Dynamic updated key distribution encryption scheme with the wireless rate of 102†Gb/s based on a syncretic W band-PON transmission system.

In this paper, a dynamic updated key distribution encryption scheme based on syncretic W band-passive optical network (PON) is proposed. The 102 Gb/s encrypted data rate using 64QAM is successfully transmitted over the 50 m wireless distance under 15% soft-decision forward error correction (SD-FEC) for a pre-FEC bit error rate (BER) threshold of 1.56 × 10-2. The scheme can realize an error-free public key transmission and public key updates up to 1014 times. In the encryption transmission system, there is a small deviation of the private key, and the received BER is more than 0.45. As far as we know, this is the first time to complete a dynamic key distribution based on a syncretic W band-PON system.

Enhancing secure transmission and key distribution for ultrahigh-order QAM via delta-sigma modulation and discrete memristive-enhanced chaos.

In this Letter, we propose a method for ultrahigh-order QAM secure transmission and key distribution based on delta-sigma modulation (DSM) and discrete memristive-enhanced chaos (DMEC). The disturbance vectors generated by the DMEC scramble the DSM signals in both frequency and time domains, resulting in highly secure DSM signals. Through the key modulation and power adjustment and then superimposing them on the encrypted signals, the method achieves simultaneous transmission of keys and signals without the need for additional spectral resources. This approach allows for secure communication with continuous key iteration and updates, offering an effective solution for implementing "one-time pad" encryption. In the experimental demonstration, we achieved a secure transmission and key distribution of a 16384QAM signal at a rate of 17.09 Gb/s over 25 km in an intensity-modulated direct detection (IMDD) system, based on DSM.

Sliced chaotic encrypted transmission scheme based on key masked distribution in a W-band millimeter-wave system.

In order to guarantee the information of the W-band wireless communication system from the physical layer, this paper proposes the sliced chaotic encrypted (SCE) transmission scheme based on key masked distribution (KMD). The scheme improves the security of free space communication in the W-band millimeter-wave wireless data transmission system. In this scheme, the key information is embedded into the random position of the ciphertext information, and then the ciphertext carrying the key information is encrypted by multi-dimensional chaos. Chaotic system 1 constructs a three-dimensional discrete chaotic map for implementing KMD. Chaotic system 2 constructs complex nonlinear dynamic behavior through the coupling of two neurons, and the masking factor generated is used to realize SCE. In this paper, the transmission of 16QAM signals in a 4.5 m W-band millimeter-wave wireless communication system with a rate of 40 Gb/s is proved by experiments, and the performance of the system is analyzed. When the input optical power is 5 dBm, the bit error rate (BER) of the legitimate encrypted receiver is 1.23 × 10-3. When the offset of chaotic sequence x and chaotic sequence y is 100, their BERs are more than 0.21. The key space of the chaotic system reaches 10192, which can effectively prevent illegal attacks and improve the security performance of the system. The experimental results show that the scheme can effectively distribute the keys and improve the security of the system. It has great application potential in the future of W-band millimeter-wave wireless secure communication.

Secure high-density constellation mapping OTFS modulation scheme with low PAPR.

In this paper, a secure orthogonal time-frequency space (OTFS) modulation transmission system based on 3D dense constellation mapping (DCM) geometric shaping is proposed, and a selective reduction amplitude algorithm (SRA) for DCM to reduce peak average power ratio (PAPR) is presented. The DCM is based on regular tetrahedron construction to improve its space utilization efficiency. The proposed SRA involves reducing high PAPRs transmitter and restoring them at the receiving end, which only requires an additional 0.57% of the total transmission capacity. The algorithm reduces PAPR while ensuring the bit error rate performance of the system, so it is suitable for systems that need to process large amounts of transmitted data quickly. By verifying the actual transmission performance on a 2 km of 7-core optical fiber transmission system, the optical transmission with a bit rate of 33.93Gb/s is achieved. The experimental results show that when the bit error rate (BER) reaches the 3.8×10-3 threshold, the OTFS system using DCM and SRA could improve the receiver sensitivity by 3.7 dB compared with the OTFS system using concentric cube mapping and SRA, and 2.7 dB compared with the OFDM system using DCM. After adding the SRA, the PAPR of the OTFS system is reduced by more than 2.2 dB. When the received optical power reaches near the bit error rate threshold, the SRA valid data can be fully recovered by optimizing the SRA.

