light, and the two paths of light can be split by adopting an optical fiber coupler, and are respectively injected into two slave lasers, and the two slave lasers obtain different paths of chaotic laser in a free running state; when the injection intensity and frequency detuning condition of a proper chaotic driving source are selected, the two slave lasers can realize chaotic synchronization under the same external chaotic driving light disturbance and injection locking effect, and in the embodiment, the chaotic synchronization of the first chaotic signal and the initial chaotic signal is realized.
The Lang-Kobayashi rate equation based on the laser can be deduced, when the first chaotic signal and the initial chaotic signal realize chaotic synchronization, the first chaotic signal and the initial chaotic signal can meet the amplitude-phase locking relation, namely, the time domain amplitude mode values of the two signals are identical through a method of controlling delay and optical power of the two signals, namely, the amplitude mode values of the two signals meet the requirement。
In this embodiment, the complex amplitudes (the complex amplitudes include the modulus and the phase) of the initial chaotic signal and the first chaotic signal have extremely high consistency with the change rule of time, but because the transmission distances are different, the consistent change rule has time delay, so that the time delay can be compensated by using the optical link delay control module, so that the amplitude ratio of the initial chaotic signal and the first chaotic signal is fixed at any moment, and the phase difference is constant. At this time, if there is no additional phase modulation, the phase difference between the initial chaotic signal and the first chaotic signal after the compensation delay should be constant to 0, and at this time, the amplitude ratio of the initial chaotic signal and the first chaotic signal is made to be 1 by power modulation, that is, the amplitudes of the two signals are equal at any moment, so that the necessary condition that the cancellation is 0 can be satisfied, otherwise, the weights of the two signals are not equal, and even if the two signals are cancelled, the combined light field will not be 0.
In one embodiment of the present application, the step of subjecting the initial chaotic signal to signal modulation includes: the initial chaotic signal is modulated into a second chaotic signal which is coherently cancelled with the first chaotic signal after being subjected to phase modulation, polarization modulation, optical power modulation and delay modulation in sequence.
The initial chaotic signal emitted from the second slave laser is only a signal in chaotic synchronization with the first chaotic signal, but cannot be coherently cancelled with the first chaotic signal, and the conditions of coherent cancellation can be met only by carrying out phase modulation, polarization modulation, optical power modulation and delay modulation again.
The phase modulation may include modulating the phase of the initial chaotic signal to be different from the first chaotic signalWherein/>Is a natural number.
Illustratively, the polarization modulation includes modulating a polarization direction of the initial chaotic signal to coincide with the first chaotic signal.
Illustratively, the optical power modulation and the time-delay modulation include modulating a time-domain amplitude, a time-domain phase of the initial chaotic signal to be consistent with the first chaotic signal.
In one embodiment of the present application, the phase modulation order is flexible, and can be placed before or after all steps, so that the phase modulation effect of the present application can be achieved,
In one embodiment of the present application, based on the above-mentioned chaotic secure communication method, the present application further provides a chaotic communication system, which includes a transmitting module and a receiving module,
The transmitting module is used for generating a modulated optical signal and a first chaotic signal,
The receiving module is used for generating a second chaotic signal and receiving the descrambled modulated optical signal.
In one embodiment of the present application, the transmitting module includes:
the chaotic driving source is used for generating chaotic driving signals, and all structures capable of generating the chaotic signals can be used as the chaotic driving source;
The chaotic driving signals generated by the chaotic driving source are divided into two paths, and an optical fiber coupler can be used for branching, wherein one path of the branched chaotic driving signals is injected into a first slave laser of the scrambling module, and the first slave laser generates a first chaotic signal; the other path of injection receiving module is used for driving the second slave laser to generate synchronous initial chaotic signals.
A signal source for generating a modulated optical signal, as which any optical component that can generate an optical signal can be used, and the signal source may be selected from one or more of an optical module (incoherent modulation format), a direct modulated laser (DML, EML), or an intensity modulated optical signal generated by a cascade of intensity modulators of a continuous laser, for example.
The first beam combining module may be, for example, a beam combiner, the chaotic driving signal and the first chaotic signal are injected into the first beam combining module to combine into a first signal, and then are injected into the receiving module again, and the second beam combining module of the receiving module may be used to receive the first signal.
In one embodiment of the application, the chaotic driving source comprises a vertical cavity surface emitting laser, an optical fiber coupler, an adjustable optical attenuator and an optical reflector which are sequentially arranged along the emergent direction of the chaotic driving signal. The chaotic driving source provided in the embodiment is a typical structure for generating chaotic signals through external cavity feedback.
In one embodiment of the application, the receiving module comprises:
a second slave laser for receiving the chaotic driving signal outputted by the scrambling module to generate an initial chaotic signal, wherein the initial chaotic signal is a signal in chaotic synchronization with the first chaotic signal,
Common continuous lasers, such as semiconductor lasers, CO 2 lasers, etc., can be used as the first slave laser and the second slave laser to generate the chaotic signal. Among them, semiconductor lasers are more commonly used because of their low price and wide chaotic bandwidth. To generate a chaotic signal with high quality synchronization performance, parameters of the first slave laser and the second slave laser need to be adjusted, such as a linewidth enhancement factor, a gain coefficient, an inner cavity length, a threshold current and other hardware parameters are good in consistency, and meanwhile, external parameters such as working current and injection optical power of the chaotic signal need to be basically consistent. In practical cases, the important parameters are well controlled, and two chaotic signals generated by the lasers are injected by using the common drive, so that the cross correlation characteristic can reach 95% -98%.
