Enhancing secure transmission of ultra-high order QAM via delta-sigma modulation integrated with radial basis function neural network enhanced chaos.

This paper proposes and experimentally demonstrates an ultra-high order signal security enhancement method based on delta-sigma modulation (DSM). We employ a radial basis function neural network (RBFnn) to enhance Henon chaos, effectively avoiding the degradation of chaotic dynamics, and increasing the key space from 10 to 10. In the experimental demonstration, we achieved high-security transmission of 16384QAM over 25 km in an intensity-modulated direct detection (IMDD) system based on DSM.

The neutrophil-to-lymphocyte ratio is associated with in-hospital heart failure in patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention.

Objective: To explore the association between the neutrophil-to-lymphocyte ratio (NLR) and in-hospital heart failure (HF) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

Methods: Our present study included 413 patients diagnosed with STEMI and treated with primary PCI. We performed logistic regression models to evaluate the relationship between the NLR and in-hospital HF risk in subjects diagnosed with STEMI.

Enhancing long-term frequency stability of an actively mode-locked optoelectronic oscillator via a phase-locked loop.

A method to improve the frequency stability of microwave frequency comb (MFC) signals generated by an actively mode-locked optoelectronic oscillator (AML-OEO) is proposed and experimentally demonstrated. In the experiment, fundamental mode locking in the constructed AML-OEO is achieved, producing MFC signals with a center frequency of 2.165 GHz and a repetition rate of 396.

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.

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 10 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.

Unveiling out-of-loop attosecond timing jitter precision in Ti:sapphire mode-locked lasers with an optical heterodyne technique.

The out-of-loop timing jitter exhibited in free-running Ti:sapphire mode-locked lasers with attosecond resolution is demonstrated using an optical heterodyne technique. To assess the feasibility of the experiment and discrimination signal properties, numerical simulations were conducted for Ti:sapphire mode-locked lasers. For accurately characterizing the genuine phase noise exhibited by Ti:sapphire mode-locked lasers, out-of-loop measurements were conducted, and a straightforward yet improved optical heterodyne setup was employed, allowing simultaneous low-bandwidth locking and out-of-loop timing jitter measurements with two Ti:sapphire mode-locked lasers.

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.

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).

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.

Performance improvement of non-orthogonal multiple access with a 3D constellation and a 2D IFFT modulator.

In this paper, we propose a performance improvement of non-orthogonal multiple access (NOMA) with a three-dimensional (3D) constellation and a two-dimensional Inverse Fast Fourier Transform IFFT modulator (2D-IFFT) for the passive optical network (PON). Two kinds of 3D constellation mapping are designed for the generation of a three-dimensional NOMA (3D-NOMA) signal. Higher-order 3D modulation signals can be obtained by superimposing signals of different power levels by pair mapping.

4-D constellation construction and encryption scheme based on bit-level dimension dissecting and reorganization.

A 4-dimensional (4-D) constellation construction and encryption scheme of dimension dissecting reorganization are proposed in this paper. In this scheme, the high-dimensional constellation is constructed by gradually decomposing and superimposing the low-dimensional constellation, and the mapping dimension, phase, and arrangement order of signals are scrambled to realize the encryption. This scheme uses the evolution from low dimension to high dimension to reduce the difficulty of constructing a high-dimensional constellation, and the confusion between dimensions facilitates the encryption of high-dimensional information.

Fiber re-circulating emulator for precise 504-km optical frequency combs transmission.

The propagation distance confines the development of precise time-frequency transmission using optical frequency combs due to the dispersion of the link. Here we disseminate a fiber re-circulating loop to emulate 504-km comb-based transmission. An optical filter in combination with a spool of dispersion compensation fiber is utilized to restrict the dispersion effect.

Wafer-Level Filling of MEMS Vapor Cells Based on Chemical Reaction and Evaporation.

Micro-electro-mechanical system (MEMS) vapor cells are key components for sensors such as chip-scale atomic clocks (CSACs) and magnetometers (CSAMs). Many approaches have been proposed to fabricate MEMS vapor cells. In this article, we propose a new method to fabricate wafer-level filling of MEMS vapor cells based on chemical reaction and evaporation.