High-security multidimensional data protection system based on the Hartley algorithm-driven chaotic scheme.

This paper proposes a high-security multidimensional data protection system based on the Hartley algorithm-driven chaotic scheme. We utilize the fast Hartley algorithm instead of the fast fourier computation, and we employ chaotic sequences generated by the multi-winged chaotic system to achieve chaos-driven 3D constellation mapping, effectively integrating the chaotic system with the stochastic amplitude modulator. We reduce the signal's peak-to-average power ratio (PAPR) by deploying a random amplitude modulator. Simultaneously, this approach enhances the security of the physical layer of the signal. The PAPR reduction can reach up to 2.6 dB, while the most robust and stable modulator scheme can gain 2 dB. Finally, in the Hartley frequency domain, the signal's frequency is disrupted, providing the entire system with a key space of 10131 to resist violent cracking and thus improving the system's overall security. To validate the feasibility of our scheme in comparison to conventional IFFT-based encrypted 3D orthogonal frequency division multiplexing, We achieved a transmission rate of 27.94 Gb/s over a 2 km multicore fiber. Experimental results show that since the random amplitude generator effectively reduces PAPR, our proposed encryption scheme increases the forward error correction threshold range by 1.1 dB, verifying that our proposed scheme has highly reliable security performance.

Physical layer security scheme for key concealment and distribution based on carrier scrambling.

The purpose of this study is to present a physical layer security scheme for key concealment and distribution based on carrier scrambling. The three-dimensional (3D) Lorenz system is used to generate independent chaotic sequences that encrypt the information with bit, constellation and subcarrier. In order to realize the flexible distribution of the key and ensure its security, the key information is loaded into a specific subcarrier. While key subcarrier and the ciphertext subcarrier are scrambled simultaneously. The encrypted key position information is processed and transmitted in conjunction with the training sequence (TS) to facilitate demodulation by the legitimate receiver. The processed TS can accommodate up to 10 key position information, thereby demonstrating the scheme's exceptional scalability. Experimental results show that the proposed scheme can safely transmit 131.80 Gb/s Orthogonal frequency division multiplexing (OFDM) signals across 2 km 7-core fiber. Meanwhile, the scheme enables simultaneous flexible distribution and concealment of the key, thereby offering a promising solution for physical layer security.

Chaos key enhanced physical layer secure transmission method based on the convolutional long short-term memory neural network.

In this paper, we propose a method for training a key-enhanced chaotic sequence using the convolutional long short term memory neural network (CLSTM-NN) for secure transmission. This method can cope with the potential security risk posed by the degradation of chaotic dynamics when using chaotic model encryption in traditional secure transmissions. The simulation results show that the proposed method improves the key space by 1036 compared to traditional chaotic models, reaching 10241. The method was applied to orthogonal chirp division multiplexing (OCDM). To demonstrate the feasibility of the proposed scheme, we conducted transmission experiments of encrypted 16 quadrature amplitude modulation (QAM) OCDM signals at a speed of 53.25 Gb/s over a 2 km length of 7-core optical fiber and test different encryption schemes. After key enhancements, the overall number of keys in the system can increase from 18 to 105.The results show that there is no significant difference between the bit error rate (BER) performance of the encryption method proposed in this paper and the traditional encryption method. The maximum performance difference between the different systems does not exceed 1 dBm. This fact proves the feasibility of the proposed scheme and provides new ideas for the next generation of secure transmission.

High-security space division multiplexing optical transmission scheme based on constellation grid selective twisting.

