Long distance laser chaos synchronization system based on conjugate injection

Abstract

The application relates to a long-distance laser chaos synchronization system based on conjugate injection, and belongs to the technical field of optical fiber communication. Driving laser emitted by a driving laser source is divided into two paths through a coupler, one path is injected into a first optical phase conjugator to obtain a phase conjugate signal, the phase conjugate signal is injected into a sending-end response laser chaos source through a first circulator to drive sending-end chaotic laser; the other path is injected into a second optical phase conjugator after being transmitted through N optical fibers to obtain a link phase conjugate signal, the link phase conjugate signal is transmitted through another N optical fibers and then injected into a receiving-end response laser chaos source through a second circulator to drive receiving-end chaotic laser. The scheme drives the sending-end and receiving-end response laser chaos sources by using the phase conjugate signal, and can improve the bandwidth of chaotic laser, enhance the complexity of chaotic laser and hide feedback time delay.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber communication, and in particular to a long-distance laser chaos synchronization system based on conjugate injection. Background Art

[0002] Laser chaos has noise-like characteristics, is extremely sensitive to initial conditions, and is unpredictable. It is often used in secure communications, high-speed physical random numbers, and other fields. In laser chaos secure communications, the noise-like characteristics of chaotic lasers can be used to hide useful information, or the high-speed physical random numbers generated by chaotic lasers can be used to encrypt transmitted information. Regardless of the method, long-distance, high-quality laser chaos synchronization must be constructed to be compatible with existing fiber-optic communication system architectures and match existing fiber-optic communication distances and rates. In 2005, a European Union team achieved 1Gbit / s OOK signals and 120 kilometers of secure transmission based on semiconductor lasers (Nature, 2005, vol. 438, pp. 343-346). In 2010, they achieved 2.5Gbit / s OOK signals and 120 kilometers of secure transmission (Optics Express, 2010, vol. 18, pp. 5188-5198). In 2019, a team from Shanghai Jiao Tong University demonstrated that using OEO intensity chaos on a radio frequency carrier signal can hide duobinary signals, achieving high-bit-rate chaotic secure communication at a distance of 100 kilometers (Optics Letters, 2019, vol. 44, pp. 5776-5779). Subsequently, a co-driven chaotic synchronization coherence scheme proposed by a research group from Taiyuan University of Technology in 2020 achieved modulation and demodulation of 16QAM signals at 40 Gbit / s over a distance of 100 km (Optics Letters, 2020, vol. 45, pp. 4762-4765). Previously published laser chaos secure communication system schemes had a maximum transmission distance of no more than 120 km and a maximum transmission rate of less than 30 Gbit / s. This was due to the effects of dispersion and nonlinearity in the transmission link, which caused chaotic signals to be distorted during transmission, affecting the synchronization distance. In recent years, the fiber optic communication team of Shanghai Jiao Tong University in China has used coherent detection to use DSP algorithms in the digital domain to compensate for fiber channel damage, and achieved a bit rate error of less than 1000km in simulation (Journal of Lightwave Technology, 2020, vol.38, pp.4648-4655). In the same year, the optical team of Southwest Jiaotong University proposed a chaotic decryption scheme combining coherent detection and blind polarization tracking, and experimentally verified it in a 28Gbit / s on-off keying (OOK) and 56Gbit / s orthogonal phase-shift keying system on a 2000km dispersive transmission link and a 1Gbit / s 16-level orthogonal amplitude modulation system on a 1040km dispersive tubeless transmission link (Optics Express, 2021, vol.29, pp.12750-62). However, although these schemes have achieved chaotic synchronization and chaotic secure communication at the level of thousands of kilometers, they involve complex optoelectronic conversion and change the existing fiber optic communication structure.

