Broadband chaos generation and synchronization method based on light injection and photoelectric feedback

Abstract

The invention discloses a broadband chaos generation and synchronization method based on light injection and photoelectric feedback, and the method comprises the steps: injecting a laser chaos generated by a master laser through mirror surface feedback into a slave laser, and obtaining a driving chaos source; the driving source is used as an optical carrier and is injected into a photoelectric feedback loop consisting of an adjustable dispersion module, a Mach-Zehnder modulator, a photoelectric detector and a radio frequency amplifier, so that the flatness of a chaotic signal can be improved; meanwhile, after optical fiber transmission and link dispersion compensation are carried out on the driving chaos source, a photoelectric feedback loop which is the same as that of the sending end is injected into the receiving end, and broadband chaos synchronization with the flat characteristic can be achieved. According to the invention, the chaos signal flatness can be improved, broadband chaos synchronization is realized, and the method can be used for high-speed chaos secret communication.

Description

Technical Field

[0001] The invention belongs to the field of chaotic communication, and in particular relates to a broadband chaotic generation and synchronization method based on light injection and photoelectric feedback. Background Art

[0002] With the development of modern technologies such as big data, distance education, telemedicine, and virtual reality, global data traffic has exploded, and the proportion of personal user traffic has continued to rise. As the cornerstone of today's data communication network, fiber-optic communication carries more than 90% of the world's data traffic. However, fiber-optic communication systems are extremely vulnerable to eavesdropping, and eavesdroppers can obtain transmission information simply by bending optical fibers. In the "2023 Global Advanced Persistent Threat Research Report" released by 360 Digital Security Group in January 2024, it was mentioned that 16 industries in my country are deeply affected by cyber attacks, of which the top five are education, government, scientific research, national defense and military industry, and transportation. With the emergence of quantum computers and the general improvement of traditional computer computing power, the widely used mathematical algorithm encryption technology for the data link layer will face an increasingly high risk of cracking. As the lowest layer of the open system interconnection model, the physical layer introduces a wealth of physical mechanisms for secure fiber-optic communication. Among them, optical chaos encryption uses the nonlinear dynamics of physical devices to generate optical chaotic carriers. In the classical fiber channel, the chaotic carrier is superimposed on the transmitted information to achieve the concealment of the information by the chaotic carrier. The legitimate receiving end can extract the transmitted information by reconstructing the chaotic carrier. In 2005, optical chaos encryption technology has been applied to actual fiber-optic communication systems, but the system transmission rate is only 1.5Gbit / s. Since the information needs to be completely covered by the chaotic carrier, this requires that the bandwidth of the chaotic carrier needs to be greater than or equal to the transmission signal bandwidth. Therefore, increasing the chaotic bandwidth and achieving high-quality chaotic synchronization between the transmitter and receiver are necessary conditions for achieving high-speed chaotic secure communication. In the past 20 years of development, many research teams at home and abroad have carried out a lot of research on how to improve the transmission rate of chaotic communication systems, how to generate broadband chaos, and how to achieve high-quality synchronization.

[0003] In 2015, Ryohsuke Sakuraba and others from Saitama University in Japan generated chaotic signals with an effective bandwidth of 26 GHz based on a three-cascade semiconductor laser scheme. In 2021, Guillaume Bouchez and others from the University of Lorraine in France used phase conjugate feedback to complete a 29 GHz broadband chaos generation experiment. In 2020, Zhang Mingjiang's team from Taiyuan University of Technology used an optical feedback scheme with highly nonlinear optical fiber to increase the bandwidth of chaotic signals to 38.9 GHz. In 2024, Yan Lianshan's team from Southwest Jiaotong University increased the 10 dB bandwidth of the chaotic source to 40 GHz based on chirped Bragg gratings and phase modulation feedback. In order to achieve high-quality chaotic synchronization between the transmitter and receiver, in 2022, Yi Lilin's team from Shanghai Jiaotong University used neural networks to achieve 15 GHz chaotic signal synchronization at 340 km, and demonstrated a 30 Gbit / s chaotic security communication experiment. In 2023, Wang Longsheng's team from Taiyuan University of Technology demonstrated a 5GHz chaotic synchronization experiment at a transmission distance of 1040km based on a hybrid amplification scheme.