In this paper, we propose a high-security space division multiplexing optical transmission scheme based on constellation grid selective twisting, which adopts the Rossler chaos model for encrypting PDM-16QAM signals, being applied to a multicore, few-mode multiplexing system. The bitstream of the program is passed through XOR function before performing constellation grid selective twisting and rotation of the constellation map to improve the security of the system. The proposed system is verified experimentally by using 80-wave and 4-mode multiplexing in one of the 19-core 4-mode fibers. Based on the proposed encryption method, a net transmission rate of 34.13 Tbit/s, a transmission distance of 6000 km, and a capacity distance product of 204.8 Pb/s × km is achieved under encrypted PDM-QPSK modulation. Likewise, a net transmission rate of 68.27 Tbit/s, a transmission distance of 1000 km, and a capacity distance product of 68.27 Pb/s × km is achieved based on encrypted PDM-16QAM modulation. It is experimentally verified that the sensitivity of the initial value in Rossler's chaotic model is in the range of 10-16∼10-17. Meanwhile, the proposed encryption scheme achieves a large key space of 10101, which is compatible with the high-capacity distance product multicore and few-mode multiplexing system. It is a promising candidate for the next-generation highly-secured high-capacity transmission system.

High spectral efficiency modulation scheme based on joint interaction of orthogonal compressed chirp division multiplexing and power superimposed code.

In this paper, we propose a high spectral efficiency modulation scheme based on joint interaction of orthogonal compressed chirp division multiplexing (OCCDM) and power superimposed code (PSC) under the intensity modulation and direct detection (IM/DD) system. OCCDM is a novel orthogonal chirp division multiplexing technology featuring spectral compression through the implementation of processing similar to a discrete Fourier transform, enhancing the spectral efficiency (SE) through bandwidth savings without loss of orthogonality of each chirp. Meanwhile, PSC technology enables multiple code words being transmitted superimposed on the same chirp. This technique involves allocating varying power levels to different users, thereby distinguishing them, increasing the transmission's net bit rate and substantially boosting the SE. The transmission has been performed experimentally using a 2 km 7-core fiber span. The impact of the above-mentioned technologies on the bit error rate (BER) performance is assessed in the power, frequency, and joint domain. The BER and enhancements in the SE can be balanced when the spectral bandwidth compression factor (α) and power distribution ratio are equal to 0.9 and 4, respectively. The observed outcome leads to the transmission's SE increase to more than double the baseline value, at 2.22 times. Based on the above analysis, we believe this structure is expected to become a potential for developing next-generation PON.

Highly secure non-orthogonal multiple access based on key accompanying transmission in training sequence.

This paper proposes a high-security chaotic encrypted power sparse coding division (CE-PSCD) scheme for 7-core fiber based on non-orthogonal multiple access (NOMA) technology. The method utilizes power multiplexing to realize parallel transmission of two signals. Joint encryption of the four-dimensional region is realized using constellation mapping encryption, carrier frequency encryption, symbol scrambling, and sparse code scrambling. What we believe to be a new dimension for encryption of autonomously designed sparse codes is proposed. Meanwhile, we hide the chaotic key in training sequence (TS) to realize the co-transmission of the key and the message. A 70 Gb/s CE-PSCD signal transmission over 2 km of 7-core fiber is demonstrated experimentally. At the limit of forward error correction (FEC) ∼3.8 × 10-3, the difference in the encrypted sensitivity among different users at the equal power level is 0.36 dB, which means that the fairness of users will not be destroyed. The key space can reach 10134, with a bit error rate (BER) of about 0.5 for brute-force cracking at illegal receivers. As long as the key bits in the hidden TS are wrong by one bit, the BER stays around 0.5. The results show no significant attenuation of the signal before and after encryption at either high or low power, verifying the high-security performance of our proposed scheme.

Ultrahigh-order QAM secure transmission based on delta-sigma modulation using discrete memristive-enhanced chaos.

This Letter proposes a high-security and high-order signal transmission method that is based on delta-sigma modulation (DSM) and discrete memristive-enhanced chaos (DMEC). We employ the DMEC for the encryption of DSM signals to achieve a key space of 1098 in size. Moreover, we demonstrated a high-security transmission of 16384QAM signals using the DSM over a 25 km single-mode fiber in the intensity-modulated direct detection (IMDD) system. The experimental results show that the proposed ultrahigh-order transmission scheme based on DMEC and DSM guarantees high signal transmission performances with improved security and a key sensitivity level of 10-17.

16QAM OFDM-PON based on polar code and CCDM joint chaotic encryption.