The phase shifting module, the polarization control module, the optical power control module and the optical link delay module are sequentially arranged according to the transmission direction of the initial chaotic signal, and the initial chaotic signal is modulated into a second chaotic signal which can be coherently cancelled with the first chaotic signal after sequentially passing through the modules; here, the phase shift module may also be moved to the optical link delay module, so that the same technical effect can be achieved.
The second beam combining module, which may be an exemplary beam combiner, is configured to receive the first signal and the modulated second chaotic signal transmitted by the transmitting end, and output a modulated optical signal after beam combination.
And a sink for receiving the decrypted modulated optical signal. Illustratively, the sink typically selects the photodetector and the back-end digital signal processing system.
In one embodiment of the present application, a chaotic communication system is provided, see fig. 3.
In one embodiment of the present application, the optical link delay module may be disposed before the phase shift module.
In one embodiment of the application, the phase shifting module is selected from one or more of a phase modulator and a phase shifter, which can effectively achieve the technical effect of modulating the phase of the chaotic signal and modulate the phase of the initial chaotic signal and the phase of the first chaotic signal to be differentI.e. satisfy/>Conditions of (2);
In one embodiment of the present application, the polarization control module is a polarization control module, specifically, may be a polarization controller, and may regulate and control the polarization directions of the initial chaotic signal and the first chaotic signal to be consistent, i.e. to satisfy Is a condition of (2).
In one embodiment of the application, the optical power control module is a tunable optical fiber attenuator.
In one possible implementation, the optical link delay module is a fiber delay. By simultaneous adjustment of the optical power module and the optical link delay module, the method can meet。
In a specific embodiment of the application, a B2B (back-to-back) simulation system is built using optical communication simulation software to verify the feasibility of the solution.
Please refer to fig. 4 (a) -fig. 4 (e), the first slave laser and the second slave laser generate two chaotic signals locked in amplitude and phase based on the master laser co-driving injection of the front end.
Fig. 4 (a) -4 (e) illustrate two high synchronization quality chaotic signals generated by the main laser co-drive injection, the higher the synchronization quality, the better the consistency of both amplitude and phase in the time domain, i.e., the higher the cross-correlation. Fig. 4 (a) is an intensity time domain waveform of a first chaotic signal; fig. 4 (b) is a time domain phase variation of the first chaotic signal; fig. 4 (c) is an intensity time domain waveform of an initial chaotic signal; fig. 4 (d) is a time domain phase variation of the initial chaotic signal; fig. 4 (e) is a plot of correlation between the intensities of the first chaotic signal and the initial chaotic signal, wherein the plot is made by aligning the intensity waveforms of the first chaotic signal and the initial chaotic signal in the time domain, sequentially taking the intensity value of the first chaotic signal at the same time as the X axis, taking the intensity value of the initial chaotic signal as the Y axis, showing that the closer the plot is to a straight line, the higher the correlation between the two is, and calculating according to a cross-correlation formula, wherein the cross-correlation coefficient of the first chaotic signal and the initial chaotic signal reaches 99.8%.
Fig. 5 (a) -5 (f) exemplarily show a result diagram of the chaotic secure communication method provided by the embodiment of the present application. Wherein, fig. 5 (a) is an intensity time domain waveform of the modulated optical signal; the signal adopts OOK modulation format, and the baud rate in simulation is set to 10 Gbps; fig. 5 (b) is an eye diagram of a modulated optical signal; fig. 5 (c) is an intensity time domain waveform of the first signal, that is, an intensity time domain waveform of an optical signal transmitted in a channel after the source optical signal is buried by the first chaotic signal; fig. 5 (d) shows an eye diagram of the first signal, which is completely closed, and the Bit Error Rate (BER) reaches 0.178 according to the simulation result, so that the original information is effectively protected; FIG. 5 (e) is a waveform of the intensity time domain of the decrypted optical signal; fig. 5 (f) is an eye diagram of the decrypted optical signal, which is re-opened, and BER is as low as 1.00×10 -10 according to the simulation result, and original information is effectively recovered.
In one embodiment of the application, the technical effects of polarization modulation, optical power modulation and delay modulation can also be achieved by setting the polarization, delay and amplitude of the first slave laser and the second slave laser to be consistent，/>，/>Condition of/>The phase modulation conditions of (a) can be achieved by arranging a phase modulator after the second slave laser, so that the system can be further simplified by adjusting the parameters of the laser.