[0004] As mentioned above, these studies on improving chaos bandwidth and chaos synchronization performance have promoted the development of chaotic secure communication towards high speed and long distance, but there is currently no solution to achieve broadband chaos generation and high-quality synchronization at the same time. Therefore, it is of great research significance to study a broadband chaos generation and synchronization method based on light injection and photoelectric feedback. Summary of the invention

[0005] In order to realize broadband chaos generation and high-quality synchronization, the present invention provides a broadband chaos generation and synchronization method based on light injection and photoelectric feedback.

[0006] The invention discloses a broadband chaos generation and synchronization method based on light injection and photoelectric feedback. After the chaotic signal generated by the light injection method passes through a photoelectric feedback loop, the remodulation effect of the photoelectric feedback loop increases the power of the low-frequency component of the chaotic signal, reduces the power difference between the relaxation oscillation frequency and the low-frequency component, and improves the flatness of the chaotic signal. Specifically, the method includes the following steps:

[0007] Step 1: Connect the laser generated by the main laser, i.e., discrete mode laser 1, to a mirror feedback link consisting of circulator 1, circulator 2, polarization controller 1, attenuator 1, 50:50 coupler 1, and a mirror; the output of discrete mode laser 1 is connected to port 1 of circulator 1, port 2 of circulator 1 is connected to port 1 of circulator 2, and port 2 of circulator 2 is connected to the mirror; the reflected light generated by the mirror is output through port 3 of circulator 2, and after polarization adjustment by polarization controller 1 and light splitting by 50:50 coupler 1, two paths of light are output, one of which is connected to port 3 of circulator 1 through attenuator 1 and re-injected into discrete mode laser 1; at this time, discrete mode laser 1 will continue to generate chaotic laser.

[0008] Step 2: In step 1, another beam of light separated by the 50:50 coupler 1 is connected to port 1 of circulator 3 after passing through polarization controller 2 and attenuator 2; after the laser is emitted from the slave laser, port 2 of circulator 3 is connected to the slave laser, and broadband chaos with poor flatness is output through port 3 of circulator 3.

[0009] Step 3: After the broadband chaos with poor flatness is amplified by Erbium-doped fiber amplifier 1, it is connected to 50:50 coupler 2 to obtain driving source 1 and driving source 2.

[0010] Step 4: After the polarization of the driving source 1 is adjusted by the polarization controller 3, it is connected to the photoelectric feedback loop consisting of the adjustable dispersion module, the Mach-Zehnder modulator 1, the 20:80 coupler 1, the photodetector 1, and the radio frequency amplifier 1; the driving source 1 after polarization adjustment is connected to the adjustable dispersion module, and after dispersion, it is injected into the Mach-Zehnder modulator 1 as an optical carrier; the output of the Mach-Zehnder modulator 1 is connected to the 20:80 coupler 1, wherein 20% of the output light is connected to the photodetector 1 and the radio frequency amplifier 1 in sequence, and is input into the Mach-Zehnder modulator 1 as a radio frequency signal; 80% of the output light is connected to the photodetector 2, and a flat broadband chaos 1 is obtained.

[0011] Step 5: After the driving source 2 is transmitted through the optical fiber and compensated for the link dispersion by the adjustable dispersion module and amplified by the erbium-doped fiber amplifier 2, the polarization is adjusted by the polarization controller 4 and connected to the same optoelectronic feedback loop as in step 4 to obtain flat broadband chaos 2.

[0012] Step 6: Use a real-time oscilloscope to collect flat broadband chaos 1 and 2, and calculate the correlation using the Pearson coefficient.

[0013] The beneficial technical effects of the present invention are:

[0014] 1. After the broadband chaos generated by the optical injection scheme is injected into the optoelectronic feedback loop composed of a dispersion module, a Mach-Zehnder modulator, a radio frequency amplifier, and a photodetector, the optoelectronic feedback loop will output a flatter broadband chaos, and after optical fiber transmission and optical fiber link dispersion compensation, the chaos between the transmitting end and the legal receiving end still has a high correlation.