[0003] Therefore, it is very important to compensate for link dispersion and nonlinearity while maintaining an all-optical environment as much as possible, build a long-distance chaotic synchronization system, and generate a high-complexity, large-bandwidth chaotic carrier signal in order to realize laser chaotic secure communication. Summary of the Invention

[0004] The present invention overcomes the deficiencies of the prior art and provides a long-distance laser chaos synchronization system based on conjugate injection.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The present invention provides a long-distance laser chaos synchronization system based on conjugate injection, comprising: a driving laser source, a first optical phase conjugator, a transmitting end response laser chaos source, a transmission link, and a second optical phase conjugator, a receiving end response laser chaos source;

[0007] The transmission link includes: an erbium-doped fiber amplifier and an optical fiber;

[0008] The first optical phase conjugator and the second optical phase conjugator both include: a pump light source, a nonlinear medium, an optical coupler and an optical filter;

[0009] The driving laser emitted by the driving laser source is divided into two equal paths through a coupler, one path is injected into the first optical phase conjugator to obtain a phase conjugated signal, the phase conjugated signal is injected into the sending end response laser chaotic source through the first circulator, and the sending end response laser chaotic source is driven to output the sending end chaotic laser; the other path is injected into the second optical phase conjugated signal after being transmitted through N sections of optical fiber to obtain a link phase conjugated signal, the link phase conjugated signal is injected into the receiving end response laser chaotic source through the second circulator after being transmitted through another N sections of optical fiber, and the receiving end response laser chaotic source is driven to output the receiving end chaotic laser.

[0010] Preferably, the driving laser source is a chaotic laser source or a broadband random noise light source.

[0011] Preferably, the first optical phase conjugator and the second optical phase conjugator are implemented using four-wave mixing effect.

[0012] Preferably, the pumping mode in the four-wave mixing process adopts one of a single-pump structure and a double-pump structure.

[0013] Preferably, the nonlinear medium is one of a semiconductor optical amplifier, a highly nonlinear optical fiber and a nonlinear waveguide.

[0014] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0015] By using phase-conjugated signals to drive the chaotic laser response source at both the transmitter and receiver, this approach can improve the bandwidth of chaotic lasers, enhance their complexity, and conceal feedback delay. Furthermore, a second optical phase conjugator can be used within the transmission link to compensate for link dispersion and nonlinearity, improving the synchronization quality of the chaotic laser response source at both the transmitter and receiver, and extending the system's synchronization distance. Furthermore, this solution is compatible with existing fiber-optic communication networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, they can also obtain drawings of other embodiments based on these drawings.

[0017] Figure 1 This is a block diagram of a long-distance laser chaos synchronization system based on conjugate injection according to the present invention;

[0018] Figure 2 This is a block diagram of the optical phase conjugation principle based on the four-wave mixing effect;

[0019] Figure 3 This is the time domain waveform of the chaotic laser generated by the driving laser source;

[0020] Figure 4 It is the time domain waveform of the chaotic laser generated by the transmitter in response to the laser chaos source;

[0021] Figure 5 This is the time domain waveform of the chaotic laser generated by the receiving end responding to the laser chaotic source in the back-to-back situation;

[0022] Figure 6 Schematic diagram of the mutual correlation coefficient between the chaotic lasers generated by the laser chaotic source in response to the transmitter and the chaotic laser source in response to the receiver in the back-to-back situation;

[0023] Figure 7 This is the time domain waveform of the chaotic laser generated by the laser chaos source at the receiving end after transmission through an 800km transmission link;

[0024] Figure 8 Schematic diagram of the mutual correlation coefficient between the chaotic laser generated by the sending end's response laser chaotic source and the receiving end's response laser chaotic source after transmission through an 800 km transmission link. DETAILED DESCRIPTION

[0025] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner. Therefore, they only show the structures related to the present invention. It should be noted that, unless there is a conflict, the embodiments in this application and the features in the embodiments can be combined with each other.

[0026] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0028] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0029] The general overview of a long-distance laser chaos synchronization system based on conjugate injection in this embodiment is as follows: The block diagram of a long-distance laser chaos synchronization system based on conjugate injection in this embodiment is as follows: Figure 1 shown.

