An encrypted optical communication system based on amplified spontaneous emission (ASE) light

Abstract

This invention proposes an encrypted optical communication system based on amplified spontaneous emission (ASE) light. The system integrates the wide bandwidth, high noise characteristics of the ASE light source, and a dynamic key mechanism. It employs wavelength division multiplexing (WDM) technology, combined with Mach-Zehnder modulators, phase modulators, and polarization modulators, to achieve efficient modulation of data and key signals. The system introduces a dynamic key mechanism, which, with each data transmission, not only sends the encrypted data signal but also simultaneously transmits the encrypted key to the authorized user, ensuring the key's one-time use and thus significantly improving the system's anti-hacking capabilities. This efficient method of updating the key with each transmission effectively reduces the risk of long-term key breaches through quantum computing, enhancing the system's data confidentiality. Furthermore, the system meets the requirements for flexibility and scalability, providing a feasible research approach for high-security communication.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, specifically to an encrypted optical communication system based on amplified spontaneous emission (ASE) light. The system aims to utilize ASE light as an optical carrier, leveraging its noise characteristics and wide bandwidth coverage to achieve encrypted and covert transmission of communication signals. This system is suitable for high-security communication scenarios, including military communications, secure government communications, and other critical areas requiring protection against eavesdropping. Background Technology

[0002] With the accelerating pace of global informatization, information security has increasingly become a focus of attention for all sectors of society. In fiber optic communication systems, ensuring that data is not eavesdropped on or tampered with during transmission is crucial. Currently, many communication systems rely on digital encryption algorithms (such as AES and RSA) to ensure data security. These encryption algorithms theoretically possess strong security, but with the improvement of computing power, especially the gradual development of quantum computers, traditional algorithms face increasingly severe risks of being cracked.

[0003] In modern fiber optic communication systems, the continuous upgrading of eavesdropping techniques renders communication systems relying solely on upper-layer encryption insufficient in certain scenarios. For example, military communications, confidential government communications, and secure data transmission in the financial sector require not only defense against algorithmic attacks but also physical-layer security to prevent detection or extraction during transmission. Therefore, physical-layer security design is crucial and serves as an important supplementary means of combating eavesdropping.

[0004] In recent years, researchers both domestically and internationally have proposed numerous methods to improve the security of the physical layer of optical fiber communication. These include chaotic laser communication, quantum noise stream cryptography, optical code division multiple access (OCDMA), all-optical XOR, optical frequency hopping, and optical covert communication. However, for chaotic laser communication, the design and implementation of the laser are relatively complex and require precise synchronization; quantum noise stream cryptography requires specialized quantum communication equipment, which is costly; while optical code division multiple access is effective, its encoding and decoding processes rely on complex algorithms, undoubtedly increasing the difficulty of implementation; and optical frequency hopping technology is limited by the finite spectrum resources, hindering its development. Optical covert communication achieves a certain degree of concealment in signal transmission, but its security still faces serious challenges in the absence of strong encryption mechanisms and efficient key management. Therefore, there is still room for further improvement in the physical layer security of optical communication. Traditional optical communication systems widely use continuous wave lasers as carriers; however, due to their concentrated frequency and high predictability, they are easily detected by external devices. In contrast, the wide bandwidth and high noise characteristics of amplified spontaneous emission (ASE) light sources can effectively conceal transmitted signals, allowing them to absorb noise signals in eavesdropping devices, thus greatly improving the concealment of communication. Simultaneously, combined with specific encryption methods, signal encryption can be further enhanced at the physical level, providing the system with higher security in complex eavesdropping environments. This solution proposes a key improvement to existing schemes using ASE light sources for phase encryption: a dynamic key mechanism. That is, with each transmission, not only is the encrypted data signal sent, but the encryption key is also transmitted to the authorized user, making the key a one-time key. This improvement greatly enhances the system's resistance to cracking, strengthens key security and confidentiality, and makes key management more flexible and efficient. By updating the key with each transmission, this solution effectively reduces the risk of long-term keys being cracked by quantum computing, enhancing the system's data confidentiality. Summary of the Invention

[0005] To improve the security and concealment of communication systems, this invention provides an encrypted optical communication system based on amplified spontaneous emission (ASE). This system can effectively enhance the security and concealment of communication systems and ensure the confidentiality and integrity of information.