[0015] 2. In the optoelectronic feedback loop of the present invention, the working bias voltage of the Mach-Zehnder modulator can be set to the linear region of the modulation curve, which is conducive to achieving broadband chaotic synchronization.

[0016] 3. The present invention can be applied as a broadband chaotic signal source, broadband chaotic synchronization and chaotic secure communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a structural principle diagram of the broadband chaos generation and synchronization method based on light injection and photoelectric feedback of the present invention.

[0018] Figure 2 This is a chaos timing diagram of the broadband chaos generation and synchronization method based on light injection and photoelectric feedback of the present invention.

[0019] Figure 3 This is an autocorrelation coefficient diagram of the broadband chaos generation and synchronization method based on light injection and photoelectric feedback of the present invention.

[0020] Figure 4 This is a chaotic signal spectrum diagram of the broadband chaos generation and synchronization method based on light injection and photoelectric feedback of the present invention.

[0021] Figure 5 This is a partial chaos timing diagram of the transmitting end and the receiving end of the broadband chaos generation and synchronization method based on light injection and photoelectric feedback of the present invention.

[0022] Figure 6 This is a partial chaos timing diagram of the transmitting end and the common driving source of the broadband chaos generation and synchronization method based on light injection and photoelectric feedback of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] The invention discloses a broadband chaos generation and synchronization method based on light injection and photoelectric feedback. After the chaotic signal is remodulated by the photoelectric feedback loop, the power of the low-frequency component is increased, which helps to improve the flatness of the chaotic signal. In addition, the working bias voltage of the Mach-Zehnder modulator in the photoelectric feedback loop can be set to the linear region, which is conducive to the realization of chaotic synchronization. The implementation of the scheme specifically includes the following steps:

[0025] Step 1: Connect the laser generated by the main laser (discrete mode laser 1) to a mirror feedback link consisting of a circulator 1, a circulator 2, a polarization controller 1, an attenuator 1, a 50:50 coupler 1, and a mirror; the output of the discrete mode laser 1 is connected to port 1 of the circulator 1, the port 2 of the circulator 1 is connected to port 1 of the circulator 2, and the port 2 of the circulator 2 is connected to the mirror; the reflected light generated by the mirror is output through port 3 of the circulator 2, and after the polarization is adjusted by the polarization controller 1 and the 50:50 coupler 1 is split, two paths of light are output, one of which is connected to port 3 of the circulator 1 through the attenuator 1 and re-injected into the discrete mode laser 1; at this time, the discrete mode laser 1 will continue to generate chaotic laser.

[0026] Step 2: In step 1, another beam of light separated by the 50:50 coupler 1 is connected to port 1 of circulator 3 after passing through polarization controller 2 and attenuator 2; after the laser is emitted from the slave laser, port 2 of circulator 3 is connected to the slave laser, and broadband chaos with poor flatness is output through port 3 of circulator 3.

[0027] Step 3: After the broadband chaos with poor flatness is amplified by Erbium-doped fiber amplifier 1, it is connected to 50:50 coupler 2 to obtain driving source 1 and driving source 2.

[0028] Step 4: After polarization adjustment by polarization controller 3, driving source 1 is connected to an optoelectronic feedback loop consisting of an adjustable dispersion module, a Mach-Zehnder modulator 1, a 20:80 coupler 1, a photodetector 1, and a radio frequency amplifier 1; after polarization adjustment, driving source 1 is connected to the adjustable dispersion module, and after dispersion, it is injected into Mach-Zehnder modulator 1 as an optical carrier. At this time, the optoelectronic feedback loop plays a re-modulation role. Only by using a low-bandwidth radio frequency amplifier and a photodetector, the optoelectronic feedback loop can increase the low-frequency component power of driving source 1, reduce the power difference between the low-frequency component and the relaxation oscillation frequency, and improve the flatness of the chaotic signal. In addition, the dispersion effect provided by the adjustable dispersion module can mask the time delay characteristics of the chaotic signal, and the dispersion effect causes the chaotic signal pulse to be broadened, further improving the bandwidth of the chaotic signal. The output of Mach-Zehnder modulator 1 is connected to 20:80 coupler 1, of which 20% of the output light is connected to photodetector 1 and radio frequency amplifier 1 in turn, and is input into Mach-Zehnder modulator 1 as a radio frequency signal; 80% of the output light is connected to photodetector 2 to obtain a flat broadband chaos 1.