A new optical transmitting scheme based on chaotic constant component distribution matcher (CCDM) and Polar coding was proposed. The data is first encrypted by Polar coding using a five-dimensional chaotic sequence. Then the encrypted data is divided into two paths to perform chaotic CCDM encryption operations with different schemes. Finally, the two channels are merged, and the subcarriers are scrambled. The transmission experiment of 16QAM-OFDM signal on 2 km seven-core fiber is conducted to verify the scheme's feasibility. The experimental results show that the received optical power of all ONUs is less than -15dBm when the BER of all ONUs is reduced to less than 10-3. In addition, the key space of the proposed system reaches 1085, and the security performance is further enhanced. The advantages of BER and safety performance make this two-path chaotic encrypted OFDM-PON with an optimistic application prospect in the current optical transmission systems.

High-security three-dimensional optical transmission mechanism utilizing time-frequency-space interleaving disruption.

In this paper, we propose a high-security three-dimensional optical transmission system utilizing time-frequency-space interleaving chaos, which simultaneously enhances the reliability and security of the system. The four-wing 3D chaos model encrypts the time-frequency space interleaved modulation domain of a orthogonal time-frequency space (OTFS) modulation signal and the modulated phase information simultaneously, improving the system's security. We also experimentally validate the proposed high-security 3D-OTFS method, utilizing the hexadecimal modulation technique. The modulated OTFS signal achieves a transmission rate of 34.1 Gb/s over a 2-km seven-core fiber link, with the OTFS signal exhibiting a maximum of 1.31 dB receiver sensitivity gain compared to orthogonal frequency division multiplexing (OFDM) signals under the forward error correction threshold of the bit error rate. The achieved keyspace is equal to 5 × 1048. The findings demonstrate that the proposed high-security three-dimensional optical transmission mechanism, based on time-frequency-space interleaved disruption, exhibits excellent anti-interference ability and confidentiality performance. Consequently, it holds promising prospects for future applications in optical communications.

Enhancing the performance of 16384QAM based on delta-sigma modulation using geometric shaping in an IMDD system.

In this Letter, a new, to the best of our knowledge, geometric shaping method for an ultrahigh-order 16384-ary quadrature amplitude modulation (16384QAM) constellation based on the delta-sigma modulation technique is proposed. Based on the characteristics of delta-sigma modulation, the constellation was optimized to obtain greater constellation gain and improve the maximum performance of the system. Finally, the proposed scheme was demonstrated on an intensity-modulated direct detection (IMDD) system through a 25 km single-mode fiber transmission. On performing experiments, it was found that the suggested approach increases the receiver sensitivity of ultrahigh-order QAM communication systems based on delta-sigma modulation by around 0.5 dB and further enhances the error performance limit.

NOMA security scheme based on constellation camouflage and selective mapping: publisher's note.

This publisher's note contains corrections to Opt. Lett.48, 4101 (2023)10.1364/OL.493540.

Three-dimensional power sparse code division non-orthogonal multiple access scheme with constellation pair mapping.

This paper proposes a three-dimensional power sparse code division non-orthogonal multiple access (3D-PSCD-NOMA) scheme with 3D constellation pair mapping. The proposed sparse code is based on a balanced incomplete block design (BIBD). Its correlation matrix performs the overall signal mapping of multi-user information. Power multiplexing is realized by overlaying multi-level power signals with different path losses through pair mapping. Compared with the conventional 2D standard square 32 Quadrature Amplitude Modulation (QAM), the proposed 3D constellation pair mapping can improve the constellation points' minimum Euclidean distance (MED) by 17.7%, which is beneficial for the performance of the system. Based on obtaining the optimal power distribution ratio (PDR) for different schemes, a 3D-PSCD-NOMA signal with a rate of 15.22 Gb/s over a 25 km single-mode fiber (SMF) is experimentally performed. The experimental results show that 3D-PSCD-NOMA has a clear superiority. At the same rate, 3D-PSCD-NOMA2 can obtain a sensitivity gain of about 1.6 dB and 1.9 dB over the conventional 2D constellation. Moreover, 3D-PSCD-NOMA reduces the system's peak-to-average power ratio (PAPR) by 1.3 dB. The difference in sensitivity of the system before and after sparse code is about 0.15 dB, and no significant degradation occurred. Due to its advantages in transmission performance, 3D-PSCD-NOMA is a potential solution for future optical access systems.