[0006] To achieve the above objectives, this invention establishes a wavelength division multiplexing (WDM) based communication link. The devices in the link include an amplified spontaneous emission light source, an arbitrary waveform generator, a variable optical power attenuator, a Mach-Zehnder modulator, a polarization modulator, a phase modulator, a polarization controller, a polarization beam splitter and a polarization beam combiner, a wavelength division multiplexer, an optical coupler, an optical amplifier, an optical filter, an optical fiber, a photodetector, a data recovery module, and a bit error rate testing module.

[0007] The process of the encrypted optical communication method system based on amplified spontaneous emission (ASE) light described in this invention is as follows:

[0008] Step 1: The amplified spontaneous emission light carriers output from the amplified spontaneous emission light source 1 and the amplified spontaneous emission light source 11 are injected into the polarization modulator 4 and the Mach-Zehnder modulator 14 respectively after passing through the polarization controller 2 and the polarization controller 12.

[0009] Step 2: The optical carrier of the Mach-Zehnder modulator 14 is modulated by the data signal m(t) generated by the arbitrary waveform generator 13; the optical carrier of the polarization modulator 4 is modulated by the key signal v(t) generated by the arbitrary waveform generator 3.

[0010] The signal output by the Mach-Zehnder modulator 14 is represented as follows:

[0011]

[0012] Among them, E in (t) represents the amplitude of the light field output from the amplified spontaneous emission source 11, m(t) is the data signal, and β1 = πV0 / V π1 V is the modulation index of the Mach-Zehnder modulator 14. π1 V0 represents the half-wave voltage of the Mach-Zehnder modulator 14, and V0 represents the amplitude of the data signal. Fixed phase difference.

[0013] The Mach-Zehnder modulator 14 operates at the quadrature point. Equation (1) can be converted to:

[0014]

[0015] The signal output by polarization modulator 4 is represented as follows:

[0016]

[0017] Among them, E x (t), E y E0(t) represents the optical field in orthogonal polarization, E0(t) represents the amplitude of the optical field output from the amplified spontaneous emission source 1, ω represents the angular frequency of the optical signal, and v(t) represents the key signal. π2 This is the half-wave voltage of polarization modulator 4.

[0018] Step 3: The optical signal after passing through the Mach-Zehnder modulator 14 is introduced into the dispersion 15 and then injected into the phase modulator 16; the optical signal after passing through the polarization modulator 4 is split into two branches by the polarization beam splitter 6.

[0019] The transfer function of dispersion 15 is expressed as:

[0020]

[0021] Where ω0 is the center angular frequency of the optical signal and β is the dispersion coefficient.

[0022] The output signal after dispersion 15 is represented as follows:

[0023] E' out (t)=F -1 [F[E out (t)]·H D (ω)] (5)

[0024] Where F(·) is the Fourier transform, F -1 (·) represents the inverse Fourier transform.

[0025] By adjusting the polarization controller 5, the two signals output by the polarization beam splitter 6 are represented as follows:

[0026]

[0027] Step 4: Input the key signal into the phase modulator 16 to perform phase encryption on the data signal; encrypt the two branch signals after the polarization beam splitter using optical filters, and then combine them into one signal using the polarization beam combiner 9.

[0028] The output signal of the encrypted phase modulator 16 is represented as follows:

[0029]

[0030] Where v(t) is the driving signal of phase modulator 16, i.e., the key signal, v π3 The half-wave voltage of phase modulator 16

[0031] The two signals output by the filter are represented as follows:

[0032] E BPF (t)=F -1 [F[E out1 (t)]·H BPF (ω)] (9)

[0033] E BRF (t)=F -1 [F[E out2 (t)]·H BRF (ω)] (10)

[0034] Among them, H BPF (ω) is the transfer function of the bandpass filter 7, H BRF (ω) is the transfer function of the band-stop filter 8.