[0029] Step 5: After the driving source 2 is transmitted through the optical fiber and compensated for the link dispersion by the adjustable dispersion module and amplified by the erbium-doped fiber amplifier 2, the polarization is adjusted by the polarization controller 4 and connected to the same optoelectronic feedback loop as in step 4 to obtain flat broadband chaos 2.

[0030] Step 6: Use a real-time oscilloscope to collect flat broadband chaos 1 and 2, and calculate the correlation using the Pearson coefficient.

[0031] The structure principle of the broadband chaos generation and synchronization method based on light injection and photoelectric feedback of the present invention is as follows: Figure 1As shown, the discrete mode laser module 1011 emits a laser signal and is connected to port 2 of the circulator 1021, port 3 of the circulator 1021 is connected to port 1 of the circulator 1022, and port 2 of the circulator 1022 is connected to the optical mirror module 103. The laser signal emitted by 1011 is output from port 3 of the circulator 1022 after mirror reflection, and is connected to port 3 of 1021 after passing through the 50:50 beam splitter module 1041, polarization controller 1051, and attenuator 1061, and is re-injected into 1011. In this process, the attenuator 1061 is used to adjust the feedback power, and the output optical power of 1061 is 8dB lower than the output power of 1011. At this time, the discrete mode laser 1011 will continue to generate chaotic lasers. After the chaotic laser is split by 1041, a beam of light is connected to 1052 and 1062 to adjust the polarization state and optical power. Then it is connected to port 1023, and port 2 of 1023 is connected to the discrete mode laser 1012. When feedback light is injected, 1012 will generate chaotic laser, which is output from port 3 of 1023. The chaotic laser generated by 1012 is amplified by erbium-doped fiber amplifier 1071 and then connected to 50:50 beam splitter 1042 to obtain driving source 1 and driving source 2.

[0032] After the driving source 1 is transmitted through the standard single-mode optical fiber 108, the dispersion compensation module 1091 compensates for the link dispersion, and the optical amplifier 1072 compensates for the fiber loss and the insertion loss of 1091. Then, the driving source 1 is polarized by 1053 and connected to the photoelectric feedback loop composed of the Mach-Zehnder modulator 1101, the dispersion compensation module 1092, the attenuator 1063, the photodetector 1121, the RF amplifier 1131, and the 20:80 beam splitter 1111. The 80% optical power signal of 1111 is regarded as the receiving end chaotic signal 1141, and the 20% optical power signal is used in the feedback loop. The dispersion value of 1092 is 400ps / nm.

[0033] The driving source 2 is polarized by 1054 and connected to the photoelectric feedback loop composed of Mach-Zehnder modulator 1102, dispersion compensation module 1093, attenuator 1064, photodetector 1122, RF amplifier 1132, and 20:80 beam splitter 1112. 80% of the optical power signal of 1112 is regarded as the chaotic signal 1142 at the transmitting end, and 20% of the optical power signal is used in the feedback loop. The dispersion value of 1093 is 400ps / nm.

[0034] The Pearson's coefficient is then used to calculate the correlation between 1142 and 1141. The Pearson's correlation coefficient can be calculated according to (1).

[0035]

[0036] Where cov(X,Y) represents the covariance of X and Y, σ X With σY They represent the standard deviations of X and Y. X and Y are 1141 and 1142 respectively.

[0037] Figure 2 This is a partial timing diagram of the chaotic signal at the transmitting end 1142. Figure 2 It can be observed that according to the above operation process, the signal at this time has shown noise-like characteristics and is a chaotic signal.