High-security optical transmission system with multi-dimensional multiplexing based on quaternion chaotic encryption.

In this paper, we propose a multi-dimensional multiplexing scheme for space division multiplexing optical transmission systems based on quaternion chaotic encryption. A constellation compression shaping mapping method is designed to replace the traditional 2n mapping scheme, which leads to flexible encoding modulation. In order to achieve orthogonality between data symbols and effectively suppress crosstalk, the spectrally superposed transmission of three-dimensional (3D) constellation data is carried out by code division multiplexing and 4D carrier-less amplitude phase joint modulation techniques based on orthogonal basis. The Chen's chaotic model is utilized to generate the rotation angle of the constellation points, which enables data encryption without changing the transmitted power, enhancing system's security. The feasibility and superiority of the proposed scheme are successfully verified by constructing an experimental platform for a seven-core fiber transmission system.

116.66-Tb/s WDM transmission over 16†Km field deployed 7-core fiber based on sub-constellations overlap constellation shaping.

Constellation shaping (CS) has always been a popular research hotspot in optical communication. Recently, most researchers have focussed on using constellation-shaping technology to improve the system's performance, ignoring the additional penalty it brings to the coherent system. This paper proposes a method of constellation truncation using sub-constellation overlap to perform CS on quadrature amplitude modulation (QAM). The experimental results show that compared with the traditional probabilistic shaping 16QAM, the proposed scheme can effectively avoid the extra penalty brought by CS and achieve a gain from 0.5 to 1.5 dB in optical signal-to-noise ratio. To practically verify the proposed scheme's performance, 7-core 16 km fiber span is deployed in the field to experimentally perform space division multiplexed coherent transmission. The wavelength division multiplexing (WDM) of 93 carriers was used to achieve coherent transmission at a net rate of 116.66-Tb/s.

NOMA security scheme based on constellation camouflage and selective mapping.

This study aims to present a non-orthogonal multiple access (NOMA) security scheme based on constellation camouflage and selective mapping. To improve the security of the system, we use a four-dimensional chaos model to camouflage high-power signals at the transmitter. The constellation diagram of high power is disguised from binary phase-shift keying (BPSK) form to quadrature phase-shift keying (QPSK) form, and after power multiplexing, further camouflaged from 8 points to 16 points. To improve the transmission performance of the designed system as much as possible and not increase the computational complexity, we use the selective mapping method in the process of power multiplexing and use the region decision method for demodulation at the receiving end. The proposed scheme is verified by experiments on a 2-km 7-core optical fiber, and achieves the safety transmission of a power division multiplexing-orthogonal frequency-division multiplexing (PDM-OFDM) signal with a net rate of 97.38 Gb/s without signal damage. The maximum achievable key space of the proposed scheme is 10135. Hence, it is a feasible and secure non-orthogonal multiple access-passive optical network scheme.

Highly secure 3D-OFDM transmission scheme based on two-level noise masking key-accompanying transmission over seven-core fiber.

In this Letter, we propose a highly secure three-dimensional orthogonal frequency division multiplexing (3D-OFDM) transmission scheme based on two-level noise masking key-accompanying transmission. The original signal is encrypted with a spherical constellation to ensure the system's security with a 4D Lorenz-like model. The key realizes two-level noise masking by introducing additional noise bits at the bit level and hiding in a noise-like spherical shell at the constellation level. Moreover, the proposed method of placing the key in the encrypted signal can simultaneously transmit the encrypted signal and the key. A 101.06-Gb/s 3D-OFDM encrypted signal with the proposed scheme over a 2-km 7-core fiber experiment was successfully implemented. Experimental results show that the security performance of the system can be guaranteed under the conditions of partial key leakage and key misplacement at the illegal receiver. At the same time, the key masking degree (KMD) of the proposed two-level noise masking can reach 3267, which effectively guarantees the safe transmission of the key.