[0030] like Figure 1As shown in the figure, a long-distance laser chaos synchronization system based on conjugate injection consists of a driving laser source, a first optical phase conjugator ( Figure 1 The optical phase conjugator 1 in the transmitter responds to the laser chaos source, the transmission link and the second optical phase conjugator ( Figure 1 The optical phase conjugator 2 in the receiving end responds to the laser chaos source. The driving laser emitted by the driving laser source is divided into two equal paths through the coupler. One path is injected into the first optical phase conjugator ( Figure 1 The optical phase conjugator 1 in the circuit obtains the phase conjugated signal. The phase conjugated signal is passed through the first circulator ( Figure 1 The circulator 1 in the transmitter is injected into the transmitter in response to the laser chaos source to generate the transmitter chaos laser. The other path is injected into the second optical phase conjugator ( Figure 1 The link phase conjugated signal is transmitted through another N segments of optical fiber and then passes through the second circulator ( Figure 1 The circulator 2 in the transmission link is injected into the receiving end response laser chaotic source to drive the receiving end chaotic laser. This solution uses phase conjugated signals to drive the sending end and the receiving end response laser chaotic source, which can improve the bandwidth of the chaotic laser and enhance the complexity of the chaotic laser. At the same time, a second optical phase conjugator can be used in the middle of the transmission link to compensate for link dispersion and nonlinearity, improve the synchronization quality of the sending end and the receiving end response laser chaotic source, and extend the system synchronization distance. The optical phase conjugator is realized by using the four-wave mixing effect in the nonlinear medium. Figure 2 Schematic diagram of the principle of achieving optical phase conjugation by dual-pump four-wave mixing.

[0031] like Figures 3 to 6 As shown in the figure, the time domain waveform of the driving chaotic laser generated by the driving laser source, the time domain waveform of the chaotic laser generated by the sending end responding to the laser chaotic source, the time domain waveform of the chaotic laser generated by the receiving end responding to the laser chaotic source in the back-to-back case, and the mutual correlation coefficient of the chaotic laser generated by the sending end responding to the laser chaotic source and the receiving end responding to the laser chaotic source in the back-to-back case.

[0032] Figure 7 This is the time domain waveform of the chaotic laser generated by the laser chaos source at the receiving end after transmission through an 800km transmission link. The first and second halves of the transmission link are respectively composed of five 80km sections of standard single-mode optical fiber. Figure 8 is the mutual correlation coefficient between the chaotic laser generated by the laser chaotic source at the transmitter and the chaotic laser source at the receiver after transmission through an 800km transmission link. Figure 8As can be seen in the figure, after a total transmission length of 800 km, the entire link can still achieve high-quality synchronization with a cross-correlation coefficient of up to 0.9552 without the need for additional dispersion compensation modules. At the same time, feedback delay is also perfectly hidden.

[0033] In summary, by utilizing phase-conjugated signals to drive the chaotic laser response source at both the transmitter and receiver, this approach can improve the bandwidth of chaotic lasers, enhance the complexity of chaotic lasers, and conceal feedback delay. Furthermore, a second optical phase conjugator can be used within the transmission link to compensate for link dispersion and nonlinearity, improving the synchronization quality of the chaotic laser response source at both the transmitter and receiver, and extending the system's synchronization distance. Furthermore, this solution is compatible with existing fiber-optic communication networks.

[0034] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0035] The above description is based on the ideal embodiment of the present invention. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the content of the specification, but must be determined according to the scope of the claims.

Claims

1. A long-distance laser chaos synchronization system based on conjugate injection, characterized in that: include: A driving laser source, a first optical phase conjugator, a transmitting end response laser chaotic source, a transmission link, a second optical phase conjugator, and a receiving end response laser chaotic source; The transmission link includes: an erbium-doped fiber amplifier and an optical fiber; The first optical phase conjugator and the second optical phase conjugator both include: a pump light source, a nonlinear medium, an optical coupler and an optical filter; The driving laser emitted by the driving laser source is divided into two equal paths through a coupler. One path is injected into the first optical phase conjugator to obtain a phase conjugated signal. The phase conjugated signal is injected into the transmitting end response laser chaotic source through the first circulator, and the transmitting end response laser chaotic source is driven to output the transmitting end chaotic laser; the other path is injected into the second optical phase conjugator after being transmitted through N sections of optical fiber to obtain a link phase conjugated signal. The link phase conjugated signal is injected into the receiving end response laser chaotic source through the second circulator after being transmitted through another N sections of optical fiber, and the receiving end response laser chaotic source is driven to output the receiving end chaotic laser; The driving laser source is a chaotic laser source or a broadband random noise light source; The first optical phase conjugator and the second optical phase conjugator are implemented by utilizing the four-wave mixing effect.

2. A long-distance laser chaos synchronization system based on conjugate injection according to claim 1, characterized in that: The pumping mode in the four-wave mixing process adopts one of a single-pump structure and a double-pump structure.

3. The long-distance laser chaos synchronization system based on conjugate injection according to claim 1, characterized in that: The nonlinear medium is one of a semiconductor optical amplifier, a highly nonlinear optical fiber and a nonlinear waveguide.

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