[0035] The output signal of polarization combiner 9 is expressed as follows:

[0036]

[0037] in, It is the unit vector in the x-direction. It is the unit vector in the y-direction.

[0038] Step 5: Combine the signal after phase modulator and the signal synthesized by polarization combiner using wavelength division multiplexer 17 to form a single signal and transmit it to optical fiber 18.

[0039] Step Six: After the optical signal is transmitted through optical fiber 18, dispersion compensation is performed using dispersion compensation optical fiber 19. The signal is then transmitted through optical amplifier 20 to demultiplexer 21 for complete reception. The key signal is then decrypted by a filter. It is then recovered as an electrical signal by photodetector 23, and the key signal is restored to its original state using data recovery module 24. The recovered key signal is then input to phase modulator 26 for phase decryption of the data signal. After phase decryption, the introduced dispersion is compensated. It is then recovered as an electrical signal by photodetector 28, and data recovery and bit error rate testing are performed using data recovery module 29 and bit error rate test 30.

[0040] First, the key signal is filtered and processed, and the output signal is represented as follows:

[0041] E k (t)=F -1 [F(E PC (t))·H BRF [(ω)]=αE out2 (t) (12)

[0042] Where α is the fiber attenuation factor.

[0043] The filtered key signal is sent to photodetector 23, and the resulting key signal current is expressed as:

[0044]

[0045] in, Let v(t) be the responsivity of photodetector 23, and v(t) be the recovered key signal.

[0046] The recovered key signal v(t) is injected into the decryption phase modulator 26, and the output signal is expressed as:

[0047]

[0048] Dispersion compensation 27 is applied to the output signal of the decryption phase modulator, and the output signal is:

[0049]

[0050] Among them, H * D (ω) is H D (ω) complex conjugation.

[0051] The dispersion-compensated signal is sent to photodetector 28, and the resulting data signal current is expressed as:

[0052]

[0053] in, The responsivity of photodetector 28, m(t) is the recovered data signal. Attached Figure Description

[0054] Figure 1 This is a flowchart of an encrypted optical communication system based on amplified spontaneous emission (ASE) light, as described in this invention.

[0055] Figure 2 This is a schematic diagram of the optical link of an encrypted optical communication system based on amplified spontaneous emission (ASE) light proposed in this invention.

[0056] Figure 3 The images show the optical and electrical signals after the data signals have been modulated, encrypted, and decrypted.

[0057] Figure 4 This is the spectrum of the two signals after wavelength division multiplexing;

[0058] Figure 5 The electrical spectrum of the two signals after wavelength division multiplexing;

[0059] Figure 6 This is the electrical time-domain diagram of the two signals after wavelength division multiplexing; Detailed Implementation

[0060] The present invention will be further described below with reference to the accompanying drawings:

[0061] Figure 1 The flowchart of the encrypted and covert communication system based on amplified spontaneous emission (ASE) light described in this invention specifically includes the following steps:

[0062] Step 1, such as Figure 2 As shown, the amplified spontaneous emission light carriers output by the amplified spontaneous emission light source 1 and the amplified spontaneous emission light source 11 are injected into the polarization modulator 4 and the Mach-Zehnder modulator 14 respectively after passing through the polarization controller 2 and the polarization controller 12.

[0063] Step 2: The optical carrier of the Mach-Zehnder modulator 14 is modulated by the data signal m(t) generated by the arbitrary waveform generator 13; the optical carrier of the polarization modulator 4 is modulated by the key signal v(t) generated by the arbitrary waveform generator 3. For example... Figure 3 As shown, the signal is hidden in the noise.