[0038] Figure 3 is the autocorrelation coefficient diagram of the chaotic signal at the transmitting end 1142. Since the discrete mode laser has the external cavity resonance characteristic, the chaotic signal generated by the traditional mirror feedback and light injection method has a periodic time delay characteristic. Through the autocorrelation function, it can be clearly seen that there is a correlation peak with a time delay characteristic near the feedback delay, which will greatly reduce the security of chaotic optical secure communication. In the present invention, since the dispersion modules 1092 and 1093 are used in the optoelectronic feedback loop, the dispersion effect reduces the correlation peak caused by the external cavity resonance characteristic. Figure 3 In the data, the correlation peak value is only 0.026.

[0039] Figure 4 This is the spectrum diagram of the chaotic signal of the transmitter 1142. Under the effect of the temperature detuning between the master and slave lasers and the optoelectronic feedback loop, the relaxation oscillation component is weakened and the chaotic spectrum becomes flatter.

[0040] Figure 5 Partial timing diagram and correlation results of chaotic signals at the transmitting end 1142 and the receiving end 1141. After 50 km transmission, the correlation between the chaotic signals at the receiving end and the transmitting end is calculated using formula (1). The chaotic correlation between the transmitting end and the receiving end of the present invention is still 0.92. This result can support high-speed chaotic secure communication.

[0041] Figure 6 Part of the timing diagram and correlation results of the chaotic signal 1142 at the transmitting end and the co-driven source 1. The correlation value is only 0.34, which proves that even if the eavesdropper obtains the chaotic signal of the co-driven source during the optical fiber transmission process, it is difficult for the eavesdropper to obtain information related to 1142 or 1141 due to the extremely low correlation between the co-driven source and 1142, ensuring the secure transmission of 1141 and 1142 between the transmitting end and the legitimate receiving end.

Claims

1. A broadband chaos generation and synchronization method based on light injection and photoelectric feedback, characterized in that: The specific steps include: Step 1: Connect the laser generated by the main laser, i.e., discrete mode laser 1, to a mirror feedback link composed of circulator 1, circulator 2, polarization controller 1, attenuator 1, 50:50 coupler 1, and mirror; the output of discrete mode laser 1 is connected to port 1 of circulator 1, port 2 of circulator 1 is connected to port 1 of circulator 2, and port 2 of circulator 2 is connected to the mirror; the reflected light generated by the mirror is output through port 3 of circulator 2, and after polarization adjustment by polarization controller 1 and light splitting by 50:50 coupler 1, two paths of light are output, one of which is connected to port 3 of circulator 1 through attenuator 1 and re-injected into discrete mode laser 1; at this time, discrete mode laser 1 will continue to generate chaotic laser; Step 2: The other beam of light separated by the 50:50 coupler 1 in step 1 is connected to port 1 of circulator 3 after passing through polarization controller 2 and attenuator 2; after the laser is emitted from the slave laser, port 2 of circulator 3 is connected to the slave laser, and broadband chaos with poor flatness is output through port 3 of circulator 3; Step 3: After the broadband chaos with poor flatness is amplified by the erbium-doped fiber amplifier 1, it is connected to the 50:50 coupler 2 to obtain the driving source 1 and the driving source 2; Step 4: After polarization adjustment by polarization controller 3, driving source 1 is connected to a photoelectric feedback loop consisting of an adjustable dispersion module, a Mach-Zehnder modulator 1, a 20:80 coupler 1, a photodetector 1, and a radio frequency amplifier 1; the polarization-adjusted driving source 1 is connected to the adjustable dispersion module, and injected into Mach-Zehnder modulator 1 as an optical carrier after dispersion; the output of Mach-Zehnder modulator 1 is connected to 20:80 coupler 1, 20% of the output light is connected to photodetector 1 and radio frequency amplifier 1 in sequence, and input into Mach-Zehnder modulator 1 as a radio frequency signal; 80% of the output light is connected to photodetector 2, and a flat broadband chaos 1 is obtained; Step 5: After the driving source 2 is transmitted through the optical fiber and compensated for the link dispersion by the adjustable dispersion module and amplified by the erbium-doped fiber amplifier 2, the polarization is adjusted by the polarization controller 4 and connected to the same optoelectronic feedback loop as in step 4 to obtain the flat broadband chaos 2; Step 6: Use a real-time oscilloscope to collect flat broadband chaos 1 and 2, and calculate the correlation using the Pearson coefficient.

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