Flexible non-linear physical security coding scheme combined with chaotic neural network for OFDM-WDM-PON.

In this paper, a flexible physical security coding scheme integrating chaotic neural network (CNN) and non-linear encryption is proposed for orthogonal frequency division multiplexing wavelength division multiplexing passive optical network (OFDM-WDM-PON). The scheme improved the flexibility, adjustability and the key space of chaotic encryption system by introducing chaos into neural networks. The system will encrypt the bit series, probability shaping points, and subcarriers position of the OFDM signal through linear encryption and non-linear encryption concurrently.

Outdoor atmospheric optical two-way time transfer with serial time code.

We demonstrated an optical two-way time transfer scheme in the outdoor free-space link using a simple complex programmable logic device-based serial time coder/decoder. With this scheme, we have transferred a 100 Hz signal with time information over a 120-m outdoor atmospheric link. The time drift, time deviation, and frequency instability are all measured to estimate the quality of the transferred time signal during the transfer process.

Deep-ultraviolet femtosecond laser source at 243 nm for hydrogen spectroscopy.

This paper reports on the generation of a 100 MHz repetition rate, 1.7 mW average power and femtosecond deep-ultraviolet (DUV) 243 nm laser source. The infra-red output of a broadband Titanium-Sapphire (TiSa) laser containing 729 nm light is mixed with its second harmonic in a β-barium borate (BBO) crystal.

Chaotic constant composition distribution matching for physical layer security in a PS-OFDM-PON.

This paper proposes a probabilistic shaping orthogonal frequency division multiplexing passive optical network (PS-OFDM-PON) based on chaotic constant composition distribution matching (CCDM). With the implementation of a four-dimensional hyperchaotic Lv system, probabilistic shaping and chaotic encryption are realized with low complexity on the process of signal modulation, so as to enhance the system performance in the presence of bit error rate (BER) and security. An 8.

Security-enhanced OFDM-PON with two-level coordinated encryption strategy at the bit-level and symbol-level.

A novel security-enhanced scheme combining improved deoxyribonucleic acid (DNA) encoding encryption at the bit-level with matrix scrambling at the symbol-level is proposed in OFDM-PON for the first time in this paper. In our proposed scheme, firstly each subcarrier is encrypted by improved DNA encoding encryption, which includes the functioning of key base series and the cross interchange. And the selected encoding rules, decoding rules, key base series, operating principles and the positions of cross interchange are dynamically changing, which enhances the robustness against malicious attacks by illegal attackers.

Enhanced 3D-CAP modulation with information-inserted time slots for seven-core fiber transmissions.

An enhanced three-dimensional carrier-less amplitude phase (3D-CAP) modulation with information-inserted time slots is proposed in this paper. Compared with the traditional 3D-CAP, the proposed scheme can reduce the value of the up-sampling factor by loading information on the time slots position, thus achieving better bit error rate (BER) performance under the same bit rate. An experiment demonstrating 43.

5D data iteration in a multi-wavelength OFDM-PON using the hyperchaotic system.

In this Letter, a novel five-dimensional (5D) data-iteration-based encryption model is proposed at physical layer for multi-wavelength optical frequency division multiplexing passive optical network (OFDM-PON) by using a hyperchaotic system. The proposed scheme can generate five chaotic sequences at a time. The sensitivity of 10 can be achieved, along with a key space of 10.

High security OFDM-PON with a physical layer encryption based on 4D-hyperchaos and dimension coordination optimization.

In this article we have enhanced the security of an orthogonal frequency division multiplexed passive optical network (OFDM-PON) based on four dimensional (4D) encryption, including constellation, subcarrier, symbol and time, which is proposed for the first time in this paper. 4D-hyperchaotic mapping is used to generate four masking factors to achieve ultra-high security encryption in four different dimensions. During the encryption, dimension coordination optimization is adopted, which effectively reduces the time cost of the system and improves the encryption efficiency by 3 times.