[0064] The signal output by the Mach-Zehnder modulator 14 is represented as follows:

[0065]

[0066] Among them, E in (t) represents the amplitude of the light field output from the amplified spontaneous emission source 11, m(t) is the data signal, and β1 = πV0 / V π V is the modulation index of the Mach-Zehnder modulator 14. π1 V0 represents the half-wave voltage of the Mach-Zehnder modulator 14, and V0 represents the amplitude of the data signal. Fixed phase difference.

[0067] The Mach-Zehnder modulator 14 operates at the quadrature point. Equation (1) can be converted to:

[0068]

[0069] The signal output by polarization modulator 4 is represented as follows:

[0070]

[0071] Among them, E x (t), E y E0(t) represents the optical field in orthogonal polarization, E0(t) represents the amplitude of the optical field output from the amplified spontaneous emission source 1, ω represents the angular frequency of the optical signal, and v(t) represents the key signal. π2 This is the half-wave voltage of polarization modulator 4.

[0072] Step 3: The optical signal after passing through the Mach-Zehnder modulator 14 is introduced into the dispersion 15 and then injected into the phase modulator 16; the optical signal after passing through the polarization modulator 4 is split into two branches by the polarization beam splitter 6.

[0073] The transfer function of dispersion 15 is expressed as:

[0074]

[0075] Where ω0 is the center angular frequency of the optical signal and β is the dispersion coefficient.

[0076] The output signal after dispersion 15 is represented as follows:

[0077] E' out (t)=F -1 [F[E out (t)]·H D (ω)] (5)

[0078] Where F(·) is the Fourier transform, F -1 (·) represents the inverse Fourier transform.

[0079] By adjusting the polarization controller 5, the two signals output by the polarization beam splitter 6 are represented as follows:

[0080]

[0081] Step 4: Input the key signal into the phase modulator 16 to perform phase encryption on the data signal, such as... Figure 3 As shown, the two branch signals after the polarization beam splitter are encrypted using optical filters, and then combined into one signal using polarization beam combiner 9.

[0082] The output signal of the encrypted phase modulator 16 is represented as follows:

[0083]

[0084] Where v(t) is the driving signal of phase modulator 16, i.e., the key signal, v π3 The half-wave voltage of phase modulator 16

[0085] The two signals output by the filter are represented as follows:

[0086] E BPF (t)=F -1 [F[E out1 (t)]·H BPF (ω)] (9)

[0087] E BRF (t)=F -1 [F[E out2 (t)]·H BRF (ω)] (10)

[0088] Among them, H BPF (ω) is the transfer function of the bandpass filter 7, H BRF (ω) is the transfer function of the band-stop filter 8.

[0089] The output signal of polarization combiner 9 is expressed as follows:

[0090]

[0091] in, It is the unit vector in the x-direction. It is the unit vector in the y-direction.

[0092] Step 5: The signal from the phase modulator and the signal synthesized by the polarization combiner are combined into a single signal using wavelength division multiplexer 17 and transmitted to optical fiber 18. For example... Figure 4 , Figure 5, Figure 6 As shown, after wavelength division multiplexing, both the signal and the key are hidden in the optical and electrical domains.

[0093] Step Six: After the optical signal is transmitted through optical fiber 18, dispersion compensation is performed using dispersion compensation optical fiber 19. The signal is then sent to demultiplexer 21 via optical amplifier 20 to complete the reception of the optical signal. The key signal is then decrypted by a filter. The signal is recovered as an electrical signal by photodetector 23, and the key signal is restored to its original state using data recovery module 24. The recovered key signal is then input to phase modulator 26 for phase decryption of the data signal, such as... Figure 3 , Figure 4 As shown, the phase is decrypted and then the introduced dispersion is compensated. The signal is recovered into an electrical signal by the photodetector 28, and the data recovery module 29 and the bit error rate test 30 are used to perform data recovery and bit error rate testing on the data signal.

[0094] First, the key signal is filtered and processed, and the output signal is represented as follows:

[0095] E k (t)=F -1 [F(E PC (t))·H BRF [(ω)]=αE out2 (t) (12)

[0096] Where α is the fiber attenuation factor.