In summary, the present embodiment provides a chaotic secure communication method and a communication system, where decryption is implemented by coherent cancellation of coherent optical signals, and the information encryption and decryption process is implemented completely in an optical layer, without electrical domain processing, without complex electrical subsystems such as photoelectric detection, high-speed ADC sampling, high-speed FPGA processing, and the cost and power consumption of the whole system are lower.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (17)
1. A chaotic secure communication method, comprising the steps of:
the method comprises the steps that a sending end generates a modulated optical signal and a first chaotic signal, and the modulated optical signal and the first chaotic signal are subjected to beam combination and scrambling to obtain a first signal which is injected into a receiving end; the central angular frequency of the first chaotic signal and the modulated optical signal is the same as the polarization direction;
The receiving end generates a second chaotic signal, and the first chaotic signal and the second chaotic signal are coherent and destructive optical signals; the first chaotic signal and the second chaotic signal have the same polarization direction, the same wavelength, the same amplitude and the phase difference Wherein/>Is a natural number;
and the first signal and the second chaotic signal are combined again and then can be descrambled to obtain a modulated optical signal, and the modulated optical signal is input to a signal sink.
2. The chaotic secure communication method according to claim 1, wherein the step of generating the modulated optical signal and the first chaotic signal at the transmitting terminal comprises:
the chaotic driving source generates a driving signal, and a first slave laser is injected to generate a first chaotic signal;
the signal source emits a modulated optical signal.
3. The chaotic secure communication method of claim 1, wherein: modulation formats of the modulated optical signals include, but are not limited to, NRZ-OOK, RZ-OOK, PAM.
4. The chaotic secure communication method of claim 3, wherein: the modulated optical signal is an amplitude modulated optical signal.
5. The chaotic secure communication method according to claim 1, wherein the receiving end generates the second chaotic signal comprising:
the chaotic driving source is injected into the second slave laser to generate an initial chaotic signal;
the first chaotic signal and the initial chaotic signal are synchronous chaotic signals generated by adopting common external driving light injection;
the initial chaotic signal is modulated and then converted into a second chaotic signal which is coherently cancelled with the first chaotic signal, and then the second chaotic signal is combined with the first chaotic signal.
6. The chaotic secure communication method according to claim 5, wherein: the step of modulating the initial chaotic signal comprises the following steps:
the initial chaotic signal is modulated into a second chaotic signal which is coherently cancelled with the first chaotic signal after being subjected to phase modulation, polarization modulation, optical power modulation and delay modulation in sequence.
7. The chaotic secure communication method according to claim 6, wherein: the phase modulation includes modulating a phase of the initial chaotic signal to be different from the first chaotic signalWherein/>Is a natural number.
8. The chaotic secure communication method according to claim 6, wherein: the polarization modulation includes modulating a polarization direction of the initial chaotic signal to coincide with the first chaotic signal.
9. The chaotic secure communication method according to claim 6, wherein: the optical power modulation and the time delay modulation comprise modulating the time domain amplitude and the time domain phase of the initial chaotic signal to be consistent with the first chaotic signal.
10. A chaotic communication system based on the chaotic secure communication method of any one of claims 1 to 9, which is characterized in that:
The chaotic communication system comprises a transmitting module and a receiving module,
The transmitting module is used for generating a modulated optical signal and a first chaotic signal,
The receiving module is used for generating a second chaotic signal and receiving the descrambled modulated optical signal.
11. The chaotic communication system according to claim 10, wherein:
the transmitting module includes:
the chaotic driving source is used for generating a chaotic driving signal;
the chaotic driving signal generated by the chaotic driving source is divided into two paths, one path is injected into a first slave laser of the scrambling module, and the first slave laser generates a first chaotic signal; the other path is injected into the receiving module;
a signal source for generating a modulated optical signal;
and the first beam combining module is used for injecting the chaotic driving signal and the first chaotic signal into the first beam combining module to combine the first signal, and then injecting the first signal into the receiving module again.
12. The chaotic communication system according to claim 11, wherein: the chaotic driving source comprises a vertical cavity surface emitting laser, an optical fiber coupler, an adjustable optical attenuator and an optical reflector which are sequentially arranged along the emergent direction of the chaotic driving signal.
13. The chaotic communication system according to claim 10, wherein:
The receiving module includes:
A second slave laser for receiving the chaotic driving signal output by the scrambling module, thereby generating an initial chaotic signal,
The phase shifting module, the polarization control module, the optical power control module and the optical link delay module are sequentially arranged according to the transmission direction of the initial chaotic signal, and the initial chaotic signal is modulated into a second chaotic signal which can be coherently cancelled with the first chaotic signal after sequentially passing through the modules;
The second beam combining module is used for receiving the first signal and the second chaotic signal, and outputting a modulated optical signal after beam combination;
and a sink for receiving the decrypted modulated optical signal.
14. The chaotic communication system according to claim 13, wherein: the phase shifting module is selected from one or more of a phase modulator and a phase shifter.
15. The chaotic communication system according to claim 13, wherein: the polarization control module is a polarization controller.
16. The chaotic communication system according to claim 13, wherein: the optical power control module is an adjustable optical fiber attenuator.
17. The chaotic communication system according to claim 13, wherein: the optical link delay module is an optical fiber delay line.
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