[0097] The filtered key signal is sent to photodetector 23, and the resulting key signal current is expressed as:

[0098]

[0099] in, Let v(t) be the responsivity of photodetector 23, and v(t) be the recovered key signal.

[0100] The recovered key signal v(t) is injected into the decryption phase modulator 26, and the output signal is expressed as:

[0101]

[0102] Dispersion compensation 27 is applied to the output signal of the decryption phase modulator, and the output signal is:

[0103]

[0104] Among them, H * D (ω) is H D (ω) complex conjugation.

[0105] The dispersion-compensated signal is sent to photodetector 28, and the resulting data signal current is expressed as:

[0106]

[0107] in, The responsivity of photodetector 28, m(t) is the recovered data signal.

[0108] In summary, this invention exhibits the following features: 1) Simple and efficient structure: This invention employs a simple encrypted optical communication system capable of supporting ultra-high-capacity data transmission. By concealing the modulated signal within the optical and electrical domains, covert information transmission is achieved, significantly reducing the possibility of information being detected and intercepted, thereby ensuring a high level of data transmission security. 2) Dynamic key update mechanism: This invention introduces dynamic key transmission technology. During each information transmission process, the system automatically updates the key and modulates and encrypts these keys. This strategy not only enhances the security of data transmission but also effectively reduces the risk of keys being illegally cracked, providing strong protection for the secure transmission of information.

Claims

1. An encrypted optical communication system based on amplified spontaneous emission (ASE), characterized in that, Includes the following steps: Step 1: The amplified spontaneous emission light carriers output from the amplified spontaneous emission light source 1 and the amplified spontaneous emission light source 11 are injected into the polarization modulator 4 and the Mach-Zehnder modulator 14 respectively after passing through the polarization controller 2 and the polarization controller 12. Step 2: The optical carrier of the Mach-Zehnder modulator 14 is modulated by the data signal generated by the arbitrary waveform generator 13; the optical carrier of the polarization modulator 4 is modulated by the key signal generated by the arbitrary waveform generator 3. Step 3: The optical signal after passing through the Mach-Zehnder modulator 14 is introduced into the dispersion 15 and then injected into the phase modulator 16; The optical signal after passing through polarization modulator 4 is split into two branches by polarization beam splitter 6. Step 4: Input the key signal into the phase modulator 16 to perform phase encryption on the data signal; encrypt the two branch signals after the polarization beam splitter using optical filters respectively, and then combine them into one signal using the polarization beam combiner 9. Step 5: Combine the signal after phase modulator and the signal synthesized by polarization combiner using wavelength division multiplexer 17 to form a single signal and transmit it to optical fiber 18. Step Six: After the optical signal is transmitted through optical fiber 18, dispersion compensation is performed using dispersion compensation optical fiber 19. The signal is then sent to demultiplexer 21 via optical amplifier 20 to complete the reception of the optical signal. The key signal is then decrypted by a filter and recovered into an electrical signal via photodetector 23. The key signal is then restored to its original state using data recovery module 24. The recovered key signal is then input into phase modulator 26 to perform phase decryption on the data signal. After phase decryption, the introduced dispersion is compensated, and the signal is recovered into an electrical signal via photodetector 28. The data recovery module 29 and bit error rate test 30 are used to perform data recovery and bit error rate testing on the data signal.

2. The encrypted optical communication system based on amplified spontaneous emission (ASE) light according to claim 1, characterized in that, The polarization modulator 4 uses the broadband noise light generated by the amplified spontaneous emission light source 1 as a carrier to modulate the key signal onto a pair of orthogonal polarization states, thereby generating a complementary polarization modulated light signal hidden in the broadband noise, thus achieving information hiding at the physical layer.

3. The encrypted optical communication system based on amplified spontaneous emission (ASE) light according to claim 1, characterized in that, The arbitrary waveform generator 3 is configured to generate a new key signal in each data communication session or each data frame transmission. The new key signal is then used for modulation and encryption and sent to the receiving